Laboratory investigation of Suffusion on dame core of glacial till

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Laboratory investigation of Suffusion on

dame core of glacial till

Daniel Yadetie Tuffa

Civil Engineering, master's level (120 credits) 2017

Luleå University of Technology

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Laboratory Investigation of Suffusion

on dam cores of Glacial Till

Daniel Yadetie Tuffa

Master programme in Civil Engineering, with specialization in

mining and Geotechnical Engineering

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Abstract

The objective of this study is to provide a better understanding of suffusion characteristics of glacial soils and to present a simple yet reliable assessment procedure for determination of suffusion in the laboratory.

Internal erosion by suffusion occurs in the core of an embankment dam when the ability of the soil to resist seepage forces is exceeded and voids are large enough to allow the transport of fine particles through the pores. Soils susceptible to suffusion are described as internally unstable. dams with core of broadly graded glacial moraines (tills) exhibit signs of internal erosion to a larger extent than dams constructed with other types of materials.

The Suffusion behavior of glacial soils has been investigated through two different permeameter suffusion test have been employed, small scale permeameter and big scale permeameter. Details of the equipment along with its calibration, testing and sampling procedures are provided.

The testing program were performed 9 test with different compaction degree in small scale permeameter and 2 test in big permeameter on internally stable categories of till soil. The categories are defined based on the soil grain size distribution and according to the methods developed by Kenney & Lau and Burenkova.

Layers are identified with suffusion if the post-test gradation curve exhibit changes in distribution compared to the initial condition and also the tests revealed that the effect of grain size distribution and relative degree of compaction on the internal erosion susceptibility of glacial till soils at different hydraulic gradients.

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Acknowledgement

This thesis would not have been possible without the encouragement and constant support of my supervisor, Professor Juan Lau. I am deeply grateful to my supervisor for his inspiration, ideas, guidance, and constructive comments.

I wish to express my warm and sincere thanks to my Examiners, Ingrid Silva and Jenny Lindblom, for your broad experience, encouragement and support.

I am very grateful to PhD student Ingrid Silva, research Eng. Thomas Forsberg for their assistance in setting up the laboratory equipment and sample preparation.

I am obliged to many of my colleagues and classmates who supported me, especially Yonas Lemma, Dr. Stefan, Deniz Dagli and Samuel Kebed who were with me all the time, from the beginning to the end.

I would like to show my gratitude to associate Professor Hans Mattsson, for his repetitive encouragement and guidance in many ways during my research.

I would like thank Lulea University of Technology, department of civil environmental and Natural Resource Engineering, for organizing this research

I owe my loving thanks to my friend, Sara Hagos, who provided great support and encouragement during the entire period of my study. Finally, I offer my regards and blessings to my mother Etete for her endless support.

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1 INTRODUCTION

1.1 OVERVIEW AND STATEMENT OF PROBLEM

Evaluating internal erosion resistance glacial soil in embankment dams is of concern in many geotechnical and hydraulic engineering problems. This is mostly the case internal erosion investigations of core materials in dams and embankments which is constructed to impound water in reservoirs for various purposes stability assessment of slopes and banks, as well as in erosion control of excavation irrigation canals.

Internal erosion is the second most frequent reason of failure of embankment dams for both new and existing dams after overtopping (ICOLD 2016). Figure 1 shows a famous case of internal erosion failure at Teton dam in the USA (1976).

Internal erosion is the phenomenon of water seepage within earth structures, such as embankments, dams or dikes, can cause a detachment and a transport of particles from the soil constituting the structure or its foundation. To assess the internal erosion and the potential failure modes, four type mechanical processes should be considered ICOLD (2013)

1) Concentrated leak erosion, involves when tractive seepage forces along a surface erosion of (i.e., a crack within the soil, adjacent to a wall or conduit, along the embankment-foundation contact) are sufficient to move soil particles into an unprotected area, or at the interface of a coarse and fine layer in the embankment or foundation.

2) Backward erosion, involves detachment of soils particles when seepage exits to a free unfiltered surface

3) Contact erosion, occurs at an interface between a fine soil layer and another layer made of a coarser soil and

4) Suffusion is an internal erosion mechanism, which evolves selective erosion of fine particle are removed through the void between the larger particles by seepage force.

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Figure 2 gap-graded soil and coarsely graded soil which are internally unstable and susceptible to suffusion from ICOLD (2013

In this last case, many attempts have been made to investigate the criteria that should be satisfied for suffusion. The identified criteria are;

1) The size of the fine soil particles must be smaller than the size of the constrictions between the coarser particles, which form the basic skeleton of the soil.

2) The amount of fine soil particles must be less than enough to fill the voids of the basic skeleton formed by the coarser particles. If there are more than enough fine soil particles for void filling, the coarser particles will be “floating” in the matrix of fine soil particles, instead of forming the basic soil skeleton; and

3. The velocity of flow through the soil matrix must be high enough to move the loose fine soil particles through the constrictions between the larger soil particles

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A glacial soil is derived from the action of the pull, crush, mix and transport generated by the progression and regression of the glaciers, is extensively used in many parts of the world as impervious core material in embankment dams. This type of material is found in areas once glaciated and typically broadly or widely graded with a mixture of content from fines up to boulders. Coarse widely graded or gap graded soils such as those show figure 2 are susceptible to suffusion

Furthermore, statistics indicate that dams with cores of glacial till are relatively more vulnerable to internal erosion compared to other soil types and its deserving more investigation.

1.2 Objectives and methodology

This master thesis presents an experimental investigation suffusion and analysis of data on glacial core of embankment dams. The investigation was conducted at Geotechnical Engineering at Lulea University of Technology.

The main objective of this study is to provide a better understanding of suffusion characteristics of glacial soils and to present a simple yet reliable assessment procedure for determination of suffusion in the laboratory. Suffusion characteristics of saturated tills in a big and small

permeameter are investigated and compared. The findings are presented in a unified framework. More specifically, this study intends to:

1) To investigate the hydraulic gradient for suffusion to initiate in glacial material 2) Understand the suffusion behavior of saturated glacial soils using laboratory testing 3) Provide simple assessment procedures for suffusion of glacial till soils and to present key factors affecting erosion of these soils.

4) The effect filter used in small scale apparatus to the tests of specimens. 5) Compare the effect of suffusion in different compaction degree

1.3 Scope and limitations

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1.4 Thesis structure

The structure of the thesis is as follows.

Chapter 1: Introduction to the topic of internal soil erosion and suffusion, and description of the objective and scope of this study.

Chapter 2 A review of research literature dealing with internal erosion as the principal mechanism in suffusion with focus on the constant head test,

Chapter 3 Documents the Properties of Soil Samples Used in the Current Study such classification of soil sample, pipet analysis, modified compaction test and defined categories of test sample Chapter 4 Description of the big and small scale permeameter test), including a seepage test review of the standard constant head, followed by details about the test program, setup, testing procedure. Chapter 5. Results

Chapter 6 Result Analysis

Chapter 7: Conclusion and Recommendation Chapter 8 references

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2 Literatures review

This thesis enquiry has theoretical knowledge from previous studies in similar topic. Between these previous works, some of the key works are reviewed below.

These literatures refer to experiments on internal erosion performed on glacial material in many different place

2.1 Kenney and Lau (1984, 1985)

They hypothesized that a soil would behave as a stable system when the size of the loose particle was larger than the controlling constriction size of the primary fabric. Kenney et al(1984) verified their hypothesis by applying downward flow test system on three mixture of gap-graded gravel and sand based on their hypothesis results of the seepage showed their prediction were correct.by extending their works (1985,86) downward flow seepage tests on14 cohesionless sand-gravel soil sample particle size up to 100mm.

Kenney and Lau postulated the H: F shape curve with H/F as stability index, where F denotes mass passing (%) at grain size D and H denotes mass increment (%) between D and 4D, with D as an arbitrary particle size. The evaluation range for widely graded soils (uniformity, Cu = d60/d10 > 3) is defined by F≤ 20%. A stability index less than one within the evaluation range ((H/F)min<1) indicates that a soil is deficient in the finer fraction, thus, potentially internally unstable, which means that fine particles can be washed out by seepage. Shape curves for the unstable and stable samples tested by Kenney and Lau are shown in figure 3 a and b

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Figure 3 Grain size distribution of internally (a ) stable and (b) unstable material tested by Kenney and Lau(1984,85)

2.2 Burenkova (1993)

Burenkova planned a predictive method built on the results of laboratory tests on 22 cohesion less sand gravel soils of maximum sizes up to 100mm, and coefficients of uniformity, Cu, up to 200. The basic assumption was that a smaller size fraction did not form part of the basic soil skeleton if it did not cause volume increase when mixed with a coarser size fraction. If the volume of the specimen increased after addition of a finer fraction this finer fraction was estimated as belonging to the soil skeleton. If additional fraction did not increase the volume of the specimen, the fraction was considered as belonging to the loose particles.

According to, Burenkova (1993) proposeda geometric condition for internal stability of a soil that depends on the conditional factors of uniformity d90 /d60 and d90 /d15 ratios where d90 is the sieve size for which 90% of the sample by weight passes. The d90 /d60 ratio represents the slope of the coarse part of the particle size distribution plot. High values represent near single size coarse particles which will have large constriction spaces compared to a well graded soil. The d90 /d15 can be regarded as a measure of the filter action between the coarse fraction and the finer fraction.

Burenkova (1993) defined boundaries separating suffusive soil from non suffusive soil. According to represents a zone of non suffusive compositions and Zone

Boundaries were defined separating “suffusive soils” from “non-suffusive soils”. Zones I and III represent zones of suffusive compositions; Zone II represents a zone of non-suffusive compositions; and Zone IV represents a zone of artificial soils. Zone II (non-suffusive) Figure 4. Boundaries are defined as follows: 0.76·log (h″) 1 < h′ < 1.86·log (h″)

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Burenkova (1993) also carried out a series of seepage test to study the effects of suffusion the size of eroded particle. The eight test confirmed 4 suffusive and 4 non suffusive soil sample whose grain size distribution curve are shown in figure 5.the seepage tests were carried out at hydraulic gradient up to 2,5.

Figure 5 grain size distribution of eight soil samples tested by seepage test (Burenkova (1993)

2.3 Skempton and Brogan (1994)

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𝑖𝑖𝑐𝑐 = (1 − 𝜂𝜂)(𝐺𝐺𝑠𝑠− 1) =_𝛾𝛾𝛾𝛾

𝑤𝑤… … … (1) Where ic: Critical hydraulic gradient,

Ƞ: Porosity of the material,

Gs: Specific gravity of the soil grains, Ƴ: Submerged unit weight of soil, Ƴw: Unit weight water.

They suggested that, in an internally unstable soil, the overburden load was probably carried on a primary fabric so that sand was relatively under small pressure. Table 1 summarizes the result of four seepage tests carried out by Skempton and Brogan (1994) and the proprieties of the soil sample.

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Figure 7 Gradation curve of test sample (Skempton and Brogan 1994) Table 1 Properties of test sample and test result (Skempton and Brogan 1994)

Test sample A B C D Porosity,ƞ (%) 34 37 37.5 36.5

D15 (mm) 0.60 0.90 0.98 1.6

Cu 24 10 7 4.5

Permeability(cm/s) 0.45 0.84 0.86 1.8

Filter ratio component, dc15/df85

11 3.9 3.2 3.2

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Note sample A and B, with (H/F) min <1, were assessed as internal unstable, whereas sample C and D were assessed as stable

2.4 Foster and Fell (1999, 2001)

They presented the boundary of no erosion and continues erosion filter test behavior by studied analyzing of experimental data on several filter tests carried by other and by performing the continual erosion filter test against bases which included a non-plastic glacial till sourced from the Australian.

Foster and fell (1999,2001) also reviewed the performance of the filter in existing dam. Based on the result of their investigation, they proposed the boundary of the filter behavior related to Df15 of filter which is a concentrated leak was simulated by punching a 1mm or 2mm (Continuing erosion tests) diameter stiff wire through the compacted base and some characteristic of base material related to Db85Db90 and Db95, and fine contentment of base material, in terms of broadly graded base soils, these eroded at filter opening sizes much smaller than that of the fine-grained bases. Foster and Fell attributed this to the shape of the gradation curve and its fine to medium sand size range (0.075mm to 1.18mm). Thus, the lower the amount of fine to medium sand sizes in the base, the finer the filter needed to arrest erosion

Generally, Foster and Fell investigation is not related to the study of internal stability of soil. Their investigation, even though provide useful information to help assessing the likelihood of moving fine particle through the void of coarser soil Skelton, as happen in suffusion process

2.5 Wan and Fell (2004a, 2008)

They postulated by extending Burenkova (1993) work, who did not put a clear a clear boundary between internally stable and unstable soils in the data set hence, Wan and Fell (2004,2008) developed contours for forecasting the probability of internal instability by logistic regression of h′ and h″. Their “modified Burenkova method” for broadly graded and gap-graded soils is shown in Figure (8) the probability contours are represented by the following equations (Wan and Fell 2004a):

𝑃𝑃𝑃𝑃 =_{1 + 𝑒𝑒𝑒𝑒 … … … 𝑒𝑒𝑒𝑒𝑒𝑒 2}𝑒𝑒𝑒𝑒

For silt-sand-gravel soils and clay-silt-sand-gravel soils percent of limited clay content and plasticity

𝑒𝑒 = 2.378. log(´´) − 3.648(ℎ´)3.701………equ.3 For sand-gravel soils with less than 10 percent non-plastic fines

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The probabilities should not be used directly in a risk assessment, but rather used to help develop a list of more likely and less likely factors during an elicitation of probability estimates.

Figure 8 probability of internal instability for silt-sand-gravel and clay-silt-sand-gravel soils of limited clay content and plasticity (Wan and Fell 2004a)

2.5 Li and Fannin (2008)

Li and Fannin (2008) studied two commonly used methods to define the susceptibility to internal instability: Kézdi (1979) and Kenney and Lau (1985, 1986). Kézdi allocated a soil into a coarse fraction and a fine fraction at one point along its grain -size distribution curve and applied Tirzah’s (1939) rule for designing protective filters (D′15/d′85) to the two fractions, with the fine fraction as the “base” and the coarse fraction as the “filter,” to assess if the soil would self-filter and be internally stable. The mass increment (H) over D′15 and d′85 is constant and equal to 15 percent, resulting in a criterion for instability of H less than 15 percent.

Kenney and Lau postulated the H: F shape curve with H/F as stability index, where F denotes mass passing (%) at grain size D and H denotes mass increment (%) between D and 4D, with D as an arbitrary particle size. They originally proposed a criterion in 1985 for internal instability of H/F < 1.3, applicable within F ≤ 30 percent (and cu ≤ 3) for narrowly graded soils and within F ≤ 20 percent (and cu > 3) for widely graded soils. This criterion was subsequently revised in 1986 to H/F < 1.0. This method is commonly used for cohesion less sand-gravel soils.

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3 Properties of Soil sample

3.1 Experimental program

Glacial core sample that are from dam site were provided by dam owner to geotechnical laboratory of Luleå University of technology for physical index and seepage test. Before starting the seepage tests, a series of pre-test (index) were performed to know the classification and some geotechnical properties of the material. The pre-test done are summarized as follow

3.2 Particle size analysis

The particle size distribution of the glacial core material is primarily used for classification purposes and to evaluate the gradation carachetrsitcs suffusion after the test. Figure 11 shows the particle size distribution curve of the natural glacial soil before the test have done.it can represent the pre-sieve gradation curve for small permeameter test specimens.

The distribution of particle sizes larger than 0.063 mm is determined by sieve, while distribution of particles sizes smaller than 0.063 mm is determined by sedimentation process using a pipette analysis.

3.2.1 Wet Sieving

The sieve analysis determines the grain size distribution curve of soil samples based on the available mass of fines, grains smaller than 63 μm in the samples, either hydrometer or pipette analysis has been adopted.

3.2.2 Sedimentation

The theory of sedimentation is since large particles suspended in a liquid settle more quickly than small particles, if all particles have similar densities and shapes.

By assuming that, particles are approximately spherical, the relation between the velocity and particle diameter is given by Stokes’ law, which is stated as:

𝜈𝜈𝜈𝜈𝐷𝐷2………equ .5

A total of 8 samples like the sieving were gone through sedimentation test. Pipette analysis were employed based on the mass of the soil passing sieve size 0.063mm.

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3.2.3 Pipette Analysis

This is for the determination of the sieve of fine particle distribution (smaller than 63µm) in a soil sample by mechanical analysis. An analysis of this kind expresses quantity the proportions by weight of various sizes of particles present in the soil. Like hydrometer test, it is recommended as a standard procedure to use dispersion agent to avoid flocculation.

The apparatus used consists of regular sampling pipette, capable of measuring 10 ± 0.2 mL of liquid, with a lowering and raising support. (Figure 10), Dispersion apparatus (1000ml), 500 ml of stock solution of sodium hexa-metaphosphate prepared as in the hydrometer test, many sedimentation cylinders, thermometer, ranging from 0 to 50°C, accurate to 0.5°C, stopwatch, and balance which is accurate to 0.001 g.

During the test, it is observed that Pipette analysis has several advantages over hydrometer analysis which is also supported by (Bardet, 1997). It takes less time because the sampling depth is adjustable, whereas it is fixed in hydrometer analysis. The calculations are also simpler and there is no need to account for the correction of meniscus or hydrometer dilation. However, compared to hydrometer analysis, pipette analysis is less adapted to the conditions encountered in a field laboratory. It requires accurate weight measurement

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Procedure and analysis of this test were adopted from (Bardet, 1997), which is based on British Standard

Figure 11 combined Grain size distribution curve sieve and pipette analysis of material used for the test sample

3.2 Plasticity

The Atterberg limit test were carried out on the soil sample according to (ASTM D4318) reveled that soil have non plastic fines. Generally, cohesionless soils are less resistant to erosion than plastic soils (ICOLD, 2013; Sherard, 1953) and, in terms of glacial till soils, PI > 4 inhibits internal instability (Crawford-Flett, 2014).

3.3 Proctor compaction

Modified proctor compaction was conducted on a glacial core material, to obtain information maximum dry density and optimum moisture content. It was conducted according to ASTM standard for laboratory compaction characteristics of soil using modified effort (2,700KN/m3). (ASTM D1557) on D < 20mm. The compaction tests are summarized in Table 2 with complete density curves in Figure3.3.

This information was essential for controlling the dry density and the molding water content of the specimens. 0 10 20 30 40 50 60 70 80 90 100 0,001 0,01 0,1 1 10 100 M ass p assi n g [ % ] Grain size [mm]

PARTICLE SIZE DISTRIBUTION -natural glacial soil

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3.3.1 Relative density and Molding water content

Test sample were prepared at the modified optimum water content (OWC). To attained desire molding water content, the appropriate amount of water was added to soil sample, which was cured for at least one day before a test sample was prepared. Water content test were carried out on remaining soil trimmed from compaction to find out the actual molding water content of the test sample.

The Samples were prepared at three degree of compaction defined respect to the modified Proctor test. The degrees of compaction considered are: a) 90%, well-compacted representing a material on the borderline of acceptance based on the recommendation of the current Swedish dam safety guidelines (Svensk Energy, 2012). The well-compacted specimen is to create a dense state according to standard, thus representing a well-engineered homogenous filling with acceptable erosion resistance b) 85% representing low compacted material; and c) 80% representing poorly compacted material.

Table 2 Modified Procter data on natural gradations

Sample Water content Dry density

Test-1 5 2,07

Test-2 6 2,1

Test-3 6,5 2.11

Test-4 7,5 2.11

Maximum Dry Density (g/cm3)

2.11

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Figure 3.3 Modified Proctor results on natural soils

3.4 Define the testing natural glacial soil

The testing program includes three categories of till soil: i) internally stable, ii) internally unstable; and iii) soils in the transition zone between the two first categories. The categories are defined by applying the current available methods developed by Kenney & Lau (1985, 1986), Burenkova (1993).In this master thesis, the tests have been done only till soil internally stable.

Based on Kenney and Lau (1985,1986) the method described in section (2.1) the test material has stability index greater than one which is defined a stable show in the figure 12a

The Burenkova (1993) method is based on d90 /d60 and d90 /d15 ratios. The d90 /d60 ratio represents the slope of the coarse part of the particle size distribution plot, whilst d90 /d15 ratio is regarded as a measure of the filter action between the coarse fraction and the fine fraction. The results are reported in Figures 12b based on Burenkove (1993) a test material showed in zone 4 which define not a clear.

2,02 2,04 2,06 2,08 2,10 2,12 2,14 4,70 5,70 6,70 7,70 D ry D ens it y ( g/ c m 3) Moisture Content (%) Moisture Density Test Results

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Table 4Grading characteristics of test specimen

a)

b)

Figure 12 a) a graph of the test material defined based on Kenney and Lau stability index>1. b) A graph of the test material defined showed based on Burenkova

Test sample C lay s ize fra ct io n s (% ) (< 0.002m m ) F ine C ont ent (< 0.075m m ) G rav el F ra ct io n (> 4.75m m ) S and fr ac ti on( 0.075 -4.75m m ) p la stic ity Cu = d6 0 /d1 0 C o ef fi ci en t o f u n if o rmity Cc =( d30 ) 2 /(d 1 0 *d 6 ) C o ef fi ci en t o f C ur va tur e S o il C la ss if ic atio n (A S T M D 2488) F in er f ract io n es tima tio n ( % ) B-S1 2.5 46.1 6.6 47.3 None-plastic 50 0.9 SW 53 1 3 5 7 9 11 13 1,5 15 150 1500

D90/

D60

D90/D15

0 5 10 15 20 25 30 35 40 0 10 20 30 40 M as s I nc rimen t,H (%)

Mass passing Diamater D,F(%)

Natural galacial soil Kennya-Lau limit curve H/F=1

Kenney-Lau Evaluation Range F<20%

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4 Test program on glacial till

A glacial till soils, named dam-B, was provided by dam owners from dam sites. In total 9 tests have been performed in small scale and 2 tests in big scale permeameter in this study according to the scheme in Fig13. 9 tests were conducted on different Dam-B till; three on 80% relative density; three on 85% and three 90% on Dam-B till and two on 80% relative density for big permeameter. The specimens are identifiable by their denotation: in falling order by i) the source soil (e.g. Dam-B), ii) category of soil (stable) iii) relative density, iv) test number and, Vi) filter type

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4.1 Laboratory Apparatus

4.1.1 Small Permeameter

The apparatus consists of a cylindrical stainless-steel seepage cell of 100mm internal diameter and height of cylinder is 115mm mounted on a detachable plastic cap plate on the top and bottom with inlet and outlet, which have to be connected to the constant level tank and seepage out flow collecter .

A different porous disc used such as wire-mesh and plastic-prous disc placed in the top and the bottom of soil sample for tests to check the effect.the objective of the porous disc used to prevent migration of material through valves and tubing during test Figure15

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4.1.2 Big Permeameter

The big permeameter apparatus, designed and build to accommodate sample contain particle size up to 30mm. The permeameter cell was comprises rigid wall stainless steel cylinder that is 300mm internal diameter and internal height the cylinder is 450mm long containing the soil sample to be tested. Figure 16

The cell was fitted with lockable silicon O-rings with through an inlet tube of 15mm diameter on the top plate of loading position and a shaft passing through a pre-drilled hole around the external wall part of permeameter of the sample. The sample shaft is which allow a force to hold down the upper part of the O- rings plate. The bottom plate is mounted on a square steel and through the bottom plate the outlet tube of 15mm diameter connect to the lower tank to facilitate measurement the rate of flow through the system.

The higher hydraulic gradient can have achieved by changing the position of the constant head tank manually, however, head roughly 2600mm for test sample B-S1-80a-F1and 200mm test sample B-S1-80b-F1 which generate 13 and 10 average hydraulic gradient respectively

The transparent manometer (piezometer) mounted on a stand with gradual scales. Seven piezometer points embedded at different depth of soil sample to provide the water pressure within soil sample.

The drainage layer, located on the top of the sample, is 200 mm height and its maximum grain size is 20mm. This layer serves to disperse the incoming flow to ensure more uniform water pressure on the upper surface of the soil sample.

The filter layer at the bottom most of the permeameter cell is 50mm long a filter to the soil tested based on sherard and dunningan (1989) filter criteria provided the soil are internally stable. The objective of to deliver filtering against the bottom of the specimen meanwhile it allows for an open system for unhindered seepage

The piezometers consisted of ordinary transparent tube, piezometer 1, 3,5,6,7 are in the same side and piezometer 2, 4 on their opposite side. Piezometer one and two gives the pore water pressure in the drainage. It is used for defining any losses in the supply system from the constant head reservoir, and for confirmation on the actual head applied on the top surface of the specimen. Piezometer 3,4,5,6 indicate on head losses through the specimen and piezometer 7 gives the pore water pressure in the filter layer.

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4.2 Sample Preparation and Testing Procedure

4.2.1 Sample Preparation

Compacted glacial soil samples were tested in this study, for both big and small permeameter. To make homogenization and to avoid segregation the samples were manually compacted to relative density and a desire molding moisture content Particles > 20mm and > 10mm were removed by hand (limiting D > 20mm and > 10mm to only infrequent particle) for both permeameter respectively. The specimen was thereafter divided into five equal sized streaks for small permeameter whereas for big permeameter the specimen divided in five equals sized including filter layer.

The compaction was performed for both permeameter using 2,05kg steal cylinder rammer dropped from 50cm, subjected the soil to achieved target relative density. The target relative density was found from the maximum Modified Proctor density which is considered on tests performed on D < 20mm (see section 3.3: compaction). For big permeameter the first layer is compacted above the filter layer. The dry density of a test sample to ensure known mass of soil was compacted to pre-calculated thickness corresponding to the desired dry density. Lastly the amount of soil and the molding water content of the tested sample were measured so as actual dry density of the soil.

4.2.2 Testing Procedure

Suffusion test procedure included the following stage

1) De-air the sample using CO2 (carbon die oxide): before upward saturation of the sample with water. The air content in the gaseous phase is replaced by upward incorporation of CO2 (carbon dioxide) by connecting in the bottom inlet of the sample cell. The aim of this procedure is to enhance quicker saturation of the sample.

2) Place the tested sample in the constant headsets. The connection tube which is subjected to the test is connect to test sample and allow the saturation in upward system in the low hydraulic gradient

3) Change the system to downward seepage to start the suffusion test once it has saturated

4) increase the hydraulic gradient by increasing the level of the constant head tank for big permeameter and whereas the small permeameter by changing the cell and allow water to flow through the sample until the condition appear to steady and the water levels in the manometer become recorded and observe if there is any erosion of the base that is transported through the filter into the collector can.

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6) Calculation of hydraulic gradient and flow rate

For small permeameter the hydraulic conductivity can be determined as the difference between the constant head height and the height of spacemen placed over the sample length (eq. a Darcy law) thus for big apparatus there are seven piezometers each of them give the water pressure at different depth of the test sample which was manually recorded. Average gradient (iavg) is defined as H/ (p3-p7) and local gradients are defined as icore-1Top = (p3-p4)/ (Z3-Z4), icore-2 = (p4-p5)/ (Z4-Z5),

icore-3 = (p5-p6)/ (Z5-Z6), and icore-4Bottom = (p6-p7)/(Z6-Z7), similarly for the head loss profiles

of the 𝑖𝑖 =ℎ_{𝐿𝐿 (𝑒𝑒𝑒𝑒 8)} 𝑘𝑘 = 𝑄𝑄 𝐴𝐴𝑖𝑖̇ (𝐸𝐸𝑒𝑒 9) Where Q=flow K=hydraulic conductivity I=hydraulic gradient A=area of spaceman L=length of spaceman H=head

The rate of the flow inside the test sample was determined at regular time interval by taking measurement of the volume of water collected from the overflow chute of the lower reservoir with specified period

7) Report results

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5 Result

This chapter presents the results of the small and big permeameter suffusion tests. Aiming used for defining internal instability, including Kenney and Lau (1985) proposed a curve matching technique, to evaluate the size of the largest eroded particle and estimated mass loss in which effect of grain size distributions of layers related to an initial gradation is used to evidence internal instability and suffusion.

5.1 A curve matching technique

It is a graphical technique proposed by Kenney and Lau (1985, 1986) can be used to investigate and estimate size of larger particles eroded by suffusion process and approximately fraction of materials eroded by the process. The techniques involve extending initial grain size distribution curve of the test sample to matches the grain size distribution curve of the same sample after the test or by extending the bottom layer of grain size distribution curve of the tested sample to matches the grain size distribution curve of each layer of the tested specimen specially the top layers after exhumed sublayer of tested specimens, Fig (20). In this thesis, the comparison of curve matching techniques checked by the both. The application the curve matching illustrated by a selection of results and graphs. The complete results are compiled in Appendix1

5.2 Hydraulic gradient for suffusion

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Table 5 Laboratory program schedule

Specimen Compaction (relative

Modified Proctor max. Dry density) (%) Average gradient (end-of-test) Test duration (hours) B-S1-90a-f1 90 21 303.6 B-S1-90b-f1 90 21 276.6 B-S1-90c-f2 90 10 70.5 B-S1-85a-f1 85 21 916 B-S1-85b-f1 85 21 244.2 B-S1-85c-f2 85 11 90.5 B-S1-80a-f1 80 21 336 B-S1-80b-f1 80 21 220 B-S1-80c-f2 80 21 205 B-S1-80a-F1 80 10 392 B-S1-80b-F1 80 13 210

5.3 Small-scale permeameter suffusion studies

A total of 9 tests have been performed with 80%,85% and90 % degree of compaction and with two types of filter, from the sample name f1 represent the pores stone whereas f2 represent the wire mesh. Results and graphs each of the specimen take out in layers. The layers are sequenced as follows: I) L 1 (the top most layer) ii) L 2, L3 and L 4 iii) L 5

(Lower layer) onto which the either porous stone or wire mesh filter layer was placed. These subsamples are subsequently compared to layer-1 and layer-5 that has been subjected to testing, layer-1 representative of the suffusion may experience by Compared to layer-5, the diagnosis criterion was that any coarsening of the top(layer-1) transition zone relative the layer-5 proved the existence of loose movable particles.

5.3.1 B-S1-80a-f1

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Figure 18 Specimen B-S1-80a-f1: particle size distributions of the post-test gradations layer 1 to5

5.3.2 B-S1-85c-f2

Test B-S1-85c-f2 was performed over the length 90.5 hours at an average gradient of 10

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Figure 19 Specimen B-S1-85c-f1: particle size distributions of the post-test gradations layer 1 to5

Figure 20 Specimen B-S1-85c-f1-Curve matching for estimated the fraction of materials loss by suffusion and the largest erodible particles 0 10 20 30 40 50 60 70 80 90 100 0,01 0,1 1 10 M ass pa ssi ng [%] Grain Size[mm]

B-S1-

85-c-f2-L1

B-S1-

85-c-f2-L5

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Figure 21 open channel surface post-test in the bottom layer(5)

5.3.3 B-S1-90a-f1

Test B-S1-90a-f1 had duration of 303.58 hours at an average gradient of 21.7 (end-of-test)

(Table 5), compacted to a relative density of 90% of maximum Proctor. There is no obvious change in post gradation to each layer (Fig 22).

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Figure 22 Specimen B-S190a-f1: particle size distributions of the post-test gradations layer 1 to5

5.4 Big-Scale Permeameter Suffusion studies

In this permeameter there were two tests have been performed on B-S1 till on the natural soil. Each of specimen release in layers. The layers arranged as follow Figure Layer-1 underlain drainage layer, followed layer-2, layer-3 and finally layer -4 against the filter layer, those sample layer compare to pre-grain size distribution that has not been subjected to test. To evaluate the stability of the sample based on the curve matching technique described in section and the also using a head loss profile, the technique was introduced by Lafleur and Nguyen (2007) and hydraulic gradient profile through the sample.

5.4.1 Specimen B-S1-80a-F1

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Figure 23 Specimen B-S1-80a-F1: particle size distributions of the initial gradation and post-test layer

Figure 24 temporal progression of head loss profile across specimen B-S1-80a-F1.not the drainage and the filter part as well

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Figure 25 Sample B-S1-80a-F1 temporal variation of hydraulic gradient and flow rate

Figure 26 Specimen B-S1-80a-F1-Curve matching for estimated the fraction of materials loss by suffusion and the largest erodible particles 0,00 2,00 4,00 6,00 8,00 10,00 12,00 14,00 16,00 18,00 20,00 0 5 10 15 20 25 30 0 50 100 150 200 Fl ow ra te, Q (ml /mi n) Hy dr au lic gr ad ei an t Measurment number Averge haydraulic gradient

measured flow rate i core L1 i core L2 i core L3 i core L4 0 10 20 30 40 50 60 70 80 90 100 0,001 0,01 0,1 1 10 100 M ass p assi n g [ % ] Grain size [mm] B-S1-80-b-F1-L1-Post B-S1-80-b-F1-L1-Pre

larger eroded particle 1.2-4mm

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5.4.2 Specimen B-S1-80b-F1

Test B-S1-80b-F1 ran for 210 hours at an average gradient of 13. Compaction

Was done to 80% relative density of MDD Modified Proctor. The post-test gradation curves show a shift in distribution from the initial gradation (Fig.27 ), indicating most mass loss in the lower core-L4 together with a formation of a homogenous central part of the specimen (core-L 2 and 3) (probably due to a combination with BEP), however the topmost core-L1 shows no obvious loss. The head loss profiles reveal that the specimen initially exhibited a uniform shaped profile, but progressed to ultimate head loss in the center and bottom part at end-of-test and significant increase in seepage in the (core-3) Furthermore, the seepage reduced significantly in the bottom layer(core-4) suggesting clogging against the filter (Fig 28;29)

Figure 27 Specimen B-S1-80b-F1: particle size distributions of the initial gradation and post-test layer

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Figure 28 temporal progression of head loss profile across specimen B-S1-80b-F1. not the drainage and the filter part as well

Figure 29 seepage measurement and gradient across Sample B-S1-80b-F1

0 20 40 60 80 100 120 140 160 180 200 0 10 20 30 40 50 60 70 80 90 100

Loc

at

ion

[mm]

Head loss[%]

Top

Center

Bottom

0,00 2,00 4,00 6,00 8,00 10,00 12,00 14,00 16,00 18,00 20,00 0 5 10 15 20 25 30 0 50 100 150 200 250 300 Flo w ra te ,Q (m l) Hy dr au lic gr ad ei an t number of measurment

Averge haydraulic gradient measured flow rate i core L4

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6 Analysis of result

General

In this section presents the analysis of the results of small and big permeameter tests. The analysis assesses at detecting potentially affect internal stability based on the observations during downward flow test on those samples.

Identifying attempts which might influence the hydraulic gradient at which selective erosion of fine particle by the process of suffusion would initiate using the following

Mass loss

Data on mass loss and the behavior of grain size distribution is shown in table5 and determine by gradation curve comparison, and curve matching technique as described in (section 6.1) in small scale seepage test the comparison done between layer -1(top) and layer-5(bottom) whereas the big scale between the initial gradation which is not subjected to test and the post gradation. Sample which failed by backward erosion the mass loss is not calculated. The maximum mass loss of erosion revealed in big permeameter may be due to scaling factor

Table 6 Post grading characteristics and mass loss for unstable test specimens

specimens

Grading characteristics layer-1 with respect

to

Assessment Mass loss using curve matching Loss due erosion Size of larger particle eroded (mm) Fraction of soil loss by suffusion Average (%) L-2 L-3 L-4 L-5 B-S1-90a-f1 No change No change No change

Slight finer No Loss

B-S1-90b-f1 Slight Finer finer No change No change No loss B-S1-90c-f1

coarser coarser coarser coarser Obvious

loss(GBE)

1.2-4.1 3

B-S1-85a-f1

coarser coarser Slight coarser Slight coarser Obvious loss 2.1 2.6 B-S1-85b-f1 Slight coarse

Coarser Coarser Coarser Obvious

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B-S1-80a-f1

Finer Finer finer

Coarser >1mm<finer Loss by GBE B-S1-80b-f1

loss

0.6-2.0 4.1

B-S1-80c-f1

loss

1.0-2.0 2.95

B-S1-80a-F1

loss

1.2-4 17.05

B-S1-80a-F1

Fine Fine Finer finer Loss by

GBE Failed by backward erosion (GBE)

.

Effect of filter on small scale permeameter result

The effect of porous- plastics filter and wire mesh in small scale permeameter were identified in sample B-S1-90a-f1 and B-S1-90b-f1with similar filter have no significant change in gradation but sample B-S1-90c-f2 with wire mesh had a relatively more vulnerable to change in gradation and also a sample with wire mesh filter showed higher seepage velocity than a sample with plastic-porous filter(figure 30) which all were internally unstable but a sample B-S1-85c-f2 was tested a hydraulic gradient approximately 10 show in figure 6.1

,

Figure 30 Sample with porous plastic and wire mish filter Average flow velocity versus hydraulic gradient

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Effect of Soil relative density

In small permeameter three type of compaction degree test sample performe.from the result found a sample had with 80% and 85% compaction degree internally unstable whereas a sample with 90% compaction degree showed no signs of internally instability. It should be noted that all the test were carried out at approximately the same hydraulic gradient of 20 except sample B-S1-85c-f2 and B-S1-90c-B-S1-85c-f2 which were approximately 10 even if both sample have showed some difference gradation wise. In big scale permeameter no enough data to compare the effect of compaction degree to have significant effect on the result.

Head loss profile

Water head along the specimen delivers understanding into the specimen homogeneity (Lafleur and Nguyen, 2007). A uniform shaped head loss profile suggests homogenous soil characteristic and conversely, an irregular shaped may, therefore, suggest inhomogeneity soil characteristics (Rönnqvist, 2015). A graph of head loss profiles (end-of-test) in B-S1-80a-F1 test specimens are shown in Fig31. Which reveals that the unstable specimens’ exhibit irregular profiles also sample B-S1-80b-F1 indiscretion because of clogging occurred in the bottom of the layer.

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Gradient data

The upward concavity of the gradation increases with decreasing fines content of the till, which would make gradually more susceptible to suffusion (Lafleur and Nguyen, 2007).

According to (Lafleur and Nguyen, 2007; Rönnqvist, 2015) unstable material exhibit when a local hydraulic significantly higher than the average gradient. This confirm by plotting in figure 32 of average gradient against local gradient at the end of the test for each layer of samples. Both Sample B-S1-80b-F1 and sample B-S1-80a-F1 confirmed, core-L4 which is unstable.

For sample assessed to be internally unstable in small scale permeameter test namely B-S1-80b-f1, B-S1-80c-f2, and B-S1-85a-B-S1-80b-f1, B-S1-85b-B-S1-80b-f1, B-S1-85c-f2, all sample at which the first sign of erosion fine particle, indicated by changing the color in the flow was observed during saturation stage which was carried by upward flow system however for big permeameter test specimen B-S1-80a-F1 the gradient profile showed (figure25 ) ,at 6 averge hydraulic gradient for suffusion to begin in specimens because at this point the seepage start to increase.

Figure 32 seepage measurement and gradient across Sample B-S1-80a-F1

0,00 2,00 4,00 6,00 8,00 10,00 12,00 14,00 16,00 18,00 20,00 0 5 10 15 20 25 30 0 50 100 150 200 Fl ow ra te, Q (ml /mi n) Hy dr au lic gr ad ei an t Measurment number Averge haydraulic gradient

measured flow rate i core L1

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Figure 33 Maximum local gradient relative average gradient at end-of-test for each layers of the specimens 10,25 12,9 9,6 5,8 1,08 13 25,7 3,0 4,4 1,0 0 5 10 15 20 25 30

i

end

-o

f-te

st

B-S1-80b-F1

Averger Gradient Vs Local gradient

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Possible causes of error

The below list of possible causes of error is given to allow for transparency of Testing and for future studies to improve on the techniques used.

• Pore-pressure was measured by hand with a folding ruler (meter stick) with unit of measure of 1 mm.

• Seepage was measured by hand with bucket and stopwatch, and the collected seepage water was weighed on a scale with unit of measure of 1 g.

• No side-material was used (i.e., barrier against the cylinder wall) to restrict preferential seepage

• Possible loss of mass in the handling of the specimens (e.g., in the post-test exhumation, transportation, drying, washing, sieving etc.).

• Occasional particles were coarser than the recommended limiting value of 1/10 of the permeameter diameter

• Possible evaporation of the outflow collector tab was not accounted for in the seepage measurement.

• Unfiltered municipal tap water was used in the tests. A potential variation in water temperature was not accounted for.

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7 Conclusion and recommendation

Based on the results of laboratory tests conclusions and recommendations for future work has been drawn

Conclusions

 All unstable soil has showed by suffusion onset diagnosis after compare post-test gradation of exhumed layers to initial gradation gives the fine particles has eroded.

 The maximum hydraulic gradient for suffusion iG ≈ 6 found in defined for material internally stable and poorly compacted (80% of modified Proctor test).

 By using (Kenney & Lau, 1985) curve matching method for small scale test has investigated the results showed the largest eroded particle was found 1.5 mm with average mass loss 5.6 percent and in big permeameter test was 4.00 mm with average mass loss 17.5 percent but the actual condition of the test is not allowed to erode the such large particle due to the smaller size filter used in both permeameter so the curve matching method need further investigation.

 The comparison of post-test gradation has investigated in different compaction degree sample, 80 and 85 percent were unstable and 90 percent was stable.

 The small-scale seepage test has carried out with wire mesh and plastic porous filter, the sample with wire mesh was unstable.

Recommendation

It is apparent that there is still a large uncertainty in the method described here for assessing weather soil will be internally unstable and the seepage gradient which will cause initiation

More laboratory testing is needed with a wider range of soil placed at varying void ratios and tested at range of hydraulic gradient

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REFERENCES

1. ASTM D2487 (1998). Classification of soils for engineering purposes (Unified soil classificationSystem). Philadelphia, USA.

2. ASTM D422 (1998). Standard test method for particles- size analysis of soils.

Philadelphia, USA.

3. ASTM D4318 (1998). Liquid limit, plastic limit, and plasticity index of soils. Philadelphia,

USA.

4. ASTM D1557 (1998). Laboratory compaction characteristics of soil using modified effort

(56,000 ftlbf/ft3 (2,700 kN-m/m3)). Philadelphia, USA

5. Burenkova, V.V. (1992) Assessment of suffusion in non-cohesive and graded soils, Proceedings, the First International Conference “Geo-Filters”, Karlsruhe, Germany, 20-22 Oct 1992, Filters in Geotechnical Engineering, Brauns, Heibum & Schuler (eds), 1993 Balkema Rotterdam, pp. 357-360.

6. Foster, M.A., Fell, R. (1999) Assessing embankment dam filter which do not satisfy design

criteria, UNICIV report NO. R-376, The University of New South Wales.

7. Foster, M.A. and Fell, R. (2001) Assessing Embankment Dam Filters that do not satisfy Design Criteria, Journal of Geotechnical and Geoenvironmental Engineering ASCE, Vol. 127, no. 4, May, pp. 398-407.

8. ICOLD (1995) Dam failure, Statistical Analysis, ICOLD Bulletin 99, Paris, 73 p.

9. Kenney, T.C. and Lau, D. (1995) Internal stability of granular filters, Canadian Geotechnical Journal, vol 22, no. 2, pp.215-225.

10. Ingrid Silva, Jenny Lindblom, Peter Viklander, Jan Laue (2017) Assessment of Internal

Erosion In The Glacial Till Core Of A Swedish Dam,85th Annual Meeting Of International Commission On Large Dams

11. Kenney, T.C. and Lau, D (1986). Internal Stability of Granular Filters: Reply, Canadian

Geotechnical Journal, Vol. 22 No. 2, pp. 215-225.

12. Lafleur, J., Mlynarek, J. and Rollin. A.L. (1989) Filtration of Broadly Graded

Cohesionless Soils, Journal of Geotechnical Engineering ASCE, 115 (12), pp. 1747-1768. 13. Nilsson, Å., Ekström, I. and Söder, C. (1999) Sinkholes in Swedish embankment dams,

Elforsk Report 99:34, English summary.

14. Nilsson, Å. and Rönnqvist, H. (2004) Measures to strengthening Embankment Dams in order to stop or control a possible through-flow process, International Seminar on Stability and Breaching of Embankment Dams, Oslo, Norway.

15. Norstedt, U. and Nilsson, Å. (1997) Internal Erosion and Ageing in some of the Swedish

Earth and Rockfill Dams, 19th ICOLD Congress, Florence, Vol II, pp. 307-319.

16. Rönnqvist, H. (2006) Predicting Internal Erosion in Glacial Moraine Core Embankment

Dams, HydroVision 2006 HCIPub inc, Portland OR, USA.

17. Rönnqvist, H. (2007) Assessing Potential for Internal Erosion in Glacial Moraine Core Embankment Dams, Dam Engineering, IWP&DC, received Nov 2006, accepted June 2007, to be published in Aug/Sept 2007.

18. Sherard, J.L. (1979) Sinkholes in Dams of Course, Broadly Graded Soils, 13th ICOLD Congress, India, Vol. II, pp. 25-35.

19. Sherard, J.L., Dunnigan, L.P. and Talbot, J.R. (1984a) Basic Properties of Sand and Gravel

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20. Sherard, J.L. and Dunnigan, L.P. (1989) Critical filters for impervious soils, Journal for

Geotechnical Engineering, ASCE, 115 (7), pp. 927-947.

21. U.S. Army Corps of Engineers (1953) Filter experiments and design criteria, Technical

memorandum No. 3-360, Waterways Experiment Station, Vicksburg.

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Appendix

Figure 35 Specimen B-S1-80b-f1: particle size distributions of the post-test gradations layer 1 to5

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Figure 36 Specimen B-S1-80b-f1-Curve matching for estimated the fraction of materials loss by suffusion and the largest erodible particles

0 10 20 30 40 50 60 70 80 90 100 0,01 0,1 1 10

m

as

s p

as

sin

g(

%

)

Grain size(mm)

B-S1-80-c-f2-L1 B-S1-80-c-f2-L2 B-S1-80-c-f2-L3 B-S1-80-c-f2-L4 B-S1-80-c-f2-L5 0 10 20 30 40 50 60 70 80 90 100 0,01 0,1 1 10 M ass p assi n g [ % ]

B-S1-80-b-f1-L1

B-S1-80-b-f1-L5

Larger eroded particle 0.6-2mm

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Figure 38 Specimen B-S1-80c-f1-Curve matching for estimated the fraction of materials loss by suffusion and the largest erodible particles

0 10 20 30 40 50 60 70 80 90 100 0,01 0,1 1 10 M ass p assi n g [ % ]

B-S1-80-c-f2-L1

B-S1-80-c-f2-L5

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Figure 40 Specimen B-S1-85a-f1-Curve matching for estimated the fraction of materials loss by suffusion and the largest erodible particles

0 10 20 30 40 50 60 70 80 90 100 0,01 0,1 1 10 M ass p assi n g [ % ]

B-S1-85-a-f1-L1

B-S1-85-a-f1-L5

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Figure 42 Specimen B-S1-85b-f1-Curve matching for estimated the fraction of materials loss by suffusion and the largest erodible particles

0 10 20 30 40 50 60 70 80 90 100 0,01 0,1 1 10 M ass p assi n g [ % ]

B-S1-85-b-f1-L1

B-S1-85-b-f1-L5

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Figure 44 Specimen B-S1-85c-f2-Curve matching for estimated the fraction of materials loss by suffusion and the largest erodible particles

0 10 20 30 40 50 60 70 80 90 100 0,01 0,1 1 10 M ass p assi n g [ % ]

B-S1-

85-c-f2-L1

B-S1-

85-c-f2-L5

(60)

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Figure 48 Specimen B-S1-85c-f2-Curve matching for estimated the fraction of materials loss by suffusion and the largest erodible particles 0 10 20 30 40 50 60 70 80 90 100 0,01 0,1 1 10 M ass p assi n g [ % ]

B-S1-90-c-f2-L1

B-S1-90-c-f2-L5

Larger eroded particle 1.2-4.1mm

Laboratory investigation of Suffusion on dame core of glacial till

Laboratory investigation of Suffusion on

dame core of glacial till

Daniel Yadetie Tuffa

Laboratory Investigation of Suffusion

on dam cores of Glacial Till

Daniel Yadetie Tuffa

Master programme in Civil Engineering, with specialization in

mining and Geotechnical Engineering

Abstract

Acknowledgement

Contents

1 INTRODUCTION

1.1 OVERVIEW AND STATEMENT OF PROBLEM

1.2 Objectives and methodology

1.3 Scope and limitations

1.4 Thesis structure

2 Literatures review

2.1 Kenney and Lau (1984, 1985)

2.2 Burenkova (1993)

2.3 Skempton and Brogan (1994)

2.4 Foster and Fell (1999, 2001)

2.5 Wan and Fell (2004a, 2008)

2.5 Li and Fannin (2008)

3 Properties of Soil sample

3.1 Experimental program

3.2 Particle size analysis

3.2 Plasticity

3.3 Proctor compaction

PARTICLE SIZE DISTRIBUTION -natural glacial soil

3.4 Define the testing natural glacial soil

D90/

D60

D90/D15

4 Test program on glacial till

4.1 Laboratory Apparatus

4.2 Sample Preparation and Testing Procedure

5 Result

5.1 A curve matching technique

5.2 Hydraulic gradient for suffusion

5.3 Small-scale permeameter suffusion studies

B-S1-

85-c-f2-L1

B-S1-

85-c-f2-L5

5.4 Big-Scale Permeameter Suffusion studies

Loc

at

ion

[mm]

Head loss[%]

Top

Center

Bottom

6 Analysis of result

i

end

-o

f-te

st

B-S1-80b-F1

Averger Gradient Vs Local gradient

7 Conclusion and recommendation

Conclusions

Recommendation

REFERENCES

Appendix

m

as

s p

as

sin

g(

%

)

Grain size(mm)

B-S1-80-b-f1-L1

B-S1-80-b-f1-L5

B-S1-80-c-f2-L1

B-S1-80-c-f2-L5