N. Dixon, K. Zamara, D.R.V. Jones, G. Fowmes

ABSTRACT: Despite the relative maturity of landfill design practice, world-wide there are still significant numbers of large scale failures of waste bodies, often incorporating the lining system. In addition, there is growing evidence that post waste placement deformations in the lining system are leading to loss of function (i.e. discontinuous drainage layers, loss on protection and leaking liners). Best practice has established that both stability and integrity of the lining system must be assessed during the design process, and specifically that interaction between the waste body and lining system should be considered both in the short-term (i.e. during construction) and long-term (i.e. following waste degradation). The paper introduces available analysis approaches, reviews knowledge of waste behaviour required for such analyses and provides guidance on the mechanisms to consider. The need for field monitoring to validate numerical models is established as is the need for extensive measurements of waste mechanics properties linked to a standard classification system to aid comparison and use. The benefits of using probability of failure analysis to incorporate material and test variability in design are highlighted.

Wrinkling of a Geomembrane on a Compacted Clay Liner on a Slope

R. K. Rowe, P. Yang, M.J. Chappel, R.W.I. Brachman , W.A. Take

ABSTRACT: The development of wrinkles in a 1.5 mm thick textured HDPE geomembraneover a compacted clay liner on a 3H:1V (33%; 18°) slope is reported at different times of the day on 25 August 2008. The width of wrinkles did not vary significantly throughout the day once notable wrinkling had developed. The mean wrinkle width (0.31 m) is greater than that at other sites with a GCL below the geomembranereported in the literature (0.21-0.23m). The maximum connected wrinkle ranged from less than 20 m at 08:40 to 1370 m at 15:10. Given the size of the area monitored(0.26 ha) one might expect about four such wrinkles per hectare. Wrinkles covered less than 2% of the area at 08:40 but exceeded 8% after 10:10 with a maximum of 20% at 15:10. The practical implications of the time of day the geomembrane is covered and the effect this could have on leakage are discussed.
KEYWORDS: geomembranes, wrinkles, landfills, liners, leakage

Diffusion of phenolic compounds through an HDPE geomembrane

N. Touze-Foltz, M. Ahari, M. Mendes, C. Barral, M. Gardoni and L. Mazeas

ABSTRACT: The experimental results obtained regarding diffusion through a high density polyethylene geomembrane of phenol, o-cresol, p-cresol, 2,4-xylenol, 3,4-xylenol, 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, 2,3,5,6-tetrachlorophenol, pentachlorophenol and bisphenol A are presented. Partitioning coefficients range from 0.3 to 205 respectively for phenol and pentachlorophenol. Diffusion coefficients lie in the range 1.1×10 -13 to 4.3×10 -13 m 2 /s respectively for 2-methylphenol and bisphenol A. The effect of aqueous solubility, n-octanol/water partitioning coefficient, molecular diameter and molecular weight on partitioning coefficient, diffusion coefficient and permeation coefficient were studied. Different trends from the ones previously given in the literature for volatile organic compounds (VOCs) were observed. An increase in the number of chlorine atom on the phenolic nucleus results in an increase of the partitioning coefficient and permeation coefficient, probably linked to the polarity of the molecules under study.

Shear-Induced Geomembrane Damage due to Gravel in Underlying Compacted Clay

P. J. Fox, C. Athanassopoulos, S. S. Thielmann, and A. N. Stern

ABSTRACT: Lining systems for landfills and heap leach pads are often constructed with compacted clay liners (CCLs) containing significant amounts of gravel. Geomembranes placed against gravelly CCLs are vulnerable to damage due tohighoverburden stress andinterface shear displacement. This invited paper reports results from the first experimental investigation of shear-induced damage to geomembranes placed in contact with gravelly compacted clay. A series of large-scale direct shear tests was conducted for the interface between smoothHDPE geomembranes and CCLs with 20 percent gravel. The tests were performed for normal stress levels ranging from 72 to 1658 kPa to simulate overburden stresses associated with bottom liner systems. Replicate interface shear tests were also performed for normal stresses up to 4145 kPa with a geosynthetic clay liner (GCL) placed in between the geomembrane and the CCL to evaluate protection provided by the GCL. Results indicate that shear displacement between a geomembrane and a gravelly CCL under high normal stress conditions can cause severe damage to the geomembrane. The testing program also found that placing a GCL between a geomembrane and a gravellyCCL can essentially eliminate such damage.

Evaluation of mineral barriers against acid rock drainage

A. Naka, T. Katsumi, G. Flores, T. Inui, T. Ohta, T. Urakoshi, and T. Ishihara

ABSTRACT: The barrier performance of geosynthetic clay liners (GCLs) containing Na-bentonite, zeolite, and ferrihydrate against acid rock drainage (ARD) was evaluated through hydraulic conductivity and sorption tests in order to determine their applicability as adsorption layers in waste rock containment facilities. The hydraulic conductivity (k) of GCL permeated with water was 1.4×10-11 m/s and this increased by one order of magnitude with ARDpermeation (k= 5.0×10-10 m/s). The k of zeolite permeated with water was 3.0×10-10 m/s and this also increased with ARDpermeation (k = 1.4×10-9 m/s). The k value of ferrihydrate was 7.3×10-9 m/s when permeated with water and this remained constant after ARD permeation (k= 8.6×10-9 m/s). Metal sorption of bentonite, zeolite, and ferrihydrate were different in terms of sorption capacity and selectivity, which can be summarized as follows: bentonite: Cu>Fe>Zn>Al>As>Pb, zeolite: Cu>Fe>Zn>Pb Al As, and ferrihydrate: Cu>Zn>Al>As>Pb. According to experimental results, the tree minerals appear to be good candidates for ARD mitigation.

Improvement on the Performance of Geosynthetic Clay Liners Using Polymer Modified Bentonite

Y. Liu, W. P. Gates and A. Bouazza

ABSTRACT: Polymers have been added to improve bentonite swelling capacity with the view of improving the hydraulic performance of GCLs. This paper presents an on-going study in which three bentonites were polymer-treated (0.5%, 1%, 2% by weight) and polymerincluded changes to swell index and Atterberg limits were determined. The liquid limit values generally increased with polymer content, although a decrease appeared at higher concentration of some polymers. However, polymer addition had only slight effects on plastic limits. Higher polymer concentration, regardless of type, generally resulted in higher swell index values and swell percentages. Different response of bentonites to polymers occurred which is mainly due to the individual characteristics of bentonites, such as chemical composition, type of gel formation etc.

Effect of Settlement rate and Geogrid reinforcement on the Deformation Behaviour of Soil barriers of Landfill Covers: Centrifuge Study

S. Rajesh and B.V.S. Viswanadham

ABSTRACT: The objective of this paper is to examine the influence of settlement rate and geogrid reinforcement on the deformation behaviour of soil barriers of landfill covers subjected to differential settlements. A series of centrifuge tests were performed on soil barriers at 40 gravities. Two different settlement rates were induced using motor-based differential settlement simulator designed for a high gravity environment. Centrifuge tests on a 1.2 m thick unreinforced soil barrier subjected to two different settlement rates without provision of any overburden pressure was found to experience identical deformation profiles and cracking pattern. A slight delay in the occurrence of crack initiation and an increase in the strain at crack initiation was noticed when the soil barrier was tested at slow settlement rate. An increase in the limiting distortion level from 0.044 to 0.069 was noticed when the unreinforced soil barrier was subjected to an overburden pressure equivalent to that of cover system. When the soil barrier was reinforced with a geogrid layer without any overburden pressure, the limiting distortion level was increased from 0.044 to 0.064. An increase in the maximum mobilized tensile load of model geogrid from 77 kN/m to 120 kN/m was observed with the provision of overburden pressureequivalent to that of cover system.

Effect of differential settlements on the sealing efficiency of GCLs compared to CCLs: Centrifuge Study

B.V.S. Viswanadham, S. Rajesh and A. Bouazza

ABSTRACT: Geosynthetic clay liners (GCLs) are being used as an alternative to compacted clays in landfill cover systems because of their very low hydraulic conductivity to water and ease of placement. The main objective of this paper is to examine the performance of GCLs subjected to continuous differential settlements during a centrifuge test at 40 gravities. This paper presents results to two centrifuge model tests, one on clay-based cover system and another on GCL-based cover system. Both models were subjected to an overburden equivalent to that of landfill covers and are instrumented to measure sealing efficiency at the onset of differential settlements. Limiting maximum distortion level at which the barrier system loses it sealing efficiency could be established. For the type of cover systems investigated, the ability of GCL-based cover system to withstand differential settlements without losing their sealing efficiency was found to be superior to that of clay based cover system.

Geosynthetic Lining System for Modern Waste Facilities – Experiences in Developing Asia

H. B. Ng and B. Ramsey

ABSTRACT: The applications of geosynthetic liner systems are being used with increasing frequency, particularly for the environmental engineering applications in developing countries at recent years. Polyethylene geomembrane sheets have been widely accepted as a standard component of geosynthetic lining system in the waste containments for decades, which includes solid waste sanitary landfill and wastewater treatment lagoons. The paper presents the application of impervious Polyethylene geomembrane used as bottom liners and final capping systems in waste containment facilities in developing Asia. This paper discusses the characteristics and durability of polyethylene geomembrane as a lining solution to the waste containments. Successful case histories on the application of polyethylene geomembranes in bottom liner and final capping systems of modern solid waste facilities are illustrated.

MALAYSIA SPECIAL ISSSUE

Editors: Thien Seng Yee, Swee Huat Chan and Teik Aun Ooi

Sponsored by: Asian Institute of Technology

Contents and Abstracts

Professionalism and Ethics of Engineering
By Z.C. Moh

Recent Advances in Pile Testing and Diaphragm Wall Constructions in Japan
By K. Ishihara

Innovation in Soil Improvement Methods
By J. Chu

Lessons Learned from Designing High-rise Building Foundations
By H.G. Poulos

A Critical Review of Rail Track Geotechnologies Considering Increase Speeds and Axle Loads
By Buddhima Indraratna, Sanjay Nimbalkar and Cholachat Rujikiatkamjorn

Performance and Analyses of Thick Soft Clay Deposit Improved by PVD with Surcharge Preloading and Vacuum Consolidation – A Case Study at CMIT
By P.V. Long, L.V. Nguyen and A.S. Balasubramaniam

Characteristics of Hardpan Calcrete of the Nyalau Formation and Impact on Design of Foundations
By A.C.Y. Sim, D.E.L. Ong, L.Y. Tai, W.H. Ting, E.P.S. Chai and J. Bachat

Ground Improvement via Vacuum Consolidation Method in Vietnam
By T.H. Seah, T.B. Kim and T.D. Nguyen

Laboratory Study on Dynamic Properties of Compacted Residual Soil in Malaysia
By Y. Tanaka and M.L. Lee

On The Preconsolidation Pressure: Experience Based on Testing the Holocene Marine Clay of Peninsula Malaysia
By M.J. Dobie

Tunnelling Past Critical Structures in Kuala Lumpur: Insights from Finite Element Analysis and T-Z Load Transfer Analyses
By C.W. Boon and L.H. Ooi

A Comparison of Performance of Deep Excavation using the Top Down and Bottom Up Methods in Kenny Hill Formation
By J.G. Tan and L.H. Ooi

Fallacy of Capacity Performance & Innovation Improvement of Jack-In Piling in Malaysia
By Liew, S.S. and Ho, S.F.

An Overview of Slope Failure during Monsoon Seasons in Malaysia
By M.L. Lee, Y. Tanaka and S.Y. Chong

Considerations of Deep Excavation in Kenny Hill and Kuala Lumpur Limestone Formations at the KVMRT
By J.G. Tan, L.H. Ooi & H.K. Yeoh

Grain Crushing under Pile Tip Explored by Acoustic Emission
By W. Mao, I. Towhata, S. Aoyama and S. Goto

A Vibro Stone Column Supported Test Embankment for a High-speed Rail Project in Malaysia
By Y.W. Yee, L.H. Ooi and J. Daramalinggam

HONG KONG AND SINGAPORE SPECIAL ISSUE

Editors: Sing Lok Chiu (Part A: Hong Kong), Tiong Guan Ng (Part B: Singapore) and
Prof. San-Shyan Lin (Part C: Contributed Papers)

Sponsored by: Asian Institute of Technology

Contents and Abstracts

PART A: HONG KONG

Challenges in Improving Slope Safety in Hong Kong through the Landslip Prevention and Mitigation Programme
By Ken K.S. Ho and Raymond W.M. Cheung

Rock Caverns – Hong Kong’s Hidden Land
By K.C. Ng, K.J. Roberts and Y.K. Ho

The First Subsea TBM Road Tunnel in Hong Kong
By Albert Liu, Stephen Chan, Conrad Ng, Joseph Lo, C. K. Tsang and Dunson Shut

Achievements of and Challenges to the Hong Kong Landslide Risk Management
By Rick CK Tam and Michael MK Chang

Subsea Horizontal Directional Coring (HDC)
By C. K. Tsang, S. F. Chau and Jimmy Chan

7th Lumb lecture 10th October 2012 “Peter Lumb’s legacy, Soil Mechanics = Simple concepts + mathematical processes + lateral thinking”
By John Endicott

PART B – SINGAPORE

Singapore Case Histories on Omission of Strut by Observation Approach For Circle Line and Down Town Line Projects
By David Ng C. C. and Simon Low Y. H.

Vacuum preloading methods: an update
By Jian Chu, Shuwang Yan and Wei Guo

A New Lithostratigraphical Framework Proposed for Singapore
By K.K Lat, K.H Goay, S.G Lau, S.L Chiam and K.C Chew

Economical Design for NSF Piles in Soft Clays using Soil-Structure Interaction
By Siew Ann Tan

Towards a Design Framework for Spatial Variability in Cement Treatment for Underground Construction
By Y. Liu, Y. Jiang and F. H. Lee

Advances and Challenges in Underground Space Use in Singapore
By Y. Zhou and J. Zhao

PART C – Contributed Papers

Effect of Ageing Environment on Fiber-Reinforced Polymer/Granular Interface Shear Behaviour
By H.A. Shaia and H.M. Abuel-Naga

Groundwater Flow Modeling and Slope Stability Analysis for Deepening of Mae Moh Open Pit Lignite Mine
By A.B.N. Dassanayake, N. Phien-wej and P. H. Giao

A Study on Internal Erosion of Low-Plasticity Silty Sand
By Jing-Wen Chen, Bo-Rung Lin, Wei F. Lee and Yie-Ruey Chen

Analysis of Influencing Factors on Brazilian Test Results Based on A Complex-shaped Grain Model for Brittle Rock
By Guangcheng Yang and Xinghua Wang

Effect of Infill Moisture Content and Thickness on Shear Behavior of Planar and Rough Rock Joints
By Tsu-Chiang Cheng, Shuh-Gi Chern, Shin-Ru Wu and Yu-The Lin

Role of Bentonite in Improving the Efficiency of Cement Grouting in Coarse Sand
By T.G. Santhoshkumar, Benny Mathews Abraham, A, Sridharan, and Babu T Jose

Chinese Taipei Special Issue

Editor:  Prof. Meei-Ling Lin

Sponsored by: Asian Institute of Technology

Contents and Abstracts

Rock Tunneling Applied to Steady Water Resources Supply in Taiwan: Challenges and Examples
By Chia-Han Lee, Tai-Tien Wang, Shih-Hsien Chang, Shang-Yao Lien and Shih-Wei Huang

State-of-the Art of the Tunnel Maintenance in Taiwan and Challenges to Sustainable Development
By Ya-Chu Chiu, Tai-Tien Wang, Tsan-Hwei Huang

Tunneling Issues Regarding the Rock Tunnel-Shaft Intersection in Taiwan
By Tai-Tien. Wang, Tzu-Tung. Lee, Shun-Min. Lee, Kwei-Shr. Li and Cheng-Hsun Chen

Assessment of Hard Rock Tunnel Stability: A Note on the Influence of Post-peak Strength Degradation
By F. Y. Hsiao, H. C. Kao and S. Y. Chi

Deep Excavations in Taipei Basin and Performance of Diaphragm Walls
By R. N. Hwang, C. H. Wang, C. R. Chou and L. W. Wong

Hydraulic Characteristics of Jingmei Formation and Dewatering for Deep Excavations in Taipei Basin
By G. R. Yang, L. W. Wong and R. N. Hwang

Forensic Investigation of A Subway Tunnel Construction Failure
By W. F. Lee, C. C. Wang, K. Ishihara, R. N. Hwang

Case Study of Renovation on Alishan Route 18 after Typhoon Morakot
By Kung-Tai Chou, Wen-Long Wu, Chiao-An Hsiao, Kun-Hsien Chou

Combining rainfall parameter and landslide susceptibility to forecast shallow landslide in Taiwan
By C.F. Lee, C.M. Huang, T.C. Tsao, L.W. Wei, W.K. Huang, C.T. Cheng, and C.C. Chi

Dynamic Analyses for Performance-Based Seismic Design of Geotechnical Structures with Examples in Deep Foundations
By D.W. Chang, C.W. Lu, S.S. Lin and J.R. Lai

Time-Dependent Dynamic Characteristics of Model Pile in Saturated Sand during Soil Liquefaction
By Chia-Han Chen, Yung-Yen Ko, Cheng-Hsing Chen and Tzou-Shin Ueng

Geological Investigation and Sliding Mitigation in Jiufen Area
By Lee-Ping Shi, Jen-Cheng Liao, Sheng-Hsiung Hung and Chien-Shui Huang

Interpretation and Analysis of Potential Fluidized Landslide Slope
By H. M. Shu, T. C. Chen, W.C. Yang and Y.X. Luo

SPECIAL FEATURE STORY ON “Recent Diaphragm Wall Technologies and Future Challenge”
By Hosoi Takeshi and Matsushita Shinya

HISTORICAL NOTE ON “Experiences of Geotechnical Development in Japan and Future Directions”
By Masami Fukuoka

OBITUARY of Masami Fukuoka
By Fumio Tatsuoka (DOI: 10.14456/seagj.2016.51)

Vietnam Special Issue

Editors:   Dr. Phung Duc Long & San Shyan Lin

Sponsored by: Asian Institute of Technology

Contents and Abstracts

Prediction of Piled Raft Foundation Settlement – A Case Study
By Phung Duc Long

Geotechnical Adaptation to the Vietnamese Coastal and Riverine Erosion in the Context of Climate Change
By K. Yasuhara, M. Tamura, Trinh Cong Van and  Do Minh Duc

Bidirectional Tests on Two Shaft-Grouted Barrette Piles in Mekong Delta, Vietnam
By H. M. Nguyen, B. H. Fellenius, A. J. Puppala, P. Aravind, and Q. T. Tran

Soil Characterization and Land Subsidence Prediction for the First MRT Line in HCM City
By Pham Huy Giao and Ta Thi Thoang

Soft Ground Improvement by Deep Cement-Mixing Technique in Southern Vietnam
By Dinesh Raj Shiwakoti and Ryuji Manai

Over Consolidation Feature of Clayey Soils in Southern Vietnam According to Piezocone
By Bui Truong Son, Le Hong Quang, Lam Ngoc Qui

Ground Improvement Using Soil-Cement Method: A Case Study with Laboratory Testing and In-Situ Verification for a Highway Project in Southern Vietnam
By Phan To Anh Vu

Wide Storage Tanks on Piled Foundations
By Bengt H. Fellenius and Mauricio Ochoa

Discrete Modelling of Excavation in Fractured Rock by NSCD Method
By Tran Thi Thu Hang and Frederic Dubois

A Method for Estimating Pile Group Settlement Considering Distribution of Pile Shaft Friction (SDF) – Application for Pile Groups in Vietnam
By Duong Diep Thuy, Pham Quang Hung, and Le Thiet Trung

Mechanical behaviour of Hai Duong Medium Sand in Triaxial Test and its DEM Simulations
By Nguyen Quang Tuan and Heinz Konietzky

Influence of Geometrical Parameters of Soil-Cement Columns on the Average Settlement of Embankment on Reinforced Soft Soil – Numerical Analysis
By Tran The Truyen, Nguyen Van Hung, and Tran N. Hoa

Evaluation of Performance of Diaphragm Walls by Wall Deflection Paths for Deep Excavations in Central Ha Noi
By Benson Hsiung, Dao Sy Dan, and William Cheang

Effect of Vacuum Pressure Distribution on Settlement Analysis Results for an Improved Thick Soft Clay Deposit at Sai Gon-Hiep Phuoc Terminal Port, South of Vietnam
By Hoang Hiep and Pham Huy Giao

Characteristic of Unsaturated Soil of Earth Fill Dams in Vietnam
By Nguyen Thi Ngoc Huong and Trinh Minh Thu

Settlement management for urban tunnels: an example from France
By Alain Guilloux and Hervé Le Bissonnais

Vol. 43 No.3 September 2012

Waste/Lining System Interaction: Implications for Landfill Design and Performance

N. Dixon, K. Zamara, D.R.V. Jones, G. Fowmes

ABSTRACT: Despite the relative maturity of landfill design practice, world-wide there are still significant numbers of large scale failures of waste bodies, often incorporating the lining system. In addition, there is growing evidence that post waste placement deformations in the lining system are leading to loss of function (i.e. discontinuous drainage layers, loss on protection and leaking liners). Best practice has established that both stability and integrity of the lining system must be assessed during the design process, and specifically that interaction between the waste body and lining system should be considered both in the short-term (i.e. during construction) and long-term (i.e. following waste degradation). The paper introduces available analysis approaches, reviews knowledge of waste behaviour required for such analyses and provides guidance on the mechanisms to consider. The need for field monitoring to validate numerical models is established as is the need for extensive measurements of waste mechanics properties linked to a standard classification system to aid comparison and use. The benefits of using probability of failure analysis to incorporate material and test variability in design are highlighted.

KEYWORDS: Waste, Lining System Interaction, Implications, Landfill Design, Performance

DOI: 10.14456/seagj.2012.9

Vol. 43 No.3 September 2012

Wrinkling of a Geomembrane on a Compacted Clay Liner on a Slope

R. K. Rowe, P. Yang, M.J. Chappel, R.W.I. Brachman , W.A. Take

ABSTRACT: The development of wrinkles in a 1.5 mm thick textured HDPE geomembraneover a compacted clay liner on a 3H:1V (33%; 18°) slope is reported at different times of the day on 25 August 2008. The width of wrinkles did not vary significantly throughout the day once notable wrinkling had developed. The mean wrinkle width (0.31 m) is greater than that at other sites with a GCL below the geomembranereported in the literature (0.21-0.23m). The maximum connected wrinkle ranged from less than 20 m at 08:40 to 1370 m at 15:10. Given the size of the area monitored(0.26 ha) one might expect about four such wrinkles per hectare. Wrinkles covered less than 2% of the area at 08:40 but exceeded 8% after 10:10 with a maximum of 20% at 15:10. The practical implications of the time of day the geomembrane is covered and the effect this could have on leakage are discussed.

KEYWORDS: Geomembranes, Wrinkles, Landfills, Liners, Leakage

DOI: 10.14456/seagj.2012.10

Vol. 43 No.3 September 2012

Diffusion of phenolic compounds through an HDPE geomembrane

N. Touze-Foltz, M. Ahari, M. Mendes, C. Barral, M. Gardoni and L. Mazeas

ABSTRACT: The experimental results obtained regarding diffusion through a high density polyethylene geomembrane of phenol, o-cresol, p-cresol, 2,4-xylenol, 3,4-xylenol, 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, 2,3,5,6-tetrachlorophenol, pentachlorophenol and bisphenol A are presented. Partitioning coefficients range from 0.3 to 205 respectively for phenol and pentachlorophenol. Diffusion coefficients lie in the range 1.1×10 -13 to 4.3×10 -13 m 2 /s respectively for 2-methylphenol and bisphenol A. The effect of aqueous solubility, n-octanol/water partitioning coefficient, molecular diameter and molecular weight on partitioning coefficient, diffusion coefficient and permeation coefficient were studied. Different trends from the ones previously given in the literature for volatile organic compounds (VOCs) were observed. An increase in the number of chlorine atom on the phenolic nucleus results in an increase of the partitioning coefficient and permeation coefficient, probably linked to the polarity of the molecules under study.

KEYWORDS: Diffusion of Phenolic Compounds, HDPE Geomembrane

DOI: 10.14456/seagj.2012.11

Vol. 43 No.3 September 2012

Shear-Induced Geomembrane Damage due to Gravel in Underlying Compacted Clay

P. J. Fox, C. Athanassopoulos, S. S. Thielmann, and A. N. Stern

ABSTRACT: Lining systems for landfills and heap leach pads are often constructed with compacted clay liners (CCLs) containing significant amounts of gravel. Geomembranes placed against gravelly CCLs are vulnerable to damage due tohighoverburden stress andinterface shear displacement. This invited paper reports results from the first experimental investigation of shear-induced damage to geomembranes placed in contact with gravelly compacted clay. A series of large-scale direct shear tests was conducted for the interface between smoothHDPE geomembranes and CCLs with 20 percent gravel. The tests were performed for normal stress levels ranging from 72 to 1658 kPa to simulate overburden stresses associated with bottom liner systems. Replicate interface shear tests were also performed for normal stresses up to 4145 kPa with a geosynthetic clay liner (GCL) placed in between the geomembrane and the CCL to evaluate protection provided by the GCL. Results indicate that shear displacement between a geomembrane and a gravelly CCL under high normal stress conditions can cause severe damage to the geomembrane. The testing program also found that placing a GCL between a geomembrane and a gravellyCCL can essentially eliminate such damage.

KEYWORDS: Shear-Induced Geomembrane Damage, Gravel in Underlying Compacted Clay

DOI: 10.14456/seagj.2012.12

Vol. 43 No.3 September 2012

Evaluation of mineral barriers against acid rock drainage

A. Naka, T. Katsumi, G. Flores, T. Inui, T. Ohta, T. Urakoshi, and T. Ishihara

ABSTRACT: The barrier performance of geosynthetic clay liners (GCLs) containing Na-bentonite, zeolite, and ferrihydrate against acid rock drainage (ARD) was evaluated through hydraulic conductivity and sorption tests in order to determine their applicability as adsorption layers in waste rock containment facilities. The hydraulic conductivity (k) of GCL permeated with water was 1.4×10-11 m/s and this increased by one order of magnitude with ARDpermeation (k= 5.0×10-10 m/s). The k of zeolite permeated with water was 3.0×10-10 m/s and this also increased with ARDpermeation (k = 1.4×10-9 m/s). The k value of ferrihydrate was 7.3×10-9 m/s when permeated with water and this remained constant after ARD permeation (k= 8.6×10-9 m/s). Metal sorption of bentonite, zeolite, and ferrihydrate were different in terms of sorption capacity and selectivity, which can be summarized as follows: bentonite: Cu>Fe>Zn>Al>As>Pb, zeolite: Cu>Fe>Zn>Pb Al As, and ferrihydrate: Cu>Zn>Al>As>Pb. According to experimental results, the tree minerals appear to be good candidates for ARD mitigation.

KEYWORDS: Evaluation, Mineral Barriers, Acid Rock Drainage

DOI: 10.14456/seagj.2012.13