1、GEOTECHNICAL SPECIAL PUBLICATION NO. 271 GEO-CHICAGO 2016 SUSTAINABLE GEOENVIRONMENTAL SYSTEMSSELECTED PAPERS FROM SESSIONS OF GEO-CHICAGO 2016 August 1418, 2016 Chicago, Illinois SPONSORED BY Geo-Institute of the American Society of Civil Engineers EDITED BY Anirban De, Ph.D., P.E. Krishna R. Reddy
2、, Ph.D., P.E., D.GE Nazli Yesiller, Ph.D. Dimitrios Zekkos, Ph.D., P.E. Arvin Farid, Ph.D., P.E. Published by the American Society of Civil Engineers Published by American Society of Civil Engineers 1801 Alexander Bell Drive Reston, Virginia, 20191-4382 www.asce.org/publications | ascelibrary.org An
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9、merica. Preface Geo-engineers and geo-scientists have been playing a major role in providing, protecting, and preserving infrastructure and the environment. Many innovative technologies and practices are constantly being developed and implemented. Evolving global climate change and exploding world p
10、opulation are leading to major concerns such as extreme geohazards, increased environmental pollution, and rapid depletion of natural resources. These new challenges can be addressed with new and innovative concepts, materials, energy sources, technologies, and practices. Sustainability and resilien
11、cy have become essential in the development of new materials and infrastructure systems. Geo-Chicago 2016: Sustainability, Energy, and the Environment held in Chicago August 14-18, 2016, provided a unique opportunity to highlight recent advances, new directions, and opportunities for sustainable and
12、 resilient approaches to design and protect infrastructure and the environment. The Geo-Chicago 2016 Conference attracted a significant amount of interest and in the end more than 350 papers were accepted for publication. The papers are divided into five Geotechnical Special Publications (GSPs) that
13、 capture the multidisciplinary aspects and challenges of sustainability and resiliency, energy and the geoenvironment. The first GSP, Sustainability and Resiliency in Geotechnical Engineering, addresses major broad issues related to sustainability and resilience in geotechnical and geoenvironmental
14、engineering, including carbon sequestration as well as characterization, analysis, monitoring, and response to geohazards and natural disasters, including earthquakes and landslides. Advances in emerging technologies and materials such as bio-mediated soils and nanomaterials are also presented. The
15、second GSP, Geotechnics for Sustainable Energy, tackles the new and innovative ways of storing and extracting energy in and from geotechnical media and structures such as shallow and deep ground, piles and foundations, and landfills. The second GSP also presents the challenges of the energy storage
16、and extraction at the field and lab scales as well as its numerical and experimental modeling. The third GSP, Sustainable Geoenvironmental Systems, addresses recent advances in landfill engineering and geosynthetics used for geoenvironmental systems, as well as advances in sustainable barrier materi
17、als and systems. The third GSP also presents studies into slopes, dikes, and embankment, the application of ground improvement in geoenvironmental applications, and the geoengineering of mine wastes and industrial byproducts. *HR Arvin Farid, Boise State University and Anirban De, Manhattan College
18、Short Courses Chair Michael A. Malusis, Bucknell University Workshops Chair James L. Hanson, California Polytechnic State University, San Luis Obispo Technical Tours/Social Program Co-Chairs Doug Hermann, Independent Consultant; and Dhooli Raj, Collins Engineers, Inc. Sponsorships and Exhibits Co-Ch
19、airs Carsten H. Floess, AECOM and Charles Wilk, ALLU Group, Inc. G-I TCC Liaison Susan E. Burns, Georgia Institute of Technology The Editors sincerely appreciates the help and patience of Ms. Helen Cook and Mr. Brad Keelor of Geo-Institute of the ASCE for their help in managing the paper submissions
20、 and organization of the conference. We hope that these GSPs will serve as valuable references to all working in geoengineering. The Editors Nazli Yesiller, Ph.D., A.M.ASCE, Global Waste Research Institute / California Polytechnic State University, San Luis Obispo Dimitrios Zekkos, Ph.D., P.E., M.AS
21、CE, University of Michigan Arvin Farid, Ph.D., P.E., M.ASCE, Boise State University Anirban De, Ph.D., P.E., M.ASCE, Manhattan College Krishna R. Reddy, Ph.D., P.E., D.GE, F.ASCE, University of Illinois at Chicago *HR and B. Munwar Basha, M.ASCE21Research Scholar, Dept. of Civil Engineering, Indian
22、Institute of Technology Hyderabad, Kandi, Sangareddy 502285, India. E-mail: 2Assistant Professor, Dept. of Civil Engineering, Indian Institute of Technology Hyderabad, Kandi, Sangareddy 502285, India. E-mail: bashaiith.ac.in Abstract: Anchor trenches for MSW landfills subject to various uncertainti
23、es arising from inconsistency in parameter measurement and determination, placement of fresh waste on the geomembrane (GM) liner, improper compaction of cover and backfilled soils, construction practices, assumption of relative slippage, and invention of new design methods. A wide range of variabili
24、ty is associated with the design parameters of the anchorage. Conventional factor of safety approach cannot account for the uncertainties involved. The drawback can be well addressed through reliability based approaches. The objective of the analysis discussed herein is to produce estimates of the p
25、robability of anchor trench failure as opposed to the conventional factor of safety. Therefore, a framework for the target reliability based design optimization (TRBDO) methodology is presented for the design of anchor trenches. This paper emphasizes the importance of allowable design strength of th
26、e liner considering the variability for rectangular and L-shaped rectangular anchor trenches. INTRODUCTION The conveyance of hazardous waste derivatives (e.g. leachate) from the bottom of an MSW landfill facility can be halted using natural or synthetic barriers. In general, natural materials like c
27、lays with low hydraulic conductivity (k) (an order of k = 10-8to 10-11m/sec) or geosynthetic materials like geomembrane (an order of k = 10-12to 10-15m/sec) or the combination of these two can be employed. Among the different types of anchors used in practice include: simple runout, rectangular, and
28、 V shaped anchors. This paper addresses the design of rectangular and L-shaped rectangular anchor trenches which are used widely in practice. An anchor trench is typically dug by a small backhoe or a trenching machine with the same geometry along the length and depth. Geomembrane (GM) liners are the
29、n installed in the trench and backfilled with soil. The liners are subject to various stresses during and after their installation due to self-weight, wind effect, temperature disparity, and pressure from cover soil respectively. Appropriate anchorage should be provided to ensure the liner to be in
30、its installed position. Anchorage can be provided with a trench (rectangular, L-shaped, *HR e.g., immediate and creep deformation behavior, deformation at the end-of-immediate shear deformation, rate of creep deformation, and deformation as a function of creep stress ratio. Analytical models were ap
31、plied to evaluate GCL shear deformation behavior. Analysis of available data suggests that shear deformation behavior and model parameters are dependent on aspects such as specimen dimensions, reinforcement type (e.g., needle punching or stich bonding), test temperature, short-term peak shear streng
32、th, and method of shear stress application (i.e., stepwise loading versus constant creep stress). INTRODUCTION Geosynthetic clay liners (GCLs) are hydraulic barriers consisting of a layer of bentonite clay encapsulated between layers of geotextiles or adhered to a geomembrane (ASTM D 4439). The use
33、of GCLs in barrier systems that include slopes subjects the GCL to an induced normal and shear stress that must be resisted externally and internally. External resistance is developed via interface shear strength between the geosynthetic layers of the GCL and adjacent materials, which may be either
34、geosynthetic or earthen. Internal resistance is developed via shear strength of the bentonite clay and needle-punched or stitch-bonded fibers in reinforced GCLs. The external and internal shear strength of GCLs used in design are based on short-term, displacement-controlled shear tests. However, res
35、ults of short-term tests may not provide an accurate representation of long-term shear behavior (Koerner et al. 2001; Mller et al. 2008; Zanzinger and Saathoff 2012; Fox and Stark 2015). Long-term internal shear strength of GCLs is relevant to barrier system design since GCLs deployed on slopes will
36、 experience induced normal and shear stress. Prolonged internal deformation of a GCL can lead to pull-out or tensile failure of reinforcing fibers such that internal shear strength is reduced to shear resistance of bentonite clay. *HR Zanzinger and Saathoff 2012). However, there have been limited ef
37、forts in the application of mechanistic models to describe internal creep deformation of GCLs. The objectives of this paper are to (i) describe a conceptual model for internal shear deformation of reinforced GCLs, (ii) provide a synopsis of GCL internal shear tests, and (iii) apply and evaluate anal
38、ytical models to describe the mechanisms of internal GCL shear behavior. BACKGROUND Schematics of needle-punched (NP) reinforced GCLs are shown in Fig. 1 for cases of no applied shear force (Fig. 1a) and a surface-applied shear force (Fig. 1b). The presence of a surface shear force will lead to shea
39、r deformation within the GCL and offset between the cover and carrier geotextiles. In reinforced GCLs, the shear force is resisted by the tensile strength of the reinforcement fibers and their connection to the geotextiles, whereas in unreinforced GCLs, shear is resisted primarily by the internal sh
40、ear strength of the bentonite clay (Stark et al. 1998). The application of a surficial shear force to a reinforced GCL will cause the reinforcing fibers to be oriented at an angle in the direction of shear (Fig. 1b). The internal failure mechanism of reinforced GCLs depends on whether or not thermal
41、 treatment has been applied to the carrier geotextile (Mller et al. 2008). Geosynthetic clay liners can be thermally treated by melting needle punched reinforcement fibers to the carrier geotextile. In non-thermally treated GCLs, ductile failure occurs by fiber pullout / disentanglement from the car
42、rier geotextile. However, in thermally-treated GCLs brittle failure occurs due to fiber rupture, which depends on tensile strength of reinforcement fibers and thermal locking between the fibers and geotextile. Fig. 1. Schematics of needle-punched reinforced GCLs for cases of (a) no applied shear for
43、ce and (b) surface applied shear force that generates shear deformation. Shear deformation behavior of a reinforced GCL during a constant applied normal and shear stress includes three stages as shown in Fig. 2: (i) immediate deformation, (ii) creep, and (iii) failure. Immediate deformation is elast
44、oplastic and starts immediately after application of shear stress. In this stage, horizontal deformation (i.e., horizontal offset or displacement between the upper and lower geotextiles) increases at a decreasing rate until creep deformation begins. Immediate deformation depends on the creep stress
45、ratio (defined herein as the ratio of applied shear stress to (a) (b) *HR however, failure was observed for some specimens hydrated in DI water and tested at a temperature of 80 C. Zanzinger and Saathoff (2012) conducted constant stress creep experiments on stitched-bonded GCLs at a temperature of 8
46、0 C. They reported failure for specimens tested at creep stress ratios 0.4 within days (e.g., failure observed within 4 d for a creep stress ratio of 0.4). *HR&KLFDJR*63 $6&(ANALYSIS The application of mathematical models to geomaterial behavior is useful to describe mechanisms of deformation and pr
47、edict behavior. Koerner et al. (2001) applied an exponential function to GCL creep behavior to predict time-to-failure. However, there have been limited analytical modeling efforts for GCL creep behavior beyond Koerner et al. (2001). Based on similarities in deformation behavior between geosynthetic
48、s and geomaterials, analytical models commonly applied to geomaterials were adopted in this study to evaluate creep deformation behavior of GCLs. Analytical Models Horizontal displacement of the cover geotextile relative to the carrier geotextile of a GCL was normalized with respect to the length of
49、 the GCL specimen in the direction of shear for all experimental data evaluated in this study. This normalization was used to provide a more effective comparison between different studies. Relative horizontal deformation ( ) was computed as: 100( )L= (1)where is horizontal displacement and L is length of the specimen. The applied shear stress to the GCL for which horizontal displacement occurs was also normalized in this study as the creep stress ratio
