Journal of Geotechnical & Geoenvironmental Engineering

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December 2006

Volume 132, Issue 12, pp. 1519-1643

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Design Considerations for Lysimeters Used to Evaluate Alternative Earthen Final Covers

Tarek Abichou, M.ASCE, Xiaoli Liu, and Kamal Tawfiq, M.ASCE

J. Geotech. Geoenviron. Eng. 132, 1519 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1519) (7 pages) | Cited 1 time

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Alternative earthen final covers are being considered throughout North America as cost-effective alternatives to prescriptive covers. Regulatory agencies typically require field testing to demonstrate the equivalency of percolation rates from prescriptive and alternative covers. Lysimetry, which consists of collecting percolating water from the base of a test section, provides a direct measurement of the percolation rate, and can be used in equivalency demonstrations. This paper describes a modeling study that investigated how lysimeter geometry and boundary conditions affect lateral diversion and percolation rates measured using lysimeters. Lysimeters with various geometries were simulated with HYDRUS-2D using constant meteorological and vegetation data. Simulations showed that sidewalls, which are 0.35 m high, can minimize the lateral diversion of flow around the sides of the lysimeter. Up-slope and down-slope endwalls of lysimeters need to extend to the surface of the lysimeter, especially when the lysimeter is inclined (4:1 or 3:1 slope). Modeling has shown that lysimeters underestimate percolation by 8 to 14%. Based on these simulations and the writers’ experience in the design and construction of lysimeters, a recommended design of lysimeters is suggested.

Compatibility with Jet A-1 of a GCL Subjected to Freeze–Thaw Cycles

R. Kerry Rowe, F.ASCE, Toshifumi Mukunoki, and Richard J. Bathurst

J. Geotech. Geoenviron. Eng. 132, 1526 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1526) (12 pages) | Cited 3 times

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Needle-punched geosynthetic clay liner (GCL) specimens subjected to 0, 5, and 12 freeze–thaw cycles in the laboratory, and GCL specimens recovered from a composite barrier wall in the Canadian Arctic after 1 and 3 years were examined to assess the hydraulic conductivity/permeability with respect to both deionized deaired water and Jet A-l. The GCL specimens recovered from the field after 3 years had a hydraulic conductivity with respect to water that was approximately 30% less than that of the GCL specimens subjected to 12 initial freeze–thaw cycles in the laboratory, suggesting that the laboratory conditions are more severe than field conditions. The combined effects of both the freeze–thaw cycles and Jet A-l permeation increased the permeability. This increase is attributed to the creation of macropores in the GCL due to freezing and to an expansion of free-pore space due to contraction of the double layer caused by permeation of Jet A-l. Although there was an increase in permeability due to the combined effect of freeze–thaw and permeation by Jet A-l, the effect was relatively small and the results suggest that the GCL continued to exhibit good performance as a hydraulic barrier when subject to extreme climatic conditions and hydrocarbons both in the laboratory and in the field.

Case History of Geosynthetic Reinforced Segmental Retaining Wall Failure

Chungsik Yoo, A.M.ASCE and Hye-Young Jung

J. Geotech. Geoenviron. Eng. 132, 1538 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1538) (11 pages) | Cited 9 times

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A geosynthetic reinforced segmental retaining wall was collapsed during a monsoon season in Korea, three months after the completion of wall construction. The circular type global slope failure was the dominant failure mode. The as-built design was examined for its appropriateness in meeting the current design requirements and the global slope stability. A comprehensive stress-pore pressure-coupled finite-element analysis was additionally conducted with due consideration of both positive and negative pore pressures in saturated and unsaturated zones. A number of relevant tests were also carried out on the backfill and the reinforcement collected from the site. The investigation revealed among other things that the inappropriate design and the low-quality backfill were mainly responsible for the wall failure, although the primary triggering factor was the rainfall infiltration. The results of the stress-pore pressure-coupled finite-element analysis provided sound evidences as to the wall performance over the rainfall period, supporting the field observation. Practical implications of the findings from this study are also discussed in view of reinforced wall design.

Liquefaction-Induced Lateral Spreading in Near-Fault Regions during the 1999 Chi-Chi, Taiwan Earthquake

Daniel B. Chu, Jonathan P. Stewart, T. Leslie Youd, and B. L. Chu

J. Geotech. Geoenviron. Eng. 132, 1549 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1549) (17 pages) | Cited 3 times

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We document and analyze incidents of liquefaction-induced lateral ground deformation at five sites located in the near-fault region of the 1999 Chi-Chi Taiwan earthquake. Each of the lateral spreads involved cyclic mobility of young alluvial soils towards a free face at creek channels. In each case, the lateral spreading produced relatively modest lateral displacements (approximately 10–200 cm) in parts of the spreads not immediately adjacent to channel slopes. For each site, we present displacement vectors across the spread features, which are based on mapping performed within three weeks of the earthquake. We review the results of detailed subsurface exploration conducted at each site, including cone penetration test soundings, borings with standard penetration testing, and laboratory index tests. We back-analyze the field displacements using recent empirical and semiempirical models and find that the models generally overestimate the observed ground displacements. Possible causes of the models’ overprediction bias include partial drainage of the liquefied soils during shaking, low but measurable plasticity of some of the soils’ fines fraction, and the absence of nonspread sites in the empirical databases used to develop existing empirical and semi-empirical lateral spread displacement prediction models.

Lateral Response Evaluation of Single Piles Using Inclinometer Data

San-Shyan Lin and Jen-Cheng Liao

J. Geotech. Geoenviron. Eng. 132, 1566 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1566) (8 pages) | Cited 6 times

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In an effort to develop an efficient method for interpretation of lateral pile load test results via measured inclinometer data only, an analytical model is proposed based on energy conservation of a pile-soil system. A Fourier series function is used to represent deflection behavior of the pile-soil system. In order to obtain shear, moment, and soil reaction along the pile shaft, convergence of the series after differentiation is guaranteed by applying the Cesaro sum technique. The concrete cracking effect is also incorporated into the pile model to account for yielding of the pile itself. Three full-scale pile load cases are then used to verify the feasibility of the developed methodology as well as make comparison to other methods.

Correlation between Cyclic Resistance Ratios of Intact and Reconstituted Offshore Saturated Sands and Silts with the Same Shear Wave Velocity

Jian-Hua Wang, Kathryn Moran, and Christopher D. P. Baxter, M.ASCE

J. Geotech. Geoenviron. Eng. 132, 1574 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1574) (7 pages) | Cited 8 times

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The cyclic liquefaction resistance of intact medium dense specimens of sands and silts obtained from offshore platform sites was compared to that of specimens reconstituted to the same values of shear wave velocity. The shear wave velocity was measured using a new system that is comprised of torsional piezoelectric ceramic ring transducers mounted in a triaxial cell, a multiwave measuring device, and special watertight connectors. The relationship between cyclic resistance ratio and the number of cycles to liquefaction Nf of intact and reconstituted specimens was compared at the same values of consolidation pressure and shear wave velocity. There was good agreement between cyclic resistance ratios of intact and reconstituted specimens with similar values of shear wave velocity if liquefaction is defined as ⩽ 6% peak-to-peak axial strain. The results of this study support the hypothesis that the cyclic liquefaction resistance of reconstituted specimens may be restored to in situ conditions when their shear wave velocity is restored to in situ values.

Monotonic and Cyclic Behavior of Two Calcareous Soils of Different Origins

Shambhu S. Sharma and Mostafa A. Ismail

J. Geotech. Geoenviron. Eng. 132, 1581 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1581) (11 pages) | Cited 1 time

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The behavior of two calcareous soils—Goodwyn (GW) and Ledge Point (LP)—is studied through a series of monotonic and cyclic triaxial tests. These two soils are selected because they represent two extreme formation conditions in terms of their depositional environments, physical characteristics, and grain strength. The experimental investigation included isotropic compression tests to high stress levels, undrained monotonic shearing tests, and undrained cyclic shearing tests under one-way and two-way loading conditions. Tests were performed on samples with different initial conditions. The experimental results show that, although the overall qualitative stress-strain behavior of both GW and LP soils is similar to that of other silicious soils, significant quantitative differences are observed between the two soils and also between calcareous and silicious soils, especially in terms of volumetric reduction during compression, monotonic and cyclic shear strength, and the strain required to mobilize the strength. This paper explores the mechanical behavior of the two calcareous soils and highlights the similarities and differences between their behavior and also between calcareous and silicious soils.

Structural Stability of Concrete Gravity Dams Strengthened by Rockfill Buttressing: Hydrostatic Load

Pierre Léger and Farrokh Javanmardi

J. Geotech. Geoenviron. Eng. 132, 1592 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1592) (8 pages)

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Rockfill buttressing is often considered to strengthen existing gravity dams that have inadequate stability to resist the estimated hydrostatic and seismic loads. Various simplified methods for static stability analyses of composite concrete–rockfill dams, which represent the rockfill as equivalent forces, are discussed. Numerical analyses of composite dams using nonlinear rockfill and interface constitutive models are then considered. Hydrostatic stability analyses of a 35 m composite dam are carried out to compare the results obtained from simplified methods and numerical analyses. Parametric analyses are performed to investigate the effects of various modeling parameters such as the friction angle of the concrete–fill interface, the friction angle of the concrete–foundation interface, and the reservoir elevation during the fill placement. Numerical analyses results show that lowering the reservoir prior to construction of the rockfill does not have a significant effect on the stress response of the strengthened dam in the case analyzed. For design purpose, it is shown that the simplified minimum/maximum earth pressure method is always on the safe side irrespective of the concrete–rockfill friction angle.

Bearing Capacity of Piled Rafts on Soft Clay Soils

Luca de Sanctis and Alessandro Mandolini

J. Geotech. Geoenviron. Eng. 132, 1600 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1600) (11 pages) | Cited 3 times

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The conventional design of a piled foundation is based on a bearing capacity approach, and neglects the contribution of the raft. As a consequence, piled foundations are usually designed by overconservative criteria. With respect to the conventional approach, a more rational and economical solution could be obtained by accounting for the contribution of the raft toward the overall bearing capacity, but this potential is not exploited due to the lack of theoretical and experimental research on the behavior of piled rafts at failure. Based on both experimental evidence and three-dimensional finite element analyses, a simple criterion is proposed to evaluate the ultimate vertical load of a piled raft as a function of its component capacities, which can be simply evaluated by the conventional bearing capacity theories. The results presented in the paper thus provide a guide to assess the safety factor of a vertically loaded piled raft.

Seismic Site Response for Near-Fault Forward Directivity Ground Motions

Adrian Rodriguez-Marek, M.ASCE and Jonathan D. Bray, M.ASCE

J. Geotech. Geoenviron. Eng. 132, 1611 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1611) (10 pages) | Cited 1 time

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Forward directivity effects in the near-fault region produce pulse-type motions that differ significantly from ordinary ground motions that occur at greater distances from the causative fault. Current code site factors are based on empirical observations and analyses involving less intense nonpulse ordinary ground motions. Nonlinear site response analyses with bidirectional shaking are performed using representative site profiles to quantify seismic site response effects for intense near-fault motions resulting from forward directivity. Input rock motions are represented with simplified velocity pulses that characterize the amplitude and period of forward directivity motions. Results indicate that site response affects both the amplitude and period of forward directivity pulses, and hence, local site conditions should be considered when evaluating seismic designs in the near-fault region. Stiff soil sites tend to amplify the peak ground velocity and increase the period of pulse-type motions, particularly, when the period of the rock motion coincides with the degraded period of the site. Amplification is limited at soft soil sites by the dynamic strength of the weak soil, so attenuation occurs for intense input motions. This nonlinearity is not reflected in the site factors in current building codes. Guidance is provided for estimating the amplitude and pulse period for velocity pulses at soil sites.

Enhanced Criterion for Base Soil Retention in Embankment Dam Filters

Buddhima Indraratna, F.ASCE and Ashok K. Raut

J. Geotech. Geoenviron. Eng. 132, 1621 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1621) (7 pages) | Cited 4 times

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In effective filters, potentially erodible base particles are transported to the filter and retained to form a stable self-filtration layer. At any given time, the mass proportion of the filter and the base materials in this layer depends on the initial porosity of the filter and the subsequent porosity of the self-filtration layer. In this paper, an analytical procedure is given to obtain the particle size distribution (PSD) of the self-filtration layer by combining the PSDs of the filter and the base soil modified by Dc95, where 95% of filter constrictions are finer than the size denoted by Dc95. The assessment of internal stability of the PSD of the self-filtration layer forms a rational model to successfully identify the effective filters from their ineffective counterparts. The proposed model is verified by large-scale laboratory tests carried out by the writers in addition to other published data. The model performance is acceptable in relation to various base and filter materials, and provides an alternative and rigorous design approach by eliminating most limitations of the conventional particle based criteria (e.g., D15/d85 ratio).
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Degradation of Sands due to Combined Sinusoidal Loading

M. Sherif Aggour, F.ASCE and Jim X. Zhang, M.ASCE

J. Geotech. Geoenviron. Eng. 132, 1628 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1628) (5 pages)

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Dynamic loading due to earthquakes is made up of very complicated combinations of different types of waves including compressive waves, shear waves, etc. If a soil specimen is subjected to a combined longitudinal and torsional excitation, significant degradation of the specimen occurs, wherein the modulus is reduced and the damping increased more than for single excitation. This paper presents equations based on test results on clean sands for the determination of the shear modulus and damping of sandy soils for single and combined sinusoidal loadings. From the equations, the degree of specimen degradation can be determined, as well as the threshold strain ratio needed for the degradation to occur. The dynamic properties obtained from combined loadings will be more representative of actual field conditions than those from single-loading conditions.
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Discussion of “Review of Standard Penetration Test Short Rod Corrections” by Chris R. Daniel, John A. Howie, R. Scott Jackson, and Brian Walker

Fernando A. B. Danziger, A.M.ASCE, Bernadete R. Danziger, and Erinaldo H. Cavalcante

J. Geotech. Geoenviron. Eng. 132, 1634 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1634) (3 pages)

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Closure to “Review of Standard Penetration Test Short Rod Corrections” by Chris R. Daniel, John A. Howie, R. Scott Jackson, and Brian Walker

Chris R. Daniel, John A. Howie, R. Scott Jackson, and Brian Walker

J. Geotech. Geoenviron. Eng. 132, 1637 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1637) (4 pages)

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J. Geotech. Geoenviron. Eng. 132, 1641 (2006); http://dx.doi.org/10.1061/(ASCE)1090-0241(2006)132:12(1641) (3 pages)

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