Journal of Geotechnical & Geoenvironmental Engineering

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December 2005

Volume 131, Issue 12, pp. 1445-1572

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Variation in Residual Shear Strength of the Soil with the Salinity of Pore Fluid

Binod Tiwari, A.M.ASCE, Gyanu Ratna Tuladhar, and Hideaki Marui

J. Geotech. Geoenviron. Eng. 131, 1445 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1445) (12 pages) | Cited 1 time

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Slope stabilization procedures for seven landslides in the Niigata Prefecture of Japan had provided an excellent and rare opportunity to examine the composition of ground water, and residual shear strength of the sliding surface soil, as well as unsheared mudstone. Ring shear tests were conducted on the soil samples collected from sliding surface soil, revealed during the installation of 3 m diameter drainage galleries. Shear strength and index properties of the soil were measured by mixing the soil with distilled water and sea water, and after leaching the NaCl from the pore water. The residual shear strength of the soil sample with distilled water was 3–5° lower than that with the sea water. The residual shear strength of the intact rock powder after leaching the dissolved salt was close to that of the soil from sliding surface, and the residual shear strength of the soil from sliding surface after mixing with sea water was close to that of the intact rock powder. The increase in residual shear strength had a parabolic increment with the specific surface area. This research finding has very important practical implications on the postfailure stability analysis of the landslides having saline pore water.

Effect of Grain Size and Distribution on Permeability and Mechanical Behavior of Acrylamide Grouted Sand

H. Gurkan Ozgurel and Cumaraswamy Vipulanandan, M.ASCE

J. Geotech. Geoenviron. Eng. 131, 1457 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1457) (9 pages) | Cited 4 times

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In order to investigate the effects of grain size and distribution of sand on the mechanical properties and permeability of grouted sands, several gradations of sands were grouted using acrylamide chemical grout and tested. The influence of sand density, fines content [particle size <0.075 mm (0.0029 in.)], curing condition and time, and grout dilution were investigated. Groutability of sand with various fines content was investigated using injection pressure up to 138 kPa (20 psi), equivalent to injection hydraulic gradient of 155. From the groutability study a relationship between grouting pressure and fines content have been developed. Grouted sand specimens were cured in moist, submerged in water and dry (air cured) conditions for 3, 7, and 28 days and tested. The stress–strain relationships were developed to characterize effect of curing condition and curing time on the mechanical behavior of acrylamide grouted sands. The grout was diluted with water up to 50% and its effect on grouted sand mechanical properties and permeability behavior was studied. Permeability of grouted sands was measured using constant head permeability tests over a period of 120 days. Based on the test results, relationship between unconfined compressive strength and permeability of acrylamide-grouted sand was investigated. Particle size distribution and fines content influenced the strength, modulus and stress-strain relationship but had minimal effect on the failure strain and permeability of grouted sand. Grouted sand strength varied from 290 kPa (42 psi) to 820 kPa (119 psi). The behavior of acrylamide grouted sand was analyzed based on the test variables and quantified using simple mathematical relationships.

Seismic Lateral Response of Piles in Liquefying Soil

D. S. Liyanapathirana, M.ASCE and H. G. Poulos, F.ASCE

J. Geotech. Geoenviron. Eng. 131, 1466 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1466) (14 pages) | Cited 10 times

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Soil liquefaction is one of the major factors affecting the behavior of piles founded in seismically active areas. Although methods are available for seismic analysis of pile foundations, in many of them, the supporting soil is assumed to be an elastic material. Here a numerical model is presented which takes into account the reduction of soil stiffness and strength due to pore pressure generation and subsequent soil liquefaction, in addition to the material nonlinearity. Results obtained from the new method are compared with centrifuge test data and show excellent agreement with the observed pile behavior during these tests. To investigate the effects of soil liquefaction on the internal pile response, a parametric study is carried out for a range of material and geometric properties of the pile and surrounding soil. The effect of the nature of the earthquake on pile performance has been studied using 25 earthquake records scaled to different acceleration levels. It is shown that the “Arias intensity” and the natural frequency of the earthquake ground motion have a significant influence on the pile performance in liquefying soil. Existing elastic analysis methods for kinematic pile loading in layered soil deposits with soft and stiff layers are applied to the soil deposits with liquefying and nonliquefying layers. It is found that these simple design methods, which were derived assuming that the soil is a linear elastic material, do not predict bending moments accurately when nonlinear behavior of soil and effects of pore pressure generation are significant. Also a simplified limit equilibrium method proposed for the evaluation of bending response of single pile foundations subjected to lateral spreading is compared with the bending response obtained from the proposed numerical model. It is found that the limit equilibrium method, which is developed based on the centrifuge test results, does not give accurate results when the pile diameter and the thickness of the liquefied soil layer deviates from the values used for the centrifuge tests.

Pseudostatic Approach for Seismic Analysis of Piles in Liquefying Soil

D. S. Liyanapathirana, M.ASCE and H. G. Poulos, F.ASCE

J. Geotech. Geoenviron. Eng. 131, 1480 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1480) (8 pages) | Cited 4 times

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The performance of pile foundations during an earthquake significantly influences the integrity of structures supported by them. Therefore, in the overall seismic design process of the structures, modeling of the soil–pile-superstructure interaction is an essential part. Although finite element based coupled analysis of the soil–pile-superstructure interaction models have the potential to provide accurate results, they are computationally expensive and often complex to utilize. In practice, many geotechnical engineers tend to use simple methods for obtaining the internal response of piles subjected to earthquake loading. Therefore this paper presents a simple pseudostatic approach where a single pile is considered, including the contribution of the superstructure to the pile and the interaction between the pile and the soil. The method involves two main steps. First a nonlinear free-field site response analysis is carried out to obtain the maximum ground displacements along the pile and the degraded soil modulus over the depth of the soil deposit. Next a static load analysis is carried out for the pile, subjected to the maximum free-field ground displacements and the static loading at the pile head based on the maximum ground surface acceleration. The method has been verified using an independent dynamic pile analysis program developed by the writers for the seismic analysis of piles in liquefying soil. It is demonstrated that the new method gives good estimates of pile bending moment, shear force, and displacement, despite its relative simplicity. The method is then used to compute the response of pile foundations during the Kobe 1995 earthquake and some centrifuge tests found in the literature where extensive soil liquefaction has been observed. Very good agreement is observed between computed and recorded pile bending moments.

Evaluation of Shear Modulus and Damping in Dynamic Centrifuge Tests

A. J. Brennan, N. I. Thusyanthan, and S. P. G. Madabhushi

J. Geotech. Geoenviron. Eng. 131, 1488 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1488) (10 pages) | Cited 11 times

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Correct evaluation of shear modulus and damping characteristics in soils under dynamic loading is key to both the fundamental understanding of soil behavior and the practical application of soil modeling programs. Dynamic centrifuge tests can contribute significant information about soil behavior, but great care must be taken over the signal processing techniques involved, and the test conditions are different from the laboratory experiments that form the database of existing knowledge. This paper outlines several factors that require careful consideration when deriving stiffness and damping parameters from centrifuge data. Shear modulus and damping degradation curves for a dry sand, saturated sand, soft clay and a model waste are then evaluated to explore some of the factors that are introduced during centrifuge tests. Stiffness is seen to be a more reliable parameter than damping ratio. Damping during centrifuge tests for certain materials appeared to differ from the expected values.

Stiffness of Flexible Caisson Foundations Embedded in Nonhomogeneous Elastic Soil

J. P. Doherty, G. T. Houlsby, and A. J. Deeks

J. Geotech. Geoenviron. Eng. 131, 1498 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1498) (11 pages) | Cited 3 times

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Solutions are presented for stiffness coefficients to represent the elastic behavior of a caisson foundation embedded in soil. The solutions use a novel numerical technique, the scaled boundary finite element method, combined with shell elements to represent the foundation itself. The stiffness coefficients take into account the possibility of nonhomogeneity in the soil (stiffness varying with depth), the geometry of the foundation, and the contribution to the stiffness of the skirt of the caisson foundation. Tabulated values allow a simple curve fit to the stiffness values to be employed for particular cases. The accuracy of the method is tested against previous solutions for particular cases. Example calculations are given to illustrate the method.

In Situ Soil-Specific Nonlinear Properties Back-Calculated from Vertical Array Records during 1995 Kobe Earthquake

Takaji Kokusho, M.ASCE, Tomohiro Aoyagi, and Akihiro Wakunami

J. Geotech. Geoenviron. Eng. 131, 1509 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1509) (13 pages) | Cited 4 times

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In situ nonlinear soil properties are investigated based on vertical array records obtained during the 1995 Hyogoken Nambu earthquake (Kobe earthquake) at soft soil sites near the earthquake fault zone. Spectrum ratios between ground surface and deeper levels are calculated for the main shock and associated small shocks and S-wave velocities and damping ratios in surface soil layers to best reproduce them are back-calculated by means of an inversion analysis (extended Bayesian method) assuming one-dimensional vertical horizontal shear (SH)-wave propagation. Obvious differences in S-wave velocities and damping ratios are found between the main shock and the small shocks. Clear strain-dependent modulus degradations which can be differentiated for different soil types are recognized. The degradations are essentially consistent with some of laboratory test results to date for each soil type at least for G/G0 ≈ 0.5 or larger, though for gravelly soils back-calculated values tend to show milder degradations than laboratory test results presumably due to large inclusion of fines in actual ground. Back-calculated damping ratios show essentially the same trend as in laboratory tests, although the absolute values are in most case a few percent higher in the strain range smaller than 10−4.

Load Transfer Mechanisms between Underground Structure and Surrounding Ground: Evaluation of the Failure of the Daikai Station

H. Huo, A. Bobet, G. Fernández, and J. Ramírez

J. Geotech. Geoenviron. Eng. 131, 1522 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1522) (12 pages) | Cited 2 times

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The Daikai Station, a cut and cover structure in the subway system in Kobe, collapsed during the Hyogoken-Nambu earthquake of January 17, 1995 in Japan. The Daikai Station is the first well-documented underground structure not crossing an active fault that has completely collapsed during an earthquake without liquefaction of the surrounding soil. What makes this case even more interesting is that tunnel sections adjacent to the station, with similar structural characteristics and analogous soil conditions, did not collapse. Dynamic numerical analyses have been conducted to investigate the load transfer mechanisms between the underground structure and the surrounding soil and to identify the causes for different behavior of similar sections of the station subjected to the same seismic loading. A hysteretic nonlinear soil model has been used for the analysis. The model captures well the soil’s shear modulus degradation and the increase of damping with strain. The results from the analyses show that, for a given earthquake, there are two key factors that determine the response of an underground structure: the relative stiffness between the structure and the degraded surrounding ground, and the frictional characteristics of the interface. A stiff structure has small deformations; because the adjacent soil movement is restricted by the structure, the shear modulus degradation of the soil is limited which contributes to reduce further deformation of the soil and thus decreases the displacement demand on the structure. A strong interface is capable of transmitting larger shear to the structure but in turn increases the confinement of the soil surrounding the structure which limits the soil’s shear modulus degradation. The model predicts larger deformations in the section that collapsed because this section had a smaller stiffness, and thus triggered drifts in critical structural elements which were larger than at other sections of the station which remained stable.

Glossary of Grouting Terminology

Grouting Committee of the Geo-Institute and Donald A. Bruce, M.ASCE, Chairman

J. Geotech. Geoenviron. Eng. 131, 1534 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1534) (9 pages)

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This glossary is a compilation of terms used in the field of grouting, with an emphasis on the definitions that are specific to usage in grouting practice. It updates and replaces the corresponding Glossary contained in the July 1980 issue of the Journal of the Geotechnical Engineering Division.
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Drained Residual Shear Strength of Some Claystones from Front Range, Colorado

Mandar M. Dewoolkar, A.M.ASCE and Robert J. Huzjak, A.M.ASCE

J. Geotech. Geoenviron. Eng. 131, 1543 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1543) (9 pages) | Cited 3 times

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Drained residual shear strength data on claystone (shale) bedrock samples from seven sites along the Front Range in Colorado collected from various sources are summarized. The claystone bedrock specimens from these sites were from Dawson, Laramie, Arapahoe, and Denver formations. The testing procedures included reversal direct shear and torsional ring shear tests. Upper bound, lower bound, and average residual shear strength envelopes were developed using the data from the seven sites. The secant residual friction angle varied from an upper limit of about 30° to a lower limit of about 5.5° for effective normal stress ranging from 30 to 960 kPa. Selected published correlations relating the drained residual friction angle to the liquid limit, plasticity index, clay fraction, and effective normal stress were also compared to the data set. For this particular data set, the plasticity index-based correlations compared better than the liquid limit-based correlations. It is recommended that if any published correlation between residual strength and Atterberg limits and/or clay fraction is to be used, then the same sample preparation procedure should be used in the determination of these properties as were used in developing the particular correlation.

Ground Deformation Induced by Vacuum Consolidation

J. C. Chai, J. P. Carter, and S. Hayashi

J. Geotech. Geoenviron. Eng. 131, 1552 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1552) (10 pages) | Cited 13 times

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The deformation characteristics of soil subjected to vacuum pressure are discussed and an approximate method is proposed for calculating settlement and lateral displacement of the ground induced by vacuum consolidation. Laboratory oedometer test results indicate that if the vacuum pressure alone is larger than the lateral stress required to maintain an at-rest (no horizontal strain) condition, there will be inward lateral displacement and the vacuum pressure will induce generally less settlement than a surcharge load of the same magnitude. In the case of field vacuum consolidation, the confining stress acting on a soil element can be regarded as consisting of two parts: Due to vacuum pressure and earth pressure. Assuming a value of the lateral earth pressure coefficient acting in the ground under vacuum consolidation (kao), somewhere between the active and at-rest values, an equation defining the depth—below which there will be no significant inward lateral displacement—is derived. Further, assuming that the volumetric strain induced by vacuum consolidation is the same as the one-dimensional consolidation induced by application of a surcharge load of the same magnitude, an approximate method is proposed for calculating the ground settlement and inward lateral displacement induced by vacuum consolidation. This method has been applied to two case histories reported in the literature, and it is shown that the field-measured data are simulated reasonably well, suggesting that the method may be useful for the design of vacuum consolidation projects.
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Discussion of “Pile Installation in Difficult Soils” by Ben C. Gerwick

David K. Crapps

J. Geotech. Geoenviron. Eng. 131, 1562 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1562) (1 page) | Cited 1 time

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Closure to “Seismic Compression of Two Compacted Earth Fills Shaken by the 1994 Northridge Earthquake” by Jonathan P. Stewart, Patrick M. Smith, Daniel H. Whang, and Jonathan D. Bray

Jonathan P. Stewart, Patrick M. Smith, Daniel H. Whang, and Jonathan D. Bray

J. Geotech. Geoenviron. Eng. 131, 1564 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1564) (5 pages)

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J. Geotech. Geoenviron. Eng. 131, 1570 (2005); http://dx.doi.org/10.1061/(ASCE)1090-0241(2005)131:12(1570) (3 pages)

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