In lateral resistance of piles with a pile cap, marked contribution of the pile cap resistance can be expected. For seismic performance assessment of pile foundations, mobilisation of the earth pressure acting on pile caps, induced by interactions between the pile cap and surrounding soils, has to be properly considered. In this study, a series of centrifuge model tests were conducted (1) to examine the effect of strain history on the mobilization of lateral earth pressure acting on pile caps and (2) to show the importance of considering strain history when modelling the interaction between a surface soil layer and a pile cap. Observations into the physical model tests reveal that mobilisation of the earth pressure acting on pile caps under cyclic loading can drastically change depending on soil type and/or conditions. Especially, relocation of soil adjacent to the pile cap in unload-reload phase plays an important role for the earth pressure mobilisation, as it completely alters the shape of the earth pressure-displacement curves. Based on the physical model test results, a simple empirical model that can be used for the beam on non-linear Winkler foundation type analysis is proposed and compared to the test results.

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This paper presents a piezocone penetration test (CPTu) method for evaluating soil liquefaction potential covering a wider range of soil types than previous approaches and using simplified stress-based procedures. In the approach, the adjusted cyclic stress ratio is calculated with a recent formula created by Idriss and Boulanger, and the cyclic resistance ratio is determined as a function of both adjusted cone tip resistance (q_t1N) and soil behavior type index (I_c). The new method is established through artificial neural network learning of documented cases. One unique feature of this method is the inclusion of excess porewater pressure ratio (B_q) in the formulation of I_c as per Jefferies and Davies. The proposed method is shown to be more applicable to a wider range of soils, including geomaterials that were previously considered “too clay-rich to liquefy.” The ability of this method to delineate liquefied cases from non-liquefied cases is clearly depicted with 3-D and 2-D graphs. Case studies of selected ground failure sites in Adapazari using the proposed method yield results that agree well with field observations in the 1999 Kocaeli earthquake.

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This paper presents a new method of soil-water coupled finite deformation analysis of saturated soils that considers inertial forces. This method allows changes in the geometric shape of the soil to be taken into account and is capable of dealing with all types of external forces irrespective of whether they are static or dynamic. To be more specific, the paper describes the following points, which differ from the conventional methods: 1) the governing equations for saturated soil including the rate-type equation of motion containing a jerk term of the soil skeleton conforming to u-p formulation and updated Lagrangian, 2) derivation of a weak form of the rate-type equation of motion and discretization of the finite elements, and 3) use of the implicit time integration method for application of the conventional linear acceleration method (which assumes linear variation of acceleration) to the jerk term. By mounting the elasto-plastic constitutive equation (SYS Cam-clay model), which can cover a wide range of soils and soil conditions, onto the above method of analysis, examples of simulation of dynamic/static triaxial laboratory testing of saturated soil specimens are described. The soil specimens were assumed to be medium dense sand under conditions of small-amplitude cyclic loading, partial drainage, and constant cell pressure. The simulation yielded the following results: (1) In the case of low frequencies, compaction occurs during loading and compression progresses over the entire specimen. (2) In the case of high frequencies, during loading and in the period in which wave propagation continues within the specimen after the end of loading, compaction occurs at the drained end of the specimen, whereas liquefaction occurs in its interior. After this stage, massive compression takes place within the specimen, leading to consolidation (consolidation after liquefaction).

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Measures preventing an earthquake-induced soil liquefaction are of significant importance to mitigate the liquefaction hazards. An air-injection technique may be a simple, inexpensive method - this leads the saturated soils to the desaturated by injecting pressurized air, resulting in a higher liquefaction strength and lower susceptibility. The objective of this study is to investigate the evolution of desaturation process during air injection into saturated soil deposits and verify the validity of a multiphase flow simulator if it is capable of being applied for predicting the process as well as the distribution of degree of saturation after the air injection ceased. In this study simplified model tests that simulate the air injection into saturated soils using air-injection probes, are conducted using two different sizes of soil containers. The experiments using the small container are aimed to examine the nominal rates and magnitudes of the soil desaturation driven by air injection, whilst those with the large container are performed to obtain not only the rates and magnitudes but also the distributions of the desaturated zones within the soil. The results obtained indicate, although clearly depending on the physical properties of targeted soils, that the evolution of desaturation is strongly controlled by the air pressures injected and the soil permeabilities. Numerical analyses are also conducted using a multiphase flow simulator to describe the evolution of the soil desaturation, and to examine the applicability of the model as a prediction tool enabling an evolution of desaturation in situ to be followed with time and space. Predictions show a relatively good agreement with the experimental measurements regarding the rates, magnitudes, and distribution of desaturation specifically for the small-container experiments although predictions of desaturated domain slightly overestimate the measurements for the large-container experiments. Thus, this study indicates that the numerical model described is applicable to field problems when the soil properties in terms of flow transport are well-constrained.

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The effects of sites and plasticity index (I_p) on the inherent strength anisotropy of eleven different clay deposits are quantitatively examined by the unconfined compression test using a small size specimen with a different angle of inclination to the vertical. A new method for a slope stability analysis, taking the effects of the IASIA method (Inherent And Stress Induced Anisotropies) into consideration, is proposed. The applicability of the IASIA method and the optimum embankment design are examined through case histories of embankment failures on soft soils. The undrained strength anisotropy cannot be estimated by parameters such as the I_p value because of the complicated relationship with the factors influencing undrained anisotropic strength. It must be directly measured. The IASIA method was recommended from a study of a failed embankment. The probability of failure (P_f) and consumer's risk (P_c) from half of the unconfined compressive strength (q_u/2) were (2.5~25.5)% and (4.7~42.3)% less than those of the Iwai q_u/2_(IASIA) and Urayasu q_u/2_(IASIA). Therefore, the design results were underestimated by disregarding strength anisotropies. If, P_f and P_c were considered, the C_t values increased. However, the P_c values drastically decreased to 24.8% from 54.3% concerning the 75-mm sampler and n increased, thus avoiding latent risks. These mean that the IASIA method can be used for optimum embankment design based on performance provisions.

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The elastic shear modulus of natural sedimentary clay ground, G_max, is estimated based on laboratory tests for fifteen different reconstituted clays. Two types of tests were performed, i.e., Bender Element and Cyclic Triaxial tests. The proposed formulation is not based on void ratio, e, but consists of only three parameters: w_L (liquid limit), p′ (the current mean effective stress) and p′_max (the maximum mean consolidation pressure). To apply it to the field, this equation is modified for using σ′_v0 (the in situ effective overburden pressure) and OCR, instead of p′ and p′_max. Since existing formulae for G_max are mostly based on e, they are not able to apply to both reconstituted soil and field, without considering the correction factor for structure. This is because e in the field is much larger than that for reconstituted soil even though their consolidation pressures and OCR are the same for these clays. The applicability of the proposed formula was examined by using investigated results from the in-situ seismic surveys performed at eleven worldwide sites. It is well demonstrated that the proposed equation in this paper is capable of predicting G_max of natural sedimentary clay deposits with higher accuracy than the existing empirical formulae using a function of e.

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Lightweight soil technology has been widely used in construction projects to solve soft ground problems. Previous work, however, has shown that the maximum interior temperature of field test bodies reaches to about 90°C. On the other hand, industrial waste disposal is an increasing problem. PET (polyethylene terephthalate) waste is now generated in vast quantities to increased consumption of drinking water sold in PET bottles. Making effective use of PET waste as a ground material may help solve the problem of its disposal. This paper describes the effects of initial high temperature curing on unconfined compressive strength and the microstructure of foamed mixture lightweight soil containing PET flake. Increase in PET-cement ratio lessened the decrease in unconfined compressive strength with increasing initial temperature. This property makes PET flake useful as a construction material. However, unconfined compressive strength decreases with increasing initial temperature at all PET-cement ratios. Observations show that the microstructure of foamed mixture lightweight soil containing PET flake have noticeable cracks if samples are cured at 90°C for 1 day; the PET flake is not completely combined with the matrix. The formation of this microstructure is the main factor of the remarkable strength decrease based on initial high temperature curing.

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This note examines the classic passive earth resistance of cohesionless soil by using two newly developed numerical procedures based on finite element formulations of the bound theorems of limit analysis and non-linear programming techniques. Solutions using upper and lower bounds are presented to complement the previous studies of this problem. The parameters studied are soil-wall interface friction, wall inclination, backfill surface configuration and the wall's weight.

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Since scoria can be utilized in several industrial applications and the cyclic shear characteristics of scoria have not been studied sufficiently, it is important to measure the cyclic triaxial shearing response of scoria deposit. A series of laboratory tests was carried out in order to obtain the cyclic shear characteristics of scoria. Undrained cyclic triaxial tests were conducted on reconstituted scoria deposits obtained from Mt. Fuji, Yamanashi Prefecture. To evaluate the degree of particle breakage due to shearing, the grain size distribution has been evaluated before and after cyclic triaxial tests by traditional techniques. The differences in liquefaction characteristics between Scoria and other materials from previous studies were demonstrated. From the results of undrained cyclic triaxial test on the scoria, it was understood that the effect of relative density D_r on the cyclic shear strength of scoria material is small, in the range 43.8% to 97.7% of D_r. Comparison results between monotonic and cyclic triaxial tests on grain breakage due to shearing shows that the degree of grain breakage for cyclic triaxial test is relatively higher than from monotonic tests for a similar dry density.

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