To study the surface-closure curve of a circular tunnel in poorly consolidated rocks, closed-form solutions for stresses and displacement near a circular opening subjected to a uniformly distributed external stress and internal pressure are obtained. An elastoplastic model incorporating the nonlinear Hoek-Brown criterion is used, as most poorly consolidated geomaterials display a nonlinear correlation for the strength curve. Because most existing closed-form solutions as such were obtained with a linear Mohr-Coulomb criterion, the proposed solution is compared to those results by the linear criterion to evaluate the possible effect of the linear assumption. It is concluded that the calculated results by the linear Mohr-Coulomb criterion may overestimate the surface closure in low normal stress, but underestimate the opening closure under high normal stress. For the nonlinear case, a comparison is also made between the results by using the associated flow rule for plastic deformation and by a nonassociated flow rule. It is shown, by comparing the calculated results with an experimental result, that a nonassociated flow rule should be used in general. It is suggested that a nonlinear yield criterion be used with a nonassociated flow rule to achieve an appropriate prediction for the opening surface-closure curve.

To minimize the ground settlement induced by the excavation, the column type of ground improvement has been used in many parts of the world, possibly due to the fact that this type of soil improvement is relatively easily produced and conceptually understood. However, an analysis method and design concept has not yet been established at this time. In this paper, a method for evaluating composite material properties of the treated soil mass is proposed, in which the treated soil area is replaced by a single material during analysis. This allows a three-dimensional analysis to be performed with less computer storage and computation time. Furthermore, a slight modification was made on the method, which makes plane strain analysis also applicable to the column type of soil improvement. The analysis method was supported through a model test and a case history.

The response of a fixed, offshore tower is greatly affected by the nonlinear behavior of the supporting piles. An analysis of the foundation piles response to transient dynamic loading that accounts for soil nonlinearity, discontinuity conditions at the pile-soil interface, and group effect is used to assemble the stiffness matrix of the foundation piles. A foundation stiffness matrix is added to the global structural stiffness matrix at the pertinent degrees of freedom (DOF). A model for the evaluation of wave forces on the tower members that takes into account the spatial incoherence effect on wave forces is used in the analysis. Hydrodynamic damping is evaluated, and the effect of the tower foundation behavior on it is assessed. Furthermore, the tower response to random wave forces is conducted, and the effect of foundation parameters on the tower response is examined. It was found that both the hydrodynamic damping and tower response to wave forces are greatly influenced by the foundation nonlinearity and by pile-soil-pile interaction.

Peak ground accelerations recorded during the Northridge, California, earthquake of January 17, 1994 are described in relation to the observed, nonlinear soil response. Four attenuation relationships were developed specifically for this earthquake, for horizontal and vertical motions, and for “soft” and “hard” soil conditions. The results show that, within 20 km from the epicenter, seven (possibly 10) stations with “soft” soil conditions recorded smaller horizontal peak accelerations than expected. No such trend could be detected for the vertical motions. At the “soft” sites, where a reduction of peak horizontal acceleration was observed, the peak strains were larger than 10 ⁻³ . The widespread nonlinear response of soil in the same general area (sliding, liquefaction, cracked pipes, and roads) suggests that the observed reduction of peak accelerations is most probably due to nonlinear soil response.

Coating piles with bitumen down to their neutral points to debond them from embedding soil is a feasible method to minimize the adverse effects of negative skin friction. Bitumen is a petroleum product composed of numerous extremely complex organic compounds including polycyclic aromatic hydrocarbons (PAHs) that have been identified by the U.S. Environmental Protection Agency (EPA) as toxic and carcinogenic materials. To investigate the engineering behavior of bitumen-coated piles under extreme weather conditions, full-scale field tests were performed in New Orleans, Louisiana, and Edmonton, Alberta, Canada. Instrumented piles were installed at these sites from 1989 to 1990. This paper presents the results of geoenvironmental field investigations performed at these sites to determine the spatial distribution of target PAHs in the subsurface after the piles had been installed for 2–3 ¹/₂ yr. The findings of the investigation indicate that subsurface contamination, if there is any, caused by the installation of bitumen-coated piles is well within acceptable limits.

Existing buildings sometimes experience excessive settlement under their design load or face the prospect of excessive settlement in the future if a change of building use is required and increased foundation loadings will occur. Several methods of foundation enhancement are available to arrest settlements or improve the future performance of existing foundations. The method of underpinning by piles is widely used, but despite the long-standing use of this method, approaches to the design of piles for underpinning are not well developed. For practical purposes, a simple method is required for designing underpinning piles. In this paper, a design method based on the concepts of pile-raft interaction is developed. The general concept of the simplified design method is described, and then the method is formulated and explained in detail. The application of the simplified method to a series of problems analyzed by finite element methods is then described. Finally, comparisons are made between the results of the simplified analysis and data from model footing tests.

An analytic procedure for predicting threshold accelerations for movement of gravity-wall bridge abutments due to earthquake loading is first described in this paper. This method combines the well-known previous work related to the sliding mode of intermittent failure with a new theory on seismic reduction of bearing capacity leading to periodic vertical movement and consequent rotation of bridge abutments. Since the critical or threshold accelerations at which horizontal and vertical equilibrium are lost are different, mixed modes of seismic movement are also possible. The major emphasis of this paper is to then present laboratory observations on small-scale, retaining-wall bridge abutments subjected to seismic excitation to verify the critical acceleration levels predicted by this analytic analysis for the various modes of wall movement. Three different test series were performed on a shaking table on walls with different interface conditions between the wall and the foundation, backfill, and bridge deck. The abutment models were general in the sense that, while a particular mode of progressive failure could be anticipated, it was not forced.

The objective of this study was to investigate the feasibility of using shredded waste tires to reinforce sand. Direct shear tests were conducted on mixtures of dry sand and shredded waste tires. The following factors were studied to evaluate their influence on shear strength: normal stress, sand matrix unit weight, shred content, shred length, and shred orientation. From results of the tests, three significant factors affecting shear strength were identified: normal stress, shred content, and sand matrix unit weight. A model for estimating the strength of reinforced soils was also evaluated to determine its applicability to mixtures of sand and tire shreds. When the model is calibrated using results from one shred content, it may be useful for estimating the friction angle for other shred contents. In all cases, adding shredded tires increased the shear strength of sand, with an apparent friction angle (ϕ′) as large as 67° being obtained. Shred content and sand matrix unit weight were the most significant characteristics of the mixes influencing shear strength. Increasing either of these variables resulted in an increase in ϕ′. Tests were also conducted on specimens consisting of only shredded tires (no sand), and the friction angle obtained was 30°.

This study investigates the geotechnical properties of seven paper mill sludges. Paper mill sludges have a high water content and a high degree of compressibility and behave like a highly organic soil. Consolidation tests reveal a large reduction in void ratio and high strain values that are expected due to the high compressibility. Triaxial shear-strength tests conducted on remolded and undisturbed samples showed variations in the strength parameters resulting from the differences in sludge composition (i.e., water content and organic content). Laboratory permeability tests conducted on in-situ specimens either met the regulatory requirement for the permeability of a landfill cover or were very close. With time, consolidation and dewatering of the paper sludge improved the permeability of cover. Freezing and thawing cycles increased the sludge permeability about one to two orders of magnitude. Maximum permeability changes occurred within 10 freeze and thaw cycles.

The effect of a random and spatially correlated soil stiffness on the total settlement under the center of a uniformly loaded flexible-strip footing has been studied. Random field theory has been combined with the finite-element method to perform “Monte Carlo” simulations of the settlement problem with a variable Young's modulus and a constant Poisson's ratio. The soil Young's modulus field has been simulated with a fixed mean, standard deviation, and spatial correlation structure using the local average subdivision (LAS) method. The results of parametric studies have been compared with the deterministic quantities to gauge the effect of the standard deviation, correlation structure, and geometry on the settlement behavior. The results indicate a modest increase in expected settlement for presumptive ranges of soil stiffness variability.