Journal of Geotechnical and Geoenvironmental Engineering

A three-dimensional nonlinear finite-element analysis is used to study the influence of various design decisions for tieback walls. The numerical model simulates the soldier piles and the tendon bonded length of the anchors with beam elements, the unbonded tendon with a spring element, the wood lagging with shell elements, and the soil with solid three-dimensional (3D) nonlinear elements. The soil model used is a modified hyperbolic model with unloading hysteresis. The complete sequence of construction is simulated including the excavation and the placement and stressing of the anchors. The numerical model is calibrated against an instrumented case history. Then a parametric study is conducted. The results give information on the influence of the following factors on the wall behavior: Location of the tendon unbonded zone, magnitude of the anchor forces, embedment of the soldier piles, and stiffnesses of the wood lagging and the piles. The implications in design are discussed.

The complex permittivity of saturated kaolinite, bentonite, and Ottawa sand samples was studied in the range from 1 MHz to 1 GHz. Measurement procedures and equipment calibration for the whole frequency range are described. The impedance spectroscopy was used to analyze the data in the impedance and admittance complex planes. Thus, simple circuits of well-known response were obtained from the analysis. This technique is briefly reviewed. The Maxwell-Wagner loss mechanism for the saturated samples of kaolinite, bentonite, and Ottawa sand could be identified by careful analysis of the data in the impedance and admittance planes. It was observed that this mechanism is seriously distorted by ion diffusion and ohmic conductivity that make interpretation of data in the dielectric spectrum difficult. The present analysis allowed for the determination of the polar and ohmic contributions of soil particles and water to the measured permittivity. The effect of ion displacement is addressed, and its effect on soil dispersion is discussed.

The current design practice of single bored piles in residual weathered formations is based mainly on stability consideration against shear failure, and pile deformation analysis is rarely carried out. However, the acceptance criteria of single piles during pile load tests during construction is based mainly on the permissible settlement criteria as specified in the specifications/codes. In this study, a reliable method of predicting the load deformation and load distribution curves is proposed for bored piles in a residual weathered formation (Kenny Hill Formation) in Kuala Lumpur based on: (1) considerations of the weathering profiles and the engineering characteristics of this formation; (2) field performance data of fully instrumented bored pile load tests; and (3) load transfer design characteristics of the load deformation behavior. In this deformation analysis, the pile installation methods and the nonlinear behavior of the pile material are incorporated. The proposed load deformation analysis was carried out on both the instrumented and noninstrumented piles, producing good results. Therefore, this proposed method can be used to predict the load deformation characteristics of single bored piles in weathered formation during the design stage.

The growing interest in utilizing waste materials in civil engineering applications has opened the possibility of constructing reinforced soil structures with unconventional backfills. Scrap tires are a high-profile waste material for which several uses have been studied, including the use of shredded tires as backfill. A triaxial testing program was conducted to investigate the stress-strain relationship and strength of tire chips and a mixture of sand and tire chips. The test results and additional information from the literature were used in the numerical modeling of wall backfills, both unreinforced and reinforced with geosynthetics. The numerical modeling results suggest tire shreds, particularly when mixed with sand, may be effectively used as backfill.

Constructing the 245-m-high, double curvature concrete arch Ertan Dam required two high cofferdams (the upstream one exceeding 60 m) and the removal of 40 m of alluvium from the riverbed. Full penetration and partial penetration cut-offs were created at Ertan with jet-grouting techniques. Dewatering between the cofferdams and behind the cut-offs was successful and was maintained for more than 2 years against 40–70 m of water heads. This paper describes in detail the design rationale and main features, as well as the construction methods of both cut-offs. The treatment by conventional grouting of the rock below the jet-grouted wall is also outlined.

An approximate numerical procedure to compute the vertical response of a vertical pile in a linearly elastic homogeneous soil medium in the time domain is presented. The approach combines Novak's concept of energy dissipation through radiation damping and Poulos' concept of pile-soil-pile interaction based on the Mindlin elastic solution. The predictions are assessed against two experimental studies. This time domain approach has the potential to consider nonlinear soil behavior, discontinuity conditions at the pile-soil interface, and pile-soil slip. The most significant promise of this scheme is to predict the propagation of vibration along the ground surface, generated from the vibration of the pile.