This paper explores the factors that contribute to claims of changed subsurface conditions in heavy-construction contracts. It reviews methods of resolving the attendant disputes and describes a group of cases to illustrate the issues. These cases are concerned chiefly with mined tunnels, which are the most drastically affected by the unexpected. The purpose is to summarize the special requirements for preparing geotechnical information for construction and to suggest procedures for avoiding claims or bringing about their equitable resolution.

Results from the computational driving of a concrete pile below a prebored hole (referred to as a “prebored” pile for convenience) in an undrained, normally consolidated clayey soil are presented. The analysis uses a nonlinear, finite-element model that simulates the penetration of the pile into the soil. The response of the pile-soil system is examined at various preboring levels. A comparison between the responses of normally consolidated clays with various strengths is discussed. The influence of pile-soil friction and tip bearing on the response is also investigated. Emphasis is placed on the evolution of the state of stress in the soil and the development of pore-water pressure in the course of driving. Other computations are made for the case where the pile is driven some distance into undisturbed soil, referred to as a “driven” pile case for convenience. Finally, insight is gained into the difference in response between prebored and driven piles.

Rainfall-induced debris flows are flow failures in residual and colluvial soils initiated by a reduction of confining stress as a result of pore-water pressure rise during or following periods of intense rainfall. To establish appropriate stability analysis procedures, the behavior of soil from a debris flow source area is investigated. Constant-shear-drained triaxial tests, tests that mimic the field stress path, and anisotropically consolidated undrained triaxial tests performed at the in-situ stress level indicate that undrained loading is a prerequisite for flow failure. Mechanisms of stress transfer are proposed to explain how the initially drained deformation that occurs along the field stress path can lead to undrained mobilization. Because a debris flow involves both drained initiation and undrained mobilization, a complete stability analysis includes an effective stress analysis with constant-shear-drained parameters to determine the potential for failure initiation, and an undrained strength analysis using undrained residual strength to determine the potential for debris flow mobilization.

This paper examines the meaning of principal methods of system identification (SI). System identification is seen as a unique procedure to estimate in situ soil properties, especially soil subject to large strain. When applicable, parametric modeling of system processes is found to be superior to traditional Fourier methods. Several different methods have been presented to directly assess nonstationary data. These methods cover a wide range, from transforming the data into a stationary signal to full-fledged nonlinear, nonstationary analysis. The method used will depend on the nature of the data available and the nature of the requisite information. Segmentation of the data into stationary pieces gives sound results and is widely used. However, if the process of interest has time-varying parameters, a recursive technique should be used.

This paper investigates the effect of cyclic wetting and drying on the expansive characteristics of clays. For this purpose, six expansive soils were obtained from various locations in Irbid (a city in northern Jordan). After each cycle, the swell potential and swell pressure were measured. Additionally, the soil microstructure before and after cyclic swelling was investigated. The experimental data indicated that upon repeated wetting and drying, the soils show sign of fatigue after every cycle resulting in decreased swelling ability. Furthermore, it was noted that the first cycle causes the most reduction in swelling potential. As the number of cycles increases, additional reduction was observed until an equilibrium state is reached. For the six utilized soils, the equilibrium cycle ranged between 4 and 5. Scanning electron micrographs clearly showed a continuous rearrangement of particles during cyclic wetting and drying. This led to lower structural element orientation due to the integration of structure along the bedding, resulting in correspondingly lower water absorption thus reducing swelling ability.

The purpose of this technical note is to compare the triaxial A -value with the percentage of swell or collapse measured in the oedometer apparatus for three different compacted soils. Those soils that collapsed in the oedometer apparatus had a high A -value from the triaxial test that is indicative of contractive behavior, and those soils that tended to swell conversely had a low to negative A -value from the triaxial test indicative of dilative behavior. The relationship between triaxial A -values and the swell or collapse from oedometer tests may be useful in identifying soil-behavior discrepancies and laboratory testing errors. The soil behavior is independent of the dry density of the compacted soil and the confining pressure.