To improve the performance of a precast pile installed in a prebored hole, a grouted base is often made around the base of the pile. The structural capacity of a precast pile with a grouted base was studied by three series of model loading tests. Two failure mechanisms were observed, punching failure and splitting failure, which depended upon the geometry of the grouted base. Punching failure occurs in cases in which the grouted base is thin, less than twice the pile diameter. In contrast, splitting failure develops in cases in which the grouted base is thicker than twice the pile diameter. Structural capacity increases with increasing the thickness of grouted base. The effect of diameter of grouted base was also examined. Based on the experimental observations, a theoretical model was developed to evaluate the structural capacity. The theoretical prediction agreed well with the experimental results. A parametric study was performed to determine the optimum shape and strength of the grouted base.

This paper presents experimental data of earth pressure acting against a vertical rigid wall, which moved into a mass of dry sand with a stress‐free horizontal surface under various wall‐movement modes. To investigate the variation of earth pressure induced by the rotation about a point above the top (RTT) and rotation about a point below the wall base (RBT) types of wall movement, the instrumented retaining‐wall facility was developed at National Chiao Tung University. Based on experimental data it is found that, for a wall under translational movement, the passive pressure distribution is linear and in good agreement with Terzaghi's prediction based on the general wedge theory. For a wall under either RTT or RBT mode, the magnitude of passive thrust and its point of application are significantly affected by the mode of wall displacement. However, if the parameter $n$ indicating location of the center of rotation is greater than 2.0, the influence of movementmode on passive earth pressure becomes less important.

A numerical approach and parametric study for the calculation of the soil and pile interaction under lateral loading are presented. The method uses variational calculus to obtain the governing differential equations of the soil and pile system. A principal parameter $\left(\gamma \right)$ is used in this model to present the elastic foundation. The properties and the significance of the primary model parameters, such as $\gamma$, Poisson's ratio $\upsilon$, slenderness ratio $\Psi$, and flexibility factor $K_r$, are carefully investigated in order to have a better understanding of the relationships between those parameters. A number of important features, including linear relationships between the coefficients and simple analytical equations, are presented here. On the basis of the new aspect and related mathematical expressions, an improved predictive capability is obtained. This general analytical perspective allows the further improvement and simplification of the proposed model and suggests a way to predict the response of laterally loaded piles for engineering design. The practical application guide has been produced. Some graphics and examples illustrated in this paper can be used by a design engineer for engineering design.

The Charleston, S.C., earthquake of 1886 $(M=7.5-7.7)$ is the largest earthquake to occur on the Eastern Seaboard during historic times. No strong motions from the event were recorded and no causative fault was identified. Following the earthquake, accounts of widespread liquefaction and heavy structural damage were documented. Recent field studies led to the discovery of relict liquefaction features in soil exposures excavated in the Charleston area. The studies indicate that while some of the liquefaction features were caused by the 1886 event, many were caused by prehistoric earthquakes. The present study provides a geotechnical engineering perspective on the liquefaction findings, especially those associated with the 1886 earthquake. Existing liquefaction prediction methods were used to back‐calculate the magnitude and peak ground accelerations required to produce the liquefaction that occurred in 1886. The results suggest that the ground motions of the 1886 earthquake were significantly less than those currently proposed by the seismological community. Of particular significance, the approach demonstrated in this study can be used in other regions of infrequent seismicity to estimate past ground motions.

Predictions of the ultimate uplift capacity of six small‐diameter drilled shafts installed in stiff cohesive soil are compared with pullout tests conducted to failure. The shafts were installed by the dry‐hole method with gravity free‐fall concrete placement, and were 76 mm and 152 mm in diameter with lengths ranging from 1.52 to 4.57 m. Predictions of the ultimate uplift capacity were made assuming that failure takes place as a result of perimeter shear. An effective stress model was used with soil parameters obtained from in situ tests. Soil shear strength was obtained from the results of borehole shear tests, and an interpreted profile of in situ, at‐rest horizontal soil stress was obtained from the results of prebored pressuremeter tests. The results of the test program demonstrate that the borehole shear test and pressuremeter test may be used in combination to design drilled shafts for uplift resistance in stiff soils.

The mechanical properties of a kaolinite/fiber soil composite were evaluated by a series of laboratory unconfined‐compression, splitting‐tension, three‐point‐bending, and hydraulic‐conductivity tests. The inclusion of randomly distributed fibers significantly increased the peak compressive strength, ductility, splitting tensile strength, and flexural toughness of kaolinite clay. The increase in strength and toughness was a function of fiber length and content, and the water content of the composite. Increasing fiber content increased the compressive and tensile strength, and the toughness index of kaolinite clay, with the effect being more pronounced at lower water contents. The contribution of fibers to peak compressive and tensile strengths were reduced, and ductility increased, with increasing fiber length. The fiber inclusion increased the hydraulic conductivity of the composite and the increase was more pronounced at higher fiber contents. Despite the increase, the hydraulic conductivity of the composite was still low enough to be considered for some landfill applications.

The application of some nondestructive testing procedures for soils and pavements, such as the spectral analysis of surface waves method, requires the use of dynamic sources at some point on the surface of the ground to create vibrations that can be recorded and related to the material characteristics of the medium. These sources are typically accomplished by means of falling weights of various sizes. This paper applies a simple mass‐spring‐dashpot model to assess the characteristics of the forces transmitted to the ground by the falling weight so as to be able to rationally decide on its size, mass, and dropping height. It is found that if inelastic effects are disregarded, a falling weight always rebounds; that the drop height affects only the impact velocity and amplitude of the contact force—not the duration of contact; and that increases in the drop weight lead to reductions in damping, increases in contact time, increases in contact force, and enhancement of the low‐frequency components in the Fourier spectrum of the contact force.

Remote operation of a time domain reflectometry (TDR) system demonstrates the effectiveness of telemetric monitoring for early detection of rock movement. During field testing reported here, TDR data were related to shear deformation above a longwall caving operation using a correlation between the signature reflection coefficient and shear deformation established through laboratory measurements. A 175‐m (575 ft) long vertical coaxial TDR cable was grouted into the rock mass above the longwall coal‐mining operation and attached to the aboveground‐pulsing instrument. TDR data were then remotely acquired twice daily by an operator some 500 km away. Comparison of TDR signature changes with longwall‐face location showed that localized changes were detected four days before surface subsidence occurred when mining was still 64 m (210 ft) away. Since the mining was moving toward the cable at a rate of 10 m/day, a warning interval is expected to be larger for premined sites with lower deformation rates.

The basal stability of braced excavation systems in soft clay has been investigated using the finite‐element method. A linear elastic‐perfectly plastic relationship is used to model the stress‐strain behavior of the soil. The important factors affecting basal stability have been identified as the thickness of the clay layer beneath the bottom of the excavation, the depth of the wall below the bottom of the excavation, the width/height ratio of the excavation, and the stiffness of the wall. From the results of parametric studies, a simple procedure is proposed for estimating basal‐heave stability. Charts are presented that can be used to estimate basal‐heave stability quickly and reliably.

Gilgai landforms are series of mounds and depressions with amplitudes that range from 7.6 to 45.7 cm (3 to 18 in.) and wavelengths that range from 4.6 to 9.1 m (15 to 30 ft). Gilgai landforms occur in soils parented from overconsolidated expansive clays in Texas. A mechanism is proposed that may be causing these landforms and undulations in pavements. The presence of naturally occurring horizontal stresses in overconsolidated expansive clays is believed to be the essential cause of these extreme movements. It is proposed that the horizontal stresses alter the normal vertical stresses in a prebuckling mode and produce a differential vertical rebound. The behavior of gilgai and their associated shear fractures support this theory.