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A series of single-staged consolidated drained direct shear tests are carried out on recompacted completely decomposed granite (CDG) soil--a typical residual soil in Hong Kong, under different matric suctions and net normal stresses. Matric suction is controlled by applying air pressure in the pressure chamber and water pressure at the bottom of the high air-entry ceramic disk. The experimental results show that the contribution of suction to shear strength is significant. Shear strength of CDG soil increases with the increase of matric suction. Net normal stress has a remarkable influence on the shear strength of unsaturated CDG soil. The increase in shear strength due to an increase in matric suction (suction envelope) is observed as nonlinear i.e., [[phi].sup.b] value varies with matric suction. No soil dilatancy is observed for zero matric suction (saturated case) but as the suction value is increased, higher soil dilatancy is obvious in lower net normal stresses. The rate of increase of soil dilatancy is greater in lower suction range than in higher suction range. The experimental shear strength data match closely with the shear strength predicted by existing shear strength model considering the soil-dilation effect. DOI: 10.1061/(ASCE)GT.1943-5606.0000189 CE Database subject headings: Soil compaction; Shear tests; Shear strength; Suction; Dilatancy. Author keywords: Shear strength; Completely decomposed granite; Matric suction; Soil dilatancy; Axis-translation technique; Direct shear.

Grouted soil nails are widely used in slope stabilization. The influence of both grouting pressure and overburden stress on the soil-nail pullout interface shear resistance is still not well understood due to the complex of soil-grout interactions. A series of laboratory soil-nail pullout tests have been carried out on a completely decomposed granite soil in nearly saturated condition under a combination of different grouting pressures and overburden stresses. The pullout tests simulate the real construction process of a soil nail, including establishment of initial soil stresses in a soil slope, drilling a hole with stress release, grouting, and soil-nail pullout when the slope is sliding. The pullout box is well instrumented. Test data are collected automatically by a data logger. Typical test results are presented, explained, and discussed in this paper. The soil-nail interface shear resistance data from all tests are analyzed and interpreted. The study shows that the grouting pressure and overburden stress have interactional influence on the soil-nail pullout resistance. Based on the test results, a new empirical liner equation with two grouting pressure dependent parameters is proposed for calculation of soil-nail pullout resistance considering both grouting pressure and overburden stress. New understandings and findings from the study are presented. DOI: 10.1061/(ASCE)GT.1943-5606.0000045 CE Database subject headings: Grouting; Stress; Cements; Soil nailing; Pullout; Shear stress; Slopes; Soils.

Soil nailing has been widely used in many places in the world in the last two decades because of its technical and economical advantages. The nail--soil interface shear strength is an important parameter in soil nail design. This parameter is governed by a number of factors, among which the influence of the overburden pressure (or soil depth) is the most controversial. There are differing views concerning the effect of overburden on the nail--soil interface shear strength. In order to examine the influence of the overburden pressure, a series of laboratory pullout tests on soil nails installed in compacted completely decomposed granite fill have been conducted using two pullout boxes. Numerical simulations have also been carried out and the results are compared with the pullout test data. The procedures of the pullout tests and new features of the pullout boxes used are briefly described. Changes of the vertical stress in soil close to the nail throughout the course of soil nail installation and pullout are presented and discussed in detail. It is observed from the results of this study that the installation process of soil nail induced significant vertical stress changes in soil around the soil nails, and that the soil nail pullout shear resistance is independent of the overburden pressure (or soil depth). CE Database subject headings: Soil nailing; Shear resistance; Fills; Soil compaction; Shear strength; Soil pressure.

The shear stress-displacement behavior and ultimate shear strength at the interface between the cement--grout nail and surrounding soil are of practical importance in the design and safety assessment of a soil nail system. The most commonly adopted method to measure the interface shear strength of a soil nail is a pullout testing method. The current study attempts to investigate the interface shear behavior between the cement-grouted materials (soil nails) and a completely decomposed granite soil using both a large-size direct shear test apparatus and a laboratory pullout test apparatus. The laboratory testing procedures are briefly described. The main test results obtained are presented, followed by discussion on the shear behavior of the soil--grout interface. The interface shear behavior measured from both the interface shear tests and the pullout tests on the same soil tested in the same or a similar condition are compared and discussed. It is shown that the shear stress--displacement behavior of the soil--grout interface in the interface shear tests is similar to that of the soil--soil tests, but is different from the behavior in the pullout tests. DOI: 10.1061/(ASCE)1090-0241(2005)131:9(1097) CE Database subject headings: Shear tests; Shear strength; Pull-out resistance; Soil tests.

This paper examines the ultimate bearing capacity of a strip footing located at the surface of a homogeneous soil. The approach adopted involves a numerical solution of the equations governing elastic-plastic soils with a nonassociative flow rule and makes use of the finite-difference code FLAC. This code is utilized to obtain the three bearing capacity factors for a wide range of values of the friction angle for four different values of the angle of dilation. The values of the bearing capacity factors obtained from the numerical approach are then compared with results derived from classical solutions modified to incorporate the nonassociative plastic flow of soil.