This paper describes the application of two relatively simple models: a linear elastic–perfectly plastic Mohr-Coulomb and a nonlinear “brick” model for simulating the top-down construction of a multipropped excavation in the overconsolidated stiff fissured Gault clay at Lion Yard, Cambridge, with and without wall installation effects modeled. Numerical results are evaluated through comparisons with the comprehensive case record at Lion Yard. The objectives of the comparisons are to illustrate the effects of modeling wall installation and soil nonlinearity inside the yield surface on geotechnical designs. These comparisons are thus focused on aspects in which the practicing engineers are most interested, including the bending moments and deflections of the diaphragm wall, the strut loads, and the ground movements around the excavation. The results of the comparison demonstrate that the use of a Mohr-Coulomb model with a “wished-in-place” wall can reasonably predict the maximum bending moments and deflections of the wall for design purposes once the input soil parameters are correctly estimated. However, it significantly overestimates strut loads and fails to estimate the general ground deformation pattern.

A cumulative mass approach for laboratory column testing using an analytical solution for miscible transport through soil is presented. The cumulative mass approach differs from the more traditional approach for column testing in that the analysis of the measured data is in terms of mass of solute instead of solute concentration. The potential advantages of the cumulative mass approach are: (1) The influence of increment in effluent sample volume on the measured concentrations is removed from consideration; (2) the effluent sampling procedure is less labor-intensive, and therefore potentially more cost-effective; and (3) the retardation factor and effective porosity can be evaluated directly from plots of the test results. A comparison of analyses of measured data based on the cumulative mass approach with the more traditional concentration-based approach indicates slight differences (less than 3%) in the regressed values of the dispersion coefficient and retardation factor. These differences are attributed to greater scatter in the data for the more traditional approach and to slight errors involved in the traditional approach due to plotting the average, incremental concentrations at the pore volumes of flow corresponding to the middle of the sampling interval.

The study of shallow footings under plane-strain conditions became important when many researchers reported the lack of agreement between theoretical and experimental findings. A better understanding of the behavior of granular material under different stress levels and strain conditions encouraged further research in this field. In order to understand the behavior of footings and study the differences between theoretical and experimental observations, an experimental program was devised taking into account some factors that affect the theoretical assumptions. In this paper, the centrifuge has been utilized to study the effects of load eccentricity, load inclination, and initial burial on the bearing capacity of shallow strip footings on a dense sand. Fine silica sand, F-75 in a dense state with a relative density of 88%, was used. A plane-strain condition was obtained by testing three adjacent footings of the same width along one line. Footings were loaded with a stiff mechanism to give uniform displacement and, therefore, the one in the middle was under a plane strain condition. Test results indicate that plane strain conditions were modeled using this design. Experimental values of the bearing capacity factors N _q and N _γ are presented and compared to theoretical values given by different researchers. Results show that the linear pressure distribution at the base of the footing is a good approximation of observed behavior. It was noticed that single-sided failure always occurs regardless of load eccentricity and inclination. In addition, results show that failure occurs in a progressive manner.

Infiltration tests were conducted in the laboratory to study water movement during infiltration in compacted clay and to determine the suction head at the wetting front as defined in the Green-Ampt infiltration equation. Tests were conducted on two clays, having low and high plasticity indices. Results of the tests show that the wetting front is diffuse and becomes increasingly so as it penetrates deeper into the soil. The wetting front is also more diffuse for molding water contents near or wet of optimum water content and for clay with higher plasticity index. Suction head at the wetting front has been found to decrease as the wetting front penetrates into the soil, with the rate of dissipation depending on the molding water content and soil type. For the clay with low plasticity index, the initial suction head at the wetting front was largest and decreased the fastest when the molding water content was near optimum. For the clay with high plasticity index, similar initial suction head and rate of dissipation were measured at various molding water contents. Soil-specific equations are presented to estimate the suction head at the wetting front using the air-entry pressure.

Polymeric geogrids are widely used in various geotechnical-, transportation-, and environmental-related applications. Among the major uses of geogrids are reinforced soil walls, steep slopes, and landfill expansions. Current design practices are based on limit equilibrium techniques in which the geogrid is assumed to resist failure by mobilizing sufficient tensile resistance within the potential failure zone. The geogrid must also extend a sufficient distance beyond the potential failure surface to ensure sufficient anchorage resistance and thus resistance to pullout failure. This paper focuses on the anchorage behavior of geogrids under both short-term and sustained (1,000 h) conditions. An experimental investigation is conducted using five different geogrids in granular soil tested under two different normal stresses of 28 and 69 kPa. The geogrid length in all tests is taken equal to 0.9 m, which is often the requirement for the minimum anchorage length beyond the failure plane. Results of the tests are presented in terms of load-displacement curves and time-displacement curves. The results indicate that for practical purposes, the pullout strength after 1,000-h sustained loading can be assumed to be equal to the short-term pullout strength provided sufficient length of the geogrid is available to mobilize its full strength and/or the structural integrity of the geogrid is maintained during pullout over its length.

Transportation corridors and residential developments in steep terrain both require that some grading be carried out to accommodate roadways and building sites. The manner in which this grading is planned and executed and the nature of the resulting topography or landforms that are created affect not only the visual or aesthetic impact of the development but also the long-term stability of the slopes and effectiveness of landscaping and revegetation efforts. Conventionally graded slopes can be characterized by essentially planar slope surfaces with constant gradients. Most slopes in nature, however, consist of complex landforms covered by vegetation that grows in patterns that are adjusted to hillside hydrogeology. Analysis of slope-evolution models reveals that a planar slope in many cases is not an equilibrium configuration. Landform-graded slopes on the other hand mimic stable natural slopes and are characterized by a variety of shapes, including convex and concave forms. Downslope drains either follow natural drop lines in the slope or are hidden from view in swale-and-berm combinations. Landscaping plants are placed in patterns that occur in nature as opposed to random or artificial configurations. The relatively small increase in the costs of engineering and design for landform grading are more than offset by improved visual and aesthetic impact, quicker regulatory approval, decreased hillside maintenance and sediment removal costs, and increased marketability and public acceptance.

Results of hydraulic-conductivity tests conducted in the field and laboratory are presented for soils collected from 11 compacted-clay test pads or liners. The field tests were conducted with sealed double-ring infiltrometers to define the field-scale hydraulic conductivity ( K _F ). The laboratory tests were conducted using large undisturbed block specimens (diameter ≥ 0.3 m) and small specimens collected in thin-wall sampling tubes (diameter = 71 mm). Results of tests at low effective stress showed that the hydraulic conductivity of the block specimens was similar to K _F at each site. The hydraulic conductivities of block specimens from sites where K _F exceeded 10 ⁻⁹ m/s decreased by a factor of 4 when the effective stress was increased from 10 to 44 kPa. In contrast, the hydraulic conductivities of specimens from the other sites were reduced only by a factor of 1.5 under the same increment of effective stress.