Results are presented of model-scale vertical pulling tests carried out on groups of square anchor plates in row and square configurations. The tests were carried out at a single depth of embedment, which ensured shallow anchor behavior in the sand placed at a constant dry density. It is shown that the load-displacement relationships for all groups may be reduced to a common curve. The load-carrying capacity of a group of anchor plates increases with the spacing between the individual plates up to a limiting critical value, and it is demonstrated how the results of pulling tests with different numbers of plates in a group may be described in a simple unifying manner. A possible means of predicting the effect of interaction on the uplift capacity of both modeland full-scale anchors in row configurations is suggested. For laboratory tests on a linear group of five anchors, it is shown that the end anchors attain the highest loads but all loads converge to an equal value as the spacing increases to the critical value.

The search for the critical slip surface in slope-stability analysis is performed by means of a minimization of the safety factor. The procedures most widely used are deterministic methods of nonlinear programming, and random search methods have been neglected, since they are considered to be generally less efficient. In this paper, an efficient Monte-Carlo method for locating the critical slip surface is presented. The procedure is articulated in a sequence of stages, where each new slip surface is randomly generated by an appropriate technique. From a comparative analysis, the proposed method provides solutions of the same quality as the best nonlinear programming methods. However, the structure of the presented method is very simple, and it can be more easily programmed, integrated, and modified for particular exigencies.

Based on the full-scale test results of 29 shaft anchors installed in the silty alluvial soil of the Taipei basin, the anchorage behaviors of anchors having two different types of tendon assemblies, namely the singly anchored type and the multiple anchored type, are evaluated in this paper. Test results indicate that the benefits of the multiple anchored anchor system is not obvious in terms of the residual movement and the ultimate anchorage capacity when compared with the traditional singly anchored anchor. A critical fixed length of 20 m is observed regarding the ultimate anchorage capacity for both singly anchored tension anchors and triply anchored compression anchors. This critical fixed length is considerably longer than the upper fixed length limit proposed by the major anchorage specifications. For those anchors with fixed length shorter than the critical length, the anchorage capacity increases linearly with the fixed length. However, if the fixed length is extended beyond this critical length, up to 70% falloff in anchorage resistance per unit fixed length increment was found.

The compressibility of natural clays is influenced by numerous factors: strain rate, temperature, sampling disturbance, stress path, and some restructuring factors. The first part of the paper reviews the effects of these factors, in particular of strain rate and temperature. The influence of drainage conditions on the effective stress-strain curves followed in various subelements of a consolidating clay layer is also discussed. In a second part, in-situ conditions are considered. In the overconsolidated range, and at the preconsolidation pressure, the behavior is influenced by most of the aforementioned factors, and can be compared with laboratory test results only on the basis of a semiempirical approach. In the normally consolidated range, major factors are strain rate and temperature, and their effect can be evaluated. In some cases, however, structuring phenomena can exist and decrease the viscous effects. Finally, practical conclusions concerning the evaluation of long-term settlements are given.

The construction, instrumentation, and response to vehicle trafficking of an unpaved road on soft ground are described. The road is comprised of an unreinforced section, three sections with different geotextiles, and a section with geogrid. The performance of the unreinforced section compares reasonably well, at large rut depths, to prediction using the analytical approach most commonly used in current design practice. Inclusion of a geosynthetic between the base course layer and subgrade soil led to a significant improvement in trafficability. The improvement was greatest for the thinner base layer of 25 cm, and diminished with increasing layer thickness. Reasonable agreement was, again, observed between the field performance and analytical predictions at large rut depths. The analytical approach was found to significantly overpredict the number of vehicle passes to develop a 5 cm rut. The lack of agreement at small to moderate rut depths is attributed to compaction of the base course layer in response to vehicle trafficking that is not accounted for in the analytical approach. Some implications of the field observations for selection of a geosynthetic are discussed, with reference to separation and reinforcement of gravel layers over soft soils.

The 1994 Northridge and 1971 San Fernando Earthquakes subjected the Lower and Upper San Fernando Dams of the Van Norman Complex in the San Fernando Valley, Calif., to strong near-source ground motions. In 1994, these earth dams, which were out of service and retained only a few meters of water, extensively cracked and settled due to the liquefaction of their hydraulic fill. The Lower San Fernando Dam moved over 15 cm upstream as the hydraulic fill liquefied beneath its upstream slope. The Upper San Fernando Dam moved even more and deformed in a complicated three-dimensional pattern. The responses of the Lower and Upper San Fernando Dams during the 1994 Northridge Earthquake, although less significant than in 1971, provide the geotechnical engineering community with two useful case histories.

Unsaturated hydraulic conductivities were measured in the laboratory and the field for two compacted fine-grained soils used as barrier layers in landfill final covers. The instantaneous profile method was used for the laboratory and field measurements. Results of the tests show that similar unsaturated hydraulic conductivities exist in the laboratory and field for both soils. Furthermore, results of laboratory tests conducted with specimens prepared at different molding water contents and compactive efforts show that the unsaturated hydraulic conductivity function is insensitive to molding water content for matric suctions exceeding 20 m, but is strongly affected by compactive effort. Specimens compacted with modified Proctor effort had unsaturated hydraulic conductivities approximately one order of magnitude lower than those compared with a standard Proctor effort. It is also shown that estimated unsaturated hydraulic functions based on parameters describing the soil-water characteristic curve underpredict the unsaturated hydraulic conductivity functions of these barrier soils.

In the past 25 years great strides have been made in the area of static stability and deformation analysis. The widespread availability of microcomputers has brought about considerable change in the computational aspects of slope stability analysis. Analyses can be done much more thoroughly, and, from the point of view of mechanics, more accurately than was possible without computers. Still, engineers performing slope stability analyses must have more than a computer program. They must have a thorough mastery of soil mechanics and soil strength, a solid understanding of the computer programs they use, and the ability and patience to test and judge the results of their analyses to avoid mistakes and misuse. Realistic analyses of deformations of slopes and embankments were not possible until about 25 years ago. They are possible now mainly because the finite-element method has been developed and adapted to these applications. The principal requirement for achieving reasonably accurate and useful results from these analyses is suitable representation of the stress-strain behavior of the soils involved. In the past 25 years the finite-element method has been used to analyze a large number of dams, as well as other embankments and slopes. The experience gained over this period of time provides a number of valuable lessons concerning the advantages and limitations of the finite-element method for use in practical engineering problems.

The case of a relatively uniform sand site in Chicago is presented. Standard penetration test (SPT) values from samples driven using a drilling rig equipped with an automatic hammer were consistently lower than those from samples driven using a safety hammer. This is due to the higher efficiency of the automatic hammer, which results in greater energy delivered per blow. When averaged at each depth, the results indicated that SPT values using an automatic sampling hammer were approximately 75% of those recorded using the older-style safety hammer. The trend was consistent throughout the sand profile. This agrees with previously published relationships that indicate SPT results using automatic hammers can be expected to be approximately two-thirds of those recorded using safety hammers.