The bearing capacity behavior of strip footing located above a continuous void in silty clay soil was investigated experimentally and analytically. The experiment was performed in a test tank which contained a compacted silty clay. The analysis was made by using the finite element method in which the test soil was treated as an elastic perfectly plastic material. Results of the study indicate that the bearing capacity of footing above a void can be analyzed successfully by using the finite element method of analysis. For each footing, there exists a critical depth below which the presence of the void has negligible influence on the footing performance. When the void is located above the critical depth, the bearing capacity of the footing varies with various factors, such as the size and location of the void and the depth of foundation. Graphs relating the bearing capacity with the influencing factors investigated are developed. These graphs provide a data base useful for design of continuous footing centered with an underground void.

Calculations of support pressure—tunnel convergence relationships, or ground response curves are used to improve understanding or rocksupport interaction and to aid in the dimensioning of tunnel support elements. Methods of response curve calculation are presented for a tunnel of circular cross‐section excavated in a rock mass initially subjected to a hydrostatic in situ stress field. Plane strain conditions are assumed. The two solutions presented use nonlinear peak and residual rock mass strength criteria. Particular consideration is given to the influence of plastic volumetric strains in the rock mass surrounding the tunnel. A closed‐form solution is presented for an elastic‐brittle‐plastic material behavior model in which post‐peak dilatancy occurs at a constant rate with major principal strain. A second solution is presented as a stepwise sequence of calculations for an elastic‐strain, softening‐plastic model in which post‐peak dilatancy occurs at a lower rate with major principal strain in the constant strength plastic zone than in the strain softening zone. These two solutions are applied in illustrative examples.

Low‐level radioactive waste has been produced since the early 1940's. Most of it has been buried in shallow pits at 11 existing sites. Several of the existing sites have performed poorly. Inability to control flow of surface and ground water into and out of disposal pits has been the most important problem. Lack of attention to design of earthen covers over the waste and improper emplacement of the waste in the pits have also contributed to poor performance. Several steps are recommended for improving disposal practices: (1) Waste settlement can be minimized by stacking wastes neatly into pits rather than dumping them randomly; (2) the earthen cover can be made to perform better by making it thicker and by maintaining it properly; and (3) goundwater contamination can be minimized by siting disposal facilities at locations with favorable geohydrologic characteristics. In addition, improved designs are needed for earthen covers, and technology for predicting ground water contamination in the saturated/unsaturated soils that underlie the waste also needs improvement.

Conventional testing procedures produce scatter and bias in indicated properties of soils, such as desiccated clays. This paper describes and compares several conventional and nonconventional methods for characterizing the engineering properties of such soils at a site in Houston, Texas. Properties considered include undrained shear strength, stress‐deformation moduli, earth pressure coefficients, and compression indexes. Similarities and differences between soil preconsolidated by desiccation and by stress removal are noted.

A physical experiment was conducted in which dynamic torsional loadings were applied to a rigid circular model footing resting on a surcharged granular test bed. High amplitudes of strain, such as those encountered in large earthquakes, were developed. The torsional response of the footing and of selected locations within the test bed were measured. A newly developed numerical procedure, capable of solving the three‐dimensional axisymmetric nonlinear torsional wave equation, was used to simulate the experiment. The footing and test bed were modeled as a rigid disk resting on a nonlinear inelastic half space with slip permitted along the interface and on a linear elastic half space. Generally, experimental and nonlinear numerical results agreed well. It was concluded that to predict accurately the response of a soil‐foundation system when large shearing strains develop, nonlinear inelastic behavior of the soil must be taken into account. Also, it was concluded that the numerical procedure could predict accurately the response of the footing and reasonably well the response of the test bed.

A model for predicting the dynamic response and liquefaction of earth structures was developed. The model was based on Biot's theory for the propagation of elastic waves in a porous medium and an empirical relation put forth by Finn, et al. for the volumetric strain resulting from an applied shear strain. The finite element method was utilized to solve the equations. The model was applied to a hypothetical earth dam. The results of the analysis were compared to the observed liquefaction in the San Fernando dam and were shown to be reasonable.

A mathematical expression is developed for the relationship between the excess pore pressure buildup in sands during cyclic loading and the normalized number of cycles. This expression is based on the equations proposed by previous investigators, but the effects of anisotropic stress conditions are represented more accurately. The new method is capable of covering the full range of anisotropic consolidation stress values. Satisfactory agreement is found between the predictions with this analytical expression and available cyclic test results.

A technique that was used to estimate the safety factor against liquefaction by predicting the increase in SPT N-values due to driving of displacement piles in sand is presented. The prediction method involved applying previously-developed relations between relative density, grain-size distribution, overconsolidation ratio, effective stress and N-values to evaluate the relative density of site sands prior to pile-driving. Similar relations were applied to calculate increased N-values from increased relative density due to volume displacement and lateral stress increase from pile-driving. The predicted N-values were subsequently verified by carefully-controlled field penetration testing.

Rock drilling is involved in field investigations in the search for suitable sites for nuclear waste repositories. The boreholes have to be sealed with some low-permeable, ductile, and chemically stable plugs. Compacted bentonite clay confined in perforated metal pipes has been tried and laboratory as well as field tests show the merits of the technique, which should be applicable to holes of practically any length in many types of rock.

The author poses a question about what happens to the lateral stress of a normally consolidated clay aging in an oedometer at constant vertical stress. A written and verbal survey of 32 senior engineers from research and practice backgrounds showed much diversity in their answers to this question, which implies much diversity in how they perceive the behavior of soil. The profession needs answers to this and similar questions that include time effects in the behavior of geotechnical materials.