Two prototype liners were constructed at a site near Austin, Texas, using clays of low and high plasticity. The clays were compacted to 100% of standard Proctor density at a water content slightly wet of optimum using a sheepsfoot roller. The overall hydraulic conductivity (k) of each liner was determined by ponding water on the liners and measuring the rate of seepage. The field‐measured k's of the liners were surprisingly high ($4\times {10}^{-6}$ and $9\times {10}^{-6}\mathrm{cm}/s$). After water in the ponds was removed, laboratory permeability tests were performed on hand‐carved samples obtained from the liners, on samples obtained with a thin‐walled sampling tube, and on laboratory‐compacted samples. Field permeability tests were also performed with ring infiltrometers. The tests showed that: (1) Essentially all of the laboratory tests, even on undisturbed samples, produced a measured k that was approximately 1,000 times less than the field‐measured k; and (2) ring infiltration tests showed considerable scatter but the average k was close to the overall field‐measured k. The findings raise important questions about whether laboratory permeability tests on compacted clay are relevant to clay liners and reinforce previous suggestions that compacted clay liners may contain numerous hydraulic defects such as fissures, slickensides, zones of poor bonding between clods of clay, and zones of relatively poor compaction. The desirability of field permeability tests is evident from the results reported.

A microcomputer based free torsional vibration testing system is introduced; its ability to determine the shear modulus and damping ratio of soils is demonstrated. In comparing with the resonant column method, the free torsional vibration testing system seems to offer reliable results, less expensive instrumentation, easier and faster operation, and less disturbance to soil specimens. The system also offers the advantage of conveniently studying the effect of a number of parameters, such as the initial shear strain and cycle number on the dynamic modulus of soils. This nondestructive testing system may also be used effectively in the determination of dynamic response of compacted clay soil. The measured maximum shear modulus appears to relate closely to the structure of clay particles and the stiffness of the soil specimen. On that basis, the free torsional vibration test might be used to identify the fabric related stressstrain behavior of both sand and clay with little disturbance to a specimen.

Large‐scale field and laboratory tests were carried out to investigate compaction characteristics of a river terrace gravel soil at the 120‐m high Sao Simao Dam in Brazil. The coarse fraction of the deposit was typically 3 in. (7.5 cm) maximum size, while the matrix (defined as material passing No. 4 sieve) was basically a clayey sand with $\mathrm{LL}=30-35\%\text{,}$ $\mathrm{PI}=\mathrm{5minus};15$ and 35–50% passing the No. 200 sieve. The initial objective of the compaction tests was to develop the relationship between maximum density and percentage of gravel fraction which could be used for control of compaction in the field. The scope of the investigation was later enlarged to study the effects of energy of fraction, maximum particle size, mould dimensions, gradation of coarse material and water absorption on compaction of these soils. Field compaction trials were carried out to establish procedures for embankment construction and to evaluate the efficiency of two vibratory rollers.

The effect of underground void on the stability of shallow foundation supported by a compacted clay was investigated by using a three‐dimensional finite element computer program. The clay soil was a commercially available kaolinite which was compacted to 95% compaction of the standard Proctor compactive effort. The analysis was made for different conditions including footing shape (square and strip footings), void shape (continuous circular and cubic voids), orientation of continuous void axis with respect to strip footing axis (parallel and perpendicular directions), and void location. Results of the study indicate that footing stability will be affected by the underground void only when the void is located above the critical depth. The critical depth is not a constant but varies with the shapes of footing and void, void orientation, void size, and soil type. When the void is above the critical depth, the bearing capacity of the footing will decrease with decreasing distance between the footing and the void.

Recently, expanded shale aggregates of the kind used to produce lightweight concrete have been used as a substitute for ordinary fill materials in geotechnical applications where the combination of low unit weight and substantial shear strength is important. The results of triaxial compression tests on large-diameter (25 cm) specimens from several different locations in the eastern United States are presented. Depending on the degree of compaction, the angle of internal friction was found to vary from about 40° to 48° in aggregates that weigh about half as much as most naturally occurring fills. Stress-strain curves for the triaxial tests and for some preliminary consolidation tests are included in the paper so that they may be compared with data for ordinary fills when the lightweight aggregate is being considered as a design alternative.

A solution to analyze stability against base failure in layered soils having slopes and berms of any shape, surcharge and tension crack is presented. The location of critical circle and its factor of safety is obtained through equations rther than by analysis of the number of slip circles. The solution is presented through stability parameters and charts.