Construction of an inclined escalator shaft entrance to the Metropolitan Atlanta Rapid Transit Authority's (MARTA) Peachtree Center Station required tunneling under a 15‐story building over 60 yr old. Because of the age of the structure, foundation records were not available in the design phase, and surrounding streets and structures prevented access to the foundations. The final details of the tunneling procedures were determined during construction, based on information gathered as the work proceeded. The critical part of the construction occurred as the shaft excavation passed below two of the structure's footings carrying a combined load of over 1,200 kips (5,340 kN), with only 7 ft (2 m) of partially weathered rock cover over the 23‐ft (7‐m) wide sloping tunnel. The development of the tunneling methods provides an interesting case history of investigative engineering and application of geologic and geotechnical knowledge.

A case history of the widening of movement joints between two box‐units of a vehicular underpass is presented. The underpass is founded on prestressed concrete piles. During the construction of the embankment fills on both sides of the underpass, the gap of the movement joints between two box‐units was observed to have widened. This is probably due to the lateral movement of the soft soil surrounding the piles of the underpass. Circular slip analysis, bearing capacity computations and site records of excess pore water pressure observations of the piezometers in the soft clay layer, are used to evaluate the tendency for such lateral movements. The amount of widening of the movement joint was measured. With the help of a digital computer, the effects of the phenomenon on the supporting piles were studied. As a solution to the problem, platforms supported on piles were used to prevent overloading of the foundation.

Resonant column tests involving anisotropic confining conditions were conducted to evaluate static stress condition, especially stress ratio effects on the low‐amplitude dynamic shear modulus, $G_0\text{,}$ of three clean, dry sands. Six static stress paths, involving both triaxial compression and triaxial extension, developed the desired ranges of stress ratios and stress histories. The results of these tests determined that increasing the stress ratio decreased $G_0\text{,}$ up to 20%–30%, but the reduction was not significant for stress ratios below about 2.0. Stress history caused a reduction in $G_0\text{,}$ but when the final stress ratio was the maximum value attained, the loading, unloading, and reloading path followed to develop this maximum value had little influence. The results also indicated that $G_0\text{,}$ depends about equally on the static principal stresses in the direction of wave propagation and in the direction of particle motion. The effect of the third principal stress appears to be unimportant. Two empirical equations were given for $G_0\text{,}$ in term of the two significant principal stresses.

This project is aimed at the development of a technique, based on acoustic emission (AE) monitoring, to assess preconsolidation pressures (in all soils) in the field. Envisioned is a three part program: (1) Technical feasibility via testing granular soils in the laboratory; (2) technical feasibility via testing fine‐grained soils in the laboratory; and (3) field verification, in all soil types, using an “acoustic pressuremeter.” This paper presents the first part of the overall program. Remolded granular soils were loaded in a standard consolidometer, where the prestress load was first released, then reapplied in an in cremental manner. Deformation and AE were monitored during this reloading process. As the load equivalent to the originally applied preconsolidation pressure was exceeded, both deformation and AE increased markedly. The original prestress was easily detectable by both methods. Separate tests were performed on five different granular soils, each at four different saturation levels and for four different prestress conditions. Eighty (80) tests were performed in total. Results show that both deformation and AE predicted the originally applied preconsolidation pressure to within about 5% error, the exception being AE at the lowest value of prestress, which was somewhat higher. These results are presented and reviewed. It is concluded that AE is a viable method to predict prestress in granular soils, and should be extended to fine grained soils. If rea sonable results are obtained, field verification will be commenced.

Laboratory thermal probe tests performed on an AASHTO standard reference material (a silty clay) showed that the soil thermal behavior cor relates with the limit states of fine‐grained soils. Over 80 thermal resistivity measurements were made on specimens compacted to various densities and moisture contents. Results are presented which indicate that the optimum moisture content and the plastic limit can be correlated with the thermal be havior of fine‐grained soils. It was found that the minimum thermal resistivity and the critical moisture content occurred at the optimum moisture content when the soils were compacted using various compactive efforts. The knee of the thermal‐resistivity‐versus‐moisture‐content curve defines the critical moisture content. When the soils were compacted using a compactive effort of $1.42\times {10}^{5}J/m^3$ (2,970 ft‐lb per cu ft), the minimum thermal resistivity occurred at the plastic limit of the AASHTO standard reference material. Also, indices are defined which allow comparison of the thermal behavior of fine‐grained soils.

Information on the thermal properties of soils from different disciplines of science and engineering is consolidated to identify low‐cost, simple procedures for assessing the variation of the thermal resistivity of soils with changes in moisture content. Three procedures for determining the critical moisture content are presented. The critical moisture content is the moisture content at the knee of the Thermal‐resistivity‐versus‐moisture‐content curve. The optimum moisture content and plastic limit were found to be physical quan tities indicative of the critical moisture content in soils. Also, the upper flex point of the soil‐moisture‐characteristics curve appears to establish the critical moisture content in soils.

The development of the phreatic surface in a stable tailings dam is investigated by using centrifuge simulation techniques and analytical techniques. The centrifuge simulations, conducted on an 8 m radius machine, use a “modeling‐of‐models” approach to determine the effects of scaling and model construction on the development of the phreatic surface. The analytical techniques are used to predict the location of the steady‐state phreatic surface in the equivalent full‐scale prototype dam and to determine its stability in terms of the conventional factor‐of‐safety. While the analysis indicates that there should be no scaling effect on the steady‐state phreatic surface, the simulations show a rise in the phreatic surface with increased scaling. Numerical predictions of the steady‐state phreatic surface compare well with data taken below 100 g scaling.

Membrane penetration effects in drained and undrained tests are discussed. A qualitative analysis is performed to find which factors influence the membrane penetration and, at least approximately, to what extent. It is shown that apparent volumetric strain due merely to membrane penetration decreases linearly with increasing sample diameter. The factor of major influence is the grain size but confining pressure, rigidity and thickness of membrane play a non‐negligible role. A method to correct the measured values of pore pressure in undrained tests is proposed. It is shown that the correction factor depends on the volumetric stiffness of the sample which is not a constant but depends markedly on the state of stress.

Herein is developed a fundamental solution to the problem of the expansion of a cylindrical cavity in a dilatant soil which exhibits effects of large strains. A result of some importance to geomechanics concerns the development of a shear stress‐strain curve for the tested soil by using the measured pressure‐cavity wall displacement response. It is shown that in order to develop the desired stress‐strain relationship for a dilatant soil it is necessary to introduce a kinematic constraint which relates the finite volumetric strain in the soil to the components of the Lagrangian strain matrix. Particular results are developed for the case where the volumetric strains vary linearly with the radial and circumferential Lagrangian strain components.