Soil liquefaction is a major concern for structures constructed with or on sandy soils. This paper describes the phenomena of soil liquefaction, reviews suitable definitions, and provides an update on methods to evaluate cyclic liquefaction using the cone penetration test (CPT). A method is described to estimate grain characteristics directly from the CPT and to incorporate this into one of the methods for evaluating resistance to cyclic loading. A worked example is also provided, illustrating how the continuous nature of the CPT can provide a good evaluation of cyclic liquefaction potential, on an overall profile basis. This paper forms part of the final submission by the authors to the proceedings of the 1996 National Center for Earthquake Engineering Research workshop on evaluation of liquefaction resistance of soils.Key words: cyclic liquefaction, sandy soils, cone penetration test

This paper attempts to evaluate the undrained shear strength of sand during flow failures, based on both laboratory testing and field observations. In the laboratory, the minimum shear resistance during monotonic loading was taken as the undrained strength, based on the criterion of stability. Triaxial compression, triaxial extension, and simple shear test data on clean sand were examined and it was revealed that the undrained shear strength ratio could be related to the relative density of the material provided that the initial stress, piprime, was less than 500 kPa. Three previous flow failures involving sand layers with relatively low fines contents and reliable cone penetration test (CPT) data were studied. Using existing calibration chamber test results, the Toyoura sand specimen densities in the laboratory tests were converted to equivalent values of CPT penetration resistance. The undrained shear strengths measured in the laboratory for Toyoura sand were compared with those from the case studies. It was found that the behaviour of sand in simple shear in the laboratory was consistent with the field performance observations. Triaxial compression tests overestimated the undrained strengths, and triaxial extension tests underestimated the undrained strengths. From both the simple shear test result and the CPT field data, the threshold value of clean sand equivalent cone resistance for flow failure was detected. Based on these observations, a CPT-based guideline for evaluating the potential for flow failure of a clean sand deposit is proposed. Key words: liquefaction, flow, laboratory testing, in situ test, case histories.

One of the primary objectives of the Canadian Liquefaction Experiment (CANLEX) project was to evaluate in situ testing techniques and existing interpretation methods as part of the overall goal to focus and coordinate Canadian geotechnical expertise on the topic of soil liquefaction. Six sites were selected by the CANLEX project in an attempt to characterize various deposits of loose sandy soil. The sites consisted of a variety of soil deposits, including hydraulically placed sand deposits associated with the oil sands industry, natural sand deposits in the Fraser River Delta, and hydraulically placed sand deposits associated with the hard-rock mining industry. At each site, a target zone was selected and various in situ tests were performed. These included standard penetration tests, cone penetration tests, seismic downhole cone penetration tests (giving shear wave velocity measurements), geophysical (gamma-gamma) logging, and pressuremeter testing. This paper describes the techniques used in the in situ testing program at each site and presents a summary and interpretation of the results.Key words: CANLEX, in situ testing, shear wave velocity, geophysical logging, pressuremeter.

The Canadian geotechnical engineering community has completed a major collaborative 5 year research project entitled the Canadian Liquefaction Experiment (CANLEX). The main objective of the project was to study the phenomenon of soil liquefaction, which can occur in saturated sandy soils and is characterized by a large loss of strength or stiffness resulting in substantial deformations. The intent of this paper is to compare, interpret, and summarize the large amount of field and laboratory data obtained for six sites in Western Canada as part of the CANLEX project. The sites are compared in terms of both flow-liquefaction and cyclic-softening considerations. The paper presents a number of conclusions drawn from the project as a whole, in terms of both fundamental and practical significance.Key words: sand, flow liquefaction, cyclic softening, CANLEX.

No abstract