Horizontal Stress in Situ by Cone Penetrometer and Related Studies

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This is a cooperative research project between NSF and the Army Research Office (ARO). The major emphasis of this research is to develop a reliable means for the measurement of horizontal stress in the ground using a cone penetrometer. The insitu lateral stress has long been recognized as an important parameter in a wide range of applications in geotechnical engineering. A quantitative value for lateral earth pressure (the ratio of the horizontal to vertical effective stresses) is needed for virtually all stress-deformation and stability analyses; e.g. settlement, bearing capcity, pile capacity, slope stability and design of retaining structures. Safe and economical design of these earth structures and reinforcement systems requires the knowledge of the horizontal stress. The research program develops theoretical analysese of stresses around penetrometers and verifies the results with laboratory chamber tests and field tests using a recently developed lateral stress sensing cone penetrometer (LSSCP). Tests will be done at several sites in the San Francisco bay area where different soil types ranging from soft clays to clean sands are encountered. During the first year of the proposed 3-year program, the lateral stress sensing cone penetrometer testing system will be improved, theoretical analyses related to stress fields around penetrometers and in test chambers will be made, and preparations will be completed for field tests. During the second year, field tests will be done at several sites using several different test devices in addition to the LSSCP. The field and laboratory testing will be completed early in the third year.