Tenth U.S. National Conference on Earthquake Engineering Frontiers of Earthquake Engineering July 21-25, 2014 Anchorage, Alaska 10NCEE MITIGATION OF SOIL LIQUEFACTION BY DEEP SOIL MIXING FOR HOSPITALS M. Lew 1 , L. Shao 2 , M.B. Hudson 3 and M.A. Murphy 4 ABSTRACT Hospitals are considered essential critical facilities in California and many other jurisdictions. California law mandates that hospitals remain functional after a major earthquake. One of the seismic hazards that confront some hospital facilities is soil liquefaction, which can result in loss of shear strength, settlement, and sometimes lateral spreading of the ground. If there is a potential for significant soil liquefaction, the hospital will have to accommodate the liquefaction structurally, such as being supported on deep piles, or the liquefaction potential of the soil would need to be mitigated by soil improvement methods. Soil improvement by deep soil mixing is one of these technologies and involves the mixing of the soils in place with cement to form a soil- cement mixture that would have sufficient strength to avoid the triggering of liquefaction and have sufficient stiffness to limit the amount of settlement of the soil. The soil improvement may allow for use of conventional foundations. Deep soil mixing may be appropriate for soil improvement applications when other potentially less costly methods cannot adequately improve the soil and/or limit the liquefaction-induced settlements or lateral displacements; this is especially true if there is a higher fines content that limits the effectiveness of other methods (such as stone columns, for example). Two California hospital case histories are presented and the design of the deep soil mixing configurations, the resulting structural systems used in the superstructure, and the quality control/quality assurance procedures will be presented. 1 Principal Engineer, AMEC Environment & Infrastructure, Inc., Los Angeles, CA 90040 2 Chief Engineer, Hayward Baker Inc., Santa Paula, CA 93060 3 Principal Engineer, AMEC Environment & Infrastructure, Inc., Los Angeles, CA 90040 4 Associate Engineer, AMEC Environment & Infrastructure, Inc., Los Angeles, CA 90040 Lew M., Shao L., Hudson M.B., Murphy M.A. Mitigation of soil liquefaction by deep soil mixing for hospitals. Proceedings of the 10 th National Conference in Earthquake Engineering, Earthquake Engineering Research Institute, Anchorage, AK, 2014.