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SECTION: 1  GEOTECHNICAL GUIDELINES & REGULATIONS                                     SECTION: 1  GEOTECHNICAL GUIDELINES & REGULATIONS




                                                                                                                For CPT-Based liquefaction analysis, soil profiling according to Robertson
                                                                                                                1996, or similar method shall be performed to highlight localities of high
                                                                                                                fines content.
                                                                                                                Level survey (before & after improvement) shall be submitted along with
                                                                                                                soil improvement tests result report for CED approval.

                                                                                                           1.4.4   EVALUATION OF LIKELY LIQUEFACTION INDUCED HAZARDS
                                                                                                                “Special Publication 117, GUIDELINES FOR EVALUATING AND MITIGATING
                                                                                                                SEISMIC HAZARDS IN CALIFORNIA”, adopted on March 1997 by the State
                                                                                                                Mining and Geology Board.
                                                                                                                The evaluation of likely liquefaction hazard shall be carried out by
                                                                                                                competent and qualified geotechnical Engineer. The evaluation shall be
                                                                                                                based on the results of adequate number of filed tests (preferably CPTU).

                                                                                                                Wherever, the analysis indicates significant liquefiable zones, and then
                                                                                                                the site or part of it shall be recommended for further deep compaction.
                                                                                                                Wherever, minor, localized liquefiable zones within limited depth were
                                                                                                                indicated, and then it is important to assess the likely induced effects
                                                                                                                such as:
                                                                                                                a)    Liquefaction induced settlement of surface foun dations,
                                                                                                                b)    Surface Manifestation,
                                    Fig. (1.32): Cone Penetration Test Readings                                 c)    Loss of bearing strength of surface foundations,

                                                                                                                d)    Loss of lateral stiffness of piles,
                     1.4.3   CALCULATION THEORY:
                                                                                                                e)    Effects on life lines,
                          Cyclic stress ratio (CSR) induced in the soil due to earthquake shall be
                          estimated as per clause 1.2.32. Cyclic resistance ratio (CRR) induced in              f)    Any other influences…
                          the soil shall be estimated as per clause 1.2.33.
                                                                                                                1.4.4.a   Settlement:
                          Liquefaction potential shall be evaluated by calculating the factor
                          of safety against liquefaction for specific earthquake load and soil                         If shallow footings exist and no improvement has done,
                          strength.  (F.S. = CRR / [(1.2-1.5) CSR). The accepted factor of safety                      differential settlement more than the maximum liquefaction
                          against liquefaction shall be more than unity.                                               induced settlement should be expected and considered.
                          Recommended Procedures for Implementation of DMG Special                              1.4.4.b   Surface manifestation:
                          Publication – 117 Guidelines for Analyzing and Mitigating Liquefaction
                          Hazards in California. Implementation Committee, March 1999-                                 Surface manifestation such as sand boils or ground fissure
                          “Preliminary screening of Liquefaction”                                                      may be occurred during earthquake shaking emphasising that
                                                                                                                       ground  settlement  have  already  takes  place  noting  that  the
                          The ground water table adopted by the designer for liquefaction analysis                     settlement may be occurred even with the absence of surface
                          shall consider the surrounding site conditions.                                              manifestation. The evaluation of the potential for ground

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