Through the Bachu-Jiashi Ms6.8 earthquake liquefaction investigation and test, obtain the 47 the standard penetration test date, examine the existing standard applicability based on standard penetration test of soil liquefaction identification method, and put forward the new sandy soil liquefaction evaluation formula. Analysis shows that the current assessment formula base on SPT counts of soil liquefaction are not applicable to Xinjiang region, will give the risky results. In the new survey data of soil liquefaction evaluation model established of five parameters by the earthquake intensity, the measured SPT counts, datum SPT values, groundwater level, and sand buried depth. The datum SPT values, the influencing coefficients of water and sand depths are gain by a normalized method and by an optimizing method. Establish new formula of soil liquefaction evaluation to the success judging rate is higher, the model shows that constructing reasonable and calculation formula is reliable, can be employed for regional code formulation in Xinjiang area.
Cyclic triaxial tests were carried out for remodeled saturated clayey sands with the clay content varying in a relatively wide range from 0% to 40%. In the tests, saturated uniformity clayey sands were obtained by pre-freezing method, i.e. immersing samples in pure water for 12 hours under vacuum, and then, freezing the sample to -15°C for 6 hours. Experimental results indicate that the lowest liquefaction resistance in mixtures occurs when clay contents is of the order of 15%. The ratio of liquefaction shear stresses of the specimens obtained using pre-freezing method are larger than those obtained with the traditional deposit-in-water method.
CPT is a kind of relatively superior field test technology, which is one of important the liquefaction in-situ test at home and abroad. In 1987, China has formed the national standard CPT liquefaction evaluation method, which predominantly from 1976 Tangshan earthquake liquefaction data, and then has not been tested. Recently by the 40 CPT liquefaction field data of Bachu earthquake obtained a liquefied evaluation formula. Due to comparing the liquefied evaluation methods at home and abroad, found the national standard CPT liquefied critical curve is qualitatively distinct to the others liquefied evaluation methods. If it is wrong about the code of CPT liquefied evaluation method, which the liquefied critical curve will be smaller along with the direction of the depth, will direct the liquefied evaluation critically be conservative and the depth liquefaction evaluation clearly be hazardous. In theory, this problem can be attributed to the influence of sand depth for liquefied evaluation, worthy of further discussion.
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