含砾量对砂砾土液化势影响研究

The liquefaction potential and resistance of gravelly soils have not been considered in current seismic design codes over the world because of lack of full understand of gravelly soils liquefaction mechanism. Gravelly soils are commonly regarded as non-liquefiable because of large grain sizes and generally high permeability. However, gravelly soils liquefaction occurred widespread following 2008 Wenchuan earthquake, 118 liquefied sites were identified and the liquefaction distribution area is the largest since the 1976 Tangshan earthquake. The gravel content is the key index to distinguish sandy soils from gravelly soils according to the incohesive soils classification principle. The accurate evaluation of gravel content effects on the liquefaction potential of gravelly soils is very useful to reveal its liquefaction mechanism and to develop reliable gravelly soils liquefaction assessment method. This project is going to investigate the geology conditions of Chengdu Plain that covers the most liquefied sites and the characters of typical liquefied soils, to propose a preliminary geology principle for classifying liquefiable site from non-liquefiable sites, to develop correlations among the gravel content, relative density, and shear wave velocity, to determine gravel content effects on the liquefaction potential of gravelly soils, and to reveal the liquefaction mechanism of gravelly soils, and its difference from that of sandy soils.

目前国内、外对砂砾土液化的认识仍十分有限，现行抗震规范、规程中不含砂砾土内容，工程上往往不考虑砂砾土液化的可能性且不做任何抗液化措施。2008年汶川地震中砂砾土液化十分普遍其震害也十分严重，液化涉及范围为建国以来最广。根据无粘性土的工程分类，砂土与砂砾土最大的区别是含砾量的不同，正确估计含砾量对砂砾土液化势的影响，对于揭示砂砾土液化机理和建立合理、可靠的砂砾土液化判别方法至关重要。以现场考察、测试与室内试验相结合，系统开展砂砾土液化势影响研究，取得汶川地震砂砾土液化及其震害系统深入认识，掌握地质背景、土性特征，提出砂砾土液化势水文、地质初判条件；制备不同含砾量的砂砾土土样，考察含砾量与相对密度、剪切波速的相互影响规律；开展不同荷载下砂土与砂砾土小型振动台平行试验，控制剪切波速一定的条件下大粒径动三轴试验，分析含砾量对砂砾土抗液化强度的影响，初步揭示砂砾土液化机理以及与砂土液化的本质区别。

目前国内、外对砾性土液化的认识仍十分有限，现行抗震规范、规程中不含砾性土内容，工程上往往不考虑砾性土液化的可能性且不做任何抗液化措施。2008年汶川地震液化涉及范围为建国以来最广，118例液化中约70%为砾性土液化，全球其他历史地震中砾性土液化实例不足10例。正确估计含砾量对砾性土液化势的影响，对于揭示砾性土液化机理和建立合理、可靠的砾性土液化判别方法具有重要的作用。以现场考察、测试与室内试验相结合，系统开展砾性土液化势影响研究，取得汶川地震砾性土液化及其震害系统深入认识，掌握地质背景、土性特征；制备不同含砾量的砾性土土样，考察含砾量与相对密度、剪切波速的相互影响规律；开展砂土与砾性土振动台、动三轴对比试验，分析含砾量对砾性土抗液化强度的影响，初步揭示砾性土与砂土液化的区别和联系。