饱和原状黄土液化基本特征的振动台试验研究

天然黄土因其较强的结构性,制备大尺寸原状试体非常困难,国内外尚无针对饱和原状黄土实施振动台模拟试验的数据与资料。通过解决大尺寸原状黄土试体现场取备难题,利用振动台模拟试验研究饱和原状黄土液化现象及其基本特征。试验结果表明:饱和原状黄土的液化现象,在超孔隙水压力增长、持续与消散的趋势性上与饱和砂土具有可比性,二者的最大差别在于细节特征方面的不同;饱和度是决定地震作用下天然黄土液化特性的首要条件;试体饱和度约为90.3%的条件下,加载后的最大孔压比约为0.93;饱和度85%、75%和65%可能是天然黄土能否发生液化现象、似液化现象(循环失效)和不考虑循环失效现象的临界值。试验获得的资料与分析结果,对深入理解饱和土体液化物理过程与力学机制意义重大。

Shaking-table Tests on Liquefaction Characteristics of Saturated Undisturbed Loess

Acquiring large-scale undisturbed samples of natural loess is very difficult due to its special original structure.Therefore,no data or documents are available of shaking-table testing on saturated samples of undisturbed loess soil around the world.In the present study,we address the problems of preparing large-scale undisturbed loess samples in the field and conducting research on the liquefaction features of saturated natural loess by means of shaking-table testing.Previous testing results have shown that the development process of excess void water pressure during loess liquefaction,such as accumlation,continuance,and dissipation,is the same as that with saturated sand;the essential differences between the cases of loess and sand focus only on detailed characteristics.The degree of saturation is the most important factor in controlling the liquefaction behavior of natural loess under seismic loading.For this case of the shaking-table test,the void water pressure ratio of undisturbed loess samples can reach 0.93 at saturation conditions of 90.3%.Moreover,the degree of saturation at 85%,75%,and 65% may be critical values associated with liquefaction phenoment,similar liquefaction phenomena(cyclic failure),and that without consideration of cyclic failure,respectively.In short,first-hand data of liquefaction features of natural loess acquired by the shaking-table test and corresponding analysis results based on that datacould advance the present understanding of the physical process and mechanism of saturated soil under seismic loading.