软土非单调压缩固结试验

在实际岩土工程中,经常会遇到软土地基受非单调增加的荷载作用而发生的非单调压缩固结问题。虽然固结理论经过八十多余年的发展已经取得了长足的进步,但在分析这类问题时还是将加荷、卸荷过程中土体的压缩性参数视为同一常数,与实际情况并不相符。本文通过室内试验和理论分析,对软土的一维非单调压缩固结理论开展了较系统深入的研究。主要工作和研究成果如下: 1.研究了GDS先进固结试验系统的功能和特点,编制了能快速处理实验数据的程序GDSDA,并利用GDS先进固结试验系统对13组萧山饱和软土试样进行了一维压缩和渗透试验,较全面地研究了萧山软土的常规压缩和渗透特性,获得了萧山软土渗透系数k v,随有效应力p的变化规律,即:log k v-log p和e-log 10 k v均呈线性关系。 2.通过利用GDS先进固结试验系统对3组土样进行加荷-卸荷-再加荷压缩固结和渗透交叉试验以及对9组土样进行循环加载试验,进一步研究了萧山软土的非单调压缩和渗透特性,获得了在加、卸荷状态下的土性参数。试验结果表明:在非单调压缩条件下,萧山软土的e-log 10 p和e-log 10 k v的线性关系仍成立,但直线的斜率因土体所处加、卸荷状态不同而改变。 3.建立了能考虑土体在固结过程中压缩与回弹特性不同的一维非单调压缩条件下的线性固结模型,运用半解析法进行了求解,编制了相应程序,并对循环荷载下单层地基的一维非单调压缩线性固结性状进行了详细分析。结果表明:影响单层地基在循环荷载作用下固结性状的主要因素是循环荷载系数T v0,α,β,以及回弹压缩系数与压缩系数的比值α e/α v;考虑土体在固结过程中压缩与回弹特性不同时软土的固结比常规理论更快;比值α e/α v越小,固结发展越快。 4.基于e-log 10 p和e-log 10 k v线性关系,进一步建立了一维非单调压缩条件下的非线性固结模型,编制了基于半解析法的计算程序,并利用该程序较深入地分析了循环荷载下单层软土地基一维非单调压缩非线性固结性状。结果表明:除循环荷载系数T v0,α,
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In the practical project of geotechnical engineering, the non-monotonic consolidation problems of soil are often encountered when subsoil is subjected to a non-monotonic increasing loading. Though the consolidation theory has been developed for eighty years and made a great achievement in the theoretical field, the compressibility of subsoil is still just taken as a constant in the process of loading, unloading and reloading, which is not consistent with the truth of practical engineering. In this dissertation, the one-dimensional consolidation theory involved with non-monotonic compression is studied systemically through laboratory testing and theoretical investigation. The main original work and results are as follows:1. The functions and features of GDS advanced consolidation testing system （GDSACTS） are investigated, and a program GDSDA is developed for test data fast processing. One-dimensional consolidation and permeability tests are conducted with 13 groups of Xiaoshan clay by GDSACTS to investigate its compressibility and permeability. It shows that both e - log 10 p and e - log 10 k v relationships are linear.2. The compression test of loading-unloading-reloading combined with permeability test as well as the ones under cyclic loading are respectively made with 3 groups and 9 groups of Xiaoshan clay samples by GDSACTS, and the behavior of compression and permeability under non-monotonic compression is studied and the relevant geotechnical parameters representing the property of the clay in the process of loading and unloading are obtained. The test results show that, under the condition of non-monotonic compression, the linear relationships of e-log 10 p and e-log 10 k v are also true, but their slopes are different with loading or unloading.3. Considering the variable compression coefficient under loading and unloading, a one-dimensional linear consolidation model is established and solved by semi-analytical method. The corresponding computer program is developed to analyze the behavior of one-dimensional consolidation of soft soil under non-monotonic compression in detail. The