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松散砂土不稳定性试验研究

ISSN号：1000-6915
期刊名称：岩石力学与工程学报
时间：2014
页码：623-630
分类：TU43[建筑科学—岩土工程;建筑科学—土工工程]
作者机构：[1] 浙江大学滨海和城市岩土工程研究中心,浙江杭州310058, [2]温州大学建筑与土木工程学院,浙江温州 325035
相关基金：国家自然科学基金资助项目（51278383,51025827,51308420）
相关项目：饱和土动力学及其工程应用

关键词：土力学, 不稳定性, 常偏应力排水剪切试验, 变围压三轴仪, 松散砂土, soil mechanics, instability, constant shear-drained（CSD） tests, variable confining pressure triaxial apparatus, loose sand

中文摘要：

对松散丰浦砂进行三轴不排水和常偏应力排水剪切（constant shear drained，简写为CSD）试验。试验采用高精度变围压三轴仪可实现CSD试验全过程偏应力不变，得到比以往研究更为可靠的试验结果。试验发现，在不排水试验中，同一孔隙比的试样在不同围压下具有相同的不稳定线，但同一围压下不稳定线的斜率随孔隙比的增大逐渐减小并趋于稳定。试样在完全排水条件下会发生不稳定，即试样产生明显塑性变形，轴向应变和体积应变迅速增大。以往的研究中CSD应力路径的施加采用轴向力不变，试验过程中偏应力的减小会对不稳定性的判断造成影响，这可能是不同研究者得出不一致结论的重要原因。对松散砂土在不排水和排水条件下不稳定性的区别与联系进行分析，得出如下结论：松散砂土无论在不排水条件下还是在完全排水条件下，相同孔隙比的试样均是在同一应力比下达到不稳定状态。试验结果为排水条件下不稳定性机制研究提供更强有力的试验依据，可用于解释某些边坡的破坏机制。

英文摘要：

Undrained and constant shear drained（CSD） tests were conducted on loose Toyoura sand using high-precision variable confining pressure triaxial apparatus,which can maintain the deviator stress constant, more reliable results can be obtained from this study. Based on the test results,it can be concluded that the specimens of the same void ratio under different effective stresses have the same instability line,but the instability line slope of sand with the same effective stresses decreases gradually along with the increase of void ratio and tends to be stable. The instability can occur under completely drained conditions,instability as defined in this paper refers to a behavior in which large plastic strains are generated rapidly and continuously,and the axial strain and volumetric strain develop rapidly. In the previous CSD studies axial force were maintained constant;the decrease of the deviatoric stress during the process of test may affect the judgment of the instability;this may be the important reason for the researchers hold different conclusions. The instability occurring under drained conditions is different from that observed under undrained conditions. The differences and similarities between the two types of instability were elaborated. It can be included that instability of undrained tests and CSD tests occur on the similar stress ratios for a given void ratio of specimens. The test results in this study provide a more powerful evidence for the research of instability under drained condition;and they also can be used to analyze the failure mechanisms of granular soil slope.

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