CAJ | 학술논문

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。
대송산봉포사진행삼축불배수화상편응력배수전절(constant shear drained，간사위CSD)시험。시험채용고정도변위압삼축의가실현CSD시험전과정편응력불변，득도비이왕연구경위가고적시험결과。시험발현，재불배수시험중，동일공극비적시양재불동위압하구유상동적불은정선，단동일위압하불은정선적사솔수공극비적증대축점감소병추우은정。시양재완전배수조건하회발생불은정，즉시양산생명현소성변형，축향응변화체적응변신속증대。이왕적연구중CSD응력로경적시가채용축향력불변，시험과정중편응력적감소회대불은정성적판단조성영향，저가능시불동연구자득출불일치결론적중요원인。대송산사토재불배수화배수조건하불은정성적구별여련계진행분석，득출여하결론：송산사토무론재불배수조건하환시재완전배수조건하，상동공극비적시양균시재동일응력비하체도불은정상태。시험결과위배수조건하불은정성궤제연구제공경강유력적시험의거，가용우해석모사변파적파배궤제。
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.