南宁市河流冲积相黏性土抗剪强度热效应研究  

Study of the thermal effect on the shear strength of alluvial-fluvial cohesive soil in Nanning

作　　者：周东[1,2] 乐观永[1,2] 刘晨晖[1,2] 王业田[1,2] 吴恒[1,2] 

机构地区：[1]广西大学,广西南宁530004 [2]广西大学工程防灾与结构安全教育部重点实验室,广西南宁530004

出　　处：《土木工程学报》2012年第2期111-117,共7页China Civil Engineering Journal

基　　金：国家自然科学基金(40772190);广西理工科学实验中心重点项目(LGZX201103);广西区教育厅科研基金(T081007)

摘　　要：为研究不同初始状态黏性土抗剪强度的热效应规律,以南宁市河流冲积相黏性土为研究对象,选取7种初始含水量和5种初始干密度制成720个三轴试样,分别在20℃、40℃、60℃环境中养护168h后利用温控三轴仪进行剪切试验。试验结果表明:温度升高时,黏性土的黏聚力和内摩擦角有升有降,它由土样含水量以及温度变化范围所决定;黏性土抗剪强度的热效应存在一个临界含水量,此临界含水量在该土的最优含水量附近;当温度从20℃上升到40℃时,若小于临界含水量,黏聚力降低,内摩擦角升高,反之则黏聚力升高,内摩擦角降低;当温度从40℃上升到60℃时,若小于临界含水量,内摩擦角降低,反之则内摩擦角升高,而土样黏聚力均升高;在临界含水量处,黏性土的热效应最不明显,含水量与临界含水量相差越大,热效应越显著;对于含水量小于临界含水量的土样,存在一个干密度,使其热效应最显著,此干密度远小于最大干密度,大于临界含水量土样的热效应与干密度之间的规律并不明显。This paper deals with the alluvial-fluvial cohesive soil in Nanning city to investigate the thermal effect on the shear strength in different initial states. Select the soil samples with 7 initial water contents and 5 types of initial dry density for a total of 720 triaxial tests. After nurturing in the environments of 20℃, 40℃ and 60℃ for 168 hours, respectively, the samples are put into the temperature controlled triaxial apparatus to conduct the shear experiment. Results show that when the temperature rises, fluctuation appears for the cohesion and the friction angle, which are decided by the range of temperature change and water content of soil sample. There is critical water content for the thermal effect on the cohesive soil shear strength. When the temperature increases from 20℃to 40℃ and the water content is below the critical water content, the cohesive strength of the soil sample decreases and the friction angle increases, and vice versa. When the temperature rises from 40℃ to 60℃, the cohesive strength of the soil samples all increase without the consideration of the critical water content while the friction angle decreases with the water content being smaller than its critical water content, and vice versa. When the water content is within its critical water content, the thermal effect on cohesive soil is the most insignificant while the difference between the water content and its critical water content is larger, and the thermal effect becomes increasingly obvious. For those soil samples with water content smaller than the critical water content, there exists a dry density, which is far smaller than the maximum dry density, to make the thermal effect become the most significant. However, when the water content is larger than the critical water content, the relation between the dry density and the thermal effect of the soil samples is not obvious.

关 键 词：黏性土 温控三轴仪 热效应 抗剪强度 含水量 干密度 

分 类 号：TU411.7[建筑科学—岩土工程]