膨胀土干湿循环效应及其对边坡稳定性的影响  

WETTING-DRYING EFFECT OF EXPANSIVE SOILS AND ITS INFLUENCE ON SLOPE STABILITY

作　　者：曾召田[1,2] 吕海波[1,2] 赵艳林[1,2] 蒋文宇[2] 

机构地区：[1]广西岩土力学与工程重点实验室桂林理工大学,桂林541004 [2]广西大学土木建筑工程学院防灾减灾研究所,南宁530004

出　　处：《工程地质学报》2012年第6期934-939,共6页Journal of Engineering Geology

基　　金：973前期研究专项(2010CB434810);国家自然科学基金(51169005);广西自然科学基金(2010GXNSFD013012)

摘　　要：膨胀土的干湿循环性状在膨胀土边坡的稳定性分析中占有重要地位。结合膨胀土边坡的现场含水率观测数据和南宁地区大气影响深度的计算结果,确定了室内试验的干湿循环幅度并进行了膨胀土强度干湿循环室内试验,对干湿循环引起膨胀土强度指标衰减的变化规律进行了初步探讨;在此基础上,结合干湿循环效应对膨胀土边坡进行了稳定性分析。研究结果表明:(1)膨胀土的黏聚力随干湿循环次数递增而减小,第1～2次循环时黏聚力衰减程度最强,但经历2～3次循环后,黏聚力衰减程度减弱,最终趋向稳定;干湿循环次数引起内摩擦角的波动变化极小,基本保持一恒定值。(2)干湿循环的强度稳定值与稳定时所需循环次数均随含水率变化幅度的增加而减小。(3)由于干湿循环效应,膨胀土的粒间联结产生了不可逆的损伤,致使土体微结构劣化、抗剪强度降低。(4)随着干湿循环次数的增加,边坡稳定性降低,安全系数递减;结合当地大气影响深度对膨胀土边坡进行干湿循环分层的稳定性分析方法更符合工程实际,可为相关边坡设计和防护的计算参数选取提供参考。The wetting-drying effect of expansive soils plays an important role in slope stability analysis. This paper uses the field monitoring data of moisture contents of expansive soil slope and the calculation results of atmospheric influence depth at Nanling region. It then determines the wetting-drying circulate amplitudes of laboratory experi- ments. Laboratory tests on the soil strength are performed to discuss on the wetting-drying effect of expansive soil. Furthermore, the stability of expansive soil slope is studied taking into account the wetting-drying effect. The results show that the cohesion of expansive soil decreases with increasing number of cycles and its impact is especially ob- vious during the first and second cycles. After that, it reaches to a constant state. However, the friction angle keeps a stable value with little influence of the wetting-drying effect. It is also found that the value and cyclic num- ber of the constant state reduce with increase of amplitude of variation of water content. As wetting-drying cyclescause irreversible damages to soil intergranular links, the shear strength reduction of expansive soil is the result of micro-structural degradation. Furthermore, the slope stability and safe factor decrease with increasing number of cy- cles and the stability analysis method with considering the wetting-drying effect is more in line with the practical en- gineering.

关 键 词：膨胀土 干湿循环效应 边坡稳定性 大气影响深度 

分 类 号：TU443[建筑科学—岩土工程]