气候边缘地带膨胀土强度特性随冻融循环劣化规律

Deteriorating law of strength properties of expansive soil in climate marginal zone with freeze−thaw cycles

为了探究冻融循环对膨胀土静力特性的影响,以河南平顶山膨胀土为研究对象,开展不同初始含水率下膨胀土冻融循环试验,并对冻融循环后的膨胀土试样进行不固结不排水(UU)三轴剪切试验。研究结果表明:土体初始含水率变化对冻融循环后的膨胀土应力−应变关系、抗剪强度指标有显著影响;应力−应变关系随冻融次数的增加呈现出由强应变硬化型向弱应变硬化型发展的趋势;在高初始含水率下,膨胀土破坏强度、黏聚力随冻融循环次数的增加整体呈现出先快速衰减后趋于稳定的变化趋势,冻融稳定阶段黏聚力约为初始黏聚力的72.5%(含水率w=20%)和57.0%(w=23%),低含水率状态下膨胀土内摩擦角呈现出随着冻融次数增加而增大的趋势。最优含水率(w=20%)状态下,冻融稳定后膨胀土弹性模量为初始弹性模量的60.31%~64.77%。

To explore the influence of freeze−thaw cycles on the static properties for expansive soil,taking Pingdingshan expansive soil as the research object,triaxial shear tests(UU)of expansive soil samples with freeze−thaw cycle under different initial conditions were carried out.The results show that the variation of initial moisture content has obvious influence on the stress−strain relationship and shear strength parameters of the expansive soil subjected to freeze−thaw cycles.With the increase of the freeze−thaw cycle numbers,the stress−strain relationship shows a trend from strong strain hardening to weak strain hardening.Under the condition of high moisture content,the failure strength and cohesion of expansive soil show a trend of rapid decay and then gradual stabilization with the increase of the number of freeze−thaw cycles.The cohesive force at freeze−thaw stable stage is about 72.5%(w=20%)and 57.0%(w=23%)of the initial value.The elastic modulus of the expansive soil at freeze−thaw stable stage is about 60.31%−64.77%of the initial elastic modulus under the optimal moisture content(w=20%)condition.