干湿循环下红黏土斜坡裂隙性和水土响应试验研究

Experimental study on fissure properties and soil-water response of red clay slope under dry-wet cycle

为研究干湿条件下红黏土裂隙发展规律,分析斜坡变形破坏机制,进行红黏土边坡室内干湿循环模拟试验。结果表明:(1)红黏土斜坡在干湿条件下裂隙率呈阶梯状增加,坡面和坡顶裂隙发展存在一定差距,4次循环期间坡面裂隙率逐渐由3%增加至14%,而坡顶最终裂隙率仅7%;(2)红黏土斜坡初始阶段渗透性极低,基本不透水,干湿循环过程中土体裂隙极大地增强了斜坡渗透性;(3)干湿循环使斜坡土体反复胀缩,土壤含水率变化量由5%增至20%,基质吸力增至350 kPa,胶结物质的流失及结构的破坏造成土体强度不可逆性降低;(4)裂隙的产生破坏了斜坡的整体性,降雨期间随着土壤含水率的增加,基质吸力减小,强度迅速降低,在雨水浸润下斜坡裂隙逐渐软化形成潜在滑面,从而引发局部失稳破坏。

In order to study the law of red clay fissure development under dry and wet conditions and analyze the mechanism of the slope deformation damage,an indoor dry-wet cycle simulation experiment on red clay slope is carried out and the result shows that(1)the fissuring rate of the red clay slope increases in steps under dry and wet conditions,a certain difference of the fissure development is there between the surface and the top of slope.The fissuring rate of the slope surface gradually increases from 3%to 14%during four cycles,while the final fissuring rate of the slope top is only 7%;(2)the permeability of the red clay slope at the initial stage is extremely low and basically impermeable,while the fissures inside soil mass during the dry-wet cycle greatly enhance the permeability of the slope;(3)the dry-wet cycle makes the soil mass on the slope repeatedly expand and contract with the increase of the change of the soil water content from 5%to 20%and the increase of the matrix suction to 350 kPa,and then the loss of cementitious material and the destruction of structure lead to the irreversible decrease of the strength of the soil mass;(4)the integrity of the slope is destructed by the fissure generation.During rainfall,the soil strength is rapidly reduced along with both the increase of the soil water content and the decrease of the matrix suction during rainfall and the slope fissure is gradually softened to form a potential sliding surface under rainwater infiltration and then causes local instability damage.