贵州石漠化地区降雨条件下红粘土剪切强度特性随含水量变化关系探讨

西南喀斯特地区的石漠化已经严重影响了人民正常的生产生活。水土流失是石漠化过程中一个关键环节。喀斯特地区地表广泛覆盖的红粘土在降雨条件下随着含水量的增加和人工垦殖的影响，剪切强度会产生变化，更易发生水土流失。本文以贵州普定石漠化研究区（陈旗村）的红粘土为例，以原状土模拟未经扰动的土样，以重塑土来模拟经过开垦被扰动后的土样，设计了原状土和重塑土在不同含水量下的直剪试验，初步地研究了这一变化规律。结果表明:在含水量大于35%时，石漠化地区红粘土粘聚力和内摩擦角均随着含水量的增加显著降低；在同一含水量水平下，原状土的抗剪强度明显优于重塑土，且随着含水量的增加，重塑土的强度衰减较之原状土快许多，表明了经过人工垦殖后的红粘土在降雨条件下更易发生水土流失。

CHANGING OF RED CLAY SHEAR STRENGTH WITH WATER CONTENT UNDER RAINFALL IN KARST ROCKY DESERTIFICATION AREAS, GUIZHOU PROVINCE

Karst rocky desertification in the southwest of China has seriously influenced local people's life. Essentially, soil erosion is the key causing rocky desertification. The red clay, which widely distribute in karst region, is more easily to be eroded under the rainfall, because it's shear strength is changeable with water content. This paper presents a comparative analysis of direct shear test for undisturbed and remolded soil samples (modeling the reclaimed soil). The analysis preliminarily reveals the laws of the shear strength of red clay changing with water content. It is found that whenits water content 35%, the the cohesion and internal friction angle of the red clay decrease with the increasing of water content. The shear strength of undisturbed soil is significantly larger than that of the remolded soil under the same water suction. As water content increases, the shear strength of the remolded soil samples attenuates more drastically than that of the undisturbed soil. It shows that the reclaimed red clay is more easily to be eroded under the rainfall. 