摘要:元谋干热河谷区变性土的裂缝发育对沟蚀崩塌和植被恢复影响显著。通过室内对变性土收缩变形和裂缝发育的测定及干湿循环下的直剪试验,研究了变性土收缩变形对裂缝发育及土体抗剪强度的影响。结果表明,变性土失水导致土体收缩变形,收缩特征曲线呈显著的三直线模型。变性土的收缩变形与土壤中黏粒和黏土矿物含量密切相关。变性土收缩变形不均导致裂缝的出现,随着含水量的逐渐降低,裂缝条数(N)逐渐减少,裂缝面密度(A)逐渐增加。土体裂缝的发育与基质吸力的大小密切相关,当基质吸力 < 1000 kPa时,裂缝面密度显著增加。裂缝条数和面密度与土壤含水量分别呈较好的指数函数和Sigmoidal函数关系(R_N~2 = 0.968,P_N = 0.0004;R_A~2 = 0.963,P_A = 0.01)。裂隙发育,导致变性土黏聚力(c)和内摩擦角(phi)随干湿交替的进行呈不断减小的趋势,但内摩擦角下降速度明显低于黏聚力。黏聚力和内摩擦角与循环次数呈较好的反比例函数关系(R_c~2 = 0.979,P_c = 0.0002;R_phi~2=0.807,P_phi = 0.015)。该研究可为进一步研究土壤开裂导致的沟蚀崩塌提供理论基础。

Gully erosion, collapse and vegetation restoration are influenced significantly by crack development of vertisol in Yuanmou Dry- hot Valley. Effects of contraction and deformation of vertisol on crack development and shear strength were investigated by measuring the shrinkage deformation and crack development of vertisol under drying, and by direct shearing test under soil wetting and drying cycle in laboratory. The results showed that contraction and deformation of vertisol were caused by its moisture loss. Three straight lines model was very well fitted to the contraction characteristic curve of vertisol. The contraction and deformation of vertisol were significantly related to the contents of clay and clay minerals in soil. The uneven shrinkage deformation of vertisol led to crack occurrence. The number of cracks (N) gradually decreased and crack area density (A) gradually increased with soil moisture loss. Crack development of vertisol was strongly linked with the soil matric potential. The crack area density significantly increased when the matrix potential was less than 1000 kPa. The number of cracks and crack area density had good relationships of exponential and Sigmoidal functions with soil moisture (R_N~2 = 0.968, P_N = 0.0004; R_A~2 = 0.963, P_A= 0.01), respectively. Cohesion (c) and friction angle(phi) of vertisol gradually decreased with the increase of wet and dry cycle times because of crack development, and the reduction rate of friction angle was apparently lower than that of cohesion. Both the cohesion and friction angle showed significant relationships of inverse proportion function with wet and dry cycles (R_c~2 = 0.979, P_c = 0.0002; R_phi~2 = 0.807, P_phi = 0.015). These results could provide theoretical references for the further study on the gully erosion and collapse caused by soil crack.