摘要:
针对云南红土型水库因水位升降引起库岸土体干湿循环的客观实际,研究干湿循环作用下库岸红土抗剪强度与其微结构的变化规律,揭示二者之间的内在联系,为研究红土型库岸失稳提供依据。通过红土试样的干湿循环试验,模拟水库蓄水和库水位反复升降引起的库岸红土干湿循环作用。结果表明：（1）在一定初始干密度条件下,红土的黏聚力、内摩擦角和抗剪强度均随干湿循环次数的增加而非线性减小,但在干湿循环次数约10次时趋于稳定。（2）干湿循环作用导致红土微结构发生变化。当初始干密度分别为1.2,1.3,1.4 g/cm3、干湿循环次数达10次时,试样红土颗粒数量降幅依次为45.4%,38.2%,35.7%；孔隙率增幅依次为52.6%,45.9%,40.4%；孔隙面积增幅依次为64.4%,58.2%,50.8%。（3）在干湿循环作用下,红土黏聚力与红土颗粒的定向度和平均圆形度呈正相关关系,相关系数R分别为0.985和0.923。内摩擦角与孔隙率和孔隙面积呈反相关关系,相关系数R分别为-0.936和-0.912。干湿循环作用导致红土微结构的改变,从而引起红土宏观力学性质的变化。
Abstract:
In view of the objective reality of drying and wetting cycles which caused by the rise and fall of the reservoir water of the laterite reservoir in Yunnan, this article examines the change law of shear strength and microstructure of laterite under the action of drying and wetting cycles, and reveals the internal relationship between the shear strength and microstructure of laterite under the action of drying and wetting cycles. The results can provide the basis for studying the instability of the laterite reservoir. Simulation of the effect of drying and wetting cycles of red reservoir caused by reservoir water immersion and reservoir water level rise and fall is conducted by carrying out drying and wetting cycle tests of the clay sample and using geotechnical experiments and related theoretical analyses. The results show that: (1) Under certain initial dry density conditions, the cohesion, internal friction angle and shear strength of the laterite decrease with the increasing number of drying and wetting cycles, and it will keep stable when the number of times of drying and wetting cycles is 10. (2) The microstructure of the laterite is changed by drying and wetting cycles. When the initial dry density is 1.2, 1.3 and 1.4 g/cm3, respectively, the number of times of drying and wetting cycles rises to 10, the number of the laterite particles decreases by 45.4%, 38.2% and 35.7%, respectively, the porosity increases by 52.6%, 45.9% and 40.4%, and the pore area increases by 64.4%, 58.2% and 50.8%, respectively. (3) Under the drying and wetting cycles, there is a positive correlation between the cohesion of the laterite and the degree of orientation and average circularity of the laterite, and the correlation coefficients R are 0.985 and 0.923. There is a negative correlation between the internal friction angle and the porosity and pore area, and the correlation coefficients R are -0.936 and -0.912. The change of microstructure of the laterite is caused by drying and wetting cycles, which causes the changes in the macroscopic mechanical properties of the laterite.
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