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用悬滴法对纯水、酒精溶液和肥皂水(表面活性剂)3种液体的表面张力进行测量,比较3种液体表面张力的大小;用躺滴法测量混有十八胺的两种土样的接触角。在此基础上,针对不同表面张力和接触角的膨胀土试样进行收缩开裂试验。试验结果表明:孔隙水表面张力和接触角对膨胀土的收缩开裂有重要影响。表面张力越小的试样,其最终收缩开裂裂隙度越小,但在裂隙发展阶段,脱湿时间相同时,孔隙水表面张力小的土样其收缩开裂裂隙度有可能大于表面张力较大的土样。增大土颗粒与孔隙水间的接触角可以很好的抑制膨胀土的收缩开裂,接触角越大,相同的脱湿时间下土体的收缩开裂裂隙度越小。减小孔隙水表面张力或增大接触角都会使土体中的弯液面曲率半径增大,从而减小土体中的基质吸力。接触角的增大还有可能使弯液面由凹变凸,基质吸力会因此消失,从而很好的抑制膨胀土开裂。
The surface tension of three liquids, pure water, alcohol solution and soapy water (surfactant), was measured by hanging drop method, and the surface tension of three liquids was compared. The two kinds of soil mixed with octadecylamine The same contact angle. On this basis, shrinkage and cracking tests were conducted on expansive soil samples with different surface tension and contact angle. The experimental results show that the pore water surface tension and contact angle have an important effect on shrinkage and cracking of expansive soils. The smaller the surface tension of the specimen, the final shrinkage cracking crack size smaller, but in the crack development stage, the same dehumidification time, the pore water surface tension of the soil sample shrinkage cracking fracture may be greater than the larger surface tension Soil samples. Increasing the contact angle between soil particles and pore water can restrain the shrinkage and cracking of the expansive soil well. The larger the contact angle is, the smaller the shrinkage and cracking of the soil under the same dehumidification time is. Decreasing the pore water surface tension or increasing the contact angle will make the radius of curvature of the meniscus in the soil increase, thus reducing the matrix suction in the soil. The increase of the contact angle may make the meniscus concave convex, so the matrix suction will disappear, so as to well suppress the cracking of the expansive soil.