泥岩路基填料强度的干湿循环效应

Wetting-drying Cycle Effects on Filler Strength of Mudstone Subgrade

泥岩是一类遇水易崩解的岩土材料,崩解前呈现岩石特征,但崩解后呈现泥质特性.故实际工程中需要掌握泥岩崩解前后的力学性能变化幅度.以取自洞新高速泥岩为研究对象,开展了击实和强度试验,并进行直剪强度的干湿循环效应研究.结果表明,泥岩遇水泥化,强度急剧衰减;击实曲线呈明显的双峰特征.干湿循环对泥岩的强度特性有着显著的影响,粘聚力随干湿循环次数的增加而增大(增长幅度为95.8%),内摩擦角则随干湿循环次数增加而减小(减小幅度为26.5%),但总体上还是弱化了泥岩的抗剪强度.结合试验结果分析,建议取最大含水率22.6%,最大干密度1.56g/cm^3为实际填筑的控制标准.研究同时表明,当干湿循环次数达到12次附近时,干湿循环对泥岩粘聚力和内摩擦角作用的影响程度减弱.

As a kind of geotechnical material,mudstone’s road performance vary widely;many unfavorable engineering properties appear under the wetting-drying cycles in atmospheric particularly.However,it is difficult to avoid to use mudstone as roadbed filler material in actual project.To reveal the effect of the mechanism of wetting-drying cycle effect will have important significance in the control of the embankment filling.Taking the mudstone in Dongxin high-speed subgrade as objects,the direct shear strength variation research of mudstone at different degrees of compaction and moisture conditions are carried out;and typical working conditions are selected to explore its direct shear strength under wetting-drying cycle effects;and analyzed its water sensitivity from compaction curve,particle composition,contrast liquid and plastic limit,CBR intensity changes.The results show that the mudstone begins to mud when suffer water;its strength attenuates sharply.Mudstone’s compaction curve is obviously a bimodal curve,in view of characteristics that mudstone can easily disintegrate,in order to ensure standards of project quality,maximum moisture content of 22.6%is recommended;taking the maximum dry density of 1.56g/cm3 as control standards.Wetting-drying cycles have a significant effect on the strength properties of mudstone.Its cohesion increases with the increase of wetting-drying cycles;while the internal friction angle decreases with the increase of wetting-drying cycles.The sample structure begins to stabilize when the number of cycles up to 12,the effect of wetting-drying cycle weakens.The real effects of wetting-drying cycles is the destruction of the original particle structure;onthe one hand it enhances the cohesion of the disintegrating mudstone,the growth reaches 95.8%,on the other hand the internal friction angle reduces,the reduction is 26.5%.In general,wetting-drying cycles weaken the shear strength of mudstone.