煤矸石固化膨胀土干湿循环累积损伤特征

Cumulative Damage Characteristics of Coal Gangue Solidified Expansive Soil under Dry and Wet Cycling

膨胀土在外界环境中产生裂隙易造成基础设施损坏。从多场角度,利用煤矸石改良膨胀土,模拟不同湿度和温度下土样的裂隙发育试验,通过摄影及MATLAB对土样表面图像定量化分析,结合显微镜扫描裂隙表面,探讨多场耦合下膨胀土累积裂隙发育规律。结果表明,经过6次干湿循环,改良膨胀土比素膨胀土的裂隙率、裂隙总长度、裂隙平均宽度峰值在常温干燥时分别降低32.6%,67.3%和18.49%;3个裂隙参数的峰值在高温干燥时分别降低15.5%,32.6%和10.2%,煤矸石改良膨胀土约束裂隙的发展,而高温作用会促进裂隙的发生发展。20℃干燥后改良膨胀土不但裂隙率和裂隙平均宽度累积值减少明显,且裂隙面高度提高了394.3%,而50℃干燥条件增加了裂隙总长度的发育,因此干湿循环造成膨胀土产生累积裂隙,掺入煤矸石提高膨胀土样内部摩擦性能,高温降低了颗粒热稳定性,改变了膨胀土体的累积损伤参数。

Cracks in expansive soil are easy to damage infrastructure in the external environment.From the perspective of multiple fields,coal gangue is used to improve expansive soil,and the crack development test of soil samples under different humidity and temperature is simulated.The quantitative analysis of surface image of soil samples is conducted by photography and MATLAB,combined with the scanning of crack surface by microscope,and the cumulative crack development law of expansive soil under the multi-field coupling is discussed.The results of the investigation showed that,after six dry and wet cycles,the peak values of fracture rate,total length of fracture,and average width of fracture of the modified expansive soil were reduced by 32.6%,67.3%,and 18.49%than the plain expansive soil,respectively,when drying at room temperature;and the peak values of three fracture parameters were decreased by 15.5%,32.6%,and 10.2%,respectively,when drying at high temperature,the coal gangue-improved expansive soil constrained the development of the fracture,while the high temperature promoted the development of fissure occurrence.After drying at 20℃,the improved expansive soil not only has a significant decrease in the fracture rate and the cumulative value of the average width of the fracture,but also has a 394.3%increase in the height of the fracture surface,and the drying condition at 50℃increases the development of the total length of the fracture.Therefore,the dry-wet cycle causes the formation of cumulative cracks in the expansive soil,and the addition of coal gangue improves the internal friction properties of the expansive soil sample.High temperature reduces the thermal stability of granular and changes the cumulative damage parameters of expansive soil.