干湿循环作用下黄土节理裂隙发育扩张的机制研究

Mechanism Fractured Loess Expansion Joints under the Effect of Wet-dry Cycle

黄土体中的裂隙对其工程性质有很大的影响,一方面使土体的整体性减弱、强度降低;另一方面裂隙增加了土体的临空面,加剧了大气营力对土体的影响,使水分的入侵和土体的风干更为剧烈,因此研究干湿循环作用下黄土节理裂隙发育演化的机制具有重要意义。在延安市安塞县取样,通过CT扫描成像技术研究土样不同干湿循环次数下土样内部裂隙的演化规律,在此基础上探讨黄土体节理裂隙发育扩张的机制。研究结果表明:随着干湿循环次数的增加,土样CT数的ME值不断减小,SD值不断增大,4次干湿循环后,裂隙逐渐停止发育。土体产生裂隙的机制是在湿温耦合作用下,土体含水量在空间分布不均匀,进而产生较大的水力梯度,然后在土体内部产生拉应力;当土体某处的拉应力大于该处的抗拉强度时,裂隙就会产生。

Loess body fracture has a great influence on the nature of the project,which weakes the integrity of the soil,lower intensity,on the one hand increases fracture free surface soil,on the other hand exacerbates the at-mosphere of the camp forces on soil,renders the moisture intrusion and air-dried soil.It^s of great significent to study on the mechanism under wet and dry cycles in the loess joints fractured evolution.Ansai County in Yanran City,samples were scanned by a CT in different soil samples soil samples of wet and dry cycles evolution of fis-sures.The mechanism of loess joints fractured expanded was explored on this basis.The results show that,with the increase of wet and dry cycles,ME values of soil samples CT numbers continue to decrease,SD value is increas-ing,after four cycles of wet and dry,crack and gradually stops growing.Soil from cracking mechanism is in the wet temperature coupling effect of soil moisture content in the spatial distribution is uneven,and thus have a greater hy-draulic gradient,then tensile stress in the soil inside,when tensile stress is greater than the soil somewhere when there's tensile strength,cracks will be generated.