反复冲击压缩高岭土动力特性SHPB试验

SHPB Experiments of Kaolin Clay Dynamic Responding Under Repeated Impact Compressive Loadings

为了探明软黏土在反复冲击压缩荷载作用下的动力响应,利用SHPB (Split Hopkinson Pressure Bars)试验技术,建立高岭土SHPB试验系统,进行反复冲击压缩试验。通过比选确定合理的试样厚度、整形器和冲击速度用以提高试验结果的精度;开展了7组不同厚度、含水率和冲击速度的高岭土试样测试,试样厚度分别为10,15 mm,含水率分别为24%、29%和36%,冲击速度分别为3,5 m·s-1。试验结果表明:含水率29%的试样,冲击速度为5 m·s-1更有利于试样应力均匀性的实现,反复冲击次数的增加亦提高了试样的均匀性,在反复冲击后,试样应变量下降约16%,而应力峰值提高了约30%;反复冲击过程中,高岭土试样的应变出现软化现象,随着冲击次数增加,试样的应变峰值经历"降低-上升-降低"的过程;平均应变率与含水率反相关,相同试样厚度下,冲击速度为5 m·s-1,含水率为24%的试样反复冲击下的平均应变率最大为210 s-1,冲击速度为3 m·s-1,含水率为24%的试样的平均应变率依然最大为177 s-1;高岭土试样的压缩波速主要受含水率的影响,含水率越高,波速越大,含水率为36%的试样波速最大值为313 m·s-1,厚度为10 mm的试样能更有效获取冲击压缩波速。

A series of repeated impact compressive experiments were carried out based on a Split Hopkinson Pressure Bars(SHPB) system to clarify the dynamic response of kaolin clay under repeated impact loading.An SHPB testing framework for clay soil was built.To complement shaping and uniformity issues,specimen thickness and impact velocity were theoretically analyzed.Seven sets of kaolin clay experiments were carried out in which water contents were 24 %,29 %,and 36 % and the impact velocities were 3 m·s-1 and 5 m·s-1,respectively.The thicknesses of these specimens were 10 mm and 15 mm.The analyzed results are shown as follows;① The specimen in which water content was 29% responded well for stress balance under an impact velocity of 5 m·s-1.The impact numbers increased specimen uniformity.The level of specimen strain decreased by approximately 16% and the stress magnitude increased by approximately 30% when the water content was 29% and impact velocity 5 m·s-1.② The softening of the kaolin specimen during repeated impact and strain top developed a ‘down-updown’ route.③The relationship between the mean strain rate and water ratio was negative.For the 24% water ratio specimens,the maximum mean strain magnitudes of the specimen were 210 s-1 under 5 m·s-1 and 177 s-1 under 3 m·s-1,respectively.④The compressive wave velocity of kaolin clay was linked to the water content of the specimen.In addition,it was determined that the higher the water ratio levels,the higher the wave velocity.The maximum value of the wave velocity was 313 m·s-1 for the 36 % water content specimen.The effective thickness was 10 mm to calculate a more reasonable compressive velocity than that of the 15 mm thickness.