土工格室加固风积沙路基动应力响应现场试验研究

Field Experimental Study on Dynamic Stress Response of Aeolian Sand Subgrade Strengthened by Geocell

由于沙漠地区环境较为恶劣,沙漠中自采筑路材料匮乏,导致沙漠公路建设困难,同时,风积沙颗粒细小且不稳定,风积沙地基的处理难度较大,采用土工格室对风积沙进行加固作为路床结构,可为沙漠公路的修筑提供一条新路径。为了探究土工格室加固风积沙路基的效果及不同路基层动应力特性,以S21乌鲁木齐至阿勒泰土工格室加固风积沙路基试验段为例,从不同测试车重和车速2个方面分析不同试验工况下各路基层的动应力衰减系数,根据动应力衰减系数提出土工格室-等代路基层厚度计算方法,对交通荷载作用下路基动应力响应规律进行研究。结果表明:交通荷载作用下动应力时程曲线接近于正弦波,随深度增加动应力时程曲线出现一定的滞后性;测试车重越大动应力越大,测试车速提高对动应力影响不大,因此,车辆轴载是路基动力响应的最主要的因素;对土工格室加固风积沙、级配砾石和风积沙3种不同路基填料动应力衰减系数进行对比分析,发现土工格室-风积沙层的衰减系数最大,级配砾石层次之,风积沙层的衰减系数最小;动应力衰减系数是一个与路基填料性质相关的常量,与测试车速和车重的关系不大,路基填料的性质对动应力衰减系数起决定性作用;根据动应力衰减系数提出了等代路基层厚度计算方法,提出土工格室加固风积沙与砾石土填筑层之间的厚度关系,利用等代工作区域厚度法验算土工格室加固风积沙路基持力层承载力。

Due to the harsh environment in desert areas,the lack of self-collected road construction materials in desert leads to the difficulty in desert road construction.At the same time,aeolian sand particles are small and unstable,aeolian sand foundation treatment is difficult,using geocell to reinforce aeolian sand as the road bed structure can provide a new path for the construction of desert highway.In order to explore the geocell reinforcement effect of aeolian sand subgrade and the dynamic stress characteristics of different subgrade layers,taking the test section of S21 Urumqi-Altay geocell reinforced aeolian sand subgrade for example,the dynamic stress attenuation coefficients of each subgrade layer under different test conditions are analyzed from the aspects of weight and speed of test vehicle.According to the dynamic stress attenuation coefficient,the calculation method of the thickness of the geocell-equivalent subgrade layer is proposed,and the dynamic stress response rule of the subgrade under traffic load is studied.The result shows that(1)The time-history curve of dynamic stress under traffic load is close to sine wave shape,it has certain hysteresis with the increase of depth.(2)The greater the weight of the test vehicle,the greater the dynamic stress.The increase of the test speed has little influence on the dynamic stress,therefore,vehicle load is the most important factor in the dynamic response of subgrade.(3)By comparing the dynamic stress attenuation coefficients of 3 subgrade fillings,it is found that the attenuation coefficient of geocell-aeolian sand layer is the largest,that of graded gravel layer is the second and that of aeolian sand layer is the least.(4)The dynamic stress attenuation coefficient is a constant related to the nature of subgrade filler,it has little relationship with the speed and weight of test vehicle,while the nature of the subgrade filler plays a decisive role in the dynamic stress attenuation coefficient.(5)According to the dynamic stress attenuation coefficient,the calculation method of the thickness of the equivalent subgrade is proposed,and the thickness relationship between the geocell reinforced aeolian sand and the gravel soil fill layer is proposed as well.The bearing capacity of the bearing layer of the geocell reinforced aeolian sand subgrade is checking calculated by using the equivalent working area thickness method.