换填与降排水措施对寒区沟谷软弱路基冻结特征的影响
Effect of replacing-filling and dewatering-draining measures on frozen characteristics of weak subgrade in cold valley region

基于甘肃南部宕昌-迭部二级公路,选取了2个典型寒区沟谷软土路基试验段,监测了2个冻融期内路基温度、含水量、变形以及地下水位,分析了弃渣换填深度与降排水措施对路基冻结特征的影响。分析结果表明:在监测的2个冻结期内,换填深度为2.0 m的试验段K18+180的冻结深度比换填深度为1.0 m的试验段K18+330的冻结深度大0.12～0.16 m,说明换填深度越大,冻结深度越大; K18+330段初始地下水位为3.4 m,仅设置地表排水沟时,冻结期间地下水位稳定在3.4 m左右,距冻结面的最小距离为1.7 m,说明设置排水沟时地下水位在冻结期间基本没有变化; K18+180段初始地下水位是1.3 m,在设置了渗沟降水措施后,冻结期间地下水位稳定在2.0 m左右,距冻结面的最小距离为0.2 m,地下水位降低了约0.7 m,因此,渗沟降水可以降低地下水位,防止路基冻胀; K18+180段路基中心2个周期监测的最大冻胀分别为3.4、4.2 mm,而K18+330段相应位置的最大冻胀分别为10.7、14.0 mm,后者均是前者的3倍多,说明换填深度越大路基冻胀越小; 《公路路基设计规范》(JTG D30―2015)规定的二级公路容许冻胀为50 mm,软土路基容许工后沉降为500 mm,K18+180、K18+330段路基的最大沉降分别为1.5、1.8 mm,最大冻胀分别为4.2、14.0 mm,远远小于规范值,表明试验段路基的稳定性良好,采用换填与降排水措施能有效控制路基冻胀。
Based on the Tanchang-Diebu Secondary Highway in South Gansu, two typical soft soil subgrade test sections in the cold valley region were selected, the subgrade's temperature, moisture content, deformation and the groundwater level were monitored, and the influences of the muck gravel soil's replacing-filling depth and dewatering-draining measure on the frozen characteristics of the subgrade were analyzed. Analysis result indicates that in the two monitored frozen periods, the maximum frozen depths at the test section K18+180 with 2.0 m-replacing-filling thickness is 0.12-0.16 m deeper than those at the test section K18+330 with 1.0 m-replacing-filling thickness, so the bigger the replacing-filling thickness is, the bigger the frozen depth is. For the test section K18+330, the initial groundwater level is 3.4 m. When the surface drains were only adopted, the groundwater level in the frozen periods is about 3.4 m, and the smallest distance to the frozen surface is 1.7 m, which shows that the surface drains scarcely affect the groundwater level in the frozen periods. For the test section K18+180, the initial groundwater level is 1.3 m. When the seepage ditches are adopted, the groundwater level in the frozen periods is about 2.0 m and reduces by 0.7 m, and the smallest distance to the frozen surface is 0.2 m, therefore, the seepage ditches can reduce the groundwater level and prevent the frost heave of the subgrade. The maximum frost heaves of the center of the test section K18+330 are 3.4 and 4.2 mm in the frozen periods, respectively, and the values of the test section K18+180 at the relevant position are 10.7 and 14.0 mm that are more than three times as much as the formers, respectively, therefore, the bigger the replacing-filling thickness is, the smaller the frost heave of the subgrade is. The maximum frost heaves of the test sections K18+180 and K18+330 are 4.2 and 1.4 mm, respectively, the maximumsettlements