高速公路特长箱涵顶进摩阻系数试验分析

Experiment Analysis on Friction Coefficient of Oversize Box Culvert Jacked into Highway Subgrade

当前浅覆土特长箱涵在高速公路中应用越来越多,而有关其顶进就位施工技术鲜有报道。结合广东某高速公路特长箱涵顶进工程实例,基于室内模型试验,对采取不同减阻措施的箱涵侧壁与周围土体介质间的摩阻系数进行了分析,研究表明:随涵周土体中含水量减小,箱涵侧壁与周围土体间的摩阻系数呈不断增大变化趋势;涵周土体最佳注浆量为1∶4,注浆量大于或小于1∶4均可引起箱涵侧壁与涵周土体间的摩阻系数增大;纳米聚合物、石蜡+机油混合物及油漆等减阻材料均能够有效减小箱涵侧壁与周围土体间的摩阻系数,在相同试验条件下,与纳米聚合物和油漆相比较,涂抹石蜡+机油混合物的减阻效果更为显著;浅覆土特长箱涵顶进施工建议采用石蜡+机油混合物减阻材料。

The application of shallow buried super-long box culverts now gradually gains its popularity in highway projects,but its jacking and construction technology is rarely studied and reported. Combined with a project example on oversize box culvert jacked into highway subgrade in Guangdong Province,laboratory model tests were conducted to analyze the fraction coefficient among the box culvert wall,surrounding soil and the skateboard when using different drag reduction materials. The result shows that with the decrease of water content in soil around the box culvert,the friction coefficient between side wall from box culvert and the soil shows a change trend of increasing; The optimal grouting slurry for soil around box culvert is equal to 1： 4,when the grouting quantity is greater than or less than 1： 4,it can cause the friction increasing; The friction can be effectively reduced,by using of drag reduction materials from polymer,mixture with paraffin wax ＋ engine oil and paint; In the same test conditions,compared with polymer and nanometer paint, the drag reduction effect on mixture with paraffin wax ＋ engine oil is moresignificant. Wax-oil mixture is recommended as the drag reduction materials when doing the jacking construction of shallow buried super-long box culverts.