高速公路软基超载预压路段的卸载控制研究

Study on unloading control method during surcharge preloading for soft foundation in highways

堆载预压的卸载时机判断一直是公路工程建设中的难点问题,何时卸载才能在保证工期的前提下满足工后沉降的要求是核心内容。结合对申嘉湖杭高速公路(练杭段)的现场观测,通过提出"超载效应因子"的概念,总结了填土高度和超载预压时间对超载路基沉降的作用规律,并采用Sep98沉降预测程序对软基沉降进行了预测。结合规范中相关卸载控制标准,进一步提出了该地区超载预压软基路堤的卸载标准。结果表明:"超载效应因子"可以更为精确地描述预压期内任一时刻下地基的实际荷载状态,该因子越大,其对应的超载下沉降速率的控制标准也越高。在同一超载效应因子下,随着预压时间的增加,软土路基的工后沉降会逐渐减小。

It is difficult to determine the discharge time about the surcharge preloading method in highway construction.On condition that the time limit for the project can be guaranteed,the unload time that can meet the demands of post-construction settlement is the key elements.With the field observation data about the Shen-Jia-Hu-Hang high-way(the Lian-Hang part),the idea called"overloading effect factor"was proposed.Based on the full analysis of settlement and the field data,this paper summarized the role of filling height and surcharge preloading time on settlement rules of overloading foundation.And the results were contrasted to the forecasting results of the Sep98 to check the prediction accuracy of the Sep98 procedure.According to the analysis of results,with the relative load discharging rule in the specifications,the load discharging rule for surcharge preloading soft clay foundation in this area was proposed in the paper.The results showed that the"overloading effect factor"can accurately describe the actual load of foundation at any time under the precompression period.The factors are higher,the corresponding overload under the settlement control standard rate is also higher.Under the same"overloading effect factor",with the increase of preloading time,the settlement of soft soil subgrade will decrease gradually.