基于土压力集中效应的超厚填土明洞荷载计算方法研究

Study on the earth pressure load theory for open cut tunnels beneath super high fill based on earth pressure concentration effect

随着高速铁路进入山区城镇,面临着高填、深挖,与市政或城区规划结合建设的问题,出现了超厚填土明挖隧道的案例,目前规范中没有针对超厚填土明洞土压力的计算方法,其荷载标准和计算取值无经验可循。本文依托某超厚回填土铁路明洞隧道,通过数值仿真及现场试验对竖向土压力变化规律及影响因素进行了分析和研究,得出结论如下:(1)回填土荷载不仅与填土高度有关,而且同结构和土体刚度相关;(2)通过土压力的影响因素及作用机理分析,明确了洞顶平面内外土柱沉降差为土压力的关键影响因素;(3)提出明洞竖向土压力大于洞顶土柱重量的土压力集中效应规律,证明了洞顶内外土柱沉降差对明洞产生了附加土压力;(4)提出了指导设计的土压力集中系数变化曲线及土压力计算公式。本研究成果可为明挖隧道结构设计和施工提供借鉴。

Along with the high-speed railways have entered into mountain cities,a series of problems have emerged with high filling、deep digging、the construction combined with municipal engineering and urban planning,consequently some projects of super high backfill urban open cut tunnel have been springing up. So far there is no design specification for the calculation method of earth pressure load of super high backfill open cut tunnel,the load standard and calculation value have no experience. This paper relies on an open cut tunnel engineering of some high-speed railway,by means of numerical simulation and field earth pressure load test,the change law and influencing factors of vertical earth pressure load has been analyzed and studied. The conclusions are as follows:( 1) the paper concludes the law that backfill earth load is not only related with the earth filling height,but also with the stiffness of tunnel structure and backfill earth.( 2)In virtue of study on the influencing factors and mechanism of the vertical earth pressure,the differential settlement of inner and outer earth column on roof of cave conducts key influences on the earth pressure has been made clear.( 3)The law of earth pressure concentration effect is put forward that the vertical earth pressure is greater than the total weight of the earth column on the roof of tunnel,and it indicates that the differential settlement of inner and outer earth column on roof of cave produces additional earth pressure on the open cut tunnel.( 4) Finally the earth pressure concentration coefficient curves and calculation formula of earth pressure are proposed for guidance of design of structure. The study results can be widely used into design and construction of open cut tunnel structure.