可发性聚苯乙烯板减载条件下高填方箱涵长期受力特征与减载效果

Long-term stress characteristics and load reduction effect of high-fill box culverts with EPS slabs

在高填方箱涵顶部铺设可发性聚苯乙烯(expandable polystyrene,简称EPS)板降低其荷载已经在工程中得以应用,而EPS板的蠕变会使箱涵受到的土压力随时间发生变化。现有的箱涵设计理论未能明确的反应EPS板的长期减载效果以及箱涵长期受力特性。开展了EPS板减载条件下箱涵短期受力特性模型试验,并利用模型试验结果验证数值模型。之后利用验证后的数值模拟方法分析涵-土体系应力重分布规律以及高填方箱涵长期受力特征;在此基础上提出涵-土体系力学模型,推得涵顶长期土压力计算方法,并与数值模拟结果进行对比验证。研究表明:涵顶土压力先随时间逐渐减小,然后会出现小幅增大,最终趋于稳定,对比填土完成时土压力减小了52.12%;涵侧竖向土压力和水平土压力总体上均随着时间逐渐增大并趋于稳定,涵侧上部范围内最终水平土压力比填土完毕时增长了28.32%;基底土压力也是先增大后趋于稳定。实际工程中侧墙的设计应考虑EPS板蠕变引起水平土压力的增加,避免箱涵侧墙在长期使用中产生受弯破坏。

Laying expandable polystyrene(EPS)slabs on the top of high-fill box culverts to reduce earth pressure has been used in engineering practice,but the creep of EPS slabs will cause the earth pressure on the box culvert to change over time.The present design theory of box culverts cannot clearly reflect the long-term load reduction effect of EPS slabs and the long-term stress characteristics of box culverts.In this analysis,model tests were carried out to investigate the short-term stress characteristics of the box culvert with EPS slabs,and a numerical model was validated by the model test results.Then the verified numerical simulation method was used to analyze the stress redistribution of the culvert-soil system and the long-term stress characteristics of the high-fill box culvert.On this basis,the mechanical model of the culvert-soil system was proposed,and the calculation method of long-term earth pressure on the top of the culvert was deduced and compared with the numerical simulation results for verification.The research results showed that the earth pressure on the top of the culvert decreased gradually with time,then increased slightly and finally became stable.Compared with the earth pressure at the completion of filling,the long-term earth pressure decreased by 52.12%.The vertical and horizontal earth pressure on the culvert side increased gradually with time and tended to be stable,and the long-term horizontal earth pressure in the upper range of the culvert side increased by 28.32%compared with that when the filling was completed.The foundation contact pressure also increased slightly at first and then tended to be stable.The increase of horizontal earth pressure caused by the creep of EPS slabs should be considered in the design of sidewalls in practical engineering so as to avoid bending failure of box culver sidewalls in the long-term use.