高填方盖板涵受力特性的原位试验及数值模拟研究

摘要

通过现场测试,分析上埋式盖板涵在路堤填土荷载作用下的变形规律和受力特性;同时结合现场测试与数值模拟的方法,研究盖板涵顶板、基底土压力与侧墙水平土压力的分布特征.结果表明:在填土荷载作用下,涵洞顶板、底板垂直土压力以及侧墙的水平土压力呈非线性分布,其受力状态与规范计算的结果存在较大差异.由于涵洞与填土的模量不同,涵洞以上填土与两侧填土存在差异沉降,涵顶两侧墙土压力大于涵顶中部土压力,大于填土自重.数值模拟分析结果显示盖板涵土压力的分布特征与现场测试的分析结果一致,实际涵顶受力为涵顶附加摩擦力与填土自重之和;涵顶两侧墙分担了两侧填土竖向应力,涵洞侧墙水平土压力小于静止侧压力,实测平均值与铁路桥涵设计规范理论值的比值为0.53~0.87.由于地基土的不均匀沉降以及涵洞底板的挠曲变形,基底土压力呈非线性分布,跨中附近土压力产生卸荷现象.结合涵顶受力的理论研究与对包茂高速(粤境段)多个盖板涵涵顶数据的监测,提出了涵顶土压力的经验模型;该模型与涵顶上覆填土高度具有良好的线性关系,与现场实测值吻合较好.%Through in-suit stress measurement,the stress characterisitics of embankment installation slab-culverts under fill-load were studied.Combined in-suit stress measurement and numerical simulation,the distribution characteristics of earth pressure for slab culvert and bottom slab and the lateral earth pressure on side wall was analyzed.The results show that the distributions of pressure on the top slab,the bottom slab and the lateral walls of culverts are all nonlinear under the fill-load,they are significantly different from the results calculated by the standard.Due to the different modulus between culverts and the fill,the settlement of the culvert and the fill above the top slab is different.Earth pressure of both sides of top slab is bigger than the middle slab,and bigger than self-weight of the fill soil;the result of the numerical simulation shows that the distribution characteristics of earth pressure for slab culvert is consistent with the in-suit test's analysis.The actual earth pressure on the top slab equal to the sum of the self-weight of the fill soil and the additional friction.The self-weight of the fill soil which on both sides and above the top of the culvert slab is shared by culverts,so the lateral earth pressure on side wall is smaller than the static earth pressure.The measured average of the lateral earth pressure on side wall is about 0.53~0.87 times as much as design value of the specification of Railway Bridges and Culverts Lateral earth pressure on the wall of culverts smaller than static earth pressure;Because of the uneven settlement of foundation and the flexure deformation of culvert's baseplate,the distributions of foundation pressure is nonlinear,the pressure on the middle of the bottom slab exists unloading effects.Combined with the theory research and the monitoring-datas of the vertical earth pressure on the top of several culvers for BaoMao express way (the guangdong section),a linear empirical model is put forward.The model has a good linear relationship with the height of the fill soil that above the top of culverts,and the results calculated with the empirical formula are in good agreement with the measured values.