铁路鼎式路基结构分析方法

鼎式路基结构是通过同一板体将上部低矮的U型槽结构与下部中空的箱型结构连接为一体的新型路基结构，适于填高较大、用地局限及软弱地基的情况。为合理确定此新结构的理论计算方法，基于极限平衡理论，并结合水平条分法，分析推导出两类路基宽度下的上部槽内填土土压力与路面荷载附加应力的计算方法，进而将鼎式结构分解为上部结构与基础梁结构分别分析，前者可简化为平面刚架结构，后者可视为弹性地基梁结构，从而通过结构力学的力法与Winkler弹性地基梁理论分别对其求解，其间考虑了基础梁与上部结构的变形协调，且可分析地基差异沉降引起的上部结构附加内力与位移，并基于拟静力法分析路基结构整体地震稳定性。实例分析表明，理论分析与数值模拟结果整体上基本一致，结构内力的理论值比模拟值约高出3%～16%；地基差异沉降引起的上部结构附加内力一般不可忽视。在路基总高度不变的情况下，上部底板、基础板及腹板厚度均宜薄，所取的腹板高度应使上部底板与基础板最大弯矩之和最小，基础板外伸比宜为30%左右，以此优化鼎式结构型式。

Analysis method for a Quadra-pot-shape structure of railway earthworks

The Quadra-pot-shape earthworks structure is a reinforced concrete works composed of an upper part of short U-shaped structure and a lower part of hollow box structure which are connected by a shared plate. The novel earthworks structure is suitable for situations of high fill, limited land and soft ground. In order to determine theoretical calculation method of the structure reasonably, earth pressure and additional stress of pavement load on the upper U-shaped part for two earthworks widths are provided based on the limit equilibrium theory in conjunction with horizontal slice method of the fill. Furthermore, the Quadra-pot-shape structure is decomposed logically into a foundation beam part and the part on it. The former can be regarded as a beam on elastic ground which may be solved by Winkler foundation beam model, while the latter can be simplified as a planar rigid frame which may be solved by the force method of structural mechanics. For the analysis of the Quadra-pot-shape structure, deformation compatibility between the foundation beam and the upper structure shall be fully taken into account, and additional internal forces and deformation of the upper part of the structure due to uneven ground settlement can be determined. Besides, overall seismic stability of the earthworks structure is analyzed using the pseudo-static method. Analysis results show that the proposed theoretical solutions are basically consistent with the numerical ones, and internal forces of the structure predicted by the proposed method are about 3%～16% higher than those by numerical simulation method. Additional internal forces and deformation of the upper structure owing to uneven ground settlement shall not be ignored in most cases. In the case that the total height of earthworks is constant,configuration of  the Quadra-pot-shape earthworks structure can be optimized by reducing the upper bottom plate, foundation plate and webs as thin as possible, adjusting height of the webs to minimize the sum of the maximum bending moment of the upper bottom plate and foundation plate and controlling the ratio of extension length of the foundation plate at each end to its basic length between the two webs as about 30%.