倾滑断层对公路的致灾机理分析

Study on the break-down mechanism of road structure induced by dip-slip active fault

在有限元分析的基础上,对正断层和逆断层环境下公路的致灾机理进行了研究。结果表明,断层的活动将引起公路结构的弯曲变形,使公路处于拉、压、剪的受力状态。共中,正断层活动引起公路弯曲变形的范围主要为上盘距裂缝70 m至下盘距裂缝30 m,纵向应力剧增的主要范围为上盘内距裂缝170m 至下盘内距裂缝130 m,路面的开裂位移约为22 cm;逆断层活动时,公路弯曲变形的范围为上盘内距裂缝80m至下盘内距裂缝 40 m,纵向应力剧增的主要范围是上盘内距裂缝170 m至下盘内距裂缝180 m,路面的开裂位移约为12cm。根据公路的变形和受力规律,将正断层和逆断层环境下公路的破坏模式概化为张拉破坏、剪切破坏、弯曲压坏和复合破坏几种类型。按载荷-结构的方法,将上、下盘范围内的公路结构当作受均匀荷载的半无限弹性地基梁,把倾滑活断层环境下公路结构的位移、转角、弯矩、剪力等简化为断层地表竖向位移量、地基系数、路面荷载、路基路面等效刚度的函数。进行了算例分析,计算结果表明,断层活动主要使裂缝带的公路承受较大的变形、弯矩和剪力,这种影响范围主要分布在断层裂缝的两侧各30 m内。

The purpose of this paper is to report our research findings on the break-down mechanism of road structure induced by dip-slip active fault with a finite element model developed and established. The analysis result shows that due to the activity of dip-slip breakdown, the road structure was bended, which induced the tension of the upper block of the road and the compression of its lower block. And situated on the fissure of the road suffered the deformation due to the shearing hit. More specifically speaking, the normal fault induced the road bended in place of 70 m in upper block to 30 m in lower block, and such deformation increased the lengthwise direction stress in place of 170 m in upper block to 130 m in lower block away from the fissure, and with the yielded displacement of road is about 22 cm. However, in the environment of compressed fault, the bended road may still remain in the range of 80 m in upper block to 40 m in lower block, with the increased stress being in place of 170 m in upper block to 180 m in lower block away from its original fissure and the yielded displacement of road about 12 cm. and then, based on its distribution of stress and deformation, the failure modes of road are obtained which would be generalized as tensioned, sheared and bended-compressed, complex failure. However, when the method is used to analyze the deformation, stress and strain distribution of the road, the structure of the road should be predigested as a semi-infinite elastic grade beam which is expected to withdraw or endure asymmetrical distribution load and its displacement, angle and moment of flexion, shear force, etc. , induced by the dip-slip active fault. And, finally, a sample case has been analyzed, whose calculated results indicate that the road in fault fissure belt tends to be able to endure the maximul deformation, shear force and flexural torque, the incidence of active fault are mainly distributed in the sphere of 30 meters away from the fissure at every block.