偏压荷载作用下顶管力学响应及其影响因素

为明确顶管偏压受荷力学特性及其影响因素,分析顶管偏压受荷的承载模式,以工程实例为依托,建立顶管偏压作用下的精细计算模型,计算分析顶管在不同偏压模式下的力学特征、破坏形态及机理,并通过模型试验验证,探讨顶管偏压受荷力学响应的影响因素,且提出了顶管偏压的控制措施。研究表明:偏压荷载作用下,(1)管道轴向偏心起拱,接头处呈现单侧挤压、对侧张开,管道接触面应力集中、应变局部化;(2)单侧偏压作用效应主要表现为轴向的压剪效应,对角偏压作用效应则为对角的拉剪效应;(3)管道表现为接头处局部先开裂甚至破碎,后逐渐向中部发展的渐进破坏;(4)管道结构拉应力与偏斜角度呈同向线性关系,当管道径长比较小时,单侧偏压诱发的结构损伤较对角偏压大,且随偏斜角度的增大越发的明显;(5)管道接触面随偏斜角度的增大,分布特征经历近梯形分布→马鞍形分布→椭圆形分布的演化过程,可基于设计偏斜角度对应的影响敏感区特征制定预防偏压措施;(6)单侧偏压受管道几何尺寸的影响很小,究其原因是尺寸的变化未改变管道承载特性;对角偏压受几何尺寸的影响明显,因为尺寸的变化改变了管道空间抵抗对角错动剪切的能力;(7)管道应力随顶进力的增大线性增大,顶进力对管道受力影响明显,结构应力集中的区域在接触面周边一定范围内;(8)两种偏压模式作用下管道承载路径分布规律不同,单侧偏压时管道沿轴向延伸为主,而在对角偏压作用下,横向扩散趋势大于轴向。

Mechanical Response and Influencing Factors on Pipe Jacking under Eccentric Load

In order to explore mechanical characteristics and influencing factors of pipe jacking under eccentric load, the action pattern under eccentric load was revealed and the refined calculation model was established based on an engineering example. The mechanical characteristics, failure pattern and mechanism under different eccentric action pattern were calculated and analyzed, which was verified by model test results, and then the influencing factors were analyzed in detail as well as the preventive measures of pipe jacking bias were put forward. The results show that under eccentric load, the pipe appears axial eccentric arch, unilateral extrusion and opposite side opening as well as stress concentration and strain localization appear on the pipe interface. The unilateral eccentric action mainly manifests as the axial compression and shear effect, while the diagonal eccentric action manifests as the diagonal tensile and shear effect. The pipe cracks or even damage in local and gradually extends to the middle, finally forms progressive failure. The structure stress increases with the increase of the deviation angle in a linear relation. The structural damage induced by unilateral eccentric action is larger than that caused by diagonal eccentric action, and the greater eccentric angle, the above phenomenon more obvious. With the increase of the eccentric angle, the distribution characteristics of the pipe interface undergo the evolution from trapezoidal distribution to saddle distribution to elliptical distribution. The effect of pipe geometrical size on unilateral eccentric action is little, the reason for which is that the size doesn't change bearing characteristics. While diagonal eccentric is obviously affected by geometric dimension, because the dimension changes the diagonal shear resistance of pipe. The pipe stress increases linearly with the increase of jacking force, and the jacking force has obvious influence on the pipe stress. The stress concentration area of the structure is within a certain range around the interface. The distribution law of bearing path of two eccentric modes is different. The pipe mainly extends along the axial direction, while the transverse diffusion trend of diagonal eccentric action is greater than that in the axial direction.