穿坡油气管道的框架桩防护结构分析方法

Analysis Method of Frame-Type Stabilizing Piles for Protecting Petroleum Pipelines Through Hillslopes

针对沿山坡走向铺设的埋地油气管道存在的抗震防护问题,提出了一种新型的框架型抗滑桩式管道防护结构。在采用拟静力法确定作用于结构地震滑坡推力的基础上,将位于滑面以上的结构受荷段作为底端固定的平面框架结构,采用超静定平面刚架结构模型分析;而位于滑面以下的嵌固段则为埋置于稳定地层的两单桩结构,采用侧向受荷的弹性地基梁模型分析,由此建立了框架型抗滑桩的内力及位移计算方法。实例分析表明:框架桩前、后桩及上、下横梁弯矩与剪力的理论计算值与数值模拟结果误差均在±20%以内,理论结果偏于保守;水平地震影响系数对结构内力影响显著,结构内力最大值随水平地震影响系数增加近似呈线性增大,而竖向地震影响系数影响较弱;结构最大内力与土体重度呈线性正相关性,与黏聚力和内摩擦角呈非线性负相关性,且随着土体抗剪强度参数的增大,前、后桩以及上、下横梁的内力分别趋于接近;前、后排桩与上、下横梁的最大内力分别与桩体抗弯刚度呈非线性正相关性与负相关性,而分别与桩体嵌固深度近似呈线性正相关性与负相关性;框架桩间距对结构内力影响显著,而前后桩排间距则对结构内力影响较小。

In order to availably protect embedded petroleum pipelines through a slope particularly under seismic actions,a new frame-type stabilizing pile with the pipelines covered is proposed.On the basis of determining the seismic landslide thrust force on the structure by the pseudo-static method,the load section of the structure located above the sliding surface is taken as the plane frame structure which is taken as the plane rigid frame structure with fixed bottom.A super-static plane rigid frame structure model is used to analyze the loading section.The part of the structure below the slip surface called the embedded section is actually two independent piles buried in the stable layer,which can be analyzed using the elastic beam on foundation model under lateral loads on their tops.Thus,a calculation method of internal forces and displacements of the frame-type stabilizing pile is established by combing the two parts.The results of an example show that the deviation between the proposed and the numerical bending moments and shear forces of the front and rear piles as well as the upper and lower beams of the frame-type stabilizing pile is within 20%,and the proposed results are relatively conservative.The influence of horizontal seismic coefficient on the internal forces is obvious.The maximum value of the internal forces increases approximately linearly with the seismic coefficient,while the influence of vertical seismic coefficient is slight.The maximum internal force of the structure is linear positive correlation with soil unit weight and nonlinear negative correlation with cohesion and internal friction angle of soil,respectively.As soil shear strength parameters increase,the internal forces of the front and rear piles together with the upper and lower beams tend to be close,respectively.The maximum internal forces of the two piles and the two beams are nonlinear positive and negative correlation with flexible rigidity of the piles,respectively;But are approximately linear positive and negative correlation with embedded depth of the piles,respectively.The separation between adjacent structures has obvious influence on the structural internal forces,but the row spacing between the two piles in the same structure has slight effect on them.