【作者】 肖淑君；

【导师】 陈昌富；

【作者基本信息】 湖南大学 ， 岩土工程， 2008， 博士

【摘要】 抗滑桩尤其是锚拉抗滑桩是处治大型滑坡行之有效的支挡结构。而锚拉抗滑桩作为一种新的抗滑支挡结构,其设计计算理论远滞后于工程应用,加强对桩锚抗滑支挡结构设计计算理论和试验研究,具有重要的理论和实际意义。为此,本文结合教育部博士点基金(20050532021)、交通部西部项目(200631880237)和湖南省建设科技项目(2006012),通过室内模型试验和理论分析较系统地研究了锚杆、普通抗滑桩和锚拉抗滑桩的受力和承载特性,主要研究工作和成果如下:(1)考虑锚杆锚固段周围土体在较大拉拔力作用下有一部分可能进入塑性状态的情形,采用三折线模型模拟土体的剪切应力应变关系,基于剪切位移法研究了锚杆锚固段荷载传递机理和承载特性,导出了相应的弹性极限荷载和塑性极限荷载计算公式,并得到了锚固段剪应力和轴力计算公式。将所得公式分别应用于拉力型和压力型锚杆的受力分析,获得了一些可供工程设计参考的有益的结论。(2)针对抗滑桩设置后边坡最危险滑动面有可能发生变化的情形,以边坡最小稳定安全系数作为目标函数,基于自适应遗传算法(AGA)提出了抗滑桩支护边坡任意滑动面全局优化搜索算法,并编制计算程序。算例计算结果对于普通边坡所得滑动面和稳定安全系数,与已有结果较为接近,表明本文提出的算法可行;进一步对普通边坡和抗滑桩加固边坡的计算表明,由于抗滑桩的设置边坡最危险滑动面会发生变化。(3)引入半解析半数值的加权残值法,采用适应性较广的B样条函数作为试函数,提出了一种计算抗滑桩内力的新方法,得到了计算抗滑桩内力位移的加权残值解,编制了计算程序。此方法对抗滑桩全桩内力统一计算求解,克服了已有方法将抗滑桩分推力段和锚固段分别进行计算的缺陷,且桩周土地基系数可采用双参数法表示。将提出的方法应用于验证算例和计算实例,结果表明对于双参数地基加权残值解效果良好;同时针对抗滑桩加固后边坡最危险滑动面变化的情形,根据抗滑桩加固前和加固后搜索到的滑面分别对抗滑桩内力进行计算,结果表明两者差别较大,若不考虑滑动面位置变化对抗滑桩进行设计是不合理的。(4)总结并改进已有锚拉抗滑桩锚索设计拉力和预应力计算方法,将加权残值法引入到锚拉抗滑桩的计算,针对锚索作用于桩身的三种不同情形,考虑锚索与桩身的位移协调,提出基于加权残值法锚拉抗滑桩内力位移计算新方法。详细探讨预应力锚索抗滑桩计算过程,编制了计算程序。实例分析表明计算结果与已有结果吻合较好且计算效率高,提出的算法可行;进一步计算表明随着锚索设计拉力的增大,桩身的最大剪力值减小,最大负弯矩增大,最大正弯矩减小。采用桩身最大正负弯矩大致相等的方法(方法五)进行设计,所得弯矩最利于桩身配筋,但其施工难度可能增大,对于具体实例需综合比较各种因素采用合适设计方法。(5)自行设计并完成了普通抗滑桩和锚拉抗滑桩室内模型试验,获得了一系列试验数据,研究了土坡中抗滑桩滑坡推力、桩前土体抗力及桩身内力等分布规律,并利用加权残值法对模型试验中抗滑桩和锚拉抗滑桩进行计算,结果表明加权残值法计算值与试验实测值吻合良好,从试验上验证了本文提出的基于加权残值法计算抗滑桩和锚拉抗滑桩算法的可靠性。(6)引入统一强度理论分析抗滑桩周围土体应力状态,提出了抗滑桩和锚拉抗滑桩合理锚固深度和桩间距计算新方法。实例分析表明计算结果与已有结果差别很小,算法可行。分析了中主应力对计算结果的影响,反应中主应力影响的参数b越小,安全储备越高,b取0时统一强度理论即为Mohr-Coulomb强度理论。对比分析普通抗滑桩和锚拉抗滑桩的锚固深度和桩间距值,可知由于锚索的施加,锚拉抗滑桩锚固深度减小,桩间距增大。更多还原

【Abstract】 Anti-slide pile especially anti-slide pile with prestressed cable is an effective supporting structure for treating large landslides. The anti-slide pile with prestressed cable is used as a new anti-slide supporting structure, its design calculation theory has lagged far behind its engineering application. So it will take important theoretical and practical significance to strengthen theoretical and experimental study for reinforcement mechanism and design calculation supporting structure consist of anchors and piles. Therefor, by integrating Education Ministry Doctoral Fund (20050532021), Communication Ministry Western Project (200631880237) and Hunan Construction S&T Project(2006012), the anchor, common anti-slide pile and anti-slide pile with prestressed cable are systematically studied through laboratory model test and theoretical analysis in the paper, the main researches and results are as follows:(1) The condition that soil surrouding anchorage body will partly enter into plastic state when it is subjected to comparatively large drawing force, the soil shear stress and strain relationship is simulated by trilinear model, load transfer mechanism and bearing characteristic of anchorage body based on shear displacement method are studied, corresponding elastic and plastic limit loads calculation formulae are derived, shear stress and axial calculation formulae of anchorage body are obtained. The derived formula is applied to mechanical analysis of tension type and pressure type anchor respectively, some beneficial conclusions that can provide reference for engineering design are drawn.(2) Considering the condition that the most dangerous slip surface of slope is possible to change after setting anti-slide piles, the slope minimum stability safety factor is used as objective function, based on adaptive genetic algorithm(AGA), global optimization search method to arbitrary slip surface of slope retained by anti-slide pile is presented, and calculation program is programmed. The obtained slip surface and stability safety factor calculated by presented method are comparatively close to existing results, which shows the presented method is feasible. Furthmore, the calculation results for the common slope and slope reinforced by anti-slide pile show the most dangerous slip surface of slope will change due to the setup of anti-slide pile. (3) Semi-analytical and semi-numerical weighted residual method is imported, widely adaptive B spline function is acted as trial function, a new method to calculate internal force of anti-slide pile is put forward, the weighted residual solution for calculating internal force and displacement of anti-slide pile is obtained, calculation program is programmed. The presented method can calculate whole pile internal force unifiedly, and it overcomes the defect that existing method should separat the pile into thrust segment and anchorage segment and then calculat respectively, the foundation coefficient can be expressed as double parameter method. The presented method is applied to verification examples and calculation examples, the results show the effect of weighted residual solution in double parameter foundation are well. Simultaneously, for the case that the most dangerous slip surface of slope will change after setting anti-slide pile, according to the different slip surface of slope searched before and after setting anti-slide pile, the pile internal force is calculated, the two results are of great difference, so it is unreasonable for anti-slide pile if the change of the slip surface of slope is not considered.(4) The anchoring cable design tensile force and prestressing calculation methods of anti-slide pile with prestressed cable are summed and improved, the weighted residual method is introduced to calculate anti-slide pile with prestressed cable, direct to three different cases of anchoring cable acted on pile, displacement coordination between pile and anchoring cable is considered, the new method of internal force and displacement calculation based on weighted residual method is put forward. The calculation process of anti-slide pile with prestressed cable is discussed in detail, and program the calculation procedure. Example analysis shows the calculation results are consistent well with existing results, the presented method is feasible. According to further calculation, the more the anchoring tensile force , the less the shearing force of the pile, the more the maximum of negative bending moment, the less the maximum of positive bending moment. When the method that the maximum of negative bending moment and maximum of positive bending moment are about equal(the fifth method) is used to design, the obtained bending moment is most favorable for reinforcemet, but its construction difficulty is possible to increase, to specific example, it should compare all kinds of factors and use suitable design method.(5) Laboratory model tests on ordinary anti-slide pile and anti-slide piles with prestressed cable are self designed and accomplished. a series of testing data is obtained, The distributing rules of anti-slide pile landslide thrust, soil resistance in front of pile and internal force of pile in soil slope are studied, the weighted residual method is used to calculate anti-slide pile and anti-slide pile with prestressed cable in model test, the calculation values are fit close with testing measured values, which provide further reliability for the presented method to calculate the anti-slide pile and anti-slide pile with prestressed cable on the basis of weighted residual method.(6) A new method is put forward for calculating rational anchorage depth and pile spacing of anti-slide pile and anti-slide pile with prestressed cable by introducing unified strength theory to analyze soil stress state surrounding pile. The intermediate principle stress influences on calculation results is analyzed, the less the parameter b reacted intermediate principle stress influence, the higher the safety margin, the unified strength theory is just Mohr-Coulomb strength theory when b is equal to 0. anti-slide pile with prestressed cable has less anchorage depth and bigger pile spacing compared with common anti-slide pile because of the anchoring cable imposing.更多还原