隧道开挖引起的地层损失对静压桩端承力影响的理论与数值模拟分析

发布时间：2018-06-11 12:52

本文选题：隧道 + 桩　；参考：《北京交通大学》2017年硕士论文

【摘要】：本文研究了城市地区隧道与现有桩基之间的相互作用。文章采用了空洞理论和有限元理论进行了分析。文章提出了一种利用圆孔扩张理论估算静压桩承载力的方法,并对相关机理进行了说明。对模型参数进行了研究,以评估其对桩端承载力的影响。结果表明,静压桩的安装会对地层初始压力产生影响,且随着与桩端弹塑性界面距离的增大而减小,并且桩端承载力的增加与土壤的粘聚力、摩擦角和密度有关。提出了一种利用简化空腔收缩理论估算隧道桩端损失量对桩端承载力影响的方法,并对相关机理进行了说明。对桩-隧之间的相互作用进行了参数分析,结果表明,根据隧道与桩端的相对位置,隧道体积的损失可以造成桩端承载力的提高或减小。采用PLAXIS进行了二维数值模拟分析。重点分析了隧道开挖对现有静压桩的土体运动和应力的影响,并与分析结果进行了比较。隧道会造成桩端压力和拉力的减小,这取决于桩基础相对于影响区的位置。对于位于影响范围内的桩基础,桩主要受拉力,这是由于桩与周围土体之间的相对运动引起的。空腔理论和有限元分析都表明当有限元分析中Xp12.5m或者空腔理论Xtp11m时,拉应力会增加。随着隧道与桩的分离导致的压应力的发展规律也验证了这两种分析结果。压缩力通常要比极限承载力小。对地层深度的研究结果也表明,随着深度的增加qb,vl/qb的值也在增加。深度也会影响各向同性围岩的压力。可以采用一个关于围压的函数对地层摩擦角和膨胀角进行分析。对于工况3,这两种方法(空腔理论和有限元法)也都验证了隧道的大小对桩端承载力的影响,qb,vl/qb的数值随着隧道半径的增大而减小,隧道的半径也会影响围岩扰动区的大小(随着隧道半径增大而增大)。
[Abstract]:The interaction between tunnels and existing pile foundations in urban areas is studied in this paper. The cavity theory and finite element theory are used to analyze the problem. In this paper, a method of estimating the bearing capacity of static pile by using the theory of circular hole expansion is put forward, and the related mechanism is explained. The model parameters are studied to evaluate the effect of the model on the bearing capacity of pile tip. The results show that the static pile installation will affect the initial formation pressure and decrease with the increase of the distance between the pile end and the elastic-plastic interface, and the increase of the pile end bearing capacity is related to the cohesive force, friction angle and density of the soil. A method is proposed to estimate the influence of pile end loss on pile end bearing capacity by using simplified cavity contraction theory, and the related mechanism is explained. The parameter analysis of pile-tunnel interaction shows that according to the relative position of tunnel and pile end, the loss of tunnel volume can increase or decrease the bearing capacity of pile end. The two-dimensional numerical simulation was carried out by PLAXIS. The influence of tunnel excavation on the soil movement and stress of the existing static pile is analyzed, and the results are compared with those of the analysis. The pressure and tension at the end of the pile are reduced by the tunnel, which depends on the position of the pile foundation relative to the affected area. For the pile foundation which is located in the influence area, the pile is mainly subjected to tensile force, which is caused by the relative motion between the pile and the surrounding soil. Both cavity theory and finite element analysis show that tensile stress increases when Xp12.5m in finite element analysis or Xtp11m in cavity theory. With the separation of tunnel and pile, the development of compressive stress also verifies the two analytical results. The compression force is usually smaller than the ultimate bearing capacity. The results of the study on the formation depth also show that the value of qbnvl / qb increases with the increase of the depth. The depth also affects the pressure of isotropic surrounding rock. A function on confining pressure can be used to analyze the angle of friction and expansion. For working condition 3, both of these two methods (cavity theory and finite element method) also verify the influence of tunnel size on the bearing capacity of pile end. The numerical value of QB / vl / qb decreases with the increase of tunnel radius. The radius of the tunnel will also affect the size of the surrounding rock disturbance zone (increasing with the increase of the radius of the tunnel).
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U455;TU473.1

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