黄土区特高压输电线路杆塔全掏挖基础抗拔分析

全掏挖基础是人工在地基中直接掏挖出基础形状,插入钢筋笼,灌入混凝土形成基础的一种施工方法。采用规范中给出的土重法和剪切法,计算了输电线路杆塔基础的抗拔承载力,并与有限元计算结果做了对比,分析了土重法和剪切法计算的极限抗拔力对应的基础周围土体状态。土重法和剪切法计算的极限抗拔力均小于有限元计算的极限抗拔力,3种方法极限抗拔力土体均处于弹性状态。剪切法计算结果大于土重法,且有相应的安全度,基础设计中可以采用剪切法。

改进荷载传递方法在水闸地基土体抗拔受力变形分析中的应用研究

文章引入改进荷载传递方法对某水闸地基土体的抗拔受力进行变形特征分析,并结合静载观测试验对比分析改进前后荷载传递方法对地基土体抗拔受力变形计算精度影响。分析结果表明:改进的荷载传递方法综合考虑土地自重对土体抗拔变形受力的影响,其变形计算值与观测试验值的吻合度高于传统方法,水闸地基土层抗拔受力随轴力增大而增大,且呈现明显的非线性分布。研究成果对水闸设计地基土体的抗拔稳定分析提供参考。

荷载传递方法在水闸地基土体抗拔受力变形计算中的应用

以辽宁地区某水闸为设计工程实例,该水闸地基土体为桩固结构,采用4根桩体进行地基的构建,应用荷载传递方法对不同桩体之间的抗拔应力进行分析和计算,结果表明:荷载传递方法可综合考虑地基土体受力的分布特征,计算结果符合其实际受力分布特征,相比于传统计算方法,其在变形计算误差上降低12. 3%。研究成果对于水闸稳定性设计具有重要的参考价值。

Variation analysis of ultimate pullout capacity of shallow horizontal strip anchor plate with 2-layer overlying soil based on nonlinear M-C failure criterion

Based on the nonlinear Mohr-Coulomb failure criterion and an associated flow rule,a kinematic admissible velocity field of failure mechanism of the 2-layer soil above a shallow horizontal strip anchor plate is constructed.The ultimate pull-out force and its corresponding failure mechanism through the upper bound limit analysis according to a variation principle are deduced.When the 2-layer overlying soil is degraded into single-layer soil,the model of ultimate pullout force could also be degraded into the model of single-layer soil.And the comparison between results of single-layer soil variation method and those calculated by rigid limit analysis method proves the correctness of our method.Based on that,the influence of changes of geotechnical parameters on ultimate pullout forces and failure mechanism of a shallow horizontal strip anchor with the 2-layer soil above are analyzed.The results show that the ultimate pull-out force and failure mechanism of a shallow horizontal strip anchor with the 2-layer soil above are affected by the nonlinear geotechnical parameters greatly.Thus,it is very important to obtain the accurate geotechnical parameters of 2-layer soil for the evaluation of the ultimate pullout capacity of the anchor plate.

Upper bound analysis of ultimate pullout capacity of shallow 3-D circular plate anchors based on nonlinear Mohr-Coulomb failure criterion

Based on the nonlinear Mohr-Coulomb failure criterion and the associated flow rules,the three-dimensional(3-D)axisymmetric failure mechanism of shallow horizontal circular plate anchors that are subjected to the ultimate pullout capacity(UPC)is determined.A derivative function of the projection function for projecting the 3-D axisymmetric failure surface on plane is deduced using the variation theory.By using difference principle,the primitive function of failure surface satisfying boundary condition and numerical solution to its corresponding ultimate pullout capacity function are obtained.The influences of nonlinear Mohr-Coulomb parameters on UPC and failure mechanism are studied.The result shows that UPC decreases with dimensionless parameter m and uniaxial tensile strength increases but increases when depth and radius of plate anchor,surface overload,initial cohesion,geomaterial density and friction angle increase.The failure surface is similar to a symmetrical spatial funnel,and its shape is mainly determined by dimensionless parameter m;the surface damage range expands with the increase of radius and depth of the plate anchor as well as initial cohesion but decreases with the increase of dimensionless parameter m and uniaxial tensile strength as well as geomaterial density.As the dimensionless parameter m=2.0,the numerical solution of UPC based on the difference principle is proved to be feasible and effective through the comparison with the exact solution.In addition,the comparison between solutions of UPC computed by variation method and those computed by upper bound method indicate that variation method outperforms upper bound method.

Limit analysis of ultimate uplift capacity and failure mechanism ofshallow plate anchors in multi-layered soils

Considering the fact that in some complex cases,plate anchors are buried in multi-layered geotechnical materials,the ultimate dynamic analysis was performed to investigate the uplift capacity and failure mechanism of shallow strips and circular plate anchors in multi-layered soils.The nonlinear strength criterion and non-associated flow rule of geotechnical materials were introduced to investigate the influence of nonuniformity on the pullout performance and failure mechanism of shallow plate anchors.The expressions of the detaching curves or surfaces were obtained to reflect the failure mechanism,which can be used to figure out the ultimate uplift capacity and failure range.The results are generally in agreement with the numerical simulations and previous research.The effects of various parameters on the ultimate uplift capacity and failure mechanism of plate anchors in multi-layered soils were investigated,and it is found that the ultimate uplift capacity and failure range of shallow anchors increase with the increase of initial cohesion and dilatancy coefficient,but decrease with the unit weight,axial tensile stress and nonlinear coefficient.