Seismic uplift capacity of inclined strip anchors in sand using upper bound limit analysis

Pseudo-static approach is adopted in this paper to determine the seismic uplift capacity of an inclined strip anchor using upper bound limit analysis. Two different failure mechanisms are considered to obtain the magnitudes of unit weight component of uplift factor f_γE for different values of soil friction angle, interface friction of anchor plate, anchor inclination, embedment ratio and horizontal seismic acceleration coefficient. The failure mechanism 1 consists of a triangular and quadrilateral rigid blocks; whereas the failure mechanism 2 comprises a logarithmic spiral failure zone with varied focus, sandwiched between a triangular and quadrilateral rigid blocks. It is observed that the magnitude of uplift factor f_γE decreases significantly with the increase in seismic acceleration but increases with the increase in embedment ratio and roughness of the anchor surface. However, a mixed trend in the values of f_γE can be observed for different inclination of the anchor, which is clearly discussed in this paper. The results are compared with the existing values in the literature and the significance of the present methodology for designing the inclined strip anchor is discussed.     

预制高强预应力混凝土格构试验与数值模拟研究

概述高强预应力混凝土格构锚固的优点,建立起锚墩的三维有限元计算模型,通过有限元模拟及室内试验对比研究,探索构件的受力机制、变形及裂缝的发展过程,论证使用ANSYS软件设计预应力混凝土构件的有效性。     

福建闽侯某小区滑坡特征及成因机制分析

通过对福建闽侯某小区滑坡的地质调绘、探井及钻孔勘察等综合方法应用,结合深部位移监测,充分论证了滑面的位置,分析研究滑坡的基本特征及影响因素。研究表明,该滑坡是推移式土质滑坡,破坏模式为蠕滑-拉裂-弯曲型式,结合小区建设实际,提出切合实际且有效的锚索抗滑桩的治理方案。     

辽宁海州露天矿边坡预应力锚索远程监测系统

随着海州露天矿的闭坑,岩体结构越来越弱化,围岩的支承能力越来越小,露天矿边坡处于不稳定状态,具有发生大规模滑坡的潜在危险。根据海州露天矿工程地质条件,边坡形态,稳定状态及监测目的,研发海州露天矿边坡预应力锚索远程监测系统。系统应用GPRS远距离无线传输技术远程主动监测边坡岩体内部应力变化来获取岩体变形特征和滑移信息,实现边坡锚索应力全天候连续自动监测,其采用太阳能进行供电,适用于边坡中、长期监测。通过对海州露天矿边坡监测与边坡稳定性分析的现场应用实践证明,该系统可以对边坡稳态进行实时监测,对边坡滑坡灾害防治具有重要意义。     

Pre-stressed anchoring beam technique applicable in the reinforcement of high-steep slopes

During the construction of some large-scale rock engineering, high-steep slopes and insufficient slope stability induced by unloading fissures are often encountered. For the reinforcement of these slopes, some techniques （including conventional pre-stressed anchoring cable and unconventional anchoring hole） are usually uti- lized, however, having several obvious defects. Thus, it is very difficult for a designer to design an efficient reinforcement scheme for the high-steep slopes. For this reason, the authors develop the pre-stressed anchoring beam technique, in which tensile capacity of pre-stressed structures are fully utilized. It is analyzed that the new technique is characterized by multi-functions, including engineering investigation, efficient reinforcement, drainage, monitoring and urgent strength supplement, and hoped to be extensively applicable in the reinforcement of high-steep slopes.     

The modelling of anchors using the material point method

The ultimate capacity of anchors is determined using the material point method (MPM). MPM is a so‐called meshless method capable of modelling large displacements, deformations and contact between different bodies. A short introduction to MPM is given and the derivation of the discrete governing equations. The analysis of a vertically loaded anchor and one loaded at 45° is presented. The load–displacement curves are compared to that obtained from experiments and the effect of soil stiffness and anchor roughness is investigated. The results of the vertically loaded anchor are also compared to an analytical solution. The displacement of the soil surface above the anchor was measured and compared to the numerical predictions. Convergence with mesh refinement is demonstrated and the effect of mesh size and dilatancy angle on the shear band width and orientation is indicated. The results show that MPM can model anchor pull out successfully. No special interface elements are needed to model the anchor–soil interface and the predicted ultimate capacities were within 10% of the measured values. Copyright © 2005 John Wiley & Sons, Ltd.     

Separation of up-going and down-going wave fields of vertical cable data

The vertical cable method for acquiring and processing pre-stack 3-D marine seismic data is based on the technology developed by the US Navy for antisubmarine warfare. In order to achieve the maximum utilization of vertical cable field data, a new separation method of the up-going and down-going wave fields of the vertical cable data processing was developed in this paper, which is different from the separation of the down-going and up-going wave fields of normal VSP data processing. In tests with synthetic modeling data andactual field data, this newly developed method performs well and is also computationally simpler without pre-assumption conditions.     

用有线电视系统传输计算机信息

介绍一种利用有线电视系统来传送计算机输出的串行控制信号的特殊方法。     

滑坡治理中格构式锚杆框架结构设计

结合略阳县城狮子山滑坡的治理，讨论了格构式锚杆框架结构治理松散堆积体滑坡设计的全过程。根据防治区的工程地质情况和相应的规范要求，确定了防治工程的安全等级。利用格构式锚杆框架结构所采用的小间距、小吨位锚杆及连续格构梁柱．从而使格构梁柱受力较均匀，适合松散堆积体滑坡治理的需要，即同时满足深层抗滑和浅层护坡。给出了坡面推力的计算模型和计算公式．对于格构式锚杆框架结构中的格构梁柱、锚杆和框架间面板也分别给出了相应的结构设计方法和公式．再就施工中应注意的事项给出了明确的建议和要求。     

剪切位移传递法分析抗浮锚杆应力状态

假定锚侧摩阻力与剪切变形呈非线性变化,考虑锚侧土体在影响区域内符合非线性弹性理论,运用剪切位移传递法,建立了抗浮锚杆计算模型,推导了锚侧剪应力与剪切位移的关系式。通过模型描述受荷状态下抗浮锚杆的轴力、摩阻力、位移的变化形态,分析了锚杆应力变化的工作机理,并预估了其极限承载力。