LOAD DISTRIBUTION ALONG FULLY GROUTED BOLTS,WITH EMPHASIS ON CABLE BOLT REINFORCEMENT

Explanation for the widely reported observation that fully grouted reinforcement is more effective in hard rock that behaves as a discontinuum than in soft rock is presented. Analytical solutions are presented for the distribution of displacement and load along an untensioned fully grouted elastic bolt, of specified bond stiffness, which is activated during excavation by either a continuous or discontinuous distribution of rock displacement. The results indicate that significantly higher axial loads are developed for the discontinuous case. Since the mechanics of bond failure depend on the type of bolt and grout used, in the second part of the paper a finite difference formulation is introduced and combined with a non-linear model for the bond behaviour of a cement grouted seven-wire strand cable bolt. The results of a parametric study indicate that, because the bond is frictional and depends on confinement at the borehole wall, for the same profile of rock mass displacement lower loads are developed in soft rock. Furthermore, in soft rock, excavation induced stress changes can cause a dramatic reduction in bond strength, so that, even after significant rock mass displacement, the axial load developed is significantly less than the tensile strength of the cable. A combination of these effects can explain why failures of cable bolted ground involve debonding at the cable–grout interface in soft rock, and why instances of cable rupture are confined to hard, blocky rock masses.     

Bridge pier failure probabilities under combined hazard effects of scour, truck and earthquake. Part I: occurrence probabilities

In many regions of the world, a bridge will experience multiple extreme hazards during its expected service life. The current American Association of State Highway and Transportation Officials (AASHTO) load and resistance factor design (LRFD) specifications are formulated based on failure probabilities, which are fully calibrated for dead load and nonextreme live loads. Design against earthquake loads is established separately. Design against scour effect is also formulated separately by using the concept of capacity reduction (or increased scour depth). Furthermore, scour effect cannot be linked directly to an LRFD limit state equation, because the latter is formulated using force-based analysis. This paper (in two parts) presents a probability-based procedure to estimate the combined hazard effects on bridges due to truck, earthquake and scour, by treating the effect of scour as an equivalent load effect so that it can be included in reliability-based bridge failure calculations. In Part I of this series, the general principle of treating the scour depth as an equivalent load effect is presented. The individual and combined partial failure probabilities due to truck, earthquake and scour effects are described. To explain the method of including non-force-based natural hazards effects, two types of common scour failures are considered. In Part II, the corresponding bridge failure probability, the occurrence of scour as well as simultaneously having both truck load and equivalent scour load are quantitatively discussed.     

Evaluation of vertically and laterally loaded bucket foundation in clay using a three-dimensional displacement approach

ABSTRACT

An investigation is made to present analytical solutions provided by a three-dimensional displacement approach for analysis of bucket foundations subjected to vertical and lateral loads in cohesive soils. The nonlinear vertical and lateral stiffness coefficients along the skirt of the bucket foundation in nonhomogeneous soil are presented using three-dimensional solutions for vertical and lateral loads and taking into account the dependence of stiffness coefficients on the shear strain. The vertical, lateral, and rocking stiffness coefficients on the base of the skirt of a bucket foundation are obtained from the solutions of hollow rigid cylindrical punch acting on the surface of a soil. The ultimate vertical stress of a soil under the base of a bucket foundation subjected to vertical and moment loads is presented analytically by considering only compression and ignoring tension on the base. The vertical and lateral yields along the skirt and the compression and shear failures on the base are taken into account in analysis of ultimate load capacities. Envelopes of the combined ultimate horizontal and moment load capacities of a bucket foundation in clay are shown. Relationships between ultimate lateral and moment load capacities and the embedment ratio (skirt length to diameter) are presented.     

列车移动荷载对下穿公路隧道稳定性影响研究

将列车荷载模拟为单一的移动荷载,考虑围岩为黏弹性成层地基,利用分层法研究了移动荷载作用下围岩的动力响应,得到了围岩在动力荷载下的受影响范围,从而可评价列车荷载对下穿公路隧道稳定性的影响程度。最后将理论分析结果与现场量测结果（主要是上方列车荷载通过时量测下方公路隧道的振动响应）进行对比分析,二者吻合较好。     

EFFECTS OF WATERSHED RECLAMATION ON INFLOW AND SEDIMENT LOAD IN THE FENHE RESERVOIR

１ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅＦｅｎｈｅＲｅｓｅｒｖｏｉｒｗａｓｉｍｐｏｕｎｄｅｄｉｎ１９６１ｗｉｔｈｔｏｔａｌｓｔｏｒａｇｅｃａｐａｃｉｔｙｏｆ７２０ｍｉｌｉｏｎｍ３．ＩｔｉｓｔｈｅｌａｒｇｅｓｔｒｅｓｅｒｖｏｉｒｉｎＳｈａｎｘｉＰｒｏｖｉｎｃｅ...     

高填方减载式刚性涵洞受力特性模型试验研究

为了研究高填方减载式刚性涵洞结构的减载效果,利用模型试验分别对减载式刚性涵洞、采用一般减载方法的涵洞和未减载涵洞的涵顶垂直土压力和侧墙水平土压力进行对比分析。在此基础之上,建立了减载式刚性涵洞涵顶垂直土压力理论模型,推得了减载式刚性涵洞涵顶垂直土压力计算式,并将模型试验结果与理论分析结果进行了对比分析。研究结果表明,减载式刚性涵洞不仅能够有效缓解涵顶应力集中,而且与一般减载涵洞相比还能有效减小涵洞侧墙水平土压力;对于减载式涵洞涵顶垂直土压力,理论计算结果与模型试验结果一致且两者相差较小,从而验证了理论模型的适用性和正确性。     

Improving optimization efficiency for the total pollutant load allocation in large two-dimensional water areas: Bohai Sea (China) case study

The total pollutant load allocation (TPLA) can be transformed into an optimization problem with regards to water quality constraints. The optimization calculation may become very time consuming when the number of water quality constraint equations is great. A Trial and Error Method (TEM) to remove the redundant points was first introduced through iterative calculations under structure and non-structure model grids. The TEM was applied for the TPLA in the Bohai Sea in China. The calculation time was reduced to about 2 min under the condition that 103,433 model grids met the water quality standards. In the best case, the optimization efficiency was improved by 98.9%. The allocation results showed that approximately 90% of total nitrogen (TN) load should be reduced in the 56 pollution sources around the Bohai Sea; of these values, roughly 85% of the reduction could come from 10 pollution sources.     

黄土地区静压桩单桩承载力评价

通过黄土地区的桩载试验,研究了标准值与静压桩终止荷载、桩顶沉降5 mm时对应的桩顶荷载与静力触探估计的单桩承载力标准以及静压桩终止压载等之间的相关性。据此,评价确定单桩承载力。     

煤层气井有杆泵排采设备悬点静载荷计算方法

有杆泵排采设备悬点载荷是标志其工作能力的重要参数之一。悬点载荷中起主要作用的是静载荷。悬点静载荷是选择和正确使用排采设备的重要依据。在研究我国煤层气井开采实际的基础上,分析了排采设备的悬点载荷,给出计算悬点静载荷大小的方法及其变化规律,最终利用现场实测的数据对算法进行了验证。验证结果表明,悬点静载荷中起主要作用的是杆柱重和液柱重,但管外液柱对柱塞压力的影响不可忽略;上下冲程中静变形量相对较小。该计算方法步骤简单,结果符合实际,能够较好地满足煤层气井现场数据计算的需要。     

Stable channel analysis with sediment transport for rivers in Malaysia: A case study of the Muda,Kurau, and Langat rivers

Assessments of a stable channel were done to evaluate the conditions of three rivers in Malaysia,using an analytical method that modifies the stable channel flowchart developed by Chang(1988) and Ariffin(2004).The analytical approach was selected to calculate the suitable dimensions for a stable channel,using equations that describe the physical relation of sediment transport,flow resistance,and dynamic equilibrium.Measured field data were used as the input data for the stable channel program,wh...