桩的静载试验Q-S曲线延伸方法的探讨

现场静载试验目前仍是确定单桩竖向承载力的主要方法 ,由于条件限制 ,实际工程试桩往往很难达到规范规定的极限状态。本文推出一种曲线拟合方法 :对试桩的Q -s数据 ,采用几种不同的数学模型进行回归分析 ,从中找出相关程度最好的一种模式 ,以其推算所得作为该试桩的极限承载力推算值。作者收集了 689根试桩记录 ,以其中s已超过 40mm而未出现“骤沉”的 58根记录 ,按本文方法试算 ,结果说明该方法具有较好的实用性。本文还对该方法的应用范围作了一些限制和说明     

锚杆静压桩用于高层建筑桩基加固

夯扩桩已在桩基工程中得到了广泛应用 ,但是 ,施工中时常发生事故。本文介绍某高层建筑夯扩桩基础出现不合格桩的状况 ,采用锚杆静压桩进行基础加固补强 ,是一项取得成功的实例。     

桩土体系的有效应力地震反应计算方法研究

从土动力学的角度 ,本文认为按土的有效应力原理进行桩—土动力相互作用分析能够较好地反映土的动力特性对桩基的影响。又着重讨论了基于有效应力原理的有限元法 ,并对一个柱式桥墩桩基础进行了计算和分析。     

浅谈层压布纹白斑的改善

文章主要对PCB加工时出现的布纹白斑缺陷进行分析并阐述相应的改善方案。针对此缺陷,采用鱼骨图查找影响点,并对可能出现异常的环节进行剖析,动员工序各职能携手对布纹白斑问题进行改善。还阐述了对于有效的改善措施进行强化的内容,制定相应规范指导员工操作。     

LTE核心网中基于PCC的QoS控制和能力开放技术研究

在LTE核心网中,通过引入PCC机制,来实现应用层业务数据流QoS需求到核心网承载层QoS分组过滤器之间的一致性映射和匹配问题。文章在详细介绍和分析LTE核心网中承载层QoS机制和PCC总体架构的基础上,研究如何将二者结合起来实现基于PCC和网络能力开放平台的QoS控制,从而提升运营商掌控网络提供业务的能力并改善用户的业务体验。     

小波分析在基桩浅部缺陷检测中的应用

通过对基桩存在浅部缺陷时桩顶响应信号的小波分析，提取信号中所包含的对应于缺陷部位的应力波反射特征信息，可以实现对基桩浅部缺陷的准确定位。数值模拟试验显示了该方法的合理性；在此基础上，进行了工程桩的现场试验研究，结果表明该方法对基桩浅部缺陷的检测是可靠的。     

Clearwater Local Scour at Complex Piers

A new methodology to predict local scour depth at a complex pier is presented herein that combines existing expressions for scouring respectively at uniform piers, caisson-founded piers, pile groups with debris rafts, and pile groups alone. The method recognises the relative scouring potentials of the components of complex piers and the transition of scouring processes occurring for varying pile-cap elevation. The validity of the method is confirmed herein using the present and also historical measurements of local scour at complex piers. The proposed methodology has the advantages of being conceptually consistent with observed scour behaviours, relatively simple to apply, applicable to wide ranges of flow and sediment conditions (through incorporation into a more general analysis framework), and applicable over the entire range of possible pile-cap elevations. For design purposes, the present method highlights respective pile-cap elevations that maximize (i.e., to be avoided over the pier life) and minimize local scour at complex piers. The present method reinforces that where the pile-cap elevation relative to the bed can vary with time at a bridge site, potential local-scour depths need to be assessed over the range of possible pile-cap elevations for the pier.     

Characteristics of Bored Piles Installed Through Jet Grout Layer

When bored piles are installed through a jet grout layer, significant interaction may take place between the piles and the jet grout. Field load tests have indicated that significant enhancement of the pile shaft capacity and axial stiffness was possible for both compression and tension piles. The influence of the jet grout layer was more pronounced for piles under compression loading compared with uplift loading. The effectiveness of the jet grout in transmitting load via shearing action was dependent on the thickness of the grouted zone, the strength of the interlocks between individual jet grout columns forming the grout slab, as well as the interface bond between the pile shafts and the grout. No apparent adverse effect on the performance of permanent foundations was envisaged as a result of the presence of the jet grout layer. However, interpretation of pile behavior from load tests was complicated by the interaction between the test pile and jet grout, resulting in overprediction of pile capacity and axial stiffness. The significance of the interaction has to be carefully evaluated so that a correct interpretation of the true pile capacity and axial stiffness can be made.     

Lateral Resistance of Full-Scale Pile Cap with Gravel Backfill

A static lateral load test was performed on a full-scale 3×3 pile group driven in saturated low-plasticity silts and clays. The steel pipe piles were attached to a concrete pile cap which created a “fixed-head” end constraint. A gravel backfill was compacted in place on the backside of the cap. Lateral resistance was therefore provided by pile–soil–pile interaction, as well as base friction and passive pressure on the cap. In this case, passive resistance contributed about 40% of the total resistance. The log–spiral method provided the best agreement with measured resistance. Estimates of passive pressure computed using the Rankine method significantly underestimated the resistance while the Coulomb method overestimated resistance. The cap movement required to fully mobilize passive resistance in the gravel backfill was about 6% of the cap height. This is somewhat larger than reported in other studies likely due to the underlying clay layer. The p-multipliers developed for the free-head pile group provided reasonable estimates of the pile–soil–pile resistance for the fixed-head pile group once gaps adjacent to the pile were considered.     

三层结构防腐层在码头钢管桩上的应用

根据海洋钢管桩防腐需要研究开发的管道三层结构防腐涂层技术，已在丹东港码头钢管桩防腐工程中应用。本文介绍了码头钢管桩的结构和涂层要求、三层结构防腐层的材料选择、涂敷工艺和钢管桩的应用效果。