加筋大直径搅拌桩重力式挡土墙在基坑支护中的应用

以实际工程为例,介绍了加筋大直径搅拌桩重力式挡土墙在基坑支护工程中的应用,详细介绍了重力式挡土墙的施工工艺流程和技术措施。实践证明,格栅式大直径搅拌桩重力式挡土墙具有强度高、整体稳定性好、防渗透性好、施工方便、振动小、造价低等优点,取得了良好的社会和经济效益。     

大圆筒岸壁码头的量纲分析和离心模拟(英文)

认识土与沉入式无底大直径圆筒结构岸壁码头之间相互作用机制,对于它的安全和经济设计至关重要。基于量纲分析,首先研究确定了控制这种岸壁码头性状的无量纲项,然后,为研究这些无量纲项的相对重要性,设计了模型试验,并对试验结果分析解释。在所完成的离心模型试验中,就岸壁码头变形机制进行了观察,发现圆筒岸壁上部是偏离墙后土体向海侧倾斜,同时码头后场表面有沉降发生。离心试验结果的多元回归分析发现,圆筒岸壁的相对侧向位移对筒体前侧嵌入泥面以下的埋深比最为敏感,而侧向位移对圆筒的径高比的灵敏度不足前一因素的50%。相对来说,所测得的位移和土压力对筒壁的摩擦不很灵敏。对土压力结果的分析表明,作用于圆筒岸壁的侧向土压力可依据朗肯主动土压力理论,根据筒后土体的不排水强度进行预测。     

深厚软土基坑双排桩抗倾覆稳定安全系数计算方法的改进

双排桩支护结构常规的抗倾覆稳定性计算运用了重力式挡土墙抗倾覆稳定性的计算方法,而未考虑双排桩支护结构与重力式挡土墙变形性状和失稳机理上的差异,导致计算方法存在不合理现象。基于基床系数法,建立可考虑双排桩支护结构变形性状的抗倾覆稳定性计算公式。同时,以广州某深厚软土基坑为例,根据监测成果,分析该抗倾覆稳定性计算方法的可行性。结果表明,该计算方法较常规计算方法更符合工程实际,计算结果也更为合理。     

大圆筒岸壁码头的量纲分析和离心模拟

认识土与沉入式无底大直径圆筒结构岸壁码头之间相互作用机制,对于它的安全和经济设计至关重要.基于量纲分析,首先研究确定了控制这种岸壁码头性状的无量纲项,然后,为研究这些无量纲项的相对重要性,设计了模型试验,并对试验结果分析解释.在所完成的离心模型试验中,就岸壁码头变形机制进行了观察,发现圆筒岸壁上部是偏离墙后土体向海侧倾斜,同时码头后场表面有沉降发生.离心试验结果的多元回归分析发现,圆筒岸壁的相对侧向位移对筒体前侧嵌入泥面以下的埋深比最为敏感,而侧向位移对圆筒的径高比的灵敏度不足前一因素的50%.相对来说,所测得的位移和土压力对筒壁的摩擦不很灵敏.对土压力结果的分析表明,作用于圆筒岸壁的侧向土压力可依据朗肯主动土压力理论,根据筒后土体的不排水强度进行预测.     

大直径圆筒码头结构土压力性状模型试验

详细说明了大直径圆筒码头结构的模型试验布置、量测和试验方法。通过室内模型试验 ,研究大直径圆筒码头结构在不同的筒高、筒高与筒径之比、埋深与筒高之比、基床垫层等条件下 ,圆筒内外侧土压力、筒体基底反力的分布规律。     

浅谈复合式码头结构—板桩码头与重力式码头相结合的码头结构

分析板桩与重力式相结合的复合式码头结构计算原理及施工注意事项。     

双桩靴贯入对临近钢圆筒稳定性影响的数值分析

水下石油生产系统通常布置于海床上,其保护措施对生产系统的工作稳定性与安全性十分重要。根据实际海洋环境条件与水面航道要求,目前有工程创新性地采用大直径钢圆筒嵌入海床面一下作为水下生产系统的保护结构。对于此类型防护结构与工程应用,邻近自升式钻井船进行桩靴插拔作业时会对钢圆筒稳定性造成影响,带来安全隐患。现采用耦合欧拉与拉格朗日有限元数值方法对双桩靴贯入产生的钢圆筒扰动问题进行数值模拟分析。研究桩靴贯入过程中土体和钢圆筒基础的变形和应力变化,从而分析钢圆筒保护结构的稳定性与安全性。结果表明,钢圆筒筒壁附加应力及位移在初期随桩靴贯入深度增加而增大,达到峰值后趋于稳定;桩靴贯入到一定深度后,桩靴上部土体发生回流现象,导致对钢圆筒的影响降低;双桩靴对钢圆筒的影响随筒靴间距增大而减弱,但其影响范围较于单桩靴贯入有明显扩大。可为水下石油生产系统保护措施的设计与现场应用提供有效的参考依据。     

海上人工岛内深基坑变形与稳定分析

采用数值方法研究了某跨海大桥海上人工岛内隧道基坑的变形性状与整体稳定性。基于有限元程序Plaxis建立考虑复杂施工条件下土与结构相互作用的平面应变计算模型,分析坑中坑方案和大开挖方案两种不同基坑开挖方法对大直径钢圆筒岸壁结构及基坑围护桩变形、整体稳定性及失稳破坏模式的影响。研究表明:相对大开挖方案,最不利状态下坑中坑方案使钢圆筒相对侧向变形由1.41%降至0.69%,结构整体稳定安全系数由1.51增至1.68,结构失稳破坏模式由钢圆筒绕其下部倾覆转动转变为岛内土体绕围护桩滑移,但坑中坑方案由于增加了临时围护结构的施工,对工期和投资的影响较大。由于两种开挖方案均能满足基坑的安全度控制要求,同时又不涉及基坑变形对周边环境的影响,大开挖方案对工期及投资控制更有利。     

粉喷桩支护结构计算新方法的应用

目前粉喷桩支护结构的稳定性计算,系将桩土复合墙按重力式挡墙分析.但是在桩墙截面设计时仍按重力式挡墙检算就不尽合理.本文根据复合墙具有半刚柔这—特点,介绍了按锚固桩计算方法进行设计计算的新途径.     

沉入式圆筒结构与土相互作用的模式及位移计算方法

本文提出了沉入式无底大直径圆筒结构筒体与土协同工作的一种分析模型.该模型假设土体中任一点对筒壁竖向位移的剪切变形刚度系数与该点的土下深度和筒体水平位移成正比.在这一假设下得到的求解筒体位移的平衡方程为—非线性方程组,为此建立了求解这一方程组的迭代算法,并用模型试验结果对该模型及其计算方法进行了检验.     

Behavior of Sheet Pile Quay Wall Stabilized by Sea-Side Ground Improvement in Dynamic Centrifuge Tests

Sea-side ground improvement is one of the techniques used for increasing seismic stability of sheet pile quay wall. A series of centrifuge shaking table test is conducted to investigate the seismic behavior of sheet pile quay wall stabilized with sea-side cement deep mixing (CDM). At 50 g centrifugal acceleration, the clay ground is consolidated and four to five stages of shaking are applied to the quay wall. The recorded input-output accelerations, deflection of the quay wall, earth pressures along depth and pore pressures were used to evaluate the behavior of the stabilized sheet pile quay wall. The results indicated that an improved area provides significant resistance against seismic loading. The ground improvement can reduce 30% to 60% bending moment during the seismic loading. The horizontal deflection of the quay wall decreases rapidly with increase in area of the CDM until it reaches a certain limit. Prediction by the numerical model agrees fairly well with the results of centrifuge model tests.     

Investigation on Static Stability of Sheet Pile Quay Wall Improved by Cement Treated Sea-Side Ground from Centrifuge Model Tests

The static stability of sheet pile quay walls on a thick clay deposit against horizontal loads was studied through a series of centrifuge model tests. In the tests, an overconsolidated Kaolin clay layer was prepared over a layer of dense Toyoura sand in a rectangular container. The model quay wall was set to the bottom of the sand layer. The sea-side area adjacent to the quay wall was improved with cement-treated Kawasaki clay. Under 50 g centrifugal acceleration, the clay deposit was consolidated and horizontal line loads of about 0 to 70 kN/m were applied to the quay wall. The width and the depth of the improved area were varied and its performance was compared with that of a quay wall embedded in unimproved ground. Results of the study indicated that the improved ground provided significant resistance against horizontal loading. In addition, a numerical model to estimate the mechanical behavior of the sheet pile quay wall is presented. The outcomes of the numerical model show good agreement with the centrifuge test results.     

Behaviour of Pile Group behind a Sheet Pile Quay Wall Subjected to Liquefaction-Induced Large Ground Deformation Observed in Shaking Test in E-Defense Project

This paper aims to illustrate a large-scale test on a pile group and a sheet pile quay wall which were subjected to liquefaction-induced large ground deformation. The sheet pile quay wall was displaced laterally and the 2×3 pile group was forced by the flow of liquefied soil. This experiment was conducted in March 2006 at the National Research Institute for Earth Science and Disaster Prevention (NIED), Hyogo Earthquake Engineering Research Center, Japan. Liquefaction-induced lateral spreading was achieved, and soil moved laterally about 1.1 m behind the sheet pile quay wall. Lateral soil displacement was measured by the inclinometers, and results were in close agreement with the directly observed values. Soil lateral displacement and velocity of soil flow decreased as the distance from the quay wall increased toward the landside. Bending strain records were able to explain the damages to the piles, yielding at the top and buckling at the middle height. Lateral force of the liquefied soil exerted on the piles was obtained using earth pressure (EP) sensors and it is shown that rear row piles (close to the quay wall) received larger lateral forces than front row piles (far from the quay wall). This behaviour is explained by the distribution of displacement and velocity of the liquefied soil throughout the shaking. In addition, the lateral soil force was back calculated from strain gauge data and the results are compared with the ones directly measured by the EP sensors. Then, the limitations and advantages of the back-calculation approach are elaborated in this study. Moreover, the time history of lateral soil force showed no correlation with either soil or pile displacements, while it demonstrated a fairly close correlation with the relative velocity until a specific time. This interesting finding would confirm the rate-dependent behaviour of the liquefied soil, though more data from large scale experiments, field testing and centrifuge model tests are needed in this regard.     

某大厦基坑支护设计与施工

介绍某大厦的支护形式;重力式挡土墙、喷锚及树根桩的设计、施工及边坡变形监测。     

厦门西站大尺寸矩形人工挖孔桩施工技术

以厦门西站刚架结构铁路桥桩板墙的人工挖孔桩为例,介绍了大直径规则尺寸人工挖孔桩的施工要点。在孔壁支护中,根据不同的地质情况,分别采用了现浇式配筋混凝土护壁施工工艺和预制管沉井开挖施工工艺。同时,详细介绍了孔内混凝土浇筑的施工工艺和人工挖孔桩施工的安全注意事项。     

圆形基坑土钉墙支护结构强度的分析

从桩锚等圆筒式支护结构的内力分析和土钉支护制约机制的工作机理出发,将土钉墙视为重力式挡土墙,探讨了圆形基坑土钉支护结构的强度分析方法,提出了圆形基坑不同支护形式和支护结构制约机制的强度分析模型,得出了圆形基坑土钉支护形式优于矩形基坑土钉支护形式的结论。     

对钢筋混凝土桩基扶壁式挡土墙计算的探讨

结合工程概况，确定采用扶壁式钢筋混凝土挡土墙，从荷载、稳定性验算、挡土墙强度计算、桩基础计算五方面介绍了该挡土墙的有关计算，避免了传统重力式挡土墙的缺点。     

钻孔灌注桩孔壁稳定性分析

为了更好地预防和减少钻孔灌注桩在施工过程中出现孔壁失稳现象,总结了现有对孔壁稳定性分析方法,主要从应力方法、极限分析方法和数值方法三个方面进行分析,系统地总结分析了三种方法的分析过程、应用及优缺点。并进一步分析了泥浆相对密度、钻孔深度、孔径、土体粘聚力、内摩擦角、土体重度及施工情况等因素对孔壁稳定性的影响。