悬臂式排桩挡土墙在某铁路中的应用

本文简要介绍了悬臂式排桩挡土墙作为永久性支挡结构的设计原理、方法和施工注意事项等。     

灌注桩导管爆管与瘪管的原因分析

水下混凝土灌注是钻孔灌注桩施工中最关键工序之一,超深孔水下混凝土灌注的导管偶尔会出现爆管与瘪管现象。通过对导管受力分析,从理论上分析了造成爆管和瘪管现象的直接原因,从实践中罗列出可能导致爆管与瘪管的各种因素,并提出预防措施,有利于超深孔水下混凝土灌注质量的控制。     

滨海地区深基坑支护出现的问题及对策

在滨海地区,由于位置的特殊性和场地回填材料的复杂,基坑支护工程也有其特殊性,往往具有在一般地区难以遇到的实际困难。结合工程实例,介绍了在滨海地区典型的基坑支护工程中极易出现的问题,并介绍了设计和施工过程中的处理措施。     

Three‐dimensional nonlinear finite element analysis of pile groups in saturated porous media using a new transmitting boundary

The dynamic behaviour of pile groups subjected to an earthquake base shaking is analysed. An analysis is formulated in the time domain and the effects of material nonlinearity of soil, pile–soil–pile kinematic interaction and the superstructure–foundation inertial interaction on seismic response are investigated. Prediction of response of pile group–soil system during a large earthquake requires consideration of various aspects such as the nonlinear and elasto‐plastic behaviour of soil, pore water pressure generation in soil, radiation of energy away from the pile, etc. A fully explicit dynamic finite element scheme is developed for saturated porous media, based on the extension of the original formulation by Biot having solid displacement (u) and relative fluid displacement (w) as primary variables (u–w formulation). All linear relative fluid acceleration terms are included in this formulation. A new three‐dimensional transmitting boundary that was developed in cartesian co‐ordinate system for dynamic response analysis of fluid‐saturated porous media is implemented to avoid wave reflections towards the structure. In contrast to traditional methods, this boundary is able to absorb surface waves as well as body waves. The pile–soil interaction problem is analysed and it is shown that the results from the fully coupled procedure, using the advanced transmitting boundary, compare reasonably well with centrifuge data. Copyright © 2007 John Wiley & Sons, Ltd.     

磁梯度探测在工程基桩桩长检测中的应用

磁梯度探测方法可以高效、高精度探测具有铁磁性的地下障碍物深度,因此在工程基桩长度测试中有良好的效果。     

Idealisation of soil–structure system to determine inelastic seismic response of mid-rise building frames

In this study, a novel and enhanced soil–structure model is developed adopting the direct analysis method using FLAC 2D software to simulate the complex dynamic soil–structure interaction and treat the behaviour of both soil and structure with equal rigour simultaneously. To have a better judgment on the inelastic structural response, three types of mid-rise moment resisting building frames, including 5, 10, and 15 storey buildings are selected in conjunction with three soil types with the shear wave velocities less than 600 m/s, representing soil classes C_e, D_e and E_e, according to Australian Standards. The above mentioned frames have been analysed under two different boundary conditions: (i) fixed-base (no soil–structure interaction) and (ii) flexible-base (considering soil–structure interaction). The results of the analyses in terms of structural displacements and drifts for the above mentioned boundary conditions have been compared and discussed. It is concluded that considering dynamic soil–structure interaction effects in seismic design of moment resisting building frames resting on soil classes D_e and E_e is essential.     

Seismic response of single-column bent on pile: evidence of beneficial role of pile and soil inelasticity

While seismic codes do not allow plastic deformation of piles, the Kobe earthquake has shown that limited structural yielding and cracking of piles may not be always detrimental. As a first attempt to investigate the consequences of pile yielding in the response of a pile-column supported bridge structure, this paper explores the soil–pile-bridge pier interaction to seismic loading, with emphasis on structural nonlinearity. The pile–soil interaction is modeled through distributed nonlinear Winkler-type springs and dashpots. Numerical analysis is performed with a constitutive model (Gerolymos and Gazetas 2005a, Soils Found 45(3):147–159, Gerolymos and Gazetas 2005b, Soils Found 45(4):119–132, Gerolymos and Gazetas 2006a, Soil Dyn Earthq Eng 26(5):363–376) materialized in the OpenSees finite element code (Mazzoni et al. 2005, OpenSees command language manual, p 375) which can simulate: the nonlinear behaviour of both pile and soil; the possible separation and gapping between pile and soil; radiation damping; loss of stiffness and strength in pile and soil. The model is applied to the analysis of pile-column supported bridge structures, focusing on the influence of soil compliance, intensity of seismic excitation, pile diameter, above-ground height of the pile, and above or below ground development of plastic hinge, on key performance measures of the pier as is: the displacement (global) and curvature (local) ductility demands and the maximum drift ratio. It is shown that kinematic expressions for performance measure parameters may lead to erroneous results when soil-structure interaction is considered.     

Evaluation of the natural vibration frequencies of a historical masonry building accounting for SSI

The dynamic identification of a historical masonry palace located in Benevento (Italy) has been carried out. The case study is representative of many buildings located in historic Italian centres. Since the building has been instrumented by the Department of Civil Protection with a permanent dynamic monitoring system, some of the recorded data, acquired in various operating conditions have been analysed with basic instruments of the Operational Modal Analysis in order to identify the main eingenfrequencies and vibration modes of the structure. The experimental results have been compared to the numerical outcomes provided by a detailed three-dimensional Finite Element (FE) model of the building where Soil–Structure Interaction (SSI) has been taken into account. The comparison of experimental vs. numerical frequencies and vibration modes of the palace evidenced the role exerted by the subsoil on the dynamic response of the building.     

中国2010年上海世博会场址区地质环境条件分析与评价

文章在简要介绍世博会场址地质条件的基础上,分别分析了场址区流砂、软土和地下水等不良地质现象对工程建设的影响,然后评价了场址区天然地基工程、桩基工程以及地下工程建设的适宜性,为世博会场址区工程建设提供必要的地质依据。     

Provenance and origins of a Late Paleozoic accretionary complex within the Khangai–Khentei belt in the Central Asian Orogenic Belt,central Mongolia

We have investigated the petrography, geochemistry, and detrital zircon U–Pb LA-ICPMS dating of sandstone from the Gorkhi Formation of the Khangai–Khentei belt in the Ulaanbaatar area, central Mongolia. These data are used to constrain the provenance and source rock composition of the accretionary complex, which is linked to subduction of the Paleo-Asian Ocean within the Central Asian Orogenic Belt during the Middle Devonian to Early Carboniferous. Field and microscopic observations of the modal composition of sandstone and constituent mineral chemistry indicate that the sandstone of the Gorkhi Formation is feldspathic arenite, enriched in saussuritized plagioclase. Geochemical data show that most of the sandstone and shale were derived from a continental margin to continental island arc setting, with plutonic rocks being the source rocks. Detrital zircon ²⁰⁶Pb/²³⁸U ages of two sandstones yields age peaks of 322 ± 3 and 346 ± 3 Ma. The zircon ²⁰⁶Pb/²³⁸U age of a quartz–pumpellyite vein that cuts sandstone has a weighted mean age of 339 ± 3 Ma. Based on these zircon ages, we infer that the depositional age of sandstone within the Gorkhi Formation ranges from 320 to 340 Ma (i.e., Early Carboniferous). The provenance and depositional age of the Gorkhi Formation suggest that the evolution of the accretionary complex was influenced by the intrusion and erosion of plutonic rocks during the Early Carboniferous. We also suggest that spatial and temporal changes in the provenance of the accretionary complex in the Khangai–Khentei belt, which developed aound the southern continental margin of the Siberian Craton in relation to island arc activity, were influenced by northward subduction of the Paleo-Asian Ocean plate.