Bearing capacity optimization of T-shaped soil-cement column-improved soft ground under soft fill

During dredging activities, a large amount of dredged clay slurry or lump is produced. A dumping site composed of soft clay near the water body is often used to deposit dredged soft fill. Soil-cement columns are commonly employed to treat the soft ground for this application. Under soft fill, failure of soft clay dominates the behaviour of composite ground. Hence, a soil-cement slab is needed to form a load transfer platform above the columns, which is costly. As an alternative, the use of T-shaped column with an enlarged column cap is proposed. In this study, the responses of composite ground with T-shaped column are measured experimentally, which are used to calibrate a numerical model. The results of numerical parametric analyses show that the implementation of T-shaped column under soft fill can change the governing failure mode into column failure, once the diameter of column cap exceeds a certain value, after which the improvement efficiency is the same between T-shaped column and column-slab system. The height of column cap results in negligible difference in bearing capacity, and a minimum value of 0.3 m is suggested for use in design to avoid punching failure.     

碎石桩复合地基承载力和沉降若干问题

本文首先简要地讨论了碎石桩复合地基可能的破坏模式，随后系统地分析了三十几组复合地基的实测数据，探讨了这种加固处理技术可能达到的效果。通过对桩土应力比、面积置换率以及天然地基压缩模量对复合地基承载力的提高和沉降折减系数的影响的讨论，指出了这些参数在设计取值时所需注意的问题。     

灌注桩底的水泥土桩在三轴受力状态下的承载力分析

本文结合某工程人工挖孔灌注桩桩底旋喷水泥土桩的静载试验结果 ,分析灌注桩桩底旋喷水泥土桩 ,由于桩侧土层自重在桩周产生的侧压力 ,使旋喷水泥土桩处于三轴受力状态下的承载力情况 ,供设计与施工参考     

大型油罐深厚水泥土搅拌桩复合地基设计探讨

通过某大型油罐工程实例探讨了用 2 7m的深长水泥土搅拌桩处理 2 2 m深厚淤泥质粘土的复合地基的设计计算方法 ,并将本文方法的计算结果与实测结果进行了比较 ,提出了适宜的计算公式 ,可供工程设计参考     

考虑水浮力的桩土共同作用

对桩土共同作用理论做了探讨 ,论述了水浮力对桩与土的卸载及其对基础设计的影响 ;认为桩土应力比无法精确确定 ,桩土应力比应为一个范围值 ,在这范围地基及基础的安全均应得到保证 ;对目前复合桩基设计方法存在的问题进行了讨论 ,提出了改进的复合桩基与复合地基设计方法     

复合地基基本工作机理及存在问题综述

本文介绍了复合地基的发展现状、基本工作机理 ,并对复合地基的承载力计算方法和沉降计算方法进行了分析 ,最后对复合地基计算中存在的问题进行了探讨     

组合梁翼板的有效宽度分析

组合梁混凝土翼板有效宽度取值的合理与否对于组合梁的承载力和挠度分析非常关键。各国规范对其取值相差比较大,且一般都是考虑弹性阶段工作状态时采用,对于目前广泛用于楼盖内力分析中塑性内力重分布的方法,并不适用。为此,作者通过3根正弯矩简支组合梁和一根负弯矩组合梁进行试验,并与已有实验数据相比较,发现有效宽度的取值在弹性阶段和塑性阶段时,各国规范都偏保守,对其合理的取值提出了建议,可供工程设计参考。     

温州某工程水泥搅拌桩复合地基承载力确定的探讨

本文根据温州某工程水泥搅拌桩复合地基设计资料、现场载荷试验及及取芯试验等资料 ,对于软土上搅拌桩的复合地基的破坏模式、桩身强度的影响、褥垫层的影响 ,特别是复合地基载荷试验中承载力的确定等进行了分析探讨     

轴向压力下钢管混凝土交叉连接的性能——试验研究

在新型斜肋构架结构体系中,一般的连接有4个斜向柱和几个水平梁。提出两种钢管混凝土交叉连接,可以应用钢管混凝土斜肋直接安装在结构梁上。基于中国的钢管混凝土的规范提出了这种连接的承载力计算方法。完成了8个连接在轴压荷载下的各种性能、承载力及破坏机理。试验中考虑的变量包括连接细节、柱间斜角及荷载形式,得到试件的挠度、应力、破坏模式和承载力。研究结果显示:CFST柱构件之间的连接角度对其破坏模式具有很大影响,此外,连接板比翼板更具有约束作用,荷载类型对连接性能的影响很小。受压承载力与计算值的比在0·99到1·31,说明计算承载力是精确的,对于结构设计是偏于安全的。最后,验证了所提出的连接性能与钢管混凝土短柱相似。     

Experimental and Analytical studies of reinforced crushed limestone

This research study aims at investigating the behavior of spread footings on reinforced crushed limestone using laboratory model tests. The model tests were conducted inside a steel box with dimensions of 1.5 m (length) × 0.91 m (width) × 0.91 m (height) using a steel plate with dimensions of 152 mm × 152 mm (6 in. × 6 in.). The parameters investigated include the number of reinforcement layers and the tensile modulus and type of reinforcement. An analytical solution is also developed to estimate the ultimate bearing capacity of reinforced crushed limestone. The test results show that the inclusion of reinforcement can appreciably improve the bearing capacity of crushed limestone up to a factor of 2.85 at a settlement ratio of 10% and reduce the footing settlement down to 75% at a surface pressure of 5500 kPa. The results also demonstrate that reinforcements with higher tensile modulus performed better than reinforcements with lower tensile modulus and that steel reinforcement performed better than geogrid reinforcement. The proposed analytical solution gave a good predication of experimental results of geogrid reinforced sections, while Huang and Menq's solution (1997) gave a good predication for steel reinforced crushed limestone. The analytical results also showed that the reinforced ratio (R_r) should be high enough to form the “deep footing” effect.     

钢筋混凝土柱钢板套箍加固试验研究

在结构试验的基础上 ,给出钢筋混凝土柱钢板套箍加固的承载力计算方法 ,可供加固设计时参考。     

Limit analysis solutions for the bearing capacity of rock masses using the generalised Hoek–Brown criterion

This paper applies numerical limit analyses to evaluate the ultimate bearing capacity of a surface footing resting on a rock mass whose strength can be described by the generalised Hoek–Brown failure criterion [Hoek E, Carranza-Torres C, Corkum B. Hoek–Brown failure criterion—2002 edition. In: Proceedings of the North American rock mechanics society meeting in Toronto, 2002]. This criterion is applicable to intact rock or heavily jointed rock masses that can be considered homogeneous and isotropic. Rigorous bounds on the ultimate bearing capacity are obtained by employing finite elements in conjunction with the upper and lower bound limit theorems of classical plasticity. Results from the limit theorems are found to bracket the true collapse load to within approximately 2%, and have been presented in the form of bearing capacity factors for a range of material properties. Where possible, a comparison is made between existing numerical analyses, empirical and semi-empirical solutions.     

Earth reinforcement using soilbags

This paper describes the method of earth reinforcement using soilbags and illustrates its application for case studies involving a pond and the expansive soil slope protection for a highway. The strength properties of soilbags were investigated using unconfined compression tests and bearing capacity tests on real soilbags containing either medium grained sands or gravels. The test results show that soilbags have high strength when subjected to an external load. This is primarily attributed to the mobilization of tensile forces in the bags. It is concluded that earth reinforcement using soilbags could substantially improve the bearing capacity of soft ground as well as minimizing deformation under working loads.     

CFG桩复合地基处理技术在某高层建筑中的应用

采用理论与工程实例相结合的方法,对CFG桩复合地基设计计算、施工技术、处理效果等方面作了较全面的介绍。结果表明,对天然地基承载力较低而设计要求的承载力较高、沉降变形要求又比较严格的地质条件,采用CFG桩复合地基可以达到良好的效果。     

某大跨度网架结构承载能力分析

本文以某大跨度网架为工程背景,采用有限元分析软件MIDAS建立该网架的空间有限元模型,进行网架结构的承载能力分析,并阐述几点关于网架结构计算分析的看法。     

Bearing capacity and failure behaviors of floating stiffened deep cement mixing columns under axial load

This research aims to clarify and gain an insight into the impact of the length of the stiffened core and the strength of the deep cement mixing (DCM) socket on the behaviors of floating stiffened deep cement mixing (SDCM) columns. The observed behaviors include the axial ultimate bearing capacity, settlement and failure mode. The study begins by conducting a series of physical model tests as a preliminary investigation. The results reveal that the strength of the DCM socket can be reduced to a certain value by inserting a sufficiently long reinforced core to achieve the highest possible load-carrying capacity, indicating an optimum length of the stiffened core for a specific DCM socket strength. For a parametric study on the actual scale condition, full-scale load tests on a floating DCM and an SDCM column with eucalyptus wood as a core in the thick soft clay layer area were carried out to provide a reference case. The extended numerical analysis results suggest that the modes of failure depend on the length of the stiffened core and the strength of the DCM socket. The results from the numerical parametric study were used to establish a guideline chart for suggesting the appropriate length of the core in accordance with the strength of the DCM socket of the floating SDCM columns. The field pile load test results also confirm that core materials with a lower strength and stiffness, such as eucalyptus wood, could potentially be used as a reinforced core.     

国内钢管混凝土核心柱的研究与应用综述

钢管混凝土核心柱具有钢管混凝土和型钢混凝土的优点,其承载力高、抗震性能好,在高层、超高层建筑结构中有着较好的应用前景。本文在归纳国内钢管混凝土核心柱的研究和应用现状的基础上,对其需要进一步开展的研究工作进行了总结。