珠海地区花岗岩残积土特征

本文主要针对花岗石残积土的物质组成、形成机理及其对地基承载力，抗剪强度的影响。     

花岗岩残积土和桩基工程

分析了花岗岩残积土的成因、工程分类和工程地质特性及对桩基工程的意义以指导桩基工程的设计和施工。     

花岗岩残积土和桩基工程

分析花岗岩残积土的成因、工程分类和工程地质特性 ,及对桩基工程的意义 ,以指导桩基工程的设计和施工。     

湖南省炎陵县花岗岩残积土的岩土工程特性

本文对花岗岩残积土的物理力学性质、岩土工程特性进行了详细分析,希望为同类工程提供借鉴。     

花岗岩残积土和桩基工程

分析花岗岩残积土的成因，工程分类和工程地质特性，及对桩基工程的意义，以指导桩基工程的设计和施工。     

泉州地铁建设的岩土工程问题探讨

由于闽南地区工程地质条件的复杂性及地铁工程的特殊性,在泉州地铁建设过程中将遇到大量的岩土问题。主要有：（1）勘察方面的问题;（2）地下水的问题;（3）特殊土的处理问题;（4）深大基坑开挖的问题;（5）施工带来的环境影响问题等。对这些问题,应该使用多样化的勘察手段,查明建设场地地质水文条件;施工空间紧张的基坑支护新技术的...     

赣南地区花岗岩残积土的工程特性与承载力试验研究

花岗岩残积土是一种在我国分布广泛的特殊性土,具有较高的结构强度和较强的结构性联系,大多呈中~低压缩性,具有较大天然含水量、较大孔隙比、较低的压缩模量、较低液性指数等工程特性。花岗岩残积土与常规的黏性土工程特性不同,不可参照常规黏性土方法计算承载力,花岗岩残积土的特殊工程性质是当前工程实践的重点研究课题之一。结合相关工程,对赣南地区花岗岩残积土的工程特性及承载力试验进行研究,用多种方法进行分析对比并得出结论,为该区域的花岗岩残积土基础工程建设和研究提供参考。     

岩土工程分析评价与地质工程风险防控措施

岩土工程勘察是一项系统化、复杂化的工作,旨在为拟建建筑提供岩土工程所需的各项岩土参数,对建筑地基进行岩土工程分析评价,并针对不良地质作用、地质灾害提出有效的防范措施。基于此,本文阐述了工程勘察工作的概况,进行岩土工程分析评价,并提出相应的地质工程风险防控措施。     

灰岩地区复杂地质的岩土工程勘察措施

通过对灰岩地区特殊地层的特征分析,研究了软塑状态灰岩残积土和溶蚀灰岩两种地层对实际岩土工程勘察的影响、鉴别时应注意的问题及相应措施,研究结果对于灰岩地区的岩土工程勘察具有一定的指导作用和现实意义。     

花岗岩残积土的工程特性及边坡稳定性研究

花岗岩尤其特殊,经长期的物理化学风化作用,易形成花岗岩残积土。花岗岩残积土具有诸多特殊的工程特性,这些特性对其边坡的稳定有着很大的影响。本文主要对花岗岩残积土的工程特性做简单介绍,并对其边坡稳定进行分析。     

花岗岩残积土的试验及测试研究

本文通过对残积土的一些试验及测试数据的统计与分析,阐述残积土的特性及某些工程性能,并对工程实践中残积土的利用提出几点看法。     

Effect of cementation on the small-strain stiffness of granite residual soil

It is widely acknowledged that residual and sedimentary soils differ considerably because of how they formed. However, despite extensive advances regarding sedimentary soil, little is known about the small-strain stiffness of residual soil. This paper concerns granite residual soil from Xiamen in China, for which a typical profile is established by in situ investigations. How the stiffness varies with the soil current state, including effective mean stress, void ratio and strain, is established via systematic resonant-column tests on high-quality undisturbed and remolded specimens. Highlighted are the unique properties of the studied soil and how they affect the soil stiffness. It is found that cementation among soil particles plays a critical role in the soil stiffness. Although some existing methods can confirm the existence of cementation in the studied soil, they cannot quantify it. Therefore, a new parameter R_n is proposed to quantify the degree of cementation, with lower R_n corresponding to a more cemented structure. According to the proposed R_n, the studied residual soil in Xiamen has a different degree of cementation from that of some well-studied weathered materials, thereby necessitating separate characterization of this soil. This study improves the understanding of residual soil stiffness at small strain, especially the key effect of cementation in natural soil.     

高液限花岗岩残积土的物理特性和剪切特性

高液限花岗岩残积土广泛分布于华南地区,针对其中的含粗粒细粒土进行了物理特性和剪切强度特征的试验研究,包括土的组成和微观结构、土的物理状态、土的峰值强度和残余强度等。基于试验结果分析了细粒含水率及对土体物理状态的影响,归纳了土中粗粒含量与天然含水率之间、土的天然状态指标与抗剪强度参数之间的统计规律,探讨了应用反复剪切试验方法确定此类土残余强度的注意事项及大剪切位移时的剪应力特征。由于此类残积土具有高液限土和粗粒土的综合特征,因而需基于粗粒含量的影响来认识有关基本特性。     

Evolution of cracks in the shear bands of granite residual soil

The evolution of shear bands and cracks plays an important role in landslides. However, there is no systematic method for classification of the cracks, which can be used to analyze the evolution of cracks in shear bands. In this study, X-ray computed tomography (CT) is used to observe the behavior of granite residual soil during a triaxial shear process. Based on the digital volume correlation (DVC) method, a crack classification method is established according to the connectivity characteristics of cracks before and after loading. Cracks are then divided into six classes: obsolete, brand-new, isolated, split, combined, and compound. With evolution of the shear bands, a large number of brand-new cracks accelerate the damages of materials at the mesoscale, resulting in a sharp decrease in strength. The volume of brand-new cracks increases rapidly with increasing axial strain, and their volume is greater than 50% when the strain reaches 12%, while the volume of compound cracks decreases from 54% to 21%. As cracks are the weakest areas in a material, brand-new cracks accelerate the development of shear bands. Finally, the coupling effect of shear bands and cracks destroys the soil strength.     

Effects of dry-wet cycles on three-dimensional pore structure and permeability characteristics of granite residual soil using X-ray micro computed tomography

Due to seasonal climate alterations, the microstructure and permeability of granite residual soil are easily affected by multiple dry-wet cycles. The X-ray micro computed tomography (micro-CT) acted as a non-destructive tool for characterizing the microstructure of soil samples exposed to a range of damage levels induced by dry-wet cycles. Subsequently, the variations of pore distribution and permeability due to dry-wet cycling effects were revealed based on three-dimensional (3D) pore distribution analysis and seepage simulations. According to the results, granite residual soils could be separated into four different components, namely, pores, clay, quartz, and hematite, from micro-CT images. The reconstructed 3D pore models dynamically demonstrated the expanding and connecting patterns of pore structures during dry-wet cycles. The values of porosity and connectivity are positively correlated with the number of dry-wet cycles, which were expressed by exponential and linear functions, respectively. The pore volume probability distribution curves of granite residual soil coincide with the χ² distribution curve, which verifies the effectiveness of the assumption of χ² distribution probability. The pore volume distribution curves suggest that the pores in soils were divided into four types based on their volumes, i.e. micropores, mesopores, macropores, and cracks. From a quantitative and visual perspective, considerable small pores are gradually transformed into cracks with a large volume and a high connectivity. Under the action of dry-wet cycles, the number of seepage flow streamlines which contribute to water permeation in seepage simulation increases distinctly, as well as the permeability and hydraulic conductivity. The calculated hydraulic conductivity is comparable with measured ones with an acceptable error margin in general, verifying the accuracy of seepage simulations based on micro-CT results.     

Effect of principal stress direction during consolidation on the shear strength properties of natural granite residual soil

In numerous real-life civil engineering practices, including multi-stage embankment construction and foundation pit excavation, the direction of the major principal stress σ₁ becomes rotated. In these cases, the granite residual soil may be subjected to inclined consolidation (IC) with σ₁ being inclined, because of the relatively high permeability as a result of the fissures formed during weathering. While the effect of the σ₁ direction during the shear on the strength of granite residual soil (inherent strength anisotropy) has been primarily established, little is known about how the soil strength is affected by the direction of σ₁ during consolidation. This paper presents the effects of IC on the shear strength properties of natural granite residual soil through undrained hollow cylinder torsional shear tests. The effect of the soil structure is also considered by testing remolded soil specimens. The results reveal that while IC changes neither the shape of stress–strain curve nor the specimen features at failure, it leads to an increased ultimate shear strength in terms of both the undrained strength and stress ratio, with the remolded soil being more affected. The presented data provide new insights into the understanding of residual soil strength behaviors.     

花岗岩残积土剪切波速经验取值问题的探讨

通过福州东站附近30余个钻孔的实测波速资料,利用回归分析方法,研究花岗岩残积土标贯击数与剪切波速的定量关系及其应用。     

国际土力学及基础工程协会简介

国际土力学及基础工程协会(ISSMFE)于1936年成立,同年在美国哈佛大学召开了第一届会议,在这之后,除特殊情况外,都是每四年召开一次国际会议。我国于1957年参加国际土力学及基础工程协会,并派茅以升、陈宗基为代表出席在英国召开的第四届国际会议。此后,二十余年中,主要由于台湾问题,一直没有再出席国际土力学及基础工程协会的会议。历届会议的概要见表1。     

花岗岩残积土地基钻（冲）孔灌注桩竖向承载力研究

通过对花岗岩残积土地基的特殊性及其钻（冲）孔灌注桩单桩竖向承载力试验研究的综合分析,剖析了花岗岩残积土地基桩端阻力和桩侧阻力特性和现有计算方法存在的问题。通过分析砾、砂、黏质花岗岩残积土天然地基承载力基于标准贯入击数相关性的修正系数,提出了桩端阻力、桩侧阻力与按标准贯入击数修正的桩基规范液性指数法计算结果的经验关系,可供按JGJ 94-2008《建筑桩基技术规范》中经验公式计算花岗岩残积土地基钻（冲）孔灌注桩单桩竖向承载力时修正参考。与工程试桩的实测数据对比结果表明,文中建议的计算方法稍偏于安全,且比JGJ 94-2008《建筑桩基技术规范》中方法更接近实测值。