Strain softening of K0-consolidated Changi sand under plane-strain conditions     

D. Wanatowski  J. Chu 《Acta Geotechnica》2006,1(1):29-42

Experimental results are presented in this paper to study the strain softening behaviour of a marine dredged sand under plane-strain conditions. K₀ consolidated drained and undrained tests were conducted using a new plane-strain apparatus to characterize the strain softening behaviour of the sand under plane-strain conditions. For medium dense specimens, strain softening and shear bands were observed to occur under both drained and undrained conditions. For very loose specimens, no shear bands were observed and critical states were reached within the homogeneous deformation region in both drained and undrained tests. Strain softening was observed to occur at small strain for very loose specimens under undrained conditions. Two types of strain softening, the homogenous softening and banding softening, were identified and the conditions for strain softening were established. The results obtained from this study were compared with the studies by Han and Vardoulakis (Géotechnique 41(1):49–78, 1991), Finno et al. (J Geotech Eng ASCE 122(6):462–473, 1996, Géotechnique 47(1):149–165, 1997) and Mokni and Desrues (Mech Cohes-Frict Mat 4:419–441, 1998).  相似文献   

Assessment of Marine Clay Improvement Under Reclamation Fills by in-situ Testing Methods     

A. Arulrajah  H. Nikraz  M. W. Bo 《Geotechnical and Geological Engineering》2006,24(2):219-226

In ground improvement projects with prefabricated vertical drains, the duration of the preloading period is set in advance based on the predetermined time rate of consolidation of the compressible layer. If prediction is accurately done, the required degree of consolidation is met at the pre-determined preloading time. As such, there is a requirement for in-situ tests to be carried out just prior to the removal of surcharge to assess the degree of consolidation of the improved ground. In-situ tests were carried out after 23 months of surcharge loading at the In-Situ Test Site within the Changi East Reclamation Project in the Republic of Singapore. In-situ testing works in this research study comprises the use of field vane shear, piezocone, flat dilatometer and self-boring pressuremeter. The in-situ tests were carried out to determine the shear strength and degree of consolidation of the Singapore marine clay at Changi after 23 months of surcharge loading. The In-Situ Test Site consisted of a Vertical Drain Area as well as an untreated Control Area. Both areas were located adjacent to each other and were surcharged simultaneously to the same level and surcharge left in place for a period of 23 months. Comparison was made between the in-situ test results of the Vertical Drain Area and the untreated Control Area.  相似文献   

用强度折减法和FLAC^3D计算边坡的安全系数   总被引：4，自引：0，他引：4  

李新坡陈永波  王永杰何思明 王成华 《山地学报》2006,24(B10):235-239

对采用强度折减法和FLAC^3D计算边坡的安全系数问题进行了研究。对边坡破坏的判断标准、边坡滑面位置的确定及计算参数对安全系数计算结果的影响进行了分析。结果表明，用FLAC计算时，边坡的破坏可以通过节点最大不平衡力突变、节点最大速度突变、特定点位移的不收敛等特征进行判断，同时边坡破坏的滑面也可以由速度等值线图等方法表示出来。另外，通过分析发现，弹性常数、剪胀角等参数对安全系数计算结果的影响不大。  相似文献   

Compressibility and shear strength of a residual soil     

Yahia E.-A. Mohamedzein  Mohammed H. Aboud 《Geotechnical and Geological Engineering》2006,24(5):1385-1401

A detailed study was performed to investigate the compressibility and the shear strength of a residual soil in Omdurman, Sudan. The soil resulted from weathering of sandstone and mudstone. The soil is classified as sandy clayey silt (MH-CH) and is generally partially saturated. Consolidation tests were performed to study the compressibility of the soil and UU, CIU and insitu tests (CPT and SPT) were performed to study the shear strength characteristics of the soil. The characteristics of this residual soil can generally be predicted using correlations proposed in the literature for transported soils. The soil is of low to medium compressibility and exhibits slight apparent overconsolidation behavior. The soil dilates during shear and shows no long term effective cohesion. Problems associated with open cuts in this soil are attributed to loss of strength upon saturation.  相似文献   

A Solution to the Problem of Predicting the Suitability of Silty–clayey Materials for Cement-stabilization     

Evangelos I. Stavridakis 《Geotechnical and Geological Engineering》2006,24(2):379-398

Major geotechnical problems in construction involving silty–clayey soils are due to their low strength, durability and high compressibility of soft soils, and the swell–shrink nature of the overconsolidated swelling soils. Confronted with these problems, a suitable ground improvement technique is needed, for deep excavations in soft clays, for stability, durability and deformation control. Cement-stabilization is one of the alternatives. An increase in strength and durability, reduction in deformability are the main aims of this method. Conventional cement-stabilization methods are used mainly for surface treatment. However, the use of cement has recently been extended to a greater depth in which cement columns were installed to act as a type of soil reinforcement (deep cement–soil mixing and cement jet grouting). In situ engineering properties of these silty–clayey soils are often variable and difficult to predict. For this reason cement-stabilization methods have a basic target to control the aforementioned engineering properties of these clays so that the properties of a silty–clayey soil become more like the properties of a soft rock such as clayey shale or lightly cemented sandstone. So cement-stabilization of these soils is essential to control their engineering properties and to predict their engineering behaviour for construction. In an effort to predict, classify and study the suitability of silty–clayey soils for cement-stabilization both slaking and unconfined compressive strength tests were carried out on clayey–sand mixtures consisted of two types of clays, kaolin and bentonite. Finally diagrams were prepared to study the variation of slaking and strength due to compaction, curing time and cement percentage and also to predict areas of efficient cement-stabilization.  相似文献   

岩石三轴强度试验   总被引：2，自引：0，他引：2  

李广平王玉玲  蔡玉贞 《岩矿测试》2005,24(1):75-78

通过自制岩石三轴压力室和配备液压泵与现有万能材料试验机组成岩石三轴试验系统，进行岩石三轴强度试验研究，并与其它方法比对，结果相近，满足了科研和生产的需要。  相似文献   

三类高强度悬式瓷绝缘子的成分和物相分析     

龚国洪  唐荣炳  尹祚莹  邓华兴  伍正平 《矿物岩石地球化学通报》2002,21(3):174-176

为探讨高原牌70kN和进口120，210kN瓷绝缘子的成分和结构性能，中采用原子吸收光谱（AAS）和X射线衍射（XRD）方法，对三类产品进行了检测。结果表明，有效成分除K2O外，70kN和210kN的SiO2,Al2O3,Fe2O3含量接近，主晶相基本相同，有刚玉，莫来石、石英和长石等；结晶相总量：70kN35%，120kN40%,210kN48%，这表明机械强度愈大，结晶相含量愈高，只需调整70kN原样的部分成分，粒度和工艺，即生产出高等级（如210kN)瓷绝缘子。  相似文献   

Crack damage stress as a composite function of porosity and elastic matrix stiffness in dolomites and limestones   总被引：4，自引：0，他引：4  

V. Palchik  Y. H. Hatzor 《Engineering Geology》2002,63(3-4):233-245

Twenty-five uniaxial compression tests were performed to determine stress at onset of dilation, referred to herein as “the crack damage stress,” in heterogeneous dolomites and limestones. A simplified model for crack damage stress (σ_cd) is developed here using porosity, elastic modulus, Poisson's ratio and three empirical coefficients. The model shows that when porosity decreases and elastic modulus increases, σ_cd rapidly increases and approaches its maximum value. On the other hand, when porosity increases and elastic modulus decreases, σ_cd rapidly decreases and approaches its minimum value. The proposed model is validated for six heterogeneous limestone and dolomite formations which are widely distributed in Israel.  相似文献   

岩石圈流变机制的确定及影响岩石圈流变强度的因素   总被引：20，自引：2，他引：20  

臧绍先  李昶  魏荣强 《地球物理学进展》2002,17(1):50-60

讨论了确定岩石圈流变强度中存在的问题，根据Byerlee定律，给出了在Anderson断层系统下三种断层的摩擦滑动强度公式，利用小标本实验结果外推，用大标本实验结果作约束，得到岩石圈几种典型岩石的脆性破裂规律，利用上述结果和传统的方法，分别得到了鄂尔多斯和山西裂谷两个典型地区的流变强度随深度的变化。结果表明，以往的计算对岩石圈流变强度的估计过高，对脆性形变区估计不足，流变机制估计不对；岩石圈有力学分层的特性，但各地分层的深度范围不同，使得成层和力学作用变得复杂，讨论了水、应变率以及多相矿物对流变强度的影响。  相似文献   

多矿物岩石流变规律的研究进展及存在问题   总被引：4，自引：2，他引：4  

江燕  臧绍先 《地球物理学进展》2002,17(3):456-463

总结了近年来由多种矿物组成的岩石的流变规律的研究，阐述了多矿物岩石流变性质研究的意义和进展，再从实验和理论两个方面，详细论述了目前最具代表性的三种理论模型，算术平均方法、几何平均方法和能量极小方法，最后，指出这方面研究仍然存在的问题和进一步研究的方向。  相似文献