Mechanical Testing in Unsaturated Soils   总被引：1，自引：0，他引：1  

Laureano R. Hoyos  Lyesse Laloui  Roberto Vassallo 《Geotechnical and Geological Engineering》2008,26(6):675-689

The state-of-the-art report presented herein is aimed at documenting, to the largest extent possible, some of the recent advances in laboratory testing of unsaturated soils for stress–strain–strength–stiffness characterization under suction-controlled isotropic, axisymmetric, and true triaxial stress states. The report is intended to be neither comprehensive nor fully inclusive, offering plenty of room for further discussion on recent refinements and techniques not yet reported in the literature. The main sections in this report are devoted to describing current methods and technologies using cylindrical triaxial systems, including advances in volume change measurements; resonant column/torsional shear systems; bender element-based systems; and suction-controlled testing under true triaxial stress states. Concluding remarks are included in the last section of the report.  相似文献   

Geotechnical Characteristics of Volcanic Beach Sands with Varying Iron Contents     

Hyunwook Choo  Jaewook Hwang  Youngmin Choi  Changho Lee 《Marine Georesources & Geotechnology》2016,34(6):571-580

One of the distinguishing features of volcanic beach sand compared to typical silica sand can be found in its relatively high iron content; however, studies on the effect of iron content on the engineering properties of volcanic beach sand have been very limited until now. Consequently, this experimental investigation quantifies the effect of iron content on the engineering properties of Ulleung volcanic beach sands, including small strain stiffness, compressibility, friction angle, and cone tip resistance. Various geotechnical experiments were performed, and test results demonstrate that the small strain stiffness increases with an increase in iron content because of the increased interparticle contact stiffness. In addition, the elastic deformation of soil particles decreases with an increase in iron content because of the greater elastic modulus of iron compared to that of silica. In contrast, the effects of iron content on the intermediate strain constrained modulus and on the large strain friction angle are insignificant, and these properties are mainly determined by state variables. The relationship between the stress-normalized cone tip resistance and the state parameter of tested Ulleung sand is very similar to that on silica sands, reflecting that the effect of iron contents on the cone tip resistance is minimal.  相似文献   

Torsional Dynamic Impedance of a Tapered Pile Considering its Construction Disturbance Effect     

Wen-Bing Wu  Guo-Sheng Jiang  Shu-Hui Lü  Bang-Hua Xie 《Marine Georesources & Geotechnology》2016,34(4):321-330

The dynamic response of a tapered pile (considering its construction disturbance effect) is investigated when the tapered pile is subjected to a time-harmonic torsional loading. For most engineering conditions, the surrounding soil may be weakened or strengthened owing to the construction disturbance effect of the tapered pile, resulting in the soil becoming radially inhomogeneous. In order to consider this problem, the circumferential shear complex stiffness transfer model is proposed to simulate the radial inhomogeneity of soil. Then, the governing equations of a tapered pile-soil system subjected to torsional dynamic loading are established. By virtue of the circumferential shear complex stiffness transfer method and the impedance function transfer method, the analytical solution of torsional dynamic impedance at the head of the tapered pile is derived. Based on the presented solution, the influence of the construction disturbance effect of the surrounding soil on the torsional dynamic impedance at the pile head is investigated within the low-frequency range concerned in the design of a dynamic foundation. The results show that, even if the hardening range and softening range of the surrounding soil vary within a smaller scale, the hardening effect and softening effect also have a notable influence on the torsional dynamic impedance at the pile head.  相似文献   

Back analysis of the Kanowna Belle stope filling case history     

《Computers and Geotechnics》2016

A fully coupled multi-physics finite element model has been used to conduct a back-analysis of a stope filling case history at the Kanowna Belle (KB) mine in Western Australia. The model captures a number of important characteristics of mine backfill behaviour, including the evolution of strength and consolidation properties with cement hydration, the impact of chemical shrinkage (self-desiccation) and de-saturation. Material parameters for the constitutive model have been calibrated using published laboratory test data. A reasonable match between ideal and actual elements of response as revealed through in-situ measurements of total stress and pore pressure was obtained using these initial parameters. A parametric study was then performed which showed that the backfill strength parameters (friction angle, dilation and cohesion), the chemical volume shrinkage, the rate of cement hydration and the water retention properties all have a significant influence on the calculated states of stress within the stope.  相似文献   

Simple superposition approach for dynamic analysis of piled embedded footings     

L. A. Padrón  G. Mylonakis  D. E. Beskos 《国际地质力学数值与分析法杂志》2012,36(12):1523-1534

The effectiveness and accuracy of the superposition method in assessing the dynamic stiffness and damping coefficients (impedance functions) of embedded footings supported by vertical piles in homogeneous viscoelastic soil is addressed. To this end, the impedances of piled embedded footings are compared to those obtained by superposing the impedance functions of the corresponding pile groups and embedded footings treated separately, with the magnitude of the relative average differences being around 10–30%. The results are presented in a set of dimensionless graphs and simple expressions that can be used to estimate the dynamic stiffness and damping of piled embedded footings, provided that the impedance functions of the two individual components are known. This is precisely the reason why the superposition approach studied here is appealing, because such impedance functions for both embedded footings and pile groups are available for a wide range of cases. How to estimate the kinematic response functions of the system when those of the individual components are known is also discussed. To address the problem, parametric analyses performed using a 3D frequency‐domain elastodynamic BEM‐FEM formulation are presented for different pile–soil stiffness contrasts, embedment depths, pile‐to‐pile separations and excitation frequencies. Vertical, horizontal, rocking, and cross‐coupled horizontal‐rocking impedance functions, together with translational and rotational kinematic response functions, are discussed. The results suggest that the superposition concept, in conjunction with a correction strategy as that presented herein, can be employed in geotechnical design. For kinematic effects, the response functions of the embedded footing are found to provide reasonable estimates of the system's behaviour. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

On a multilaminate model for soil incorporating small strain stiffness     

Florian Scharinger  Helmut F. Schweiger  Gyan N. Pande 《国际地质力学数值与分析法杂志》2009,33(2):215-243

In this paper a constitutive model for soils incorporating small strain stiffness formulated in the multilaminate framework is presented. In the multilaminate framework, the stress–strain behaviour of a material is obtained by integrating the mechanical response of an infinite number of randomly oriented planes passing through a material point. Such a procedure leads to a number of advantages in describing soil behaviour, the most significant being capture of initial and induced anisotropy due to plastic flow in a physically meaningful manner. In the past, many soil models of varying degree of refinement in the multilaminate framework have been presented by various authors. However, the issue of high initial soil stiffness in the range of very small strains and its degradation with straining, commonly referred to as ‘small strain stiffness’, has not been addressed within the multilaminate framework. In this paper, we adopt a micromechanics‐based approach to derive small strain elastic stiffness of the soil mass. Comparison of laboratory test data with results obtained from numerical simulations based on the proposed constitutive model incorporating small strain stiffness is performed to demonstrate its predictive capabilities. The model is implemented in a finite element code and numerical simulations of a deep excavation are presented with and without incorporation of small strain stiffness to demonstrate its importance in predicting profiles of deformation. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

反复冻融下黄土抗剪强度劣化的试验研究   总被引：14，自引：7，他引：7  

董晓宏  张爱军  连江波  郭敏霞 《冰川冻土》2010,32(4)

以陕西杨凌黄土为研究对象,对不同初始含水率的重塑黄土进行了长期反复冻融循环,对经历不同冻融次数的试样进行了系列直剪试验.结果表明:在控制含水率不变的情况下,黄土的黏聚力和抗剪强度一般在3～5次冻融循环之后降到最低值,并趋于稳定;内摩擦角基本不变.探讨了长期冻融循环下黄土的强度劣化特性,采用插值法修正了含水率下降对强度的影响.由试验数据拟合出黄土抗剪强度和冻融循环次数之间的经验关系,推导出一种考虑冻融循环作用的黄土强度劣化模型.经试验验证,该模型可以较好描述黄土强度的劣化特性,为黄土工程力学性质的劣化研究提供了一种新的有效途径.  相似文献   

Influence of Frequency on the Behaviour of Plate Anchors Subjected to Cyclic Loading     

S. P. Singh  S. V. Ramaswamy 《Marine Georesources & Geotechnology》2013,31(1):36-50

This article reports the response of embedded circular plate anchors to varying frequencies of cyclic loading. The effects of time period of loading cycles and pre-loading on movement of anchors and post-cyclic monotonic pullout behavior are studied using a model circular (80 mm diameter) plate anchor, buried at embedment ratio of six in a soft saturated clay. The frequencies of loading cycles have showed considerable effect on movement of anchors. For given duration of loading, higher frequency cycles cause more movement of anchor than lower frequency cycles. Pre-loading reduces the movement of anchors in subsequent loading stages. When anchors are recycled at a load ratio level less than the pre-cycling load, the movement of anchor in recycling phase are very much reduced, but if the recycling is done at a higher load ratio level, the effect is not that much pronounced and the anchors behave as if they were not subjected to any cycling load in the past. Anchor subjected to cyclic loading and then monotonic pullout shows an increase in initial stiffness, whereas the peak pullout load was found to decrease marginally over that of an anchor not subjected to any cyclic loading. For the present test conditions, the relative post-cyclic stiffness of anchors is found to vary from 1.169 to 1.327.  相似文献   

Experimental simple shear study of composite soil with cemented soil core     

Feiyu Liu  Kai Zhu  Hongtao Fu  Dong Feng 《Marine Georesources & Geotechnology》2013,31(8):960-971

Abstract

Cement soil mixing piles are an effective treatment method for marine soft clay. To investigate the static and dynamic characteristics of the composite soil with cemented soil core, a series of experiments are carried out by using the cyclic simple shear test. The result shows that, the static shear strain showed strain hardening, cemented soil core can improve static shear strength of composite soil, vertical stress can enlarge reinforcement of cemented soil core. The tendency of strain development of composite soil with different area replacement ratios under cyclic loading is the same as that of pure clay, existing critical cyclic stress ratios corresponding to different area replacement ratios. In addition, improving area replacement ratio can increase cyclic strength. At same time, adding of cemented soil core does not change shape of hysteresis curve compared with it for clay either. Moreover, cemented soil core can also obstruct stiffness softening. Through regression analysis of the experimental data, relationship between cyclic number and soil softening index is proved to be linear. The results can give a reference for the dynamic characters of the marine soft clay foundation with cement soil mixing piles.  相似文献   

滞变—摩擦基底隔震支座的试验和模型   总被引：5，自引：3，他引：5  

洪峰  王前信 《地震工程与工程振动》1997,17(1):1-8

本提出了一种滞变－摩擦基底隔震支座。这种支座由钢棒和摩擦元件组成，钢棒容许摩擦元件水平滑动，同时又限制这种滑动；摩擦元件承受结构的竖向荷载，作完成了钢棒滞变恢复力特性的试验，并给出了钢棒的滞变恢复力模型的模型参数的计算公式，该模型与常用的折线模型有所不同，它仅用一个非线性微分方程来描述滞变恢复力，而不需要复杂的规则。  相似文献