Yield surfaces and flow rules for deformation of granular materials with a volume constraint     

C.M. Sands  H.W. Chandler 《Computers and Geotechnics》2010

This paper presents a procedure for developing yield functions with consistent flow rules for granular materials from a family of two parameter dissipation functions in combination with appropriate kinematic constraints. Through a mathematical procedure described in the paper, a general formulation is developed that can, by adjusting the values of the two parameters, reproduce a wide range of yield surfaces, including the Drucker–Prager, Matsuoka–Nakai, and Lade–Duncan. Specifically, an analytical expression for the yield function is obtained in terms of a parameter that is a selected solution to a high order polynomial. The roots of this polynomial can always be found using the eigenvalues of the companion matrix and instructions on how to select the appropriate root are given in the paper. Two ways of incorporating anisotropy into the procedure are explored and the role within it of the recent history of deformation is examined.  相似文献   

剪切作用下断层泥的SEM显微结构特征研究          下载免费PDF全文

郝全明  白豹  孙晶 《江苏地质》2011,35(2):177-182

在模拟断层泥的摩擦实验基础上,对辉长岩的2种主要组成矿物斜长石和辉石实验后的标本进行了SEM显微结构的观察与分析,以期从实验室角度去理解下地壳断层活动的性质和特点。斜长石模拟断层泥剪切带中边界剪切面、R1和Y剪切面比较发育,P、R2和X剪切面不发育;辉石剪切带中仅边界剪切面与R1面较为发育。然而,2种主要矿物究竟如何影响辉长岩滑动特性的问题,仍有待进一步深入研究。  相似文献   

Time domain BEM analysis of dynamic response of a cylinder embedded in soil with frictional slip at the interface     

Yang-De Feng  Yue-Sheng Wang  Zi-Mao Zhang 《Soil Dynamics and Earthquake Engineering》2003,23(4):303-311

A 2D time domain boundary element method (BEM) is developed to study the dynamic response of a cylinder embedded in soil. The interface is assumed in contact with Coulomb friction. For the incident wave strong enough, local slip may occur along the interface. We suppose a pressure enough high is applied on the interface so that separation is impossible. The present problem is indeed a nonlinear boundary value problem since the mixed boundary conditions involve unknown intervals (slip and stick regions). In order to determine the unknown intervals, an iterative technique is developed. As an example, we consider the scattering of a circular cylinder embedded in an infinite solid. Numerical results for the near field solutions are presented. The nonlinear nature of the system is discussed.  相似文献   

Effect of physical parameters on static undrained resistance of sandy soil with low silt content     

M. Maleki  A. EzzatkhahM. Bayat  M. Mousivand 《Soil Dynamics and Earthquake Engineering》2011

Previous researches concerning the behavior of sand mixed with non-plastic fine show that the void ratio related to sand grains (e_c) plays a more important role in comparison with the total void ratio, where soil undrained resistance will be improved due to increase in FC at the constant e_c. In spite of this fact, the recent works indicate that e_c is unable to show perfectly the role of the non-plastic fines that are in voids between sand grains. For this reason, an equivalent void ratio (e_c)_eq has been defined that takes into account the non-plastic fine participation ratio in the soil bearing skeleton. In the present work, the generality of the expression of (e_c)_eq is verified. For this, a set of static undrained triaxial tests were performed. The results of tests indicate that the undrained behavior of a given sand mixed with different percentages of non-plastic fine can be described by (e_c)_eq. But if the grading curves of sand change, we cannot find a logic retention between (e_c)_eq and undrained resistance of soil, unless the physical and mechanical characteristics of soil are well introduced in expression of (e_c)_eq.  相似文献   

Ambient vibration based seismic evaluation of isolated Gülburnu highway bridge     

Ahmet Can Altunişik  Alemdar Bayraktar  Barış Sevim  Şevket Ateş 《Soil Dynamics and Earthquake Engineering》2011

This paper describes ambient vibration based seismic evaluation procedure of an isolated highway bridge. The procedure includes finite element modeling, ambient vibration testing, finite element model updating and time history analysis. Gülburnu Highway Bridge located on the Giresun–Espiye state highway is selected as a case study. Three dimensional finite element model of the bridge is created by SAP2000 software to determine the dynamic characteristics analytically. Since input force is not measured, Operational Modal Analysis is applied to identify dynamic characteristics. Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are used to obtain experimental dynamic characteristics. Analytical and experimental dynamic characteristic are compared with each other and finite element model of the bridge is updated by changing of material properties to reduce the differences between the results. Analytical model of the bridge after model updating is analyzed using 1992 Erzincan earthquake record to determine the seismic behavior. EW, NS and UP components of the ground motion are applied to the bridge at the longitudinal, transverse and vertical directions, respectively. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of highway bridges. Maximum differences between the natural frequencies are reduced averagely from 9% to 2% by model updating. It is seen from the earthquake analyses that friction pendulum isolators are very effective in reducing the displacements and internal forces.  相似文献   

Estimating downwind turbulence intensity using wind and wave measurements during hurricanes     

《Applied Ocean Research》2019

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Optimal design of friction pendulum system properties for isolated structures considering different soil conditions     

《Soil Dynamics and Earthquake Engineering》2016

This study aims at evaluating the optimal properties of friction pendulum bearings to be employed for the seismic protection of elastic isolated structural systems under earthquake excitations with different characteristics in terms of frequency content. A two-degree-of-freedom model is considered to describe the isolated system behavior while accounting for the superstructure flexibility and a non-dimensional formulation of the governing equations of motion is employed to relate the characteristic parameters describing the isolator and structure properties to the response parameters of interest for the performance assessment. Seismic excitations are modeled as time-modulated filtered Gaussian white noise random processes of different intensity within the power spectral density method. The filter parameters control the frequency content of the random excitations and are calibrated to describe stiff, medium and soft soil conditions, respectively. Finally, multi-variate regression expressions are obtained for the optimum values of the friction coefficient that minimize the superstructure displacements relative to the base mass as a function of the structural system properties, of the seismic input intensity and of the soil condition.  相似文献   

不同地表通量计算方案的比较与改进     

王成刚  孙鉴泞  蒋维楣  王文兰 《气象科学》2009,29(5):591-597

利用2006年南京地区边界层外场观测资料对摩擦速度(u*)和摩擦温度(θ*)的几种计算方案进行了比较.u*计算方案的比较结果表明:在不稳定条件下,Pleim方案计算结果同实测值相比,二者在量值及变化趋势上都有较好的一致性;而在稳定条件下,计算结果较差,为此本文给出了一个新的计算方案,结果表明,改进方案有效的提高了u*计算精度,平均相对误差由56%降低到21%.θ*计算方案的比较结果表明:基于动力粗糙度和热力粗糙度相等的Lee方案计算误差较大,而引入阻尼项的Wesely方案计算结果较前者有明显改进.  相似文献   

Stick-slip behavior of Indian gabbro as studied using a NIED large-scale biaxial friction apparatus     

Tetsuhiro Togo  Toshihiko Shimamoto  Futoshi Yamashita  Eiichi Fukuyama  Kazuo Mizoguchi  Yumi Urata 《地震科学（英文版）》2015,28(2):97-118

This paper reports stick-slip behaviors of Indian gabbro as studied using a new large-scale biaxial friction apparatus, built in the National Research Institute for Earth Science and Disaster Prevention (NIED), Tsukuba, Japan. The apparatus consists of the existing shaking table as the shear-loading device up to 3, 600 kN, the main frame for holding two large rectangular prismatic specimens with a sliding area of 0.75 m² and for applying normal stresses σ_n up to 1.33 MPa, and a reaction force unit holding the stationary specimen to the ground. The shaking table can produce loading rates v up to 1.0 m/s, accelerations up to 9.4 m/s², and displacements d up to 0.44 m, using four servocontrolled actuators. We report results from eight preliminary experiments conducted with room humidity on the same gabbro specimens at v = 0.1-100 mm/s and σ_n = 0.66-1.33 MPa, and with d of about 0.39 m. The peak and steady-state friction coefficients were about 0.8 and 0.6, respectively, consistent with the Byerlee friction. The axial force drop or shear stress drop during an abrupt slip is linearly proportional to the amount of displacement, and the slope of this relationship determines the stiffness of the apparatus as 1.15×10⁸ N/m or 153 MPa/m for the specimens we used. This low stiffness makes fault motion very unstable and the overshooting of shear stress to a negative value was recognized in some violent stick-slip events. An abrupt slip occurred in a constant rise time of 16-18 ms despite wide variation of the stress drop, and an average velocity during an abrupt slip is linearly proportional to the stress drop. The use of a large-scale shaking table has a great potential in increasing the slip rate and total displacement in biaxial friction experiments with large specimens.  相似文献   

Investigation of karst collapse based on 3-D seismic technique and DDA method at Xieqiao coal mine, China   总被引：1，自引：0，他引：1  

Jian-Ping Zuo  Su-Ping Peng  Yong-Jun Li  Zhong-Hui Chen  He-Ping Xie 《International Journal of Coal Geology》2009,78(4):1800

Karst collapse is a serious geological problem in most of the coal mines in the north of China, but recently it has been found in the south as well. The present study is aimed at investigating subsidence mechanism and deformation field of a karst collapse column at Xieqiao, in the south of China. A method of three-dimensional (3-D) seismic technique has been successful in exploring the spatial morphology of the karst collapse at Xieqiao, and the discontinuous deformation analysis (DDA) method is used to calculate the deformation field and analyze the subsidence mechanism. The results indicated that DDA could approximately simulate and back analyze the subsidence process and strata deformation fields. The subsidence processes of the collapse column depend on the sizes of the karst caves. With the continuous expansion of the karst caves, a semi-elliptic stress field, local separation strata and fracture zone will be formed around the karst cave. Moreover, they will gradually expand upwards along the vertical direction. The paper also indicates that the subsidence failure stage may trigger a sudden collapse of the karst column because of the sudden energy release. Also, it will make a great impact on the vicinity working face so as to cause a rock burst. The effects of the friction angle of rock strata on the subsidence mechanism were reported firstly based on DDA.  相似文献