边坡锚杆蠕变力学特性数值分析

采用预应力锚杆加固边坡,锚杆的蠕变特性会使锚杆产生应力松弛的破坏性变形.因此,建立锚杆加固边坡蠕变力学模型,利用MSC Marc软件对所建立的模型进行蠕变分析,研究锚杆蠕变特性对锚杆预应力松弛的影响,详细给出在不同弹性模量及蠕变参数下锚杆的蠕变曲线和应力松弛曲线,从而进一步评价锚杆加固边坡的安全性能,为有效控制边坡的有害变形提供理论参考.     

基于土体流变的锚固边坡数值分析

为验证通过有限元法研究土体流变问题的可行性,采用Maxwell流变模型模拟土体流变特性．根据某工程的实际施工图,使用MSCMarc建立模型,模拟土体流变特性对锚固边坡的影响,计算得到桩顶部的冠梁在施工后3个月内的变形和沉降变化规律．将有限元计算结果与工程实际测试结果进行比较,并对土体流变模型和流变参数的选取进行讨论,模拟曲线表明计算结果与测试结果吻合较好．     

某高速公路路堑边坡FLAC数值模拟分析

本文主要阐述了对某高速公路进行数值模拟分析并加固的具体过程。首先对沿线路堑和路堤进行了边坡设计,采用合理的加固方案对边坡进行加固。通过对边坡采用锚固的治理措施,既能保持高速公路沿线整体性,又能达到加固的目的。接着应用数值模拟的方法,分析边坡加固前后的稳定性。最后简单设计了路堑边坡坡面防护。     

分数阶微积分流变模型在岩体结构加速流变破坏分析中的应用

针对采用常用的元件模型较好地拟合试验结果时需要的参数较多的缺点,将分数阶微积分理论应用于岩体结构的流变分析.将分数阶微积分的黏弹性模型和黏塑性模型的一维本构关系推广为三维本构关系,推导流变应变增量计算公式.然后将分数阶微积分流变模型应用于不同岩体结构的加速流变破坏分析.结果表明：改变分数阶次时,岩体结构加速流变性态将发生较大变化,分数阶微积分流变模型可较好地描述岩体结构不同的加速流变破坏过程,且模型简单实用.     

锚固体参数对冲击危险性巷道围岩稳定性的影响分析

针对冲击危险性的锚网支护类回采巷道,运用动力学理论分析了巷道锚固体抑制冲击矿压灾害机理,采用数值模拟软件FLAC3D研究了不同锚固体参数对冲击危险性巷道围岩稳定性的影响程度。研究结果表明,巷道围岩变形量的主要影响因素是锚杆长度与锚杆间距,巷道巷帮变形量对锚固体参数的灵敏度反应远高于巷道顶、底板。     

岩石流变对不同锚杆应力影响的数值分析

针对岩土工程中的锚杆预应力存在的时间效应,运用有限元法求解岩石流变对不同锚杆应力分布及变化趋势的影响.为验证用有限元法求解流变问题的准确性,分别求得均布载荷作用下Maxwell体和Burgers体简支梁的有限元解与解析解,其结果非常接近.建立全长黏结式锚杆轴对称模型,在不考虑流变的前提下求得锚杆轴向应力的有限元解,其与基于Mindlin问题的解析解分布趋势一致,从而验证该有限元模型的可行性,进而求得岩石流变对钢锚杆、FRP锚杆和MFRP锚杆轴向应力的影响.结果表明在工程应用中,由于抗腐蚀而采用FRP锚杆或MFRP锚杆的同时,考虑流变对其应力的影响具有重要意义.     

基于FLAC3D的岩土预应力锚固支护数值模拟

为了明确预应力锚固支护的加固效果与工作性能,使用快速拉格朗日差分软件FLAC3D,实现岩土预应力锚固支护数值模拟.考虑锚固支护施工顺序,对比分析边坡锚固支护的塑性破坏发展方向与屈服规律,构建弹塑性模型用作计算在预应力情况下岩土变形所产生的变量,通过模拟岩土的接触关系,组建锚固支护模型与预应力施加方法,同时设定模拟边界,利用有限差分软件LLAC3D构建有限差分模型,对岩土工况的预应力锚固支护完成数值仿真.仿真结果证明,FLAC3D可以精确的评定预应力的数值,为维护岩土自身强度和稳定性提供坚实理论基础,保证了工程施工安全.     

基于FLAC3D的边坡稳定性研究

边坡稳定性关乎矿山的正常生产和作业安全,长期以来对边坡稳定性的评价存在很大的局限性,传统的分析计算都没有考虑应力和应变所带来的影响.露天矿边坡稳定性评价需要一种科学全面的分析评价方法.而FLAC3D是由美国ITSCA公司开发的有限差分软件,通过模型计算和分析便可以直观的得到滑体的滑移破坏面以及应变和应力图,采用强度折减法就可以用来模拟岩体的变形、破坏,直到边坡岩体发生滑坡的整个过程,从而能够对边坡稳定性作出科学的分析评价.     

基于声发射技术的锚杆腐蚀的检测与信号处理研究

针对电塔的锚杆腐蚀性问题,使用一种基于声发射技术的锚杆腐蚀检测方法,根据经典力学和弹性力学为基础的弹性波特征,推导出锚杆在锚固状态的震动规律,进而推导出在人工给锚杆的激励下,锚固状态的锚杆内声发射信号的传播规律,利用声发射传感器接收声波信号,对得到的声信号进行小波分析得出对比结论。实验结果表明,该方法可以有效地了解锚杆的腐蚀情况。     

岩质边坡形态裂隙网络模拟系统的实现

针对岩体结构特征,结合实际勘测资料,根据结构面网络模拟的原理以及大型构造面定位处理方法,采用VC 计算机语言以及图像库OPENGL编制成了岩质边坡的结构面网络模拟程序,为进行岩质边坡稳定性分析提供可视化的技术平台。     

Estimation of elastic constant of rocks using an ANFIS approach

The engineering properties of the rocks have the most vital role in planning of rock excavation and construction for optimum utilization of earth resources with greater safety and least damage to surroundings. The design and construction of structure is influenced by physico-mechanical properties of rock mass. Young's modulus provides insight about the magnitude and characteristic of the rock mass deformation due to change in stress field. The determination of the Young's modulus in laboratory is very time consuming and costly. Therefore, basic rock properties like point load, density and water absorption have been used to predict the Young's modulus. Point load, density and water absorption can be easily determined in field as well as laboratory and are pertinent properties to characterize a rock mass. The artificial neural network (ANN), fuzzy inference system (FIS) and neuro fuzzy are promising techniques which have proven to be very reliable in recent years. In, present study, neuro fuzzy system is applied to predict the rock Young's modulus to overcome the limitation of ANN and fuzzy logic. Total 85 dataset were used for training the network and 10 dataset for testing and validation of network rules. The network performance indices correlation coefficient, mean absolute percentage error (MAPE), root mean square error (RMSE), and variance account for (VAF) are found to be 0.6643, 7.583, 6.799, and 91.95 respectively, which endow with high performance of predictive neuro-fuzzy system to make use for prediction of complex rock parameter.     

杨氏模量、切变模量测量的通用传感器

利用磁致伸缩原理和脉冲回波声速测量方法成功地设计了杨氏模量与切变模量测量的通用新型超声弹性模量传感器。实验验证,使用该传感器可以方便地测量材料的杨氏模量和切变模量,且测量不确定度低,准确度优于现有方法。该传感器的研制为弹性模量的测量提供了一种方便快捷、经济有效的测量方法。     

Mechanical property characterization of LPCVD silicon nitride thin films at cryogenic temperatures

T-shape, LPCVD silicon nitride cantilevers are fabricated to determine Young's modulus and fracture strength of silicon nitride thin films at room and cryogenic temperatures. A helium-cooled measurement setup is developed and installed inside a focused-ion-beam (FIB) system. A lead-zirconate-titanate (PZT) translator powered by a function generator and a dc voltage is utilized as an actuator, and a silicon diode is used as a temperature sensor in this setup. Resonant frequencies of identical cantilevers with different "milling masses" are measured to obtain thickness and Young's modulus of the silicon nitride thin films, while a bending test is performed to obtain fracture strength. From the experiment, the average Young's modulus of low-pressure chemical-vapor deposition (LPCVD) silicon nitride thin films varies from 260.5 GPa at room temperature (298 K) to 266.6 GPa at 30 K, and the average fracture strength ranges from 6.9 GPa at room temperature to 7.9 GPa at 30 K. The measurement setup and technique presented here can be used to characterize the mechanical properties of different MEMS materials at cryogenic temperatures.     

Interferometry of actuated microcantilevers to determine materialproperties and test structure nonidealities in MEMS

By integrating interferometric deflection data from electrostatically actuated microcantilevers with a numerical finite difference model, we have developed a step-by-step procedure to determine values of Young's modulus while simultaneously quantifying nonidealities. The central concept in the methodology is that nonidealities affect the long-range deflections of the beams, which can be determined to near nanometer accuracy. Beam take-off angle, curvature and support post compliance are systematically determined. Young's modulus is then the only unknown parameter, and is directly found. We find an average value of Young's modulus for polycrystalline silicon of 164.3 GPa and a standard deviation of 3.2 GPa (±2%), reflecting data from three different support post designs. Systematic errors were assessed and may alter the average value by ±5%. An independent estimate from grain orientation measurements yielded 163.4-164.4 GPa (the Voigt and Reuss bounds), in agreement with the step-by-step procedure. Other features of the test procedure include that it is rapid, nondestructive, verifiable and requires only a small area on the test chip     

MEMS器件贴片工艺研究

贴片工艺是MEMS封装中的关键工艺。根据残余应力理论,应用有限元方法和试验技术研究了贴片胶杨氏模量和热膨胀系数对贴片应力和芯片翘曲的影响。结果表明:杨氏模量和热膨胀系数是影响贴片应力和芯片翘曲的重要因数。杨氏模量越大,贴片后产生的应力越大,引起芯片的翘曲越大,但杨氏模量大到一定数值后,应力不会再增大,反而对应力具有一定的隔离作用;热膨胀系数越大,贴片后产生的应力越小,引起芯片的翘曲越小,反之,引起芯片的翘曲越大。在满足粘接强度和工艺条件下,选用软胶有利于减小应力和芯片翘曲。     

Measurements of material properties using differential capacitive strain sensors

This paper describes a laterally deflecting micromachined device that offers high sensitivity and wide dynamic range to electronically monitor the thermal expansion coefficient, tensile and compressive residual strain and Young's modulus of microstructural materials, as well as the temperature dependence of these properties. The device uses sidewall capacitance between interdigitated tines to sense displacement caused by the release of residual stress in a bent-beam suspension. Electrostatic force is used to obtain load-deflection profiles. The suspensions and tines are arranged such that output is a differential readout, immune to common mode parasitic capacitance. Analytical and numerical modeling results are presented and the device concept is verified by three different fabrication approaches using polysilicon and nickel as structural materials. Measured values of residual strain, thermal expansion and Young's modulus are very consistent with measurements taken by other approaches and those reported previously. For example, the residual strain in certain electrodeposited Ni structures was tracked from 68.5 microstrain at 23/spl deg/C to -420 microstrain at 130/spl deg/C, providing an expansion coefficient of 8.2 ppm/K; the best fit Young's modulus provided by the device was 115 GPa.