Inductive Strain Gage

The essential principle, technical feature, and application of inductive strain gage are described in this paper. This kind of strain gage is developed by our institute and has become product with invention patent.     

Experimental test of the calcite strain gage technique at low confining pressure

A series of experiments were conducted on Indiana limestone to test the applicability of calcite strain gage technique to deformations at low confining pressures. Experiments were conducted dry, at 13.8 MPa (138 bars, 2000 psi) confining pressure. These experiments indicate that both the least squares strain gage technique and the numerical dynamic analysis (NDA) technique locate the principal strain axes to within 5.0 degrees. Strains calculated by the least squares strain gage technique are accurate at low strains (less than 5%), and increasingly inaccurate at higher strains. At low strains, the calculated strain reflects the maximum strain (including elastic strain) experienced by the core. At higher strains, the increasing inaccuracy of calculated strain was accompanied by increasing negative expected values. In these experiments, microcracking played a significant part in deformation and effected twinning in calcite, and therefore the recorded strain.     

Development of Soil Strain Gage Instrumentation

A brief review of the errors from mechanical mismatch of ‘Spool Gage’ commonly used in field soil strain measurement is made. The behavior of a unique contactless magnetic coil gage is analyzed, which is relatively free from mechanical mismatch effects. The structure and main specifications of the instrument designed for the measurements of both static and dynamic strain in soil are presented here.     

土壤应变测试仪的研制

本文简要地评估了土力学现场测量中常用的连杆式应变传感器的力学匹配误差。对一种特殊的,匹配误差小的非接触互感式传感器的特性作出分析。设计了与这种传感器配用的,适合于动、静态测量的土壤应变仪,给出了它的主要性能指标。     

地质力学模型试验中软弱结构面内埋式位移系统的研制与应用

在高拱坝坝肩稳定地质力学模型试验研究过程中,坝肩岩体内各软弱结构面的相对位移变化趋势是判定坝肩失稳及分析坝肩整体稳定安全度的重要参考依据。目前的量测仪器,如电阻应变片、表面位移计只能对坝体应变和坝肩抗力体表面位移进行量测,而对于坝肩岩体内软弱结构面的相对位移则难以获取。因此,针对上述问题,以电阻应变技术为基础,研制了用于获取结构面相对位移的内埋式位移系统,该系统由信号采集仪器、惠斯通电桥和位移传感器组成。在模型试验中,通过内埋式位移系统,获得加载过程中相应测点的应变变化过程,再由应变-位移关系曲线,即可得出位移值。结合锦屏一级高拱坝整体稳定地质力学模型试验,将该系统安装于需量测的坝肩软弱结构面上,获得了结构面在加载过程中的位移变化过程线,同时与大坝应变和坝肩表面位移监测成果进行对比分析,验证了内埋式位移系统的可行性,其测试成果可为判定坝与地基的整体稳定提供依据。     

砂土中抗拔桩与抗压桩模型试验研究

为研究单桩在抗拔与抗压条件下承载能力、桩身轴力以及侧摩阻力分布规律的不同,进行了砂土中长径比大于40的抗拔桩与抗压桩室内模型试验,通过桩身内设置电阻应变片,测得各级荷载下桩身不同深度的应变。分析表明,抗拔桩不论是位移还是位移增长速率,都远远超过抗压桩。因此,抗拔桩设计时应综合考虑桩顶上拔量来确定抗拔承载力。抗拔桩与抗压桩的桩身轴力分布具有相似的特性,试验所得抗拔总侧摩阻力折减系数?=0.56。抗拔桩与抗压桩侧摩阻力都是从上部开始发挥并向下传递,随着荷载的增加,上部侧摩阻力变化很小,桩身中下部侧摩阻力迅速增长。抗拔桩桩端部侧摩阻力表现出弱化效应,抗压桩则表现出强化效应。     

A piezometer for Stress Wave Measurement in Rock Mass

A new type of stress piezometer, RS stress gage, is presented in this paper. This new type of stress gage make use of piezoelectricity of piezocrystal to measure dynamic stress and read the magnitude directly. To avoid the bad matching of the gage and rock mass in situ, the shell of the gage is made of rock core from in situ. It has been proved that the new stress gage can work well during the measuring of the stress of blast wave in rock mass as long as it was made fine, calibrated accurately, and inserted carefully.     

测量岩体应力波的压电应力计

本文介绍一种用于岩体爆炸测量的新型压电应力计--RS 型应力计.它利用压电晶体的压电效应直接测量应力。由于外壳采用爆炸现场测点处的岩芯材料制成,避开了应力测量中难以解决的匹配问题.实践表明:只要保证 RS 型应力计按规定工艺要求制作,并进行系统的标定和回填,对中硬和坚硬岩体中自由场和毛洞周边的爆炸应力测量是可行的。     

In-Situ strain measurement by photoelastic bar gages, 1. The method

A technique is described for measuring recoverable strain in situ using bridged photoelastic bar gages and a simple reflecting polariscope. Rosettes of 0.2 × 0.4 × 4-cm bars are bonded to the rock for 0.6 cm at each end. Change in strain is measured following overcoring with a 10-cm bit. Correction for strains in the order of 30 · 10^?6/°C, due to differential thermal expansion between rock and gage, are made by monitoring dummy gages mounted on free blocks. Bar gages have been satisfactorily tested against foil resistance gages. Rosettes mounted closely adjacent on a free granite block showed a reasonable homogeneity of response.     

3D-DIC系统在岩石力学试验中的应用

介绍了全场3D-DIC系统,在试样周围均匀布置三组3D采集元,利用散斑图像的采集,尽可能在较大范围内捕捉试样表面的变形并进行分析。为了验证3D-DIC系统测量结果的可靠性,以江持安山岩为试验材料,进行了单轴压缩条件下的恒定应变速率和交替应变速率试验。通过3D-DIC系统的测量结果与应变片测量结果的对比发现,两者吻合度较好,表明3D-DIC系统能够满足岩石力学试验非接触式、可视化变形测量的需求。另外以田下凝灰岩为试验材料,通过图像分析得到了加载过程中岩石表面的全场变形信息,发现岩石变形的不均匀性和应变局部化现象,表明利用3D-DIC系统对岩石破裂过程变形测量比传统变形测量方法更具有优越性,为岩石力学试验研究提供了一种新的、便捷的测试方法。