岩石

岩石

作者:卓声仪器 日期:2018-05-26 11:36
1. The fundamental resonance frequency measurement: critical evaluation of test  method on natural stone
Synopsis
Fundamental Resonance Frequency method (FRF) is foreseen by European Standard for the evaluation of the durability and state of conservation of natural stones. For these reason it is important to understand if this technique, widely applied in the determination of mechanical property of industrial materials as concrete and ceramics, can provide reliable results in the applications on natural stone. In this work, European Standard EN
14146:2004 (natural stone test method) has been analysed, starting from the comparison with American ASTM C215:2014 (concrete specimens test method). Four different stones have been tested with FRF method in order to obtain values of dynamic modulus of elasticity, following respectively EN and ASTM instructions. The same samples have been additionally tested with Ultrasonic Pulse Velocity (UPV) measurement, in direct mode, by means European Standard EN14579:2004. Results obtained with FRF method following both ASTM and EN Standards are comparable for all the rock samples and these values do not differ significantly from dynamic modulus of elasticity from UPV measurement. Both  STM and EN standard can be applied testing natural stones but with accurate  consideration about rock fabric, sample dimensions, position of supports and location of
the impulse. Indication suggested for artificial material as concrete can be therefore used in natural stone samples with approximate homogeneous composition and structure.

2 STUDY OF THE RELATION BETWEEN THE STATIC AND DYNAMIC MODULI OF ROCKS  
Non-destructive techniques based on the propagation of ultrasonic wave through the elastic medium were used  for determination of dynamic modulus of selected samples of rocks in laboratory. The calculated values of
dynamic modulus were compared with values of static modulus determined in laboratory on samples tested by  applied loading. A method of estimation of the static modulus in situ conditions, where the measurements
cannot be carried out,
3 地应力与岩石弹性模量关系试验研究

摘 要:在北京某深孔原岩应力测量和原岩应力测量段同等深度单轴及不同围压下的三轴岩石力学试验的基础上,结合统计 的钻孔岩体结构参数,分析了原岩应力测量段深度处修正前、后的岩石弹性模量,进而探讨了地应力与岩石弹性模量间关系。 结果表明,在花岗岩中,主应力大小与修正前、后的岩石弹性模量间均呈正相关关系,而在灰岩中,主应力大小与修正前、 后岩石弹性模量间的关系不明确,需要进一步研究;在花岗岩中,主应力大小与修正后的岩石弹性模量间的相关性系数高于 主应力大小与修正前的岩石弹性模量间的相关性系数;各向同性高的岩体(如花岗岩),实测地应力大小与岩石力学试验结 果相关性好,而各向异性大的岩体(如沉积岩),实测地应力大小与岩石力学试验结果相关性较差。
4  Analysis of the ASTM standards for impulse excitation of vibration and acoustic resonance techniques for  rectangular parallelepipeds
Abstract
Impulse excitation of vibration and acoustic resonance are techniques for determining the elastic constants of solid materials from the lowest resonance frequencies, excited by means of an impulse or by a periodic stimulus. Several geometries can be used for this purpose: parallelepipeds, disks, cylinders, etc. The details of the technique are the subject of many ASTM standards, whose suitability and precision are analyzed in this work in the case of parallelepipeds. The results show that errors of the order of 1% can be expected even if the samples dimensions and resonance frequencies are measured to a much higher precision (better than 0.1%).