The nonlinear characteristics of rock mass become more and more prominent with the increase of depth. The accurate acquisition of mechanical parameters is particularly necessary for the nonlinear characteristics of rock mass and stress monitoring in the process of in-situ stress relief. The dynamic mechanical parameters of rock mass are acquired in real time, based on the calculation of longitudinal and transverse wave velocities of rock mass, which avoids the influence of mechanical parameter errors caused by the rock mass timeliness of indoor mechanical tests and data fitting methods. In order to realize the real-time and accurate access to wave and shear wave velocity of rock mass, based on the coupling point contact small size dry sonic probe speed measuring technology and the improvement of AIC algorithm, developed a transient signal trigger, high-speed data acquisition and wireless transmission function of the digital wave speed acquisition system, the digital wave speed acquisition system through calibration test, data error within the scope of the specification allows, from conventional coupling agent influence on the stability of signal transmission, and easy to decorate in field drilling, and laminating of mining face is better. The relationships between longitudinal wave and strength, static elastic modulus and dynamic elastic modulus of sandstone samples are studied, which provides a certain feasibility for in-situ monitoring of rock mass strength and static elastic modulus.

1. Introduction

The nonlinear characteristics of deep rock mass are prominent, and the effect of ground stress is more and more obvious. Rock and rock mass deformation modulus and strength are important parameters for rock mass engineering design and geostress measurement. Because the rock mass contains not only complete blocks, but also a large number of discontinuities -- faults and joints -developed in the rock mass. Because the rock mass contains structural plane, its deformation modulus cannot be obtained by indoor rock test. At present, the value of rock mass deformation modulus is generally obtained through the following ways :(1) In situ test, such as expansion test, plate load test, flat shovel test, etc. (2) Empirical relationship methods, such as establishing the relationship between rock mass quality classification or a certain geological index and rock mass deformation modulus, so as to use the correlation relationship to estimate rock mass deformation modulus; (3) Calculation by geophysical (usually seismic wave velocity measurement) method; (4) The rock mass deformation modulus is calculated by the equivalent continuous model. The determination methods of rock mass strength parameters mainly include: a. Theoretical analysis method [HOEK E et al., 1980]. b. Rock mass classification method (Bieniawski Z T,1978; Palmstrom. A, 1996). c. Test methods (Yang Z Y et al.,1998; Kulatilake P H et al.,2001).

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