Test And Analysis Of Rock Strength By Rebound Method

The bounce-back instrument,also known as Schmidt's hammer,is characterized by fast,easy operation,portability,low cost and non-destructive detection.It has been used as an important index for rapid detection of rock strength and deformation characteristics worldwide.The uniaxial compressive strength test of rock is time-consuming,expensive and destructive,and the outdoor test requires high conditions.Therefore,it is of great significance for engineering practice and scientific research to estimate the uniaxial compressive strength by means of rock rebound test.However,more in-depth research is needed to accurately estimate the uniaxial compressive strength of rock by using the springback instrument.The specific work studied in this paper is as follows:(1)This paper firstly summarizes basic principles of springback test of rock,the analysis of the rock in the process of the springback rebound hammer,test,the influence of the Angle of the internal parts and auxiliary devices,the influence of the influence of design and manufacture according to the characteristics of the relevant factors affecting the rock springback auxiliary device,is deduced in the vertical direction under two kinds of common hammer rock can be measured by the springback function relation between actual value and the revised;(2)The use of different types of hammer to explore the applicability of rock,the ultrasonic rebound synthesis experiment and rock springback to carry out the study,by comparing the hard rock and soft rock before and after springback variation characteristics of elastic wave,the results show that l-shaped rebound hammer on the applicability of the rock,can be used for rock strength in this paper,experimental study on the relatively reliable measuring instrument;(3)This paper proposed three kinds of rock springback test scheme,including in every different part of the surveyed area location record 5 rebound value,every two springback spacing not less than the recoiling rod diameter average for the rebound value,in every different part of the surveyed area location record eight rebound value,every two springback spacing not less than a recoiling rod diameter to remove two maximum,the minimum average for the springback value and position in each different part of the surveyed area recorded 10 rebound value averaged for the springback value of the three test scheme,every two rebound point spacing not less than a recoiling stem diameter,the number three ways for A1,A2 and A3.In addition,the experiment compared 4 test programs that were recognized by many scholars.By analyzing the variation coefficient of the rebound value obtained under each test program,the A2 test program was determined to be the ideal test program in this paper.(4)Tests on springback and uniaxial compressive strength of different types of rocks were carried out.The relationship between the measured rock springback and uniaxial compressive strength was converted through the tests,including the whole sample was fitted and piecewise fitted,and the reliability of the fitting formula was analyzed.