Many accidents may occur during tunnel construction because the strata ahead of the working face are not clear; therefore the advanced percussive drilling surveying method is proposed which is one direct convenient, fast and inexpensive geological forecast method. The prediction of strata property is usually qualitative and not quantitive. In this paper, based on one type of percussive drill and much drilling data in field and rock mechanical test in the laboratory, the relationship between drilling rate and rock mechanical parameters is established. These parameters consist of rock compressive strength, density, cohesion force and internal friction angle. According to the rock classification standard, drilling data and real rock mass basic quality index (abbreviation BQ), the relationship between the drilling rate and BQ is also established, and the classification table of engineering rock mass by percussive drilling rate is obtained. Based on these conclusions, the quantitative prediction of strata property can be realized. And this work will be helpful in changing tunnel design, reducing construction cost, increasing progress and preventing accidents.
During the construction of a long tunnel there are often much unknown complicated geological conditions. In order to avoid geological disasters and accidents, it is necessary to adopt the advanced geological forecast. The advanced percussive drilling geological forecast is one direct geological forecast method which is convenient, fast and inexpensive. Compared with core drilling inspection, it has a short detecting time and low cost; compared with geophysical inspection, its forecast is more accurate. Based on the analysis of data from percussive drilling, the strata occurrence ahead of the workface can be determined, so the geologic accidents can be avoided to some degree. The strata location forecast is quantitive, but the prediction of strata property is usually qualitative.
The physical and mechanical parameters of rock mass are important data to the tunnel design and construction. They are often obtained by sampling in the rock mass using the drilling machine and testing in the lab. But because the accounts of rock sampling are limited, the obtained parameters are not the representation of all rocks in natural conditions. Simultaneously it takes much money, time and manpower. In this paper, a good method is presented. The drilling rate is used to predict the rock parameters, such as rock density and strength parameters.
