Method for Measuring Rock Mass Characteristics and Evaluating the Grouting-Reinforced Effect Based on Digital Drilling

Various types of broken rock masses, such as those in fault-fracture zones and fracture zones, which form as a result of disturbance from tunnelling, are often encountered during underground engineering construction. These rock masses have low self-supporting capacity and poor stability, which can easily cause damage to surrounding rock, such as large deformation features, collapse and falling blocks, etc., posing a threat to construction safety. During a field project, reinforcement by grouting is a primary means for addressing the aforementioned problems. The effective measurement of rock mass characteristics (e.g., rock layer interfaces and the broken area of surrounding rock) provides a basis for the reasonable design of a grouting scheme. The quantitative evaluation of the effect of rock mass grouting is essential for optimizing the grouting scheme. In view of this, in this study, a multi-functional rock mass digital drilling test system and a special polycrystalline diamond compact drill bit for digital testing were developed and were applied to conduct digital drilling tests on intact, broken and grouted rock masses. In addition, a digital drilling test (DDT) technique-based method for measuring rock mass characteristics in real time and rapidly evaluating the grouting effect was proposed. The proposed method is capable of identifying rock layer interfaces, determining the broken area and obtaining the equivalent strength of grouted rock masses. This method is advantageous for obtaining quantitative and rapid test results, which can provide a theoretical basis and technical means for optimizing the grouting parameters and designing support schemes for underground engineering construction.