Progress and trends in non-tool rock breaking theory and technology

With the gradual implementation of China’s deep-earth engineering strategy, deep resource extraction and underground space construction have brought in some new opportunities, but they also face many challenges, with extreme geological conditions such as high geopathic stresses, high ground temperatures and hard rock bodies popping up all the time. Rock breaking technology is the main engineering activity for all resource extraction and underground space construction, and it is the main factor determining the construction process and engineering efficiency. Under extreme geological conditions, tool-based rock breaking technology has become a key technical bottleneck to affect the smooth implementation of deep-earth engineering strategy due to fast tool wear and low rock breaking efficiency. In order to solve the problem of high-efficiency rock breaking in deep-earth and to guarantee the smooth implementation of deep-earth engineering strategy, there is an urgent need for a revolutionary rock breaking technology. As an important supplement to the tool-based breaking technology, the non-tool rock breaking technology is a feasible solution to break through the bottleneck of the tool-based breaking technology. To this end, the non-tool rock breaking technology is summarized into three types of technological systems, namely, impact rock breaking, thermal stress rock breaking and erosion and abrasion rock breaking. Sixteen types of rock breaking technologies, such as water jets, lasers and abrasive air jets, etc., are systematically analyzed. Also, the history of the development of each technology and their technical principles are summarized, and the advantages of the rock breaking and the technological bottlenecks are analyzed. It is concluded that the main reasons why the current non-tool rock-breaking technologies are not widely used in resource extraction and underground space construction are high energy consumption, poor adoptability and complex technical equipment. Compared with tool-based breaking, non-tool breaking technology has a lower energy utilization rate for breaking rock. The specific energy consumption of water jet breaking is 40−70 times that of a tool breaking. Microwave, laser and plasma technologies require high-standard operation environment and cannot be applied in drilling, tunneling and other restricted and harsh environments. In order to solve the problem of rock breaking in extreme geological conditions, the idea of synergistic rock breaking by multiple non-tool rock breaking technologies is proposed, giving full play to the technological advantages of each non-tool rock breaking technology. The rock breaking concept of unloading high geo-stress by jet slit and breaking hard rock by particle impact volume is constructed to minimize the energy consumption of rock breaking, simplify the system equipment, and provide a theoretical support for the development of non-tool rock breaking technology.