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B. Characteristics and construction points of the new Austrian law ( 1 ) As the surrounding rock is a component of the support member of the roadway, the disturbance and stress concentration of the surrounding rock stress around the roadway should be minimized. Therefore, as far as possible, measures such as full-face excavation and differential detonation smooth blasting should be adopted to weaken the vibration of the surrounding rock and smooth the surface of the roadway to avoid local stress concentration;
( 2 ) Establish a thin-walled flexible support system to improve its shear resistance and reduce the chances of bending moments and bending and fracture. When a thinner lining is formed by the appropriate combination of anchor spray support and plastic support, the adhesion between the surrounding rock and the support (protection) can be made good without gaps, so that it can achieve the purpose of early control of pressure and can be improved. Shear ability. In addition, when the local quality conditions need to strengthen the roadway lining, it is not to increase the thickness of the lining, but to adopt the measures of adding steel bars or encrypting the bolt net to maintain its thin-wall structure;
( 3 ) In order to adapt to the characteristics of the development of surrounding rock deformation in the roadway, it is necessary to establish the concept of two support in the initial stage and the latter stage, and carry out staged support. For the weakly expansive rheological rock stratum, the permanent support should not be carried out too early. The first flexible support should be carried out in time after the excavation. As the surrounding rock deformation develops, the accumulated energy is released and the deformation rate tends to be stable. The second support will give good results.
( 4 ) The curved full-section closed-type support is adopted to form the surrounding rock and the two supporting members to form a thick cylindrical support ring with a cylindrical shape to maximize the mechanical support. The curved guide pits advanced in advance allow the suspended half-shell (arch lining) to undergo a large deflection on the longitudinal axis, and the rock mass under the arch toe is subjected to a high load. Therefore, the arch should be raised in time to shorten the closing time of the lining and improve the stress conditions.
( 5 ) Emphasis on systematic measurement of roadway surrounding rock deformation and ground pressure to guide construction, timely adjustment of support parameters and construction technology. The traditional lining thickness is designed according to the empirical formula to calculate the ground pressure and deformation, and the new Austrian law is based on the system measurement of ground pressure, support stress, surrounding rock and support deformation parameter system, roughly quantitative design of the bolt length and Spacing, shotcrete thickness, and dynamic measurement of the system during construction, to understand the impact of time on the performance of rock mass and lining system, timely analysis and determination of deformation rate and stability trend of surrounding rock and lining members, and based on measurement Information feedback to correct the design, timely adjustment of design parameters and construction process;
( 6) It is necessary to take measures to prevent and control the water in the roadway to prevent the hydration expansion of the surrounding rock and reduce its supporting capacity. Therefore, in the aquifer, effective measures should be taken to divert water, drain or grout to stop the water, prevent the groundwater from leaching into the rock, decompose the rock, and deteriorate its physical and mechanical properties. In particular, some rock formations often cause large side pressure bases when they are inflated with water, and the roadways and their supports are damaged.
The practice of the application scope of the new Austrian law shows that as long as the construction is carried out in strict accordance with the principle of embodying the characteristics of the new Austrian law, it can be widely used not only in the general unstable rock formation, but also in the roadway construction in the weakly expansive rheological rock formation. . 
A NATM NATM is the essence from the mid-50's to the mid 60's developed a new Austrian tunneling (Lane) referred to the construction method of the road. It is a combination of engineering, construction and monitoring of tunnel (lane) roads, which is a long-term experience in the theory and construction practice of the roadway engineering. According to the measurement information feedback, the construction method of excavation, support design and process parameters is continuously adjusted. Its basic connotation is to make full use of the bearing capacity of surrounding rock during the construction of roadway, and transform the role of surrounding rock from the load system to the support system. On the basis of dynamic monitoring of parameters such as rock stratum support members and roadway morphology, with the correct excavation and support technology, the joint action between the supporting members and the surrounding rock can be fully utilized to achieve safe, rapid, high-quality and economic construction. the goal of.