Construction principle of NATM construction principle

1. According to NATM, rock mass is the main bearing unit in the structural system, and it must be fully protected to minimize its disturbance and avoid excessive damage to rock mass strength during construction.

2. In order to give full play to the bearing capacity of rock mass, the deformation of rock mass should be allowed and controlled.

3. In order to improve the mechanical properties of the supporting structure, it should be closed as soon as possible during construction and become a closed cylindrical structure.

4. In all stages of construction, field measurement and monitoring should be carried out to provide reliable and sufficient measurement information in time.

5. In order to lay the waterproof layer and bear the subsequent load caused by anchor corrosion, deterioration of surrounding rock properties, rheology and expansion, composite lining can be used.

6. In principle, the secondary lining is carried out under the condition that the deformation of surrounding rock and initial support are basically stable and the surrounding rock and support structure form a whole, thus improving the safety of support system.

In a large number of underground engineering practices, it is generally believed that the core problems of tunnel and underground cavern engineering come down to two key processes: excavation and support. That is, how to excavate can be more conducive to the stability and support of the cavern; If support is needed, how to support can ensure the stability and support of the cavern more effectively. These are two problems that promote and restrict each other in tunnel and underground engineering.

In tunnel and underground cavern engineering, people put forward different theories and gradually established different theoretical systems around the practice and research of the above-mentioned core issues, and each theoretical system contains and solves (or is studying and solving) a series of engineering problems from engineering understanding (concept), mechanical principles, engineering measures to construction methods (technology).