Extended data:
NATM is the abbreviation of NATM tunnel construction method. Austrian? Tunnel excavation? Method? Abbreviation: NATM, the concept of NATM was put forward by Austrian scholar Professor L.V.RABCEWICZ in 1950s. It is based on tunnel engineering experience and rock mechanics theory.
As a main support method, the combination of bolt and shotcrete was patented and officially named in the 1960s after many times of practice and theoretical research in some countries. Since then, this method has developed rapidly in many underground projects in western Europe, northern Europe, the United States and Japan, and has become one of the new technical signs of modern tunnel engineering.
NATM in the sixties? In the late 1970s and early 1980s, it was introduced into China and developed rapidly. It can be said that NATM is indispensable in all key and difficult underground projects, and it has almost become a basic method to build tunnels in weak and broken surrounding rocks.
Introduction:
NATM adopts millisecond blasting and smooth blasting technology, and carries out full-face excavation construction under the premise of using the bearing efficiency of surrounding rock itself, forming a tunnel body with internal and external composite lining, that is, shotcrete, anchor rod, steel mesh and steel support are used as external support forms, which is called initial flexible support, and it is a support work that must be carried out immediately after tunnel body excavation.
Because the in-situ stress contained in the mountain is redistributed due to the excavation, the tunnel space remains stable due to the cavity effect, that is to say, the surrounding rock itself is the main bearer of in-situ stress, the initial flexible support with shotcrete and anchor is used to maximize the bearing capacity of the surrounding rock itself, and the secondary lining is mainly used for safety reserve and decoration and beautification.
NATM is short for NATM. It is characterized by the timely application of thin-layer flexible shotcrete and anchor support near the excavation face to control the deformation and stress release of surrounding rock, so as to adjust the stress redistribution of surrounding rock and achieve a new balance in the process of simultaneous deformation of supporting and surrounding rock, so as to maintain the inherent strength of surrounding rock and maximize its self-supporting capacity.
Therefore, it is also a complete mechanical method to apply the dynamic properties of rock mass, and its purpose is to promote the surrounding rock to form an annular bearing structure. Therefore, it is generally necessary to build an inverted arch in time to close the section into a ring. It is suitable for all kinds of geological conditions and is more effective in weak surrounding rocks.
Although NATM principle can be used for various types of support, shotcrete and bolt support are the most suitable ones. Therefore, shotcrete, anchor rod and measurement are considered as the three major elements of NATM. The history of its emergence and development is closely related to these three aspects, but bolt-shotcrete support should not be misunderstood as synonymous with NATM.