Used Excavators

I want to introduct something about Garlic Granule(40-80 mesh). 1. Specification: 1)Appearance: Light yellow; 2)Aroma: Characteristic of garlic; 3)Taste: Pungent; 4)Moisture: Max6. 0%; 5)Total plate count: Max 100000 pcs/g; 6)Coliform Bacteria: Max 50 pcs/g; 7)E. Coli: Negative; 8)Salmonella: Negative. 2. Packing Details: 12. 5 Kg net x2 Aluminum foil bag /carton. 3. Granulation: 40-80mesh; 4. Transportaton: 18MT PER 20′ container 5. Payment by: 100%L/C at sight or 30% T/T preshipment and 70% T/T against faxed shipping documents. 6. The lead time: About 30 days. Garlic Granule(40-80 mesh) mo
“NATM” redirects here. NATM may also refer to Not Another Teen Movie or Night at the Museum.
The New Austrian Tunneling method (NATM) was developed between 1957 and 1965 in Austria. It was given its name in Salzburg in 1962 to distinguish it from old Austrian tunnelling approach. The main contributors to the development of NATM were Ladislaus von Rabcewicz, Leopold Mler and Franz Pacher. The main idea is to use the geological stress of the surrounding rock mass to stabilize the tunnel itself.
Principles
The NATM integrates the principles of the behaviour of rock masses under load and monitoring the performance of underground construction during construction. The NATM is not a set of specific excavation and support techniques.
There are seven features on which NATM is based:
Mobilization of the strength of rock mass – The method relies on the inherent strength of the surrounding rock mass being conserved as the main component of tunnel support. Primary support is directed to enable the rock to support itself.
Shotcrete protection – Loosening and excessive rock deformation must be minimised. This is achieved by applying a thin layer of shotcrete immediately after face advance.
Measurements – Every deformation of the excavation must be measured. NATM requires installation of sophisticated measurement instrumentation. It is embedded in lining, ground, and boreholes.
Flexible support – The primary lining is thin and reflects recent strata conditions. Active rather than passive support is used and the tunnel is strengthened not by a thicker concrete lining but by a flexible combination of rock bolts, wire mesh and steel ribs.
Closing of invert – Quickly closing the invert and creating a load-bearing ring is important. It is crucial in soft ground tunnels where no section of the tunnel should be left open even temporarily.
Contractual arrangements – Since the NATM is based on monitoring measurements, changes in support and construction method are possible. This is possible only if the contractual system enables those changes.
Rock mass classification determines support measures – There are several main rock classes for tunnels and corresponding support systems for each. These serve as the guidelines for tunnel reinforcement.
Based on the computation of the optimal cross section, just a thin shotcrete protection is necessary. It is applied immediately behind the Tunnel boring machine, to create a natural load-bearing ring and therefore to minimize the rock’s deformation. Additionally, geotechnical instruments are installed to measure the later deformation of excavation. Therefore a monitoring of the stress distribution within the rock is possible.
This monitoring makes the method very flexible, even at surprising changes of the geomechanical rock consistency during the tunneling work, e.g. by crevices or pit water. Such (usual) problems are not solved by thicker shotcrete, but the reinforcement is done by wired concrete which can be combined with steel ribs or lug bolts.
The measured rock properties lead to the appropriate tools for tunnel strengthening. Therefore in the last decade NATM was also applied to soft ground excavations and to tunnels in porous sediments. The flexible NATM technique enables immediate adjustments in the construction details, but this requires a flexible contractual system, too.
Philosophy and controversial names
When tunneling engineers talk on NATM, they often mean different things because some of them define it as a special technique, but others as a sort of philosophy. Recently the scene has been complicated by new terms and even alternative names, when discussing certain aspects of NATM. This is partly caused by an increased use of the method in the USA, particularly in soft ground conditions (see External links).
Besides the official name New Austrian Tunneling Method other designations are used in the last years, e.g. Sequential Excavation Method (SEM), or Sprayed Concrete Lining (SCL). In Japan sometimes other names were used, e.g. Centre Dividing Wall NATM, or Cross Diaphragm Method (both abbreviated as CDM), and even Upper Half Vertical Subdivision method (UHVS). Evidently, the scientists and the tunneling industry cannot find a unified name for this wide-used method.
As defined by the Austrian Society of Engineers and Architects, the NATM constitutes a method where the surrounding rock or soil formations of a tunnel are integrated into an overall ring-like support structure. Thus the supporting formations will themselves be part of this supporting structure.
But many engineers already refer to as NATM, when shotcrete is proposed for initial ground support of an open-face…(and so on) To get More information , you can visit some products about stainless patterned mesh, espanded plate mesh, . The Garlic Granule(40-80 mesh) products should be show more here!