1、翻译部分英文原文The optimal support intensity for coal mine roadway tunnels in soft rocksC. Wang*Mining Engineering Program, Western Australian School of Mines, PMB 22, Kalgoorlie WA6430, Australia1. IntroductionThe essence of underground roadway support is to provide the surrounding rocks of an underground
2、 roadway with assistance to help them achieve stress and strain equilibrium and ultimately stability of deformation.The approaches to this goal are either to reinforce the rock mass by rock bolting or injection(internal rock stabilization) or to provide the surrounding rocks with a support resistanc
3、e with a magnitude being described as the support intensity (external rock stabilization).When an underground roadway is located in soft rocks which are too soft to be reinforced by bolting and/or unsuitable for rock injection because of restraints imposed by either the rock mass impermeability or r
4、ock mass deterioration when water is encountered, external rock support, such as steel sets, therefore becomes the only option for the stability control of the roadway. Under this circumstance, the support intensity means a support force acting per unit surface area of the surrounding rocks of the r
5、oadway. In soft rock engineering practice, the design of a support pattern for a roadway in underground coal mining is normally based on rules of thumb. In most cases, heavy support measures are adopted to secure a successful roadway.Fig. 1(a) demonstrates the excellent condition of a sub-level road
6、way within soft rocks at an underground coal mine in north China, where an excessive capital cost was applied for the achievement of roadway stability. In some cases, such as a service roadway driven in soft rocks at the same mine (Fig. 1(b), insufficient support intensity was specified as a result
7、of a lack of relevant experience and design codes. Consequently, failure of the roadway stability was inevitable and an extra cost was incurred when the subsequent roadway repair or rehabilitation was undertaken.The critical issue in both cases lies in the determination of an optimal support intensi
8、ty which is the function of the geometry and dimension of a roadway and its geotechnical conditions including rock mass properties, stress conditions and hydrological status.Physical modelling using simulated materials based on the theory of similarity provides a direct perceptional methodology for
9、mining geomechanics study 1-6.Using simulated materials of the same composition to construct a roadway and its soft surrounding rocks, applying a certain magnitude of simulated support intensity to the surface of a roadway under simulated stress conditions, the three-dimensional physical modelling m
10、ethod depicted in this Note emonstrates a quantitative solution for strategic design of roadway support concerned with soft rocks. A relation between the support intensity and deformation of the surrounding rocks of a roadway has been established after a series of simulation tests had been conducted
11、. A discussion on the optimal support intensity for a roadway in soft rocks is also given. Fig. 1. Examples of successful and unsuccessful support of underground roadways within soft rocks: (a) Good condition of a sublevel roadway, (b) Unsuccessful support of a service roadway.2. Features of the thr
12、ee-dimensional physical modellingA physical modelling study of the interaction between support intensity and roadway deformation was carried out using the three dimension physical modelling system (see Fig. 2) at the Central Laboratory of Rock Mechanics and Ground Control, China University of Mining
13、 and Technology. Features of this system are described in the following sub-sections. Fig. 2.Three-dimensional loaded physical modelling system at the Central Laboratory of Rock Mechanics and Ground Control, China University of Mining and Technology.2.1. Size of the physical modelThe effective size
14、of a physical model is 1000 mm wide, 1000 mm high and 200 mm thick.2.2. Three dimensional active loading capabilitySix flatjacks are used to apply loads to the six sides of the physical model in the form of a rectangular prism. Each flatjack was designed to cover the full area of one of the six side
15、s and be capable of applying a pressure of up to 10 MPa on to the surface of the simulated rock mass. This means that the flatjacks are capable of applying an active load of up to 1000 tonnes and 200 tonnes simultaneously on the front and back facets, the top and bottom, and the two side facets of a
16、 model, respectively.2.3. Long-term continuous loading capabilityA high-pressure, nitrogen-operated, hydraulic pressure stabilising unit was employed to maintain a consistent magnitude of load applied to the model so that the physical modelling test is able to last continuously for weeks, months or even years without interruption. This feature ensures that the study of the long-term rheological behaviour of soft rock
