煤矿软岩巷道支护强度优化外文文献翻译中英文翻译.docx

1、煤矿软岩巷道支护强度优化外文文献翻译中英文翻译英文原文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 rock

2、s of an underground 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

3、a support resistance 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

4、impermeability or rock 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 surroun

5、ding rocks of the roadway. 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

6、of a sub-level roadway 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 spe

7、cified as a result 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 opti

8、mal support intensity 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 perception

9、al methodology for 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 p

10、hysical modelling method 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

11、 had been conducted. 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.

12、Features of the three-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 U

13、niversity of Mining 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 model

14、The effective size 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

15、one of the six sides 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 t

16、wo side facets of a 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 fo

17、r weeks, months or even years without interruption. This feature ensures that the study of the long-term rheological behaviour of soft rocks can be carried out.3. Physical modelling testsPhysical modelling of an underground roadway/ tunnel within soft rocks with a hydrostatic stress condition was ca

18、rried out. The same simulated materials were repeatedly used six times to construct six physical models. Each roadway model was provided with a different magnitude of support intensity.3.1. Geotechnical conditions for the prototype and the modelling scaleA specified underground roadway within soft r

19、ocks was assumed to be the prototype for the modelling study. Detailed geotechnical conditions of the roadway and its surrounding rocks are:circular roadway with a diameter (D) of 4.5 m and cross-sectional area of 16 m2; UCS (Rc ) of the surrounding rock was 20 MPa; bulk density of the surrounding r

20、ock was 2500 kg/m3;depth of the roadway location was 500 m below surface;rock mass stress (s0 ) was 12.5 MPa in all directions;support intensity(pa) to be applied to the roadway was 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 MPa, respectively.The geotechnical modelling scale (Cl ) determined was 1 : 25. The bu

21、lk density (gm ) of the simulated rock mass materials was 1600 kg/m3.Therefore, all the related simulation constants are:similarity constant for bulk density: Cg 1600/2500=0.64;similarity constant for strength: Cs ClCg 0:256; similarity constant for load: CF CgC1 4:096 105 ;similarity constant for t

22、ime: Ct C l:5 0:2: Geotechnical conditions of the simulated rock mass and roadway were derived from those of the prototype rock mass as presented below:strength of the simulated rock mass: Rm=RcCs=0.512;diameter of the simulated roadway: Dm=DCl=180 mm;load intensity on the facets of the model: pm=s0

23、Cs=0.32 MPa;Simulated support intensity: pam=paCs=0.00256, 0.00516, 0.00768, 0.01024, 0.0128 and 0.01536 MPa; respectively.3.2. Realization of support intensity in physical modellingDue to the restraints of the small dimensions of the model roadway on the simulation of support structure, the support

24、 pattern and structure were unable to be simulated. Instead, an equivalent support intensity was simulated and applied to the surface of the surroundingrock of the model roadway. A Static Water Support and Deformation Measurement System (SWSDMS) was designed specially. Fig. 3 illustrates the SWSDMS

25、being installed in the model roadway. The mechanism of SWSDMS is to use 4 separate water capsules to apply a support intensity to the surface of the roadway roof, two side walls and floor. Four rubber tubes, each of which was linked to a water capsule and filled with water, were used to generate a w

26、ater pressure at the capsule/rock interface and measure it through the water level reading. A certain constant simulated support intensity was achieved by applying a certain height of static water pressure. A change to support intensity could be made by changing the water height in the rubber tube.

27、The volume change of each of the four water capsules was measured at the due time by collecting and weighing the water overflow. The volume of water coming from each of the four water capsules was used to calculate the radial deformation of roadway surrounding rock, i.e., roof subsidence, wall-to-wa

28、ll closure and floor heave. The proposed simulated support intensities, i.e., Pam 0:00256, 0.00516, 0.00768, 0.01024, 0.0128 and 0.01536 MPa, were achieved by adjusting the static water level to 256, 516, 768, 1024, 1280 and 1536 mm high, respectively.Fig. 3. Static Water Support and Deformation Mea

29、surement System (SWSDMS) being accommodated in a roadway model in the real 3-D loaded physical modelling system.3.3. Construction of physical modelThe compositions and properties of materials to be used for the construction of physical models were studied prior to the physical model construction. Gi

30、ven the significant rheological deformation of roadways excavated in soft rock, sand and paraffin wax were chosen for the simulated soft rock. The properties of a series of sand/paraffin wax mixtures were studied in laboratory and are presented in Table 1. Table 1 Compositions and properties of sand

31、/paraffin wax mixturesAccording to the geotechnical conditions of the prototype rock mass and the model scale, a mixture of sand/paraffin wax of 100 : 3 was selected to construct the rock mass model. The procedures involved in the model construction include cold mixing of the sand and paraffin wax,

32、oven heating the sand/wax mixture and constructing the physical model using the hot sand/wax mixture.3.4. Process of physical modelling The real process of an underground roadway excavation, support installation and deformation of the surrounding rocks with time was simulated in the laboratory physical modelling. After the model had cooled down, prestressing the model, excavation of the roadway under pressure, installation of the SWSDMS device and measurement of the roadway deformation were carried out step by step. The whole process of modelling was s