1、翻译部分英文原文Development of high pretensioned and intensive supporting systemand its application in coal mine roadwaysKang Hongpu, Lin Jian, Wu YongzhengCoal Mining and Designing Branch, China Coal Research Institute, Hepingli, Chaoyang District, Beijing 100013, ChinaAbstract: In view of the features of
2、complicated and difficult roadways, the present problems on rock bolting technique were analyzed, and the high pretensioned and intensive supporting theory was put forward. The initial supporting stiffness and strength of bolting system should be increased largely to control the dilatant deformation
3、 and maintain the integrity of surrounding rock. The high pretensioned and intensive bolt and cable system was developed, and the mechanical properties of the bolting components were obviously improved. This system has been successfully applied in the 1000m deep entries in Xinwen coal field, and the
4、 entries affected by intense mining activities in Luan coal field. The deformation of the entries was reduced by a big margin. This system provides an effective supporting form for complicated and difficult roadways. Keywords: roadways; rock bolting; high pretensioned stress; intensive supporting; u
5、nderground applications 1 Introduction With the increases of coal mining intensity and limit, the depth of roadways in underground coal mines in China is getting larger and larger with the maximum mining depth up to 1365m; geological conditions of the roadways become more and more complicated; and t
6、he locations, sections and stress states of the roadways tend to be unfavourable to their stabilities. These trends of the roadway layout pose higher and stricter requirements to bolting technique. For this purpose, study and testing on the complete bolting technique have been carried out in several
7、 coal fields, and the research results have been utilized in different roadway conditions, and improved the supporting performance sharply. At present, in China, the rate of bolting accounts for 60% in total roadways in many coal fields, even 100% in some coal fields. However, some problems are stil
8、l present though great progress has been made in bolting technique. The supporting performance of high strength bolting is poor in deep and complicated roadways, and the bolting components are destructed severely. In general, the problems are summarized as follows: Low supporting stiffness. The supp
9、orting stiffness is associated with pretensioned stress and anchorage types, and the high supporting stiffness can only be achieved by combination of high pretensioned stress with full-length anchorage. The spin moment to install bolts only amounts to 100-150N.m, or the pretensioned force is up to 1
10、5-20kN at most cases. Low tendon strength for bolts and cables. For existing tendons used for high strength bolts, the yield strength is about only 335-400MPa, while the broken strength is about 500-600MPa. The diameter of cables is 15.2-17.8mm, and the broken force is about 260-350kN. Poor end thre
11、ad quality. Poor thread quality will increase the frictional forces between the nuts and threads, and lower the transiting rate from the spin moment of nuts to pretensioned force of tendons. On the other side, the poor thread quality will also worsen the rear stress state, result in shearing, bendin
12、g, rupture. Devaluating surface proof components, such as plate, strap, and metal mesh. Straps with low strength and stiffness are commonly used to lower the cost of material, decrease the capability of surface proof and affect the total supporting performance. High density of bolts. More bolts per
13、square meter and more installing time, will bring down the rate of roadway advance. To solve the above problems, the high pretensioned and intensive supporting system was developed based on the relative supporting theory. 2 High pretensioned and intensive supporting theory At present, there exist tw
14、o different theories for supporting complicated and difficult roadways with high stresses and large deformation. 2.1 Secondary supporting theory According to secondary supporting theory, supporting for roadways with high stresses and large deformation should be divided into two phases. The first sup
15、porting should permit the surrounding rock to deform and release the stress when the stability of roadways is secured; the second supporting should be installed to keep the long term stability of roadways at a definite interval. This theory has been widely accepted and applied, and very good perform
16、ance has been obtained in some definite conditions. But this theory is facing more and more challenges with the increase of mining depth, and the additional complicated, geological and mining conditions. In roadways with depth up to 1000m, or roadways affected by intense mining activities, or cut by geological discontinuities, weak and broken rock zones, the deformation has been still unaccepted after secondary supporting, and the third or
