During the last few decades, carbon fibre reinforced plastic (CFRP) sheets have been utilized in many civil engineering applications due to their considerable strength/weight ratio and excellent corrosion resistance, but there is no report of repairing cracks of coal mine tunnel with CFRP sheets. Some cracks occurred at the mine central pump room of Panbei mine in Huainan city. After field investigation was carried out, the location, dip angle, length and width of the cracks were got. And after the characteristics and the causes of cracks being analyzed and according to the development of the cracks, CFRP sheets were used for local repair and reinforcement. Based on the field investigation, a detailed reinforcement scheme was made. Two layers of CFRP sheets were bonded to the cracks. During the construction process, the construction procedures and quality of the project were strictly controlled, and finally, anticipated effects were achieved. Monitoring results showed that cracks in the mine central pump room are controlled, the tunnel surrounding rock is stable and the support is safe, which demonstrates that it is an effective method.
The application of carbon fibre reinforced plastic (CFRP) sheets in civil engineering structures has been growing rapidly in recent years, and is becoming an effective and promising solution for strengthening deteriorated concrete members[1–2]. Carbon fibre reinforced plastics sheets or plates are well suited to this application because of their high strength-to-weight ratio, good fatigue properties, and excellent resistance to corrosion. Because CFRPs are quickly and easily applied, their use minimizes labor costs and can lead to significant savings in the overall costs of a project[3–4]. Applications of CFRP sheets in civil engineering are growing, but there is no report of repairing cracks of coal mine tunnel with CFRP sheets. Therefore the application of CFRP sheets in coal mine tunnel is introduced in this paper.
5 rectangular beams were constructed and tested. The size of the beams is 120mm×250mm× 2400mm. Details of the test specimen are shown in Fig. 1. Table 1 gives the details of the test specimens. The test variables were CFRP wrapping.
The mechanical properties of the concrete and reinforcement were obtained from ancillary tests. The concrete mix proportions by weigh were 1 (cement): 1.35 (fine aggregate): 2.21 (coarse aggregate). The water/cement ratio was 0.39 and the cement content was 484.85kg/m3. Ordinary No. Strengthening plan Size of CFRP sheets (mm×mm×mm) DL Control beam DL1 1 layer of CFRP sheets 2300×120×0.167 DL2 2 layer of CFRP sheets 2300×120×0.334 DL3 2 layer of CFRP sheets 2300×120×0.334 DL5 2 layer of CFRP sheets with "U" stirrup 2300×120×0.334 606 portland cement and well-rounded graded gravel with maximum aggregate size of 15mm were used.
Step loading and the action of one-third loading were used.
