Optimization of Blasting Parameters for Anchored Pile Wells in Open-pit Slope
Railway blasting slope anchorage pile shaft, the first excavation pile shaft, then pouring concrete to form a concrete anchor piles with large strength, thereby enhancing the stability of the slope. There is a primary school about 100m in the southwest direction of the explosion area. Although there are some houses in other directions but far away, due to the characteristics of the anchor pile blasting, the requirements for the blasting warning range are not high. Therefore, the densely populated primary school is the focus of the blasting warning. (2) The depth of the blasthole. The hardness of the rock is large, the Platts coefficient is high, and the utilization of the blasthole depth is low. It is not suitable to use the deep blasthole. The depth of the blasthole is 1m, and the depth of the sulcus is 10~20cm deeper than the blasthole depth. Where q is the unit consumption of explosives, kg/m3; f is the firmness factor of the rock, taking 8; s is the cross-sectional area of ​​the pile well, which is 4 m2. After calculation, the explosive consumption is 2kg/m3. In the formula, the meaning of the symbol is the same as before. According to the actual and blasting effect of the anchor pile, the deficiencies of the original scheme are pointed out, and an optimization scheme for improving the blasting effect is proposed. This scheme can reduce the generation of flying stones, reduce the bulk rate, and reduce the protective facilities of flying stones. Damage to construction equipment and weakening the risk of flying stones. In addition, the on-site environmental geological conditions are complex and variable, and the blasting parameters should be optimized according to the actual geological conditions on site to ensure the safety of blasting construction and the quality of blasting construction. Author: Wu Wei strong, Liu Min, Zhang Xin; Wuzhou, Jiangxi Cathay Pacific Blasting Engineering Co., Ltd., Nanchang 330038; Copyright: Ship Launching Airbags,Ship Launch,Ship Launching Rubber Airbag,Boat Launching Airbags Shandong Nanhai Airbag Engineering Co., Ltd. , https://www.nanhaimarine.com
1 Project Overview
The blasting area belongs to the denuded hills and inter-valley valleys, and the surface layer is the Quaternary Pleistocene silty clay , which can be plasticized to hard plastic and has a thickness of 2 to 4 m. The underlying bedrocks are phyllite, argillaceous sandstone , pebbly sandstone, sandstone, shale, etc. The Platts coefficient f=6～8, the rock is explosive.
2 Insufficient of the original plan (1) The hole is too deep and the actual amount of excavation is small. There is only one free surface for the blasting of anchor piles. When the borehole is too deep, the rock at the bottom of the hole has a large clamping force. The actual length of the tunneling is insufficient, the amount of excavation is small, and the utilization of the length of the blasthole is low. The main rock component of the blasting area is dark limestone with a Platts coefficient of 8 or more, a drilling depth of 1.2 m, and an actual boring depth of only 0.8 m. The blasting effect is not good.
(2) The number of drill holes is small, and the single hole charge is excessive. The rock is hard and difficult to drill. It is not conducive to drilling. It takes advantage of the method of less drilling and more charging. As a result, the single hole charge is too much, and the blasting effect is not ideal. The specific performance is: uneven rock fragmentation, large block More, flying stones even break through the cover of the pile well, the number and distance of the blasting flying stones are too large, the large flying stones are close, but the construction equipment will be injured, and the small flying stones are far away, there is a certain The risk of injury.
(3) The pore network parameters are not suitable for the actual site. The rock on site is very hard, the Platts coefficient is very large, and the distance between the designed hole and the groove is far away. The function of creating a free surface without void is caused, which leads to the unsatisfactory groove and the subsequent blasting effect of the surrounding hole. Poor [1-3].
3 Optimization of blasting parameters There is only one free surface for blasting of anchored piles. When designing parameters, we should consider creating new free surfaces as much as possible, designing the appropriate number of holes, and reasonably matching the positional relationship between the boring holes, auxiliary holes and peripheral holes. Control the single-hole dose and use differential blasting to reduce blasting flying stones, blasting vibrations and shock waves [4-6].
(1) The diameter of the blasthole. The working surface is small in range and is drilled by hand-held rock drilling rig . The general diameter is 39~46mm and 40mm is used.
(3) Explosive unit consumption. There are many factors affecting the unit consumption of explosives, which are related to the rock solidity, rock structure and explosive power. Because the working section is small, the explosive unit consumption has a great relationship with the section size, which can be calculated according to formula (1): 
(4) Number of blastholes. According to the unit explosive consumption, the number of blastholes can be estimated according to formula (2):
The number of available holes is about 17 or so.
(5) Hole spacing. The conical groove is used, the number of holes is 3, and the hole is arranged at the center of the section. The distance between the groove and the hole is 0.4m; the distance of the auxiliary hole and the nature of the rock, the function of the explosive and the medicine volume. Relatedly, the spacing of the auxiliary holes is 0.5m; when the ordinary blasting method is used, the parameters of the peripheral holes can be referred to as auxiliary holes, which is 0.67m.
(6) Arrangement of the blasthole. The angle between the groove and the working surface is 70°-80°, and the peripheral hole is inclined outward by 3°～5°, and the hole and the auxiliary hole are perpendicular to the working surface. The specific arrangement is shown in Figure 1. The blasting sequence of the peripheral holes of the four corners should be after the blasting of other peripheral holes, and if the blasting is simultaneous, the resistance line is too large [7-8].
Through the above optimization of the blasting parameters, the main parameters of the drilling and blasting can be obtained (see Table 1). In combination with the actual rock conditions, the single-hole dose, especially the amount of the peripheral pores, is strictly controlled, and the differential detonation is used to improve the blasting effect.
4Comparative analysis of blasting effectFig. 2 is the blasting effect diagram of the original scheme. It can be seen from Fig. 2 that the blasting flying stone phenomenon is very obvious. The flying stone is scattered everywhere, the piled-hole covered iron mesh is broken by the flying stone, and the iron mesh has obvious deformation, while the iron The wooden boards and sandbags on the Internet have disappeared; the number of blasting flying stones is large and the block size is relatively large; the equipment next to the pile wells is collided by flying stones at high speed, although the initial impact does not necessarily directly destroy the equipment, but the long-term accumulation must produce equipment. damage.
Figure 3 shows the blasting effect after optimization of the scheme. It can be seen from Fig. 3 that the flying stone phenomenon is not obvious, the flying stone is produced less, almost no stone is punched out of the pile well, the rock crushing ground is very uniform, the explosion pile is mainly concentrated in the pile, and the blasting is almost There is no impact on the equipment next to the pile.
5 Conclusion
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Ye Qiong; Xingan Middle School, Jiangxi Province, Ji'an 341000 , Jiangxi, China