| In response to the instability failure phenomenon of transmission tower foundation in mining subsidence area and from the mechanical property of tensile bolts applied in mine coal, this paper conducted the research about structural design, mechanical mechanism, mechanical property and control countermeasure of Constant Stretch Resistance and Compression bolt applicable to transmission tower foundation in mining subsidence area.The instability failure phenomenon and instability property of transmission tower foundation in mining subsidence area are analyzed. According to the analysis of different types of surface deformation in mining area, the transmission tower foundation has different instability failure phenomena. The failure properties include integral sinking, non-uniform settlement, foundation crack, foundation dislocation, foundation translation, and foundation incline. The instability reasons are summarized and the influence of non-uniform settlement is significant especially for the transmission tower foundation in mining subsidence area. The influence of non-uniform settlement for big board foundation commonly used in mining subsidence area is researched in this paper. The non-uniform settlement of surface in mining area cause the non-uniform settlement of big board foundation. And the traditional rigid coupling countermeasures can't effectively resist the influence of non-uniform settlement to the transmission tower and foundation.In response to thenon-uniform settlement of transmission tower foundation, the idea of Constant Stretch Resistance and Compression bolt which is applicable to transmission tower foundation in mining subsidence area is proposed. And its structural component and mechanicalproperty are detailedly described. The main structural components are nut, constant resistance device, compression device, metal ball, connection device, and anchor rod. Compared with common bolt, CSRC bolt is a kind of new anchor bolt to integrate constant stretch resistance, large elongation, strong compression, and high energy absorption, which can improve the adjustmentcapacity of bolt in stretch and compression to control the foundation and transmission tower. It can resist the non-uniform settlement of surface, ensure the stability of transmission tower foundation, and protect the safeoperation of transmission line.The working mechanism and mechanical mechanism of CSRC bolt in static stretch experiment, compression experiment, stretch after compression experiment are analyzed. There are three stages in static stretch experiment of CSRC bolt. In the first stage, the stretch force is smaller than the constant stretch resistance. In the second stage, the bolt maintain the constant stretch resistance and has large elongation. In the third stage, the elongation of the bolt reaches the design elongation and the inner rod reaches the compression lock-self device. With the increasing stretch force the bolt is broken and the stretch force decreases to 0KN. The experiment is over at the same time. There are three stages in simulated compression experiment of CSRC bolt. In the first stage, when the stretch force from experiment system is very small, the stretch force can't make rod move with locking plates to left. In the second stage, with the simulated compression force increasing, the resultantofforce of rod and compression lock-self device can't resist the stretch from experiment system which is simulated compression force of the bolt. In the third stage, when the simulated compression force reaches the design force, the experiment system will be stopped. At the same time the rod and compression lock-self device are fixed together because of the force of each other. There are two stages in the stretch after compression experiment of CSRC bolt. In the first stage, because of the interactive force of the rod and compression lock-self device, the stretch force from experiment system can't make the rod pull out from the compression lock-self device. In the second stage, with the increasing stretch force from experiment system, when the force from experiment system can make the rod pull out from experiment system, the stretch force reaches the largest force. And then the stretch force will decrease to 0KN. The largest stretch force is the stretch force which is corresponding compression force. In the compression and stretch experiments, the CSRC bolt will undergo the repeated following stages. Through the experimental data, the property of bolt in compression and stretch after compression can be summarized. The control mechanism of CSRC bolt in transmission tower foundation in mining subsidence area is also researched. And the energy constitutive relationship of CSRC bolt and CSRC foundation applied in mining subsidence area is proposed.Through static stretch experiment, static stretch experiment, compression experiment, stretch after compression experiment of single bolt and multiple bolts, experimental data can be analyzed to get some conclusions. Firstly, the CSRC bolt with inner rod diameter of 22 mm shows the properties of constant stretch resistance and large elongation. The average constant stretch resistance can reach 51.87 KN and the total average elongation is 571.33 mm. In the stretch experiment, the sleeve of constant resistance device has a certain elongation about 16.33 mm, and the diameter of sleeve after experiment is bigger than the one before experiment. The deformation of nut part and compression part of sleeve is very small and the middle part of sleeve is more obvious than the two ends. After the experiment, the sleeve is not broken, so the deformation of diameter and elongation can't affect the stretch mechanical property of CSRC bolt. The total energy absorption is 44.29 KJ which is bigger than the one of common bolt, and the energy absorption of constant resistance part is 27.91 KJ. The larger elongation of CSRC bolt is, the energy absorption capacity of CSRC bolt is stronger. Secondly, the group of two CSRC bolts shows the properties of high constant stretch resistance and large elongation. The average constant stretch resistance can reach 102.14 KN and the total average elongation is 566.70 mm. In the stretch experiment, the sleeve of constant resistance device has a certain elongation. But the elongation of the two bolts is inharmonious through the analysis of experimental data. The diameter of sleeves of the two bolts after experiment is bigger than the ones before experiment. After the experiment, the sleeve is not broken, so the deformation of diameter and elongation can't affect the stretch mechanical property of the group of two CSRC bolts. The total energy absorption of each bolt is 54.31 KJ, which is bigger than the one of common bolt. The larger elongation of CSRC bolt is, the energy absorption capacity of CSRC bolt is stronger. Thirdly, the group of four CSRC bolts with inner rod diameter of 22 mm shows the properties of constant stretch resistance and large elongation. The average constant stretch resistance can reach 203.99 KN and the total average elongation of each bolt is 553.60 mm. In the stretch experiment, the sleeve of constant resistance device has a certain elongation about 6.9mm, and the diameter of sleeve after experiment is bigger than the one before experiment. The deformation of nut part and compression part of sleeve is very small and the middle part of sleeve is more obvious than the two ends. After the experiment, the sleeve is not broken, so the deformation of diameter and elongation can't affect the stretch mechanical property of CSRC bolt. The total energy absorption is 107.18 KJ which is bigger than the one of common bolt. The larger elongation of CSRC bolt the energy absorption capacity of CSRC bolt is stronger. Fourthly, the CSRC bolt with diameter of 42 mm and the CSRC bolt with diameter of 42 mm also have the properties of constant stretch resistance and large elongation. The average constant stretch resistance of CSRC bolt with diameter of 42 mm can reach 139.34 KN and the total average elongation of each bolt is 646 mm. The average constant stretch resistance of CSRC bolt with diameter of 32 mm can reach 90.25 KN and the total average elongation of each bolt is 634 mm. the constant stretch resistance of the two types of CSRC bolt is bigger than the one of CSRC bolt with diameter of 22 mm which is 51.87 KN. So the bigger of inner rod of CSRC bolt the constant stretch resistance is bigger. In the stretch experiment, the sleeve of constant resistance device has a certain elongation about 4mm and the sleeves of the CSRC bolts are not broken. The total energy absorption of CSRC bolt with diameter of 42 mm is 80.94 KJ and the one of CSRC bolt with diameter of 32 mm is 54.13 KJ, which is bigger than the one of common bolt and CSRC bolt with diameter of 22 mm. The bigger diameter of inner rod of CSRC bolt is, the energy absorption is lager. Fifthly, CSRC bolt can lock self through compression device and retain high compression capacity. The compression force of CSRC bolt with diameter of 42 mm can reach 800 KN. And the larger diameter of inner rod of CSRC bolt is, the compression force is larger. In the stretch after compression experiment, a little stretch force can make the inner rod pull out from the sleeve. And the smaller the compressive force is, the required stretch force is smaller. The compression self-locking device can bear repeated stretch and compression and retain the compression lock-self capacity.Through the numericalsimulation the influence of mining in Jisan coal mine on the surface transmission tower foundation is analyzed. And the transmission tower foundation in different area on the surface is also compared through numerical simulation. The sedimentationvalues in some locations on surface are beyond the specified value. So the used big board foundation can't provide the adjustment capacity. When adopting the CSRC bolt, the subsidence of foundation can be controlled in a reasonable range effectively. This states the CSRC countermeasure is effective for the transmission tower foundation in mining area.Through a lot of systematic research work, in response to the instability failure phenomenon of transmission tower foundation in mining subsidence area, this paper reveals the instability mechanism of transmission tower foundation in non-uniform settlementin mining subsidence area, developed the structure of CSRC bolt applicable to transmission tower foundation in mining subsidence area, mastered the properties of CSRC bolt in stretch experiment, compression experiment and stretch after compression experiment, and formed the control mechanism and countermeasures of CSRC bolt applicable to transmission tower foundation in mining subsidence area. |
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