| Surface movement and deformation caused by coal mining follows some regularity which has been studied more maturely in plain regions, while such regularity in hilly and mountainous areas is obviously different from in the plains. More efficiently prediction of such regularity after coal mining, could perfectly help to reduce the damage of ground buildings, and is practically significant to reasonably exploit the underground coal resources.The total length of the West-East Gas Transmission Pipeline (WEGTP) is up to50,000km, and it is close to15,000km only for the first, second and third pipeline projects. The first pipeline projects have been built, nearly1,000km of which passing through numerous coal bases such as Shenfu of Shaanxi Province, Shanxi Province (e.g. Hedong, huoxi, Qinshui), Jiaozuo of Henan Province, Yanzhou of Shandong Province, Xuzhou of Jiangsu Province, Huainan and Huaibei of Anhui Province. There have rich underground coal resources of good quality in these regions. Therefore, it has a great value in use to investigate the impact of ground deformation on gas transmission pipelines after fully underground mining, thereby guaranteeing normal operation of these pipelines and efficient development of coal resources.The present study systematically analyzed general characteristics of rock formations during movement and deformation in plains and its special features in mountainous areas, presented an overview of the prediction methods for ground movement and deformation, and then pointed out that the ground movement and deformation caused by the underground mining is very complex. So far, it has remained one of the major challenges to examine and reveal the regularity. In this study, we investigated in depth the regularity of surface movement and deformation due to the underground mining.First, the thesis utilized nonlinear features of BP nerve network to specially analyze the measured data of some working plane from Dongshan Coal located in the mountainous areas. In order to quantitatively build and measure all factors and then to construct a3-layer structure model of BP nerve network for mining subsidence in the mountainous regions, we considered the terrain and other factors including prediction points (location, slope and slope direction), mining conditions, geological factors and so on. Through contrast of the ground movement and deformation between the expected results and actual observations, we found that the BP neural network model was generally consistent with the actual surface deformation, indicating it is feasible to develop a design of underground mining subsidence based on BP nerve networks for the mountain areas.Second, a FLAC3D model has been built to predict the surface movement and deformation in mountainous regions by using the feature that the geometry is associated with the attribute data in GIS, on the basis of the DTM and the large numerical analysis software ANASYS, thus rapidly achieving in construction of the FLAC3D model of mining subsidence in mountain regions. Through combining the actual mining of Malan in Xishan coal and electricity of Shanxi Province, therefore, numerical simulation and prediction for movement and deformation were conducted for two major sections in order to obtain distribution cloud images and contour maps which are associated with their movement and deformation. Through contrast with the measured ground movement and deformation data, it is concluded that prediction of the numerical simulation is expected to be consistent with the measured surface deformation, indicating that the FLAC3D numerical simulation method can apply to prediction of the ground movement and deformation in mountainous regions.The above mentioned two methods have their own advantages and disadvantages, respectively. Although the BP nerve network and numerical simulation are relatively fast, workload small and efficiency high, it is still only an appearance design, needs big samples, and cannot intuitively reflect movement and deformation of the internal rock body. In contrast, the FLAC3D model can intuitively reflects movement and deformation for both the ground surface and the internal rock body, so that it has more practicality than the BP nerve network. Either of them can be used to predict ground movement and deformation in mountainous areas.In addition, this thesis used the real data and actual information from some part of the WEGTP in Shanxi for research background to systematically arrange the observed data from deformation of gas transmission pipelines and ground movement deformation. Considering volume of the actual terrain deformation, surface sinking and horizontal deformation, we have established a relationship between the pipeline deformation and the ground movement and deformation as follows:Stretch and compression of a pipeline overall points to bottom of the slope body, while the pipeline compression range is greater than its stretch range, and volume of the pipeline deformation is less than surface deformation volume.In the text we utilized the numerical simulation FLAC3D to build three different kinds of spatial distribution relationships between pipelines and work profiles according to the actual coal conditions below the WEGTP. Corresponding numerical modeling and simulation were respectively conducted, and the results are as follows:(1) Simulation made in a control surface at the center of the pipeline presented its shear stress distribution from different mining locations, which indicated a regularity of the stress change from small to large and then to large change due to effects of mining.(2) To simulate effects of underground mining on integral pipelines, we analyzed the move trend of pipeline sinking and horizontal displacement when mining advances from different distance from the pipeline. Three spatial relationships were indicated. Pipelines have different appearances for their vertical and horizontal displacements. Overall, the horizontal displacement paralleling the pipeline generally showed symmetric distribution, while it was not symmetric when perpendicular to the pipeline direction and mainly pointed to the downhill direction. The vertical displacement slowly increased, reached the maximum, and then decreased, demonstrating symmetrical distribution features around the mining center.(3) In this thesis we took the permissible deformation of WEGTP into consideration, and concluded that the oblique spatial relationship between pipeline and displacement is the most conducive to the pipeline operation after a comprehensive analysis, thus providing sufficient basis for exploitation of coal resources under the pipeline in future and guaranteeing the normal operation of the pipeline. |
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