Study On Deformation And Failure Mechanism Of Transmission Tower Groundwork In Karst Region

By taking the project of±800kV high voltage direct current transmission line from Yunnan to Guangdong as example, the present thesis focus on deformation and failure mechanism of the transmission tower groundwork in karst region.The present thesis analyses the geological characteristics of the crossed karst region, common foundation forms, tower types and the corresponding load in the project, and take the transmission tower groundwork contrast to the common groundwork in karst region, got the difference of this two kinds of groundwork in process mode of loads, the stress and displacement of cave, etc. Classify the transmission tower groundwork in karst region by soil-rock composition groundwork and karst cave groundwork, and select the largest of load-tower to analysis.Take the red clay of soil-rock composition foundation in this line as an example, analyses the soil-rock composition foundation under of transmission tower. And select ground deformation as a safety control indicator; select foundation width, the layer thickness under foundation bottom by pressure, clay plasticity state as affecting factors; select layerwise summation method as the calculation. According to the results summarize, educe the conclusion as: the various parameters combination corresponding the maximum value of ground deformation, and the various red clay soil-rock composition groundwork applicability. These conclusions can be applied to high, middle and low soil compression of the transmission tower soil-rock composition groundwork.Take the III, IV grades rock as an example, analyses the karst cave foundation under transmission tower. Select the foundation tilt value, whether reach ultimate destroy state as a safety control indicator; select width of the bottom of foundation, ratio between depth and span of karst cave, grade of rock mass as affecting factors; select numerical analysis as calculation method. According to the results summarize, educe that whether the cave roof enter the accelerated destruction state as normal using criterion of cave foundation under transmission tower; various parameters combination of ratio between depth and span and its responding foundation deformation threshold value; what circumstances not to consider cave impact, etc. As well as giving a special analysis to the effectiveness of the ratio between depth and span, consider that the ratio between depth and span as an affecting factor is effective when analyzing destroy course, the stable state boundary, the groundwork deformation threshold value of the karst cave groundwork; however, it is not ideal as an influencing factor in other instances.The conclusion of this paper has definite reference value on the transmission line route selection and design.