Study On The Deformation-Failure Of Anchoring Tower Footing And Its Reinforcement Decision-making System In UHV Transmission Line

Power industry is a fundamental industries and public utility to support economic and social development. Along with the national economic development and improvement of peoples’of living and material, the voltage delivered and transmitted by transmission line project has increased. On the other hand, the requirements of pull strength, compressive strength, and horizontal loadhave also increased accordingly. Thus, the application of anchoring techniqueon the tower footing has greatly reduced the consumption of materials, reduced the cost, and improved the efficiency of design and construction, and protected the geological and ecological environment. However, due to the late start of the anchoring tower footing of transmission line, insufficient the oretical research result, as well as the constantly increased transmission voltage, the construction personnel and designers lack knowledge on anchoring tower footing, which leads to the lack of theoretical research guidance and blindness in practical engineering.Based on that, with the technical methodologies of engineering geology, rock mechanics, information engineering as guide, combined with other technical methodologies of geological survey, laboratory and field test, numerical simulation, fuzzy mathematics, neural networks, information systems development etc., this thesis carries on the study on the physical property, mechanism of deformation and failure, stability impact factor and effective reinforcement policy of the tower footing of UHV transmission line, and develops the information engineering system for the anchoring reinforcement of the tower footing of UHV transmission line, which boasts the engineering application value.Firstly, this thesis carries out the study on the physical and mechanical properties property of the anchoring tower footing, which is conducive to the further understanding over the physical property of the anchoring tower footing. The thesis adoptsthe method of on-site test of setting up pilot sites throughout the country, and a total number of more than 30 different types of on-site tests have been conducted to compare the differences and change rule of the ultimate bearing capacity of tower footing under different lithological properties; compares and studies on the differences and change rule of tower footing axial force under different rock property, and matches the relation function of axial force-load, axial force-depth under different rock property; compares the impact range of the test under different rock property, and proposes a reasonable protection range of the test of 1.5-2.0m; compares the differences of effective length of anchor rod under different soil layers, which results in the effective anchor rod length of 10m in the soil layer, and the effective anchor rod length of 3.5m in the rocks, verifying the rationality of specification suggestion.Secondly, this thesis carries out the study on the mechanism of deformation and failure of anchoring tower footing. Based on the domestic and international anchor rod shear slip model under the drawing force, it is found that there will be large error and limitation on the theoretical-analytical method, because of its assumptions and limitations of laboratory tests. Thence, this thesis adopts the on-site test method to analyze the three kinds of failure modes of anchoring tower footing:anchor pulp failure, magma failure, and rock shear failure. With the numerical simulation method, the thesis carries out the inverse analysis on the three failure modes with foundation displacement and evolutionaryprocesses of plastic range, showing detailed failure process of these failure modes. Based on the inversion of the failure process, this thesis carries out the study on the transferring rules of stress and axial force, the variation rules of axial stress, further analyzing the mechanism of deformation and failure of anchoring tower footing.Thirdly, based on the stability effect of the anchoring tower footing, this thesis carries out the study on the sensitivity of the impact factor, and proposes effective reinforcement methods. In terms of comprehensive analysis, impact factors can be divided into two categories:formation lithologic physical and mechanical properties and the parameters of anchor rods. The thesis selects five impact factors of elastic modulus, cohesion, internal friction angle, Poisson’s ratio, anchorage length, and studies on the stability effect of anchoring tower footing with 15 randomly generated set of programs, adopting the with numerical simulation method. With the gray correlation method, it is shown that the anchorage length has the highest influence on the sensitivity of anchoring tower footing’s stability. While the sensitivity of other four factors almost equal to each other. Based on 150 sets of test programs, this thesis analyzes the most sensitive factor with engineering application, establishing the optimal solution program for the anchorage length of the anchoring tower footingby using neural network algorithm under different stratigraphic-lithologic conditions, and proposes a reinforcement solution methodof engineering application.Last but not the least, this thesis develops the information system for the anchoring tower footing of the UHV transmission line. Two sub-systems represents two different functions of the system:test information management system will carry out the informatization management on the on-site test results of the anchoring tower footing of the UHV transmission line, which also has the function of search, modification, and Input, greatly accelerating the achievement sharing of the industry, improving the efficiency of design and construction; while the information decision-making reinforcement system is able to evaluate whether the design parameters of design scheme can meet the requirements of the tower footing’s bearing capacity of UHV transmission line, and to propose the most effective reinforcement scheme with the comprehensive consideration over the sensitivity and design parameters of different impact factors, which results in the favorable application effect in real engineering projects.The innovationand feature of the thesis lie in:(1) the study on the differences and change rules of the ultimate bearing capacity, axial force, the range of effect, the effective anchorage length of the anchoring tower footing under different lithological properties through on-site test;(2) confirmationand acquisitionthat the anchorage length isthe most sensitive impact factor over the stability of the anchoring tower footing, and proposes the optimal solution and reinforcement decision-making method for the most sensitive impact factor (anchorage length) under different lithologic conditions, through the methods of numerical simulation, fuzzy mathematics and neural network;(3) the inversion of three different types which are anchor grouting failure, magma failure, and rock shear failure of deformation and failure processes of the anchoring tower footing with numerical simulation, and the study on the transferring rules of stress and axial force, as well as the change rules of axial stress under different failure modes;(4) the development ofthe information system for the anchoring tower footing of the UHV transmission line, which can conduct the informatization management on the test results of the UHV transmission line, and propose solutions to the reinforcement project of the anchoring tower footing, which boasts the favorable engineering application value.