Basic Research On Durability Of Mortar Bolt Anchorage Body

As a vital part of modern geotechnical supporting construction, bolt anchoring system plays an important role on the development of society and ecoeomy, so the durability and safety performance are derectly related to the stability of society and safety of people's life and wealth. However, because of the adverse working conditions where bolt anchoring system always locate in and the long term of its service life, cases of durability deterioration or even damage always happen, especially with the expanding of engineering scal and the increase of engineering quantity, together with the further worsening of working environment, problems of durability damage becomes more and more outstanding. Recently, much work about durability of engineerning structure has been done at home and abroad, but most of these research productions can not be goodly applied on the bolt anchorage system, because most of these subjects investigated are reinforced concrete structures, there exist distinct differences in no matter the service conditons or stressing state between reinforced concrete structure and bolt anchoring system, so it is very urgent and necessary to carry out research of this field.Relying on the national excellent young science fund project"disaster reduction of geotechnical engineering"(50625824),construction technology plan project of ChonqQing"durability technology of geological hazards control"and natural science fund project of ChongQing"research on durability of anti-slide supporting structure"(CSTC,2008BB0318) the basic research on durability of mortar bolt anchorage body, such as the self degeneration of bolt and mortar under the condition of corrosion, the changes of bond performance in each interface are analyzed, is conducted in this dissertation during the research cours. the concretely works and results are as follows:①Aiming at the characteristics of media erosion in anchoring system such as diffusing axial symmetrily and the limited length of diffusing. The movement characters of harmful medium diffusing in mortar is simulated by means of numerical analysis, the model of media diffusing in mortar which based in Fick's law is built . Then the effection of cracks to media movement is considered, and the model of concentration distribution around bolt in cracked is also estamblished. The model results are highly agreed with the numerical results. ②Througth synchronous corrosion of mortar specimens with bolt and specimens without bolt, the relationship between mortar strength and corrosion time and the change of bond strength in bolt-mortar interface and mortar-rock interface alonge with the corrosion are achived.The relationship between mortar corrosion level and bond strength of each interface is built,beside that the difference between nature corrosion and laboratoury testing is considered and the test results is generalized.③First, by analyzing the corrosion potential of bolt in underground water environment, the corrosion current density of bolt uniform corrosion is provided at the same time , the effection of working load on corrosion current density is considered, and the model of corrosion life of bolt under condition of uniform corrosion is built.Second , with the premise of mortar defectiveness, by using of the relationship between defectiveness size and corrosion current, also considering the stress concentration in defectiveness position, the model of bolt corrosion life under the condition of unequally corrosion is slso estambilished.④The process of motar cracking caused by bolt corrosion and its volume expansion under two tipes of conditions, one is to consider the rock initial stress and the other is not to consider the rock initial stress, the model which is suit to bolt anchoring system's characteristics is estambilished, the model is validated by finite element analysis.⑤Based on coefficient of rugosity, the model of bond strength parameter of deformed bar bolt in different corrosion level, based on the model, the anchoring character such as ultimate load in the extracting process,the distribution of bond strength in bolt-mortar interface and mortar-rock interface,changing with the bolt corrosion degree is analyzed by means of numerical analysis method, and the affection of bolt corrosion and mortar cracking to above anchoring characts are also explained..From above research procees, all of the aspects which affect the durability of bolt anchoring system are illustrated, the results is hoped to provide a reference to more deepper and more systemic research later.