Study On Shock- And Wear- Resistance Of Concrete For Debris Flow Mitigation Engineering

Since the Wenchuan earthquake,debris flow disasters have occurred frequently in mountainous areas in China.Due to the significant impact of debris flow on the structure of protective engineering,the concrete surface and structure of protective engineering are often damaged.This study is carried out in order to improve the durability of protective engineering.On the basis of previous studies,this thesis reviews the development and current situation of this subject at home and abroad,analyzes the process of debris flow scouring and grinding from the aspects of scouring and grinding mechanism and effect,and carries out field investigation of protection engineering.The main research contents are put forward as follows:the influence law of compound materials on concrete anti abrasion strength;the influence law of surface protective layer composition and thickness on anti abrasion strength;the change law of anti abrasion strength with time;the application of compound materials concrete and surface protective layer in protective engineering.The conclusions are as follows:(1)Through the underwater steel ball abrasion test designed by orthogonal method,the primary and secondary relationship between the content of each material and the significant degree of abrasion resistance strength is determined,which provides a reference for the mix design of abrasion resistance concrete in debris flow control engineering.The results show that the optimal content of each material in the anti abrasion concrete(strength grade C25)with nano silica and other materials is:nano silica 1.5%,micro silica 12%,polypropylene fiber 1.8kg/m~3,air entraining agent0.005%.(2)The influence of composition and thickness on the impact wear strength of polyurea surface protective layer was revealed by impact wear test.The impact wear strength of the elastic polyurea protective layer is higher than that of the rigid polyurea;the impact wear strength of the polyurea protective layer with the same composition increases with the increase of the thickness of the protective layer,and there is a positive correlation.When the thickness of polyurea protective layer is 1.5?3mm,the impact wear strength is about 33?48 times of that of concrete mixed with nano silica.(3)Through a long time series of shock-and wear-tests,the change of shock-and wear-strength of concrete materials with time under the action of mud and stone fluid is discussed.The shock-and wear-strength of the experimental specimens in 60h is 2-4 times of that in 12h.The main reasons are as follows:the coarse aggregate inside the concrete specimen is gradually exposed,which leads to the improvement of the anti abrasion strength of the concrete material itself;the smooth degree of the contact interface between the solid-liquid two-phase medium and the concrete specimen is gradually improved,which leads to the decrease of the impact abrasion force of the fluid High abrasion resistance of concrete materials.(4)For the rib sill energy dissipation type diversion channel,the measures of increasing the top chamfer of the rib sill facing the debris flow side and the apron at the side wall footing,and spraying polyurea protective layer can improve the anti abrasion performance of each part,so as to extend the service life of the prevention and control project.Practical engineering application conditions:according to the test results,the advantages of compound nano silica concrete are simple construction,low time cost,which can be used in the overall construction of prevention and control engineering structures,such as the bottom plate of diversion channel and overflow outlet of sand retaining dam,which are prone to abrasion damage;the advantages of polyurea protective layer in protection engineering are low material cost,high abrasion resistance,which can be used for protection Repair structural damage and strengthen vulnerable parts.