Mechanical Response Analysis Of Old Cement Concrete Pavement Under Impact Fracturing Technology

Due to its high strength and long service life and other advantages,cement concrete pavement occupies a large proportion in China's road system.Due to other factors such as traffic conditions,when the road surface is damaged,the service life will be drastically shortened,and the further development and destruction of the disease will make it unable to meet the driving requirements.Impact fracturing technology is one of the technologies to solve the problem of repairing old cement concrete pavement.Some studies have shown that this technology has a very good practical effect on the rehabilitation and repair of old roads.At present,research on this technology at home and abroad is mostly based on finite element simulation and practical engineering applications.This article through the indoor impact fracturing cement concrete scale specimens to simulate the stamping situation and the impact of outdoor impact machinery on the test section pavement impact fracturing the actual effect of the effect of monitoring,to achieve dual control of the technical application of the construction site,make more reasonable application guidance.The indoor test is based on the theory of geometric similarity and similarity theory.Through the stamping test,the best scaled specimens are determined from several different proportions of scaled specimens,and the multiple sets of specimens are well-designed and empty.The impact fracturing is performed on three different typical positions of the plate,plate corners,and plate edges of the specimens in different states.The impact fracturing device is based on the principle of falling hammer device design,and is transformed from the Marshall compaction instrument and controlled by the falling.Hammer impact times and heights provide the required impact loads,and the use of dynamic strain observation techniques for the data acquisition and analysis of the test points on the surface and side of the test specimen to achieve the purpose of studying the destruction characteristics of the test specimens,Outside the test section,select carefully the board with the same characteristics as the real indoor simulation test,select the characteristic measuring points to observe the settlement difference,bending deflection,time of crack generation and expansion before and after stamping.Combine indoor and outdoor test data analysis to achieve guidance for construction.Firstly,impact cracking can be well simulated by impact-fracturing a scaled concrete slab with a suitable size.Before the slab is destroyed,the strain at the measuring point and the number of impacts show a linear increase,and the strain response at the measuring point increases or decreases.The change is related to the failure state of the measuring point area.The strain value of the measuring point on the side of the base layer is higher than the strain of the surface of the surface layer and the measuring point of the surface layer by 1?2 orders of magnitude,and the impact energy is generated under the condition that the impact load is kept constant.The impact on the whole board is certain,but due to the different initial state of the board and the position of the load,the form,position,length and width of the initial cracks are different,and the initial cracks The width is not uniform,and the width of the first end of the same crack is wider than the width of the end.Secondly,the variation range and law of crack width and length of various plate bodies under impact damage are summarized.The influence of impact load on the initial crack length,crack propagation rate and mesh crack range of different state plate bodies is released.The larger the empty area,the higher the emptying height and the more severe the impact,according to the form and situation of the crack evolution,given the state of the board body"crack not broken" state,and think that the surface layer and the grassroots layer are better embedded to achieve stamping the best results.Finally,the damage caused by the impact fracturing of the board of the outdoor test road is basically consistent with the situation of the indoor test.Due to the different damage levels of the left and right pavements,the right road surface cracks and voids are heavier than the left road surface,so stamping The right road surface should be able to reach a better crushing effect with less impact on the road surface than the left one or two times.With the increase of the number of stamping passes,the relative settlement value of the road surface will gradually decrease and tend to be stable.The deflection values are both stable.The first changes appear to increase gradually,but the left and right road surfaces show different growth rates.