Experimental Study On Dynamic Compaction And Polymer Vibration Isolation Analysis

Dynamic compaction is a kind of foundation treatment method with the advantages of energy conservation and environmental protection.With the implementation of dynamic compaction in urban foundation treatment construction,the vibration and filling problems faced by dynamic compaction construction are also magnified.The only way to develop the application of dynamic compaction is to find a new economic and reasonable vibration isolation method for dynamic compaction construction and to explore the feasibility of building waste as dynamic compaction backfill.It is of great significance to analyze the vibration isolation method and backfill of dynamic compaction and apply the theoretical results to the engineering practice.In this paper,based on the foundation treatment test of Zhengzhou Dengling Enterprise Park,through the summary and analysis of the test monitoring results,the deep design of the dynamic compaction construction scheme is completed.Focusing on the vibration monitoring results of dynamic compaction test,the propagation characteristics of dynamic compaction vibration obtained from the test are analyzed,and the time-domain function of dynamic compaction excitation is obtained by inversion of the monitoring results of dynamic compaction vibration peak velocity.Finally,the time-domain function of dynamic compaction excitation is input into the finite element model to further study the attenuation rule of dynamic compaction vibration and the vibration isolation effect of different vibration isolation methods.The results that can be used to guide engineering practice are obtained.The specificwork completed is as follows:(1)The design and construction parameters of dynamic compaction,the impact of dynamic compaction vibration on the surrounding environment,barrier vibration isolation technology and polymer technology are summarized through extensive reference to relevant literature at home and abroad.The basic principles of dynamic consolidation,including dynamic compaction theory,dynamic consolidation theory and vibration wave compaction theory,are studied.The attenuation law of dynamic consolidation vibration and the determination of its safe distance are discussed.(2)The foundation treatment test of Dengling enterprise park has been completed.The monitoring methods include pore water pressure monitoring,vibration monitoring,standard penetration test,static penetration test and super heavy dynamic penetration test.According to the field test results,the dynamic compaction construction design scheme is improved.The bearing capacity of the foundation after dynamic compaction treatment is 225.3kpa,and that of the composite foundation after dynamic compaction replacement treatment is 279 kpa,which is greater than the required bearing capacity of the foundation.It shows that the dynamic compaction and dynamic compaction replacement with construction waste as backfill material are feasible in this site.The field vibration monitoring shows that compared with the empty ditch vibration isolation,the double-way high polymer vibration isolation has similar vibration isolation effect,and can also be used as the water curtain of the construction site,with the advantages of convenient access and maintenance.(3)Based on the in-depth study of vibration monitoring results,the characteristics of dynamic compaction vibration frequency and three-way vibration speed are studied.It is found that the distribution of vibration speed with frequency presents the characteristics of high,medium and low at both ends,and the main frequency of dynamic compaction vibration is 5Hz.The frequency-domain analysis and time-domain analysis of dynamic compaction vibration are developed,and the excitation time-domain function of dynamic compaction vibration is obtained by inversion.The analysis shows that the three-dimensional velocity value of dynamic compaction excitation function follows the rule of longitudinal > vertical >horizontal,and the peak velocity of ground vibration caused by dynamic compaction occurs in the time of about 0.06 s,which shows the characteristics of pulse excitation as a whole.(4)Through Midas GTX NX software,three dynamic analysis models of dynamic compaction,namely,no vibration isolation,empty ditch vibration isolation and double vibration isolation wall,are established.By comparing the impact stress loading,the dynamic loading mode of three-dimensional vibration speed is selected.The relationship between the distance of three models and the maximum vibration velocity is fitted by using quartic polynomials.Under the condition of empty trench vibration isolation,it is recommended to take the vibration isolation efficiency of 45% within the range of 1m ? 6m from the protected object,and 40% beyond the range of 6m from the protected object.More importantly,under the condition of two-way high polymer isolation wall,the recommended isolation efficiency is 35% in the range of 0m ? 10 m away from the protected object,and 40% in the range of10 m away from the protected object.