Research And Application Of Special Foundation Dynamic Compaction Treatment Based On Discrete-continuous Coupling Method

With the rapid development of urban expansion and traffic construction,it is common to encounter the karst cave foundation and the construction waste foundation in engineering construction.Therefore,how to deal with this kind of special foundation reasonably and effectively has become an important problem to be solved in engineering construction.At present,the existing engineering practice shows that the dynamic compaction method can effectively treat all kinds of foundation,but the case is that there are few researches on the dynamic compaction method in the treatment of karst foundation and construction waste foundation,and the related theoretical research has lagged far behind the engineering practice.During the treatment process of this kind of foundation,the systematical formula of the design and construction parameter and the theoretical basis of dynamic compaction method are blank,which set a limit on the application of dynamic compaction.Aiming at the above problems,the dynamic compaction mechanism of karst foundation and construction waste foundation is studied through discrete continuous coupling method.Then,the dynamic compaction treatment method of karst foundation is put forward and the design parameter of the construction waste foundation through dynamic compaction method is determined.Furthermore,the design parameters obtained from the foregoing research are applied to an engineering example.The main work completed is as follows:(1)The numerical model of dynamic compaction of karst cave foundation is established by using discrete continuous coupling method.The failure modes of different span roof under certain compaction energy are analyzed,and the relationship between the span of karst cave roof and the compaction energy required to break the roof is established.On this basis,the dynamic compaction treatment method of karst cave foundation is put forward,and the application of this method is explained in combination with engineering practice.(2)The dynamic compaction process of construction waste foundation is simulated by discrete continuous coupling method.The reinforcement mechanism of dynamic compaction is obtained by analyzing the force chain propagation process during dynamic compaction and the displacement distribution after dynamic compaction.On top of that,through analyzing the soil displacement and the variation of dynamic stress,the design parameters of dynamic compaction method for construction waste foundation treatment are determined.(3)Based on the analysis result of numerical simulation,a series of dynamic compaction tests with large scale are carried out on the field construction waste foundation.The properties of construction waste foundation before and after dynamic compaction were tested,and the rationality of design parameters for dynamic compaction treatment of construction waste foundation was verified.At the same time,the dynamic response data of soil during dynamic compaction are analyzed,and the acceleration propagation law and the spectrum characteristics of vibration wave are revealed.