Indoor Model Test On The Effect Of Drainage Radius And Pile Diameter On The Treatment Of Soft Soil Foundation By Drainage Pine Pile

The saturated soft soil is widely distributed along the southeast coast of China,inland lakes,plains and mountainous areas.In order to deal with the increasing problems of soft foundation treatment in engineering construction in these areas,a variety of soft foundation treatment technologies have been developed to meet the needs of engineering.With the development of reinforced concrete piles and other modern pile types,the traditional technology of treating soft soil foundation with pine piles has been gradually withdrawn from large-scale foundation treatment projects.With the deepening of the concept of environmental protection in the field of engineering construction,the advantages of pine pile as a kind of natural material in environmental protection and resource reuse have attracted the attention of the engineering circle.The engineering practice shows that pine piles have good economic and environmental adaptability in treating soft soil foundation in medium and small hydraulic structures and embankment projects in areas with abundant pine resources.References show that there are some problems such as low bearing capacity,large post-construction settlement and chaotic design and calculation basis,which limit the rational application and development of traditional technology of pine pile treatment of soft soil foundation.Under the background of the study,in order to play the advantages of traditional loose pile treatment of soft soil foundation,the research using the method of combining drainage geotextile and pine timber production of a new type of pine timber,namely drainage pine timber,its function combined with drainage consolidation and replacement treatment of soft soil foundation,make it as the main bearing can also with drainage consolidation effect,for the application of pine timber better in soft soil foundation treatment for exploring research.In the early stage,the research group conducted exploratory experimental research on the composition of drainage structure layer,the feasibility of drainage consolidation and the consolidation performance of drainage water.On the basis of previous studies,this paper plans to conduct qualitative and quantitative experimental research on the influence of drainage pine pile spacing(simplified as drainage radius),an important factor,on the drainage consolidation effect of drainage pine pile,so as to provide a supporting basis for the engineering application of drainage pine pile treatment soft foundation technology.The main contents are as follows:(1)Design of the test model.According to the research objectives,several sets of drainage and consolidation test models of columnar soil columns with different diameters were designed to study the effect of pile spacing on drainage and consolidation performance of drained pine piles;(2)Indoor model contrast test on the influence of pile spacing on the drainage consolidation performance of soft soil foundation treated by drainage pine piles.Test models with pile spacing of 100 mm,120mm,150 mm,180mm,200 mm and 250 mm were designed to carry out six loading drainage and consolidation tests,and the effects of different pile spacing on drainage and consolidation effect of drainage pine piles were compared and studied;(3)Study the influence of different pile diameters on the drainage consolidation of soft soil foundation treated by drainage pine piles.Drainage pine piles with diameters of 8mm,10 mm and 12 mm were designed to compare and analyze the effect of drainage and consolidation under different pile diameters through drainage and consolidation tests;(4)Study on pull-out characteristics of drainage pine piles after drainage consolidation.A pull-out test was carried out to study the interfacial shear properties of drained and consolidated pine piles;(5)Experimental study on shear strength characteristics of inter pile soil after drainage consolidation.The micro-cross plate shear tester was used to test the variation of soil strength between the drained pine piles after drainage and consolidation,and to evaluate the drainage and consolidation performance of the drained pine piles indirectly;(6)Calculation of average degree of consolidation and equivalent well resistance of drainage pine piles.According to the measured data of indoor model,the variation of consolidation time parameter ? under different loads is retrieved,the average degree of consolidation after consolidation is deduced,and the well resistance parameter F is calculated by inversion.Through indoor model test and theoretical analysis,the main conclusions of this study are summarized as follows:1)Drainage radius has a significant effect on the drainage consolidation performance of drainage pine piles.Under the same consolidation pressure and time,different drainage radii have a significant effect on the degree of consolidation of columnar soft soil after the reinforcement of drainage pine pole.The smaller the drainage radii,the better the effect of drainage consolidation.2)In the case of small drainage radius,the effect of drainage consolidation is better with the increase of pile diameter;in the case of large drainage radius,the effect of drainage consolidation is not significantly affected by the change of pile diameter.3)After drainage consolidation,the pull-out strength at the interface of drained pine piles and the undrained shear strength of soil between piles are improved significantly.When the pile diameter is larger,the effective contact area between the drainage pine pile and soil is larger,and the lock-lock interaction between the pile and soil is larger.In this case,the interfacial pulling force increases with the increase of pile diameter.After consolidation,the shear strength of soil increases with the increase of drainage consolidation effect.4)The consolidation time parameter ? was obtained by inversion of the action mechanism of draining pine pole in treating soft soil foundation,and the influence of drainage radius on the consolidation time parameter ? was analyzed.When the drainage radius is constant,the consolidation time parameter ? increases first and then decreases with the increase of consolidation pressure.5)The early consolidation effect of the columnar soft soil layer treated by drainage pine piles is remarkable,which is helpful to improve the early strength of the soft soil layer rapidly.According to the actual needs of the project,it is expected that the drainage pine pile technology can be applied to the foundation pretreatment of small and medium-sized hydraulic structures,and also can be applied to the treatment of subsurface soil site diseases in the micro-reinforcement in the humid environment.