| Heavy rail transport occupies a large market share in an increasingly frequent market trade environment.The stability of graded aggregates,which are used as fillers in the roadbeds of heavy railways,plays a vital role in the safe and efficient operation of heavy railways.Geocells are increasingly being used in geotechnical engineering due to their three-dimensional structure and significant reinforcement effectiveness.However,the research on its reinforced working mechanism is still not perfect,and the research on the force deformation and static and dynamic properties of geocell reinforced soil is still relatively small,with theoretical research lagging behind engineering practice,and most of the existing theories are for the study of reinforced fine-grained soil,which to a certain extent limits the development of geocell reinforced soil technology in the field of geotechnical engineering.In view of this,this study will use a combination of theoretical analysis and indoor tests to analyse the geocell reinforced gravel soil through large triaxial tests,to explore the influence of the vertical spacing of the geocell,the number of reinforcement layers,the height of the cell,the distance between the nodes and the type of cell on the strength and deformation characteristics of the reinforced gravel composite,to analyse the reinforcement effect and mechanism of the geocell,and to obtain the mechanical characteristics and deformation behaviour of the geocell reinforced composite under static and dynamic loads under different working conditions.The study also investigates the differences in the mechanical properties and deformation behaviour of reinforced composite geocells under static and dynamic loads.The main research contents and results include.(1)By carrying out static triaxial tests on graded gravel fill,the stress-strain relationship curve,shear strength and strength reinforcement factor of the soil were analysed.The results found that: The reinforcement of geocells under different working conditions can improve the bearing capacity of gravel fill to a certain extent;The optimum vertical spacing is 200 mm under 2-layer geocell reinforcement;Increasing the number of geocell layers or increasing the height of geocell is more significant in improving the reinforcement effect;As the number of layers of reinforcement increases,the tendency of reinforcement utilization rate increases first and then decreases,and in this test,the reinforcement utilization rate of 2-layer geocell reinforcement is the largest;Compared with the increase in the number of geocell layers,the multiplicative increase in the height of geocell is more obvious in improving the shear capacity of reinforced body;Reducing the distance between geocell nodes only slightly improves the reinforcement effect,and the effect of geocell node distance is affected by the number of layers of geocell,the more the number of layers of geocell,the more obvious the effect of the change in the distance between the nodes of geocell;The reinforcement effect of non-porous geocells made of high density polyethylene(HDPE)is better than that of HDPE perforated geocells and geocells made of polypropylene(PP)and polyester(PET),and the reinforcement effect of PP and PET geocells is slightly higher than that of HDPE perforated geocells.A logarithmic function was used to fit the stress-strain relationship curves of geocell reinforced gravel soils,and the fit was good.(2)As for the deformation characteristics of the specimens after loading,the1-layer geocell reinforced specimens showed bulging at the top of the specimens,while the 2-layer and 3-layer geocell reinforced specimens showed bulging at the middle of the specimens;The lateral deformation of the specimens gradually decreased as the height of the geocell increased and the number of geocell layers increased;The deformation characteristics of different types of geocell reinforced specimens were relatively similar;When the distance between the geocell nodes was85 mm,the HDPE geocell nodes and the sheet were not significantly damaged,while the PP and PET geocells were prone to brittle damage;When the distance between the cell nodes was 330 mm,the HDPE geocell nodes and the sheet were not significantly damaged.HDPE geocells are not significantly damaged when the distance between the geocell nodes is 85 mm,while the nodes and sheets of PP and PET geocells are prone to brittle damage;When the distance between the nodes of the cells is 330 mm,damage also occurs at the nodes of HDPE geocells.(3)The results found that: the increase of the perimeter pressure can effectively improve the dynamic characteristics of the specimen and inhibit the deformation of the specimen under the action of dynamic cyclic load;The reinforcement of the geogrid can significantly improve the bearing capacity of the gravel fill,and different forms of reinforcement can improve the bearing capacity of the specimen to different degrees;As the distance between the nodes of the compartment decreases,the reinforcement effect of the compartment gradually increases,but the seismic performance of the reinforced soil also decreases.As the distance between the nodes of the cells decreases,the reinforcing effect of the cells gradually increases,but the seismic performance of the reinforced soil body also decreases;Different types of cells can improve the strength and stiffness of the soil body to a greater extent,the reinforcing effect of HDPE cells is lower than that of PET and PP cells when the dynamic cyclic load is small,but as the load increases,PET and PP cells are prone to brittle damage,at this time HDPE cells can still play a stable reinforcing The damping ratio of HDPE geocell reinforcement specimens is greater than that of PP and PET geocell reinforcement specimens,which makes it possible to improve the bearing capacity of the soil while taking into account the energy dissipation capacity of the soil and ensuring the stability of the reinforced soil.In practice,the relationship between the various factors after reinforcement needs to be taken into account in order to adopt a suitable form of reinforcement. |
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