Research On The Application Of Dynamic Compaction Gravel Pier In The Treatment Of Soft Foundation With Overlying Hard Shell Layer

Karst landforms in Guizhou are eroded and eroded by water,forming funnel topography with great difference between high and low.If there is impervious layer in the low-lying area between mountains,it will form regional soft soil.Affected by the groundwater level,the surface soft soil above the groundwater level is affected by water evaporation,sunlight,load migration and other factors,and it is easy to form a hard shell layer with the compressibility less than 0.5mpa-1 and strong cementation ability,which can effectively improve the bearing capacity of the foundation.But when the load is large and the bearing capacity and deformation of the foundation can not meet the engineering requirements,it is necessary to treat the overlying hard shell layer soft foundation.If the underlying soft soil layer is treated,the overlying hard shell layer will be destroyed.Can the good characteristics of the overlying hard shell layer be retained while the underlying soft soil layer is treated? Dynamic compaction gravel pier is a soft foundation treatment technology developed and utilized in recent years.It has been more and more widely used in soft foundation treatment because of its short construction period and simple construction.However,there is little research on the application of dynamic compaction gravel pier in soft foundation treatment of overlying hard shell layer.According to the test data of the supporting project of power battery industrial park in high tech Zone,this paper analyzes the dynamic influence and consolidation settlement of the dynamic compaction gravel pier in the treatment of the overlying hard shell soft foundation by using the large-scale finite element analysis software MIDAS / GTS NX.Finally,combined with the engineering inspection results,it comes to the conclusion:(1)the increase of the load level can increase the treatment effect of the dynamic compaction gravel pier,But at the same time,it also increases the damage range of hard shell layer,so in practical application,the pier spacing should be controlled according to the tamping load;(2)The larger the compression modulus of underlying soft foundation and overlying hard shell layer,the better the treatment effect of dynamic compaction gravel pier,but it has little effect on the damage range of hard shell layer;(3)In the process of drainage consolidation,horizontal drainage softens the naturally consolidated overlying hard shell layer and causes damage to the hard shell layer.Therefore,attention should be paid to adding horizontal drainage channel in practical application to reduce the damage of drainage to the hard shell layer;(4)Dynamic compaction gravel pier is a kind of comprehensive soft foundation treatment technology,which combines dynamic compaction and gravel pier reinforcement technology with the excellent characteristics of the overlying hard shell layer,complements and strengthens each other,so as to achieve better reinforcement effect.