Study On Two Kinds Of Self-weight Consolidation Settlement In Deep And Thick Clay Strata

Decades of measured data show that the settlement of the formation around the wellbore in the Huanghuai mining area continues;considering the rapid dissipation of water pressure in the sand layer,this continuous settlement is likely to be related to the deep clay formation that is common in the area.It is necessary to study the self-weight consolidation of deep clay layers without additional external loads.In view of this and combined with engineering practice,this paper further subdivides the clay self-weight consolidation into two categories: the first type is the soil under the initial natural weight,the excess pore water pressure is generated,and the excess pore water pressure is dissipated under the drainage condition.The second type is due to water leakage in the wellbore of the mining area,which causes the water pressure in the deep aquifer to dissipate,which leads to the destruction of the pore pressure balance of the deep clay,so that the clay layer is consolidated and compressed under the action of its own weight.Based on the investigation and analysis,this paper selects Gibson one-dimensional large deformation consolidation theory,finite element simulation based on Biot consolidation theory and engineering measurement methods.Firstly,by analyzing and comparing the ABAQUS simulation results based on Biot's consolidation theory and the calculation results of Gibson's one-dimensional large deformation consolidation theory,a suitable simulation parameter selection scheme is summarized,and the Gibson one-dimensional large deformation theory is finally determined.One type of self-heavy consolidation problem;for the second type of self-weight consolidation,a reasonable study is carried out by ABAQUS simulation.Based on the Gibson one-dimensional large deformation consolidation theory,the effects of consolidation coefficient,formation thickness and formation depth on consolidation settlement and consolidation time in the first type of self-weight consolidation problems are studied.The results show that the clay layer with a thickness of about 10-20 m in the current stratum should be completed by natural gravity.The clay layer of 20-100 m,if its geological time belongs to the Holocene or late Pleistocene,its natural consolidation is very It may not be completed yet,but the corresponding annual settlement is very small and has limited contribution to formation settlement.On the whole,regardless of the thickness of the clay layer,the contribution of the first type of natural self-weight consolidation to the current formation settlement is basically negligible.The effects of soil parameters,formation thickness,stratum depth and pore pressure boundary on consolidation settlement and consolidation time in the second type of self-weight consolidation problems using ABAQUS.The simulation results show that the sedimentation of the second type of self-weight consolidation in the first 100 years after leaking from the wellbore is very considerable,and the average annual settlement is several millimeters or more,which has a greater contribution to the current formation settlement;The settlement only accounts for a small part of the total settlement,and most of the settlement will occur after 100 years.In addition,the second type of self-weight consolidation has the characteristics of large contribution and far-reaching influence on the settlement of the formation.On the basis of the above-mentioned law research,by simplifying the hypothesis,the corresponding numerical calculation model is established for the two wellbores of the China Coal Datun mining area where the surrounding stratum has been continuously settled for many years.The simulation results are basically consistent with the monitoring results;the simulation results show In the next 60 years,even in the ideal case where the wellbore is no longer leaking,the non-mining settlement of the formation around the mine shaft can not be ignored,which is mainly due to the contribution of clay formation compression;and non-mining settlement is not limited to the future 60.Year has a more lasting impact.This thesis includes 65 Figures,25 Tables and 88 References.