Study On Deformation Characteristics And Numerical Simulation Analysis Of Under-consolidated Bauxite

In recent years,with the development of large-scale mining equipment,many coal mines,bauxite mines,limestone mines,etc.have adopted the form of open-pit mining,causing the entire mountain to be turned upside down,forming a high accumulation of under-consolidated mountains.The development and utilization of new energy sources and the construction of power grids require the erection of a large number of overhead transmission lines,and the construction of transmission line tower foundations often occurs in areas with underconsolidated soil.The deformation caused by the settlement of the under-consolidated soil leads to uneven settlement and even instability of the building(structure),which has a great impact on the economy and safety.In order to explore the law of foundation settlement in the accumulation of under-consolidated soil area,this paper selects representative underconsolidated bauxite in Yangquan area.Through laboratory experimental research and numerical simulation,the physical and mechanical properties and deformation characteristics of under-consolidated bauxite are analyzed.A more comprehensive analysis and research were carried out,and corresponding reinforcement methods and basic selection schemes were proposed,which provided certain reference value for solving such practical engineering problems.This article mainly includes the following research results:(1)First,analyze the project data of the Yangquan bauxite backfill area,test the density difference of the bauxite backfill site through geophysical prospecting,divide the stratum,and provide basic data for the foundation treatment and foundation selection of the overhead transmission line;secondly,the original state is tested by conventional geotechnical tests.The basic physical and mechanical indicators of under-consolidated bauxite are analyzed,and it is concluded that the under-consolidated bauxite in the backfill area has uneven properties.The physical properties of the soil must be carefully analyzed for engineering construction here.(2)The compression test shows that the Yangquan under-consolidated bauxite is a kind of moderately compressible soil;although the bauxite backfill site has been deposited under its own weight for many years,the original under-consolidated bauxite has been tested and studied,and the results are It shows that the backfilled bauxite in this site has not been completely consolidated under the action of its own weight,and is still in an under-consolidated state;through the study of the change law of the consolidation coefficient of the under-consolidated bauxite in Yangquan,it shows that its consolidation coefficient changes with pressure A trend from decreasing to increasing and decreasing again;the collapsibility test shows that the underconsolidated bauxite within 2 meters of the site is moderately collapsible,and the underconsolidated bauxite at a depth of 2-4 meters has no collapsibility.The collapsibility of the soil is obviously affected by the water content.For the surface soil,the water content is relatively small,the soil has strong collapsibility,and the coefficient of collapsibility;for relatively deep soil layers,the soil collapsibility is weak.The collapsibility coefficient is small.(3)Through the indoor triaxial test,the confining pressure and shear rate Tables were used to design control test groups under different confining pressures and different shear rates,and the influence of the mechanical properties of under-consolidated bauxite was studied.The results show that the stress-strain curve of the triaxial test of underconsolidated bauxite presents a weak softening type.With the increase of confining pressure,the limit stress difference of under-consolidated bauxite gradually increases,and the strain corresponding to the peak value when under-consolidated bauxite fails is larger.With the continuous increase of confining pressure,the soil stress-strain curve develops from softening to hardening;under the same confining pressure,with the increase of shear rate,the phenomenon of strain softening will be more obvious,indicating high shear The shear rate will cause the occurrence of strain softening.Because of the existence of pores and cracks in the soil sample,the soil sample is affected by the shear rate.The results show that the shear rate makes the phenomenon of strain softening of saturated and under-consolidated bauxite more obvious under low confining pressure than under high confining pressure.(4)Combining the basic physical properties test of the soil,one-dimensional compression test and indoor triaxial test,using FLAC3 D simulation,creep settlement practical algorithm,and layered sum method,the settlement of the high-accumulation bauxite body foundation before and after treatment is studied.According to the consolidation characteristics,reasonable foundation treatment and foundation selection design schemes are proposed for the corresponding accumulation years of overhead transmission lines.The FLAC3 D simulation results are basically consistent with the actual deformation of the under-consolidated bauxite soil foundation.After the foundation soil is replaced,the results of the three methods for calculating settlement are analyzed.The maximum settlement of the foundation is 11.04 mm,and the maximum difference of the uneven settlement of the foundation is 6.2mm,which is less than the specified straight pole tower calculation deflection limit of 3‰;Subsidence slows down after 5 years of filling,and basically stabilize after 10 years.(5)According to the accumulation age of the backfill soil,the accumulation age of the site and the long-term settlement of the site,a reasonable foundation treatment and foundation selection design plan is proposed for the corresponding accumulation age of the overhead transmission line.The landfill is within 5 years,and the under-consolidated foundation needs to be improved.The foundation selection needs to integrate the depth of the landfill and longterm settlement to determine the design plan;the landfill is more than 5 years old,and the change in the settlement of the soil has tended It has little effect on the stability of the tower foundation,so it is not necessary to take foundation treatment measures.Only the reinforced slab-column foundation and the lengthening of the anchor bolts can meet the tower stability requirements;the settlement of the landfill will basically stabilize after 10 years.