| Concrete face rockfill dam has been used in hydropower construction because of its strong adaptability,high safety and economy.With the rapid development of China's hydropower industry and the improvement of damming technology,more and more concrete face rockfill dams begin to built on the overburden foundation,so it is very important to study the stress distribution and deformation characteristics of concrete face rockfill dam on deep overburden foundation.This paper studies the stress distribution and deformation characteristics of face rockfill dam on deep overburden foundation relying on jiudianxia face rockfill dam in the premise of find the information,summarizes the characteristics of the face rockfill dam on the overburden foundation,the characteristics of the overburden,the influence mechanism of the overburden foundation on the stress distribution and deformation characteristics of the concrete face rockfill dam and the main problems existing in the construction of the face rockfill dam on the deep overburden foundation.Through analysis and comparison,this paper selects the Duncan-Chang(Duncan-Chang E-B)model for rockfill and cladding materials and linear elastic model for concrete material.Goodman contact unit is set between the panel and the cushion to solve the contact problem between two media with large difference in elastic modulus.Separation joint unit is set between vertical joints of the panel and soft element simulation is set between peripheral joints.In this paper,MIDAS/GTS geotechnical analysis software was selected to establis h the three-dimensional finite element model of jiudianxia face rockfill dam.The layere d filling process of the dam body and the storage process of the reservoir are divided into 20 stages for loading calculation.After the calculation,three typical transverse se ctions,the maximum longitudinal section,the whole dam body and the panel are selec ted to analyze the stress distribution and deformation shape under three different worki ng conditions: completion period,dead water level period and normal water level peri od.The main conclusions of the study are as follows:(1)For the jiudianxia face rockfill dam built on the overburden foundation,the maximum vertical displacement of the dam body appears at the bottom of the dam in the middle of the downstream side where the overburden is thickest.The maximum s ubsidence is 57.95 cm,accounting for 0.44% of the dam height.The subsidence near th e top of the dam in the central part of the riverbed is approximately within the range of 38cm~48cm.Water storage has a great influence on the vertical displacement of th e upstream slope foot of the dam.(2)The deformation trend of the dam along the river is that the upstream region of the dam body moves upstream while the downstream region moves downstream.The maximum displacement value appears at 1/2 of the upper and lower dam slopes.Af ter impoundment,the upstream displacement decreases with the increase of impoundme nt depth,while the downstream displacement increases.The overburden causes the distri bution of the dam's displacement along the river during the completion period.For jiud ianxia face rockfill dam,the zero line of displacement in the completion period is inc lined to the downstream,the maximum upstream displacement is 23.30 cm,the maximu m downstream displacement is 12.52 cm,and the upstream displacement is greater than the downstream displacement.When the water storage reaches the normal water level,the zero line of displacement deflected to the upstream side of the dam body,and th e displacement of the upper and lower reaches of the dam body was basically flat,ab out 14 cm.The impoundment has great influence on the displacement of the dam body along the river.(3)The deformation of the dam body along the dam axis shows the tendency of the dam body on both sides squeezing towards the middle of the riverbed.The left bank slope of jiudianxia is steep and the right bank is relatively gentle,the whole da m body shows the tendency of "invasion" of part of the dam body on the right bank to the left bank in the longitudinal direction.During the completion period,the maxim um displacement to the left bank is 12.99 cm,and the maximum displacement to the r ight bank is 6.12 cm.After impoundment,the displacement along the axis of the dam d oes not change much,Valley shape is the main factor affecting the axial displacement of the dam.(4)The large and small principal stresses of the dam body are distributed in prop ortion to the height of the overburden column.Under the influence of the overburden,the maximum value appears at the bottom of the upstream side of the dam body.The dam body mainly bears the compressive stress,and the maximum of the major stress is 4.95 mpa and the maximum of the minor stress is 1.82 mpa during the impoundmen t period.The tensile stress of the dam is mainly concentrated in the local area near th e top of the dam near the banks.(5)The deformation of the panel shows an overall trend of the entire panel press ing on the rockfill body.The maximum deflection occurred in the middle of the riverb ed near the bottom of the panel,the maximum deflection at the completion period is10.48 cm and at normal water level is 29.55 cm.After impoundment,the subsidence of overburden in the upstream causes a large amount of panel deformation.(6)The panel is in the basic compression state,and the maximum compressive st ress is in the middle of the riverbed near the bottom 1/3 of the panel.The tensile stre ss zone is located locally near the left and right bank.The maximum stress was 4.77 m pa and the maximum stress was 2.08 mpa.From the whole point of view,the calculated results of the stress and deformation of the dam body and the face plate conform to the general law of the stress and d eformation of the face plate rockfill dam on the deep overburden,and the calculated r esults are basically reasonable.The analysis results of this paper have certain reference value for predicting the stress and deformation of similar projects. |
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