| Concrete gravity dam and concrete-faced rockfill dam are two kinds of commonly used dam type in the water conservancy project.Concrete gravity dams rely on their own gravity to maintain stability.But the strength of concrete can not be fully exerted because of the large volume of concrete material.It is prone to generate greater tensile stress at the dam heel,which will cause crack failure at the bottom of the dam.The impervious panels in the concrete-faced dams are relatively thin and the uneven settlement of the rockfill is liable to cause cracking of the impermeable panels,which resulting in leakage of the impermeable dam bodies.Some scholar introduces the concrete-rockfill combination dam(CRCD)based on the summary of the advantages and disadvantages of the concrete gravity dam and the concrete-faced rockfill dam.The concrete-rockfill combination dam is mainly composed of the upstream concrete wall and the downstream inclined rockfill body,and the seepage control system(the sealing structure and the cut-off wall),as well as the upstream and cover weighted zone.CRCD connectes the dam foundation with waterstops and is different from the concrete gravity dam.The concrete wall in the CRCD is not only used as a seepage prevention body similar to the panel,but also a structural body to withstand water pressure with rockfill body.Concrete wall of CRCD is the anti-seepage structure,it reduces the dam section area and the amount of concrete compared with the concrete gravity dam.The downstream inclined rockfill body is a support for the CRCD,it greatly reduced the amount of soil compared to the concrete-faced rockfill dam.Based on ABAQUS finite element software,the EB static model and the equivalent viscoelastic dynamic model of Shenzhujiang were used to analyze the shaking table tests of bedrock and overburden foundations respectively.The influence of CRCD acceleration response and permanent deformation were analyzed.Compared with the experimental results,the rationality and reliability of the numerical method were verified.The numerical model of CRCD with the background of practical engineering was established,and the dynamic characteristics of the CRCD were analyzed,including acceleration,dynamic stress,dynamic earth pressure,and permanent deformation.Concrete-rockfill combination dam is a new kind of dam structure.At present,the research on its dynamic characteristics is rarely reported.The shaking table test is an important means to study the dynamic characteristics,damage mechanism and seismic performance of earth-rockfill dams.Large-scale shaking table model tests in geotechnical engineering has been widely recognized and applied at home and abroad.In this paper,the physical simulation test of large-scale shaking table is carried out for the CRCD with bedrock and overburden dam foundation.In this paper,large-scale models of CRCD were constructed and key parameters,such as acceleration,dynamic earth pressure,permanent deformation and failure pattern of slope were monitored.The purpose is to reveal CRCD dynamic response characteristics and deformation failure mode and to provide some reference for the seismic design and application of CRCD.The main contents and conclusions of this paper are as follows:(1)The large-scale shaking table model tests of concrete-rockfill combination dam were carried out.The dynamic response law of CRCD under earthquakes was revealed.Results show that the amplification factors in the upper part(0.6H)increas with the height.The model dam shows obvious "Whiplash Effect" as the conventional earth-rock dams.(2)The CRCD acceleration response is weakened by water storage obviously.The acceleration amplification factors gradually decrease with the increase of seismic wave amplitudes.The high frequency components of seismic waves were gradually filtered while the low ones were enlarged with the increase of PGA,which can be attributed to spectrum characteristics of earthquake waves and the reduction of stiffness as well as the increase in damping of the rockfill materials.The acceleration response of the overburden is larger than that of the bedrock dam foundation in the same condition.The reason is that the stiffness of the bedrock is high and the deformation is small.Under the action of earthquakes,the redistribution of soil particles is more prone to deformation on the overburden,which causes the violent reaction of the superstructure.(3)The results show that the permanent displacement of the top of the bedrock and overburden dam foundation is relatively small using shaking table tests.The cumulative values of horizontal and vertical permanent displacement are 3.475 mm and-6.709 mm respectively,which are 0.35% and 0.67% of the model dam.Results show that the permanent displacements are larger than those of the bedrock dam foundation.The failure of the rockfill in the model dam begins with the part near the dam crest,and the failure mode is that the rockfill particles are loose and rolled down.The local small-scale shallow slip occurs gradually.The displacement response is evident on the top of the rockfill at a height of 1/5H model dam and some appropriate reinforcement measures in the region can be taken.(4)The concrete-rockfill combination dam is not in direct contact with the bedrock foundation but a waterstop to form a seepage control system.So the concrete wall plays an important role in the stability of the CRCD.The evaluation method of dynamic stability of concrete wall of CRCD was proposed,including displacement stability and anti anti-overturning stability index,which was based on the experimental results including the displacement of the dynamic earth pressure of wallback using large-scale shaking table test.(5)Based on ABAQUS finite element software,the EB static model and the equivalent viscoelastic dynamic model of Shenzhujiang were used to analyze the shaking table tests.The rationality and reliability of the numerical method were verified by comparing with the results from numerical model and shaking table tests.The numerical model of the CRCD with the background of practical engineering was established,and the dynamic characteristics of the CRCD were analyzed further,including acceleration,dynamic stress,dynamic earth pressure and permanent deformation.Results show that the contact surface between wall-rockfill and wall-foundation is the key part of antiseismic design,some reinforcement measures can be considered in engineering. |
PDF Full Text Request