Microscopic Deformation Mechanism And Deformation Control Of Face Rockfill Dam In Narrow Valley

In recent years,the construction level of concrete face rockfill dam in China ranks first in the world.Faced Rockfill Dam(CFRD)develops rapidly because it adapts to complex climate and various topographic and geological conditions,and has good seismic performance.It can also be filled with local materials extensively,and even make full use of excavation materials through zonal optimization,which is conducive to environmental protection and saves project investment and time.At present,the deformation law,cracking mechanism and construction technology of concrete face rockfill dam in Canyon area are systematically summarized and analyzed in China,but there is no systematic study on the deformation law of concrete face dam in narrow valley area and comprehensive control measures to deal with the deformation of concrete face rockfill dam in narrow valley area.Based on the design,construction and construction management practice of the face rockfill dam of Pingzhai Reservoir,this paper will study the influence of dam height and valley shape on the deformation characteristics of face rockfill dam in narrow valley,focusing on the calculation model of dam body stress and strain,contact characteristics between dam body and bank slope,multi-directional arch effect,failure mechanism of face slab and its zoning,jointing and water stop requirements,and surface.The design principle,technical requirement and technical scheme of high face slab dam in narrow valley area are put forward.It has been successfully applied in the construction practice of Pingzhai Reservoir face slab dam.The comprehensive deformation control technology of high face slab dam in narrow valley area is summarized and put forward.In addition,a series of discrete element tests have been carried out to study the micro-mechanism behind the macro-strength and deformation of rockfill materials for concrete face dam construction.The main research contents are as follows:1.Using the discrete element method to study the micro mechanism of the macro deformation of rockfill dam materials.The possibility of dispersive instability of granular materials is studied by loading granular materials with equal proportion strain.The internal causes of dispersive instability of granular systems are the sharp decrease of coordination number,the decrease of contact force between particles and the abrupt change of anisotropy at the mesoscopic level.Under true triaxial condition,the strength of interaction between particles in critical state is related to the medium principal stress coefficient,and the mesoanisotropic evolution law of particle system basically reflects its macro-stress characteristics.Particle breakage under different confining pressures in conventional triaxial tests has a significant effect on the macro-and micro-mechanical properties of particle aggregates.The broken particles were filled in the voids between particles,which had a certain inhibitory effect on the shear dilatancy of test materials.2.Establish the calculation model of face slab dam under different valley shape conditions,and analyze the influence of valley shape on the stress and deformation of face slab dam body and face slab.In narrow valleys,the dam body has multi-arch effect,the stress and deformation of dam body and face plate are complex,and the dam rockfill body does not reach the stable state of dam body deformation in the pre-settlement period,which leads to the slow deformation of dam body and increases the risk of cracking and leakage of face plate.For asymmetric valleys,the displacement distribution of the panel is asymmetric,and the displacement of the side plate of the gentle slope tends to squeeze towards the steep slope side.Co MPared with the gentle slope side,the gradient of displacement and stress change of the steep slope side is opposite,and the former is relatively large while the latter is relatively small.In the design and construction of face rockfill dams in narrow valleys,reasonable slab joints should be divided into blocks and special cushion zones should be set near the peripheral joints.3.Aiming at the problem of concrete face slab cracks,the design criteria of face slab dams in narrow valleys are put forward.Because of the arch effect of dam body and the complex settlement characteristics of dam body caused by the topographic characteristics of narrow valley,the face slab cracks,and the large peripheral joint dislocation and settlement displacement of the face slab may occur.In the design of concrete face rockfill dam in narrow valley area,the deformation of concrete face rockfill dam can be controlled by dealing with dam foundation and bank slope,optimizing dam body zoning and rolling construction,and setting up mode-increasing zone.A new type of surface waterproof structure with self-supporting structure is put forward to ensure the dynamic stability of the surface waterproof structure during the long-term operation of the dam.4.The laboratory test of dam materials,dam construction technology,numerical analysis of stress and deformation and deformation control measures of Pingzhai Reservoir Faced Rockfill Dam in Guizhou Central Water Conservancy Project are studied and analyzed.The deformation distribution of concrete face rockfill dam in the middle of Guizhou is closely related to the deformation characteristics of dam materials in different areas of the narrow valley.The main influencing factors include: dam body zoning,characteristics of filling materials in different areas,filling standards and construction sequence,etc.In addition,the dam body deformation is affected by the topographic and geological conditions of the valley.Controlling the relative deformation between dam body and river bank slope can reduce the deformation of dam body,improve the stress and deformation of face slab and displacement of joint around face slab.This paper introduces the new technology of GPS intelligent co MPaction system control for the integrated mechanized construction of surface seam sealing of dam face slab and dam body filling construction,and analyses its advantages,construction principles and technical requirements respectively.