The Researchs Of Seepage-proofing Engineering For Foundation For Dams And Dikes In Shandong Province

Seepage-proofing engineering is an important part in the project of consolidation and secredit maintance for reservoirs,its cost always occupys a high ratio to the total project cost.the practice of seepage-proofing engineering ,which has been taken for water resource dams and dikes in Shandong province,has passed a long zigzag distance,upto now we have gained some successful experience,but also there are some failure and faults which should be noticed highly,for the further way ,there is much technical difficulty which needs far-deep researching in the future.This essay emphasises on research of the theory and practice of seepage-proofing engineering,then analyzes and explains some difficult hard issues in seepage-proofing engineering,this eassy takes some actural projects for examples,closely concerning of the project site practice,it will summary systemically different seepage-proofing measures which will be taken for different condition and suitable range.it also discourses upon how to choose the best seepage-proofing methods ,and it tells to avoid the remark problems during the designing and construction.The suitable, seepage-proofing method should to be chosen according to geological layers parameter water head and project cost, never to copy the specific one to another without deep consideration or ignoring the pragmatic facts of different projects,especially for the geological speciality.The heights of the dams for reservoirs in the mountain and hill zone of Shandong province almost vary between 20m to 50m, if there is dank geological layer which thicks less than 5m,the replacement method is the best choice it needs first to dig out a groove in the dam,then backfill new stuff such as clay by one layer on another in tamped way; if there is dank geological layer which thicks more than 5m,the small-diameter cementsoil pile method is the best choice it is not so suitable for arranging-perpendicular -polyplastic method to pretect the dam from seepage damage ,which needs slurry to protect sidewall collapse and continuous grooving ;if the beared water head in dam is less than 15m,the dam or foundation consists of some groutable sand and gray layers, high-pressure-grouting cementsoil wall method should be first concerned;if the beared water head is less than 20m,the dam or foundation consists of some disgroutable layers.the underground continuous concrete wall which thicks from 0.3m to 0.4m is quite available;if the beared water head is more than 20m,the foundation is covered by thick dank geological layer.the underground continuous concret wall which thicks from 0.6m to 0.8m is necessary;for the river dikes and circled dams of reservoirs in plain area are almost not so high more than 10m,the seepage-proofing method can be chosen reffering to the above methods.if the dam fundation consists of loam or fine loam layers,and the depth of confining stratum is less than 15m,both arranging-perpendicular-polyplastic method and the small-diameter cementsoil pile method are available.if the dam foundation consists of sand and gray layers which thicks more than 15m, high pressure grouting cementsoil wall method should be concerned first.If the dams or dikes have been well constructed,then it is only necessary to break away theseepage trough the foundation layersjn order to economize the invest ,and reduce longitudinal meters for digging groove or drilling hole,it is better to arrange the axial line along upper side dam-slope or foot of the dam. On this condition,it needs to reduce the reservoir water elevation for the seepage-proofing construction.if the dams or dikes have been worse constructed,ie.the seepage ration is large ,there exsists thick dank layer and so on,then it needs to arrange the axis of seepage-proofing line along the axis of the whole dam or dike,then resolve the dam seepage matter totally with the foundation.Reasonablely to set the depth of seepage-proofing range, and to choose the suitable construction machines according to the geological layers condition, it is the first spot to declare the purposes for seepage-proofing program,ie.seepage stability safety,water resource loss or above both combination.additionally referring to the site construction procedure, the suitable depth of seepage-proofing should be concluded,select the available seepage-proofing wall between hung-part type and closed-through type .if the concrete wall is chosen for seepage-proofingjt should be paid more attention to evaluating effect to the dam stability which is caused by digging groove. Carefully Estmate whether it is necessary to arrange reinfoced steel in the concrete wall for seepage-proofing,according to the stress analysis results;Essentially to control the water head during the construction period,if the high pressure grouting method is chosen.Properly to deal with the problems from the downwards drinkage of humanbeings and livestocks to ecotypic water for environment after seepage-proofing,try to take the suitable measures to reduce the harmful effects to all.