Pouring Control Of Concrete And Key Demoulding Technology Of Sliding Pipe Construction For Ultra-deep Diaphragm Wall

As one of the most important anti-seepage structures for foundation treatment ofembankment dam, diaphragm wall has important effect on ensuring dam safety andreducing leakage of reservoir area. In recent years, with development of hydropowerprojects construction, hydropower exploitation was advanced to western region andhigh altitude area, and higher level for concrete diaphragm wall in the area ofultra-deep overburden layer was put forward.The whole diaphragm wall was joined by each element of wall section, and jointsof each wall section are weak links of diaphragm wall. Among all the forms of sectionlinks, Sliding pipe method is given more attention because of good quality of joints,avoiding waste of concrete and quickening construction process. Theory analysis andengineering practice show: determination time and magnitude of pipe drawn andcontrol parameters of concrete pouring are two key problems for construction ofultra-deep diaphragm wall by sliding pipe method. Time determination of pipe drawnincludes significance in two levels, and time of pipe drawn and hole deviation hasimportant effect on magnitude of pipe drawn.In this paper, as main means of theory analysis, temperature and structurecoupling numerical analysis was applied to research time of pipe drawn and drawnforce under different times and hole deviation. Field test was used to verify theoryanalysis. Control parameters of concrete construction process was studied used DEM.The results show:(1) Time of pipe drawn is controlled by stability mechanics, and influenced bymany factors, includes environment, loads and construction. Aimed on150multra-deep diaphragm wall of Pangduo project, the condition of keeping40m frompouring face to bottom of sliding pipe can satisfy construction. (2) Magnitude of drawn force is related to drawn time and hole deviation.Different time of pipe drawn can lead different contact characters between slidingpipe and concrete, then influence drawn force. Hole deviation can increase drawnforce, and with increase of deviation rate, drawn force increase quickly. Under theconditions of no hole deviation and pipe drawn at high40m of concrete, drawn forceis about500t.(3)Control parameters of concrete pouring by sliding pipe method include bestdistance between pouring pipe and bottom of hole, burden deep of pouring pipe inconcrete and fall velocity of concrete in pouring pipe. Numerical analysis results show:①when beginning concrete pouring, the distance between pipe opening and bottom ofhole is about3~4times diameter of pipe;②when ending concrete pouring, highdifference of concrete in and out pipe should be controlled in5m;③with increase ofdeep of diaphragm wall, the shape of concrete in pipe present obvious breakphenomena, and there are not obvious eduction and separate phenomena in the rangeof150m deep.(4) Field test shows that drawn time is7~8hours after concrete pouring, that is40m high concrete after pouring. Several factors has effect on drawn force whichrelates to contact characters between sliding pipe and concrete and hole deviation.Field test result is consistence with theory analysis.Analysis method for drawn time of sliding pipe and drawn force of ultra-deepdiaphragm wall is given, and selection of control parameters during concrete pouringis discussed. The results can give reference for improving quality and fasteningprocess of construction.