Abstract：Research purposes: From the integrity testing of cement － flyash － gravel pile ，it was found that the empty holes，the mud，the soil，mortar between folders，shrinkage diameter and severe maceration ( types of honeycomb and separation of sand and stones) appearred in some CFG piles． The study was done on the reasons for these defects． In order to ensure the integrity quality of cement － flyash － gravel pile，the relative construction measures should be taken and the control of the construction quality should be strengthened．
Research conclusions: The construction method of " concrete wrapping drill" should be adopted when pouring the concrete of cement － flyash － gravel pile． That is，when the concrete is poured，the pouring surface of concrete should always wrap the drill by 0． 5 － 1 metre and synchronously rise with the drill． The concrete slump constant should be controlled to 16 － 20 cm，In the anhydrous stratum，the pouring velocity of the concrete should be controlled to 2 －3 m/min． In the water stratum，the pouring velocity of the concrete should be controlled to 1 m/min． In water － rich stratum，the 80 type high － power should be used． In the soft plastic clay stratum ( including water layer) ，the slow pressure construction method should be used for pouring concrete． The pouring of concrete of cement － flyash － gravel pile should be continuous and can not be interrupted． If interrupted，the pile should continue to downward whirl to the depth of 0． 5 － 1． 0 m to drill away the mortar and severe maceration concrete for integrating the new concrete with the concrete at the bottom．
Chang Juyou，Li Zhijun，Zhou Qixiang． Research on Completeness and Bearing Capacity of End Bearing Cast － in － place Pile for Subgrade［J］． Journal of Railway Engineering Society，2008( 2) : 35 － 39．
2011, Vol. 28 
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