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．