桩身完整性检测在CFG桩施工过程中的质量控制

Quality Control of Pile Integrity Testing of Cement-flyash-gravel Pile in Construction Process

研究目的:本文通过CFG桩完整性检测,对空洞、夹泥、夹土、夹砂浆、缩径、严重离析(蜂窝状、砂石分离状)等施工原因引起的问题进行研究。为确保CFG桩质量完整,应从施工预防着手,制定施工措施,加强施工质量控制。研究结论:CFG桩混凝土灌注时要严格执行"灰包钻"施工法,即灌注混凝土时始终混凝土灌注面包着钻头0.5～1 m同步上升;混凝土坍落度控制在16～20 cm;混凝土灌注速度无水地层控制在2～3 m/min、含水地层控制在1 m/min;地下水丰富地层混凝土输送泵改为80型大功率泵;在软塑黏土地层(含水地层段)灌注混凝土要采用慢速下压施工法;CFG桩的混凝土灌注要连续,不能中断,若中断此桩要重新下旋转深度0.5～1.0 m,把砂浆及严重离析混凝土钻掉,使重灌混凝土与下端完好混凝土灌注为一体。

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.