真空预压地基非饱和带探讨  

DISCUSSION ON UNSATURATED ZONE IN SOFT GROUND IMPROVED BY VACUUM PRELOADING

作　　者：邱青长[1] 莫海鸿[1] 董志良[2] 曾庆军[1] 

机构地区：[1]华南理工大学土木工程系,广东广州510640 [2]广州四航工程技术研究院,广东广州510230

出　　处：《岩石力学与工程学报》2006年第z2期3539-3544,共6页Chinese Journal of Rock Mechanics and Engineering

基　　金：华南理工大学自然科学基金资助项目(B03-E5050960);广州四航工程技术研究院资助项目(S2005D24)

摘　　要：目前,真空预压研究中将加固地基均视为饱和土,这与工程实测的地基地下水位下降相矛盾。针对这一的现状,通过对真空泵抽水的室内模拟试验和真空预压工程中实测现象进行分析,得出不同外界条件下真空吸力可引起水、空气或气液两相对流:(1)真空预压工程中射流泵提供的真空吸力引起地基中流体气液两相对流;(2)真空预压地基存在非饱和带,真空预压工程实践中密封系统不是绝对密封的,预压地基内存在漏气,液-液气射流泵以气水两相流态抽吸地下水,导致抽真空期间地基地下水位下降;(3)真空预压地基非饱和带类似于群井抽水地基的非饱和带,射流泵抽水量来源于地下水位下以上非饱和带土体的重力排水和地下水位以下饱和土体的弹性释水。同时,提出当前真空预压研究中,理论分析、室内模型试验与实际工程中的地基加固边界密封条件不同是产生矛盾或分歧的根源所在。Aimed at the existing inconsistent state—the whole ground is regarded as saturated soil and measured groundwater level falls in current research on soft ground improved with vacuum preloading,a series of indoor simulated experiments are conducted on vacuum pump dewater and several typical phenomena are analyzed in vacuum preloading project.Laboratory experiments illuminate that vacuum suction can induce three kinds of convections in different external conditions—water flow,air-water two-phase flow and air flow as follows:(1) the flow pattern of convection is air-water two-phase flow under the action of suction provided by jet pump in vacuum preloading project;(2) there is unsaturated zone in the soft ground improved with vacuum preloading and the sealed system isn′t absolutely airproof in project practice,and there exist air supplied in the improved zone.Liquid-liquid and gas jet pumps draw groundwater by the convection of air-water two-phase flow,which results in groundwater level fall;(3) the unsaturated zone in the ground improved with vacuum preloading is quite similar to the ground of multi-row wells pumping water.The quantity of pumping water by jet pump is composed of the drained water by unsaturated gravity zone above groundwater level and elastic released water below groundwater level saturated soil induced by hydraulic head drop.It is the main reason to induce the contradiction or difference that the sealed boundary conditions of improved zone are different among current theory analyses,indoor model experiments and project practice in soft ground improved with vacuum preloading technique.

关 键 词：土力学 地下水动力学 真空预压 射流泵 气水两相流 非饱和带 

分 类 号：TU471.8[建筑科学—结构工程] P641.2[建筑科学—土工工程]