广西来宾凤凰变电站土洞塌陷形成机理及其治理

Forming mechanism of soil cave subside in the Fenghuang transformer substation and control measure

凤凰变电站位于广西来宾市北部凤凰工业园规划区,占地面积约170m×160m。场地属岩溶残丘缓坡地貌,并为土层覆盖。勘察时钻探、物探均未发现土洞等不良地质现象,但在之后的施工期间却产生了十余处土洞塌陷,土洞塌陷密度6.81个/hm2,塌陷总面积489m2。这类土洞不仅形成速度快,而且形成滞后于勘察工作,很容易造成评价上的遗漏从而引发工程事故。本文从场地岩土结构、水文气象和工程活动等方面阐述了土洞的形成机理,认为场平清除表层粉质黏土,暴露地下峰林及松散岩土,使降雨集中入渗侵蚀,是塌陷形成的原因。根据变电站土洞塌陷机理,提出了增加截水和排水沟、硬化场地等切断水动力条件的预防措施,并对浅层塌陷区采用了毛石混凝土换填、深层塌陷区采用了静压固结灌浆加固的综合治理方法,治理取得了预定的效果。

The Fenghuang substation is located in the planning industrial area in northern Laibin city of Guangxi,occupying about 170 m× 160 m in area.Landform there belongs to gentle slope on a karst monadnock covered with soil layer on the surface.Any unfavorable geology such as soil cave is not found during drilling and geophysical prospecting.But dozens of soil caves,6.81caves/hm2 in density and 489 m2 in total subsiding area,are met in construction period.The development of this kind of soil cave is not only fast,but also comes into being later than surveying works,thus it is easily to be overlooked in the evaluation and leads to constructing accidents.In this paper,forming mechanism of soil cave subside is expounded from the point of geological structure,hydrogeology and hydrometeorology as well as human engineering activities.It is thought that the main reason of the occurrence of soil cave is rainwater infiltration and erosion when the underground peak forest and loose earth exposed after the surface silt-clay layer being cleared away.According to the forming mechanism of soil cave subside,comprehensive treatment method that including increasing drainage ditches and hardening construction site to cut off infiltration pass way of the rainwater is put forth.Furthermore,cyclopean concrete infilling is adopted for treating shallow subsidence,and HIP consolidation grouting is adopted for treating deep subsidence.All the above comprehensive treatment methods have obtained good effect.