Deformation Characteristics Of Surrounding Rock And Evaluation On Support Effect In Large Underground Water Sealed Caverns

Groundwater sealed caverns are considered to be an ideal way to store energy and chemical raw materials because of their large storage capacity and less ground demand.It has unique water seal,safety tightness which can ensure by simple support after excavation.So it can shorten the construction cycle and reduce investment.The related technologies in China are still in the exploratory stage due to the late start of such projects.As the core part of the cavern,the Oil storage cavern with high side wall,large span and non-lining engineering has a higher requirement on stability of surrounding rock.It is of great significance to study the deformation characteristics of surrounding rock in the process of cavern construction and to evaluate the supporting effect for the safety and economy of the project.Based on a groundwater-sealed oil storage cavern under construction in Guangdong Province,this paper focus on using the monitoring data which gained from the cavern construction period and combining the geological,design,construction and support data,and using the means of mathematical statistics,curve fitting and numerical simulation to study the deformation characteristics of surrounding rock.It is concluded that the deformation of surrounding rock of this cavern is small due to the favorable geological conditions and reasonable design and construction support scheme.The stability value of crown settlement is between 4.4?8.7mm;the value of side wall convergence is between 3.9?8.0mm;the depth of deformation within the surrounding rock is generally less than 3m;the surrounding rock loose area is between 0.6?1.8m;the deformation of the surrounding rock of the cavern shows obvious spatial effect with gradual deformation.By fitting the deformation of surrounding rock with time,it is found that the exponential function is suitable for fitting the settlement of vault and the convergence of side wall.Numerical simulation results show that the maximum horizontal displacement is in the middle of the side wall and the maximum vertical displacement is in the center of the floor.The most obvious stress concentration appeared in the vault and the foot of the wall,and the maximum deformation of the surrounding rock is about 15 mm,which is consistent with the monitoring data.All this verified the rationality and reliability of the model and the estimation method.The evaluation of cavern support effect is mainly carried out in two aspects: maintaining the stability of surrounding rock and ensuring the water seal of the cavern.Based on the analysis of geological conditions,water seal conditions and related monitoring and evaluation indicators,the surrounding rock stability and water seal of supporting measures(structures)are evaluated.The evaluation results show that the support is good at maintaining the stability of surrounding rock.It's support structure has less stress and the surrounding rock has higher stability,which shows that the design of support scheme is reasonable.In the aspect of water seal effect evaluation,it is normal that some of the water seal indexes are not up to the standard during the construction period.According to the past engineering experience,all the indexes can reach the prescribed value after the cavern is put into use.The water seal effect evaluation is better and the supporting scheme is reasonable,but the relevant supporting measures should be implemented in time.