Vacuum Combinde Surcharge Preloading Analysis And Soil Pore Pressure Monitoting Equipment Development

Soft soil is a kind of soil foundation which is very common in our engineering.This kind of soil is not suitable for building on it because of its poor mechanical properties.However,with the rapid development of Chinese economic construction,more and more various types of buildings emerge.In addition,although our country is vast,the main economic areas are concentrated in the eastern coastal areas,the available land area is still limited.Therefore,the soft soil area is also an indispensable land resource to be developed and utilized continuously.Because of the weakness of soft soil foundation,a series of treatment and reinforcement should be carried out before our construction.As for the treatment of soft soil foundation,it is mainly divided into two types: soil improvement and drainage consolidation.In this paper,the vacuum combined with surcharge preloading method in drainage consolidation method is used to carry out engineering,construction monitoring and detection and mechanism analysis.On the other hand,at the present stage,people have done a lot of research on soft soil,pore water pressure monitoring in the soil also has a series of equipment.But there is no effective equipment for monitoring pore pressure in unsaturated soils,so our research group has been actively committed to the development of such equipment and a series of improvements.In this paper,according to the actual project,the construction technology and control requirements of this method are introduced for consolidation of soft foundation with vacuum combined surcharge preloading.The monitoring items are divided into six items: vacuum pressure under membrane,surface settlement,stratified settlement,pore water pressure,groundwater level and lateral displacement of side piles.Through the induction and analysis of the monitoring data,it is found that the vacuum pressure in the field area decreases from the vacuum pump to the surrounding.The pore pressure meter can't accurately reflect the problem of unsaturated soil pore pressure above the groundwater level.The water level in the water level pipe will continue to decrease as time goes on while the seal was opened.By Cross-electric Sounding Board Shear test and static load test,the effectiveness of Vacuum Combined Surcharge Preloading in soft foundation reinforcement is verified in this paper.Through the comparison of vacuum preloading and surcharge preloading,the micro-and macro-mechanism of this method is studied.It is proved that this method has the advantages of short reinforcement time,fast settlement rate,remarkable reinforcement effect and small post-construction settlement.A new kind of pore pressure monitoring equipment is designed and manufactured,which can be used to monitor the pore pressure in unsaturated soil.Through the field experiment on sandy beach soil,it is verified that the negative pressure will occur in the natural soil when the groundwater level drops,and the usability of our equipment in monitoring pore pressure in unsaturated soil is also illustrated.Then the soft clay in the muddy beach with low permeability was tested,and the phenomenon that the water inside the equipment is difficult to discharge in the field monitoring was found.In view of this phenomenon,our research group re-optimizes and improves it by adding drainage system to make the equipment suitable for soft clay and other soils under various working conditions.It provides a new technical support for the study of settlement mechanism of soft foundation and a new monitoring means for practical engineering monitoring.