Experimental Study On The Vibroflotation Compaction Of Hydraulic Fill Foundation Of Coral Reef Sand In Red Sea

With the inplementation of the "Belt and Road" strategic initiative,more and more land reclamation projects have been carried out.Facing the lack of building materials and the deteriorating environment,it has become a worldwide technical problem to be solved urgently whether submarine dredging materials can be used as energy-saving filler to achieve engineering land economically and environmental-friendly.As a result,based on the two coastal projects of the Saudi Red Sea basin undertaken by CCCC Fourth Harbor Engineering Co.Ltd.,this paper carried out the experimental study on the reinforcement and dredger fill of coral reef sand foundation by the method of vibroflotation compaction.Firstly,by referring to the relevant literature at home and abroad,the investigation of coral reef material composition and basic physical mechanics and chemical characteristics of Red Sea waters has been conducted,and the particle classification,compaction and CBR series soil test have been completed.After the comprehensive analysis of the dredged reef sand,it is concluded that the sand is feasible for the foundation filling,which lays the foundation for the follow-up experiments on foundation reinforcement by vibroflotation method.Then,it was proposed to form the land area by the dredger-fill in-layer technique and use the in-situ exploration test to identify the geological conditions of the dredger fill area.The field trial program was developed and the trial area was selected to carry out the experiment on foundation reinforcement with different vibro flotation techniques.The reinforcement effect detected by SPT test was analyzed,and the optimal vibroflotation technique was determined to guide the large area construction.By comparing the results of CPT test before and after the foundation reinforcement,it is found that the resistance of the foundation cone after reinforcement has been obviously increased,which can meet the design requirements.In order to fully verify the validity of the proposed technique and the reliability of the liquefaction identification of the foundation,the liquefaction performance of the foundation after vibroflotation was further calculated by the NCEER method of CPT,and the liquefaction judgment was made by Iwasaki liquefaction index method.The result indicates that the liquefaction index LPI values by both methods fall into the non-liquefaction zone and the risk of liquefaction of the sand can be eliminated.In addition,the sedimentation analysis on the post-vibroflotation foundation was conducted using the limit equilibrium method(based on CPT)and the schmertmann's method(based on SPT),and the results were compared.It is found that the results by the limit equilibrium method are partially conservative while those by schmertmann's method are too large,but both can meet the requirement of sedimentation control.The results reveal that it is practicable to deal with the sand foundation of the Red Sea coral reef by the method of vibroflotation compaction with additional backfill materials.Finally,the results of the experimental study were analyzed and summarized.This paper summarizes design method and construction guideline for the vibroflotation compaction of hydraulic fill sand foundation of the coral reef area in the Red Sea with additional backfill materials for similar engineering reference.