Experimental And Simulating Study Of Electro-osmotic Consolidation Of Dredger Fill In Liaodong Bay Region

With the development of economy, the land resource demand is more and more urgent. In the coastalregions of our country, the engineering are extensively developed for the reclamation of land from the sea,especially the Yangtze River Delta, Pearl River Delta and the coastal area of Tianjin, and the area ofdredger fill is very large. In recent years, Liaodong Bay region also has carried on large scale landreclamation projects because of the city development.. Since the dredger fill with high water content, highvoid ratio, high compressibility and low shear strength, the foundation is likely to occur many problems if itcould not be handled, such as large settlement, long settling time and instability. Though many methodsthat treat with foundation have developed more mature, for example, drainage consolidation and chemicalreinforcement, they also have exposed some disadvantages. Based on the above analysis, it have proposedhigher requirements for the applicability and effect of handling technology of dredger fill foundation,facing the new situation.. According to these practical problems, this paper performed to investigate andstudy the distribution and engineering properties of dredger fill in Liaodong Bay region and put forward thetreatment measures of electro-osmosis combined surcharge preloading method and continued to furtherstudy by establishing the laboratory model.1. Based on the field geological surveying results and the data analysis, the area of dredger fill is about192.52km2in Liaodong Bay region, which the Liaobin economic area of Panjin is144.59km2and thecoastal area of Jinzhou is47.93km2. Based on the particle component, the dredger fill types mainly divideinto silty, silty lean clay and silty sand. Their water content is15.23-33.68%, porosity is0.503-1.10and thecoefficient of compressibility a1-2is0.11-0.9936MPa-1. Mineral content and microstructure also shows thediversity, and native mineral content is54-88%. In this study region, the dredger fill is in line with thesetypical characteristics of high water content, high void ratio, high compressibility and low permeability,however, the engineering properties are different in different sites due to different soil source, time spanand complex stratigraphic structure.2. The paper carried on the simulating study of laboratory test by establishing electro-osmosiscombined surcharge preloading model box, meanwhile, parallel test was performed with preloading modelbox. Every indexes were monitored in the strengthening process, measuring water content in differentdepth, analyzing consolidation law and comparing with reinforcing effect. This study shows thatelectro-osmosis combined surcharge preloading method has good applicability in Liaodong Bay region:there is better strengthening effect for this method, and compared with preloading method, drainage andsedimentation both improve1/3and undrained shear strength increased by1.05times; electric field formsan effective driving force on the soil pore water and there is faster drainage consolidation; the method hashigher influencing depth and better applicability and is not limited by particle size.3. The paper analyzed changing routine of some parameters about electro-osmosis by treating withmonitored every indexes. Under the condition of steady voltage, these parameters was decreasing with time,including electro-osmosis coefficient, electric current, soil electric conductivity and displacement per unitenergy consumption. It had substantially uniform distribution for the electric potential in the conditions of the one dimensional electro-osmosis model and ignoring interface resistance. Then, this paper furtherresearched the constructing process of electro-osmosis. Electrode corrosion was caused by theelectrochemical reaction, and the intermittent electricity and switching electrode were adopted that couldeffectively reduce energy consumption and electrode corrosion; it would be better that combinedelectro-osmosis and traditional vacuum preloading; electric geotextile material replaced the traditionalelectrodes, etc.4. According to consolidation theory of one dimensional electro-osmotic, numerical simulating modelof testing model box was built with FLAC3D. The average electro-osmotic permeability was measured atdifferent times through parallel test and was optimized by adding dynamic coefficient. Based on the resultsof numerical simulation, it could be a good match actual monitoring subsidence curves. So it is morepractical for obtaining the phase average electro-osmotic permeability with the method, and it could beapplied in optimizing consolidation theory of electro-osmosis combined surcharge preloading and used toguide the actual engineering design and settlement prediction.The above studies indicate that the method of electro-osmotic consolidation has good prospects. It notonly has the high consolidation efficiency and good reinforcement effect, but is not limited by the particlesize and more adaptable and greater impact depth. Through the study of electro-osmotic consolidationtheory, it can well reflect the variation of electro-osmotic permeability in the process of combinedelectro-osmosis and preloading for measuring the average electric permeability at different times withparallel test. The theory of combined electro-osmosis and preloading is optimized with dynamic averageelectric permeability. Then, simulating model is established to designing engineering and predictingsettlement, and results can meet the engineering requirements.