| The soft foundation can’t meet the engineering needs.It is essential to consolidate the soft clayey soil before construction work is conducted.The popular approach for consolidating the extremely soft foundation is the vacuum preloading method.However,the vacuum preloading method for soft clay has the big challenge of sludge cliquing around prefabricated vertical drains and vacuum pressure losing along the depth of soil,affecting the effect of deep soil reinforcement.As the electro-osmotic permeability is independent of grain size.Therefore,electro-osmotic technology serves as a potential method for projects containing low-permeability soft clay.However,the increasing of interface resistance in later stage affects the effect of treatment.Adding chemical reagents to modified soft clay reinforcement is also used,but this method failed to discharge the water moisture of soil.Based on the above relationship,the electrochemical reinforcement experiment of electro-osmosis combined with chemical modification and electro-osmosis combined with vacuum preloading was carried out.The horizontal arrangement of prefabricated vertical drains pure vacuum preloading and electro-osmosis combined with vacuum preloading was firstly carried out on the soft foundation.Vacuum pressure under the membrane,volume of drainage,the soil surface settlement and pore water pressure were monitored in the process of test.After the test,vane shear strength and moisture content were measured in the different depth of soil.The results show that the treatment effect of the combined method is better than that of vacuum preloading alone.The combination between vacuum preloading and the electro-osmosis method can promote each other and show a complementary advantages.Moreover,Soft clay foundation treated by employing Vacuum preloading in combination with electro-osmosis could obtain better uniformity.And then,due to anodic corrosion,the contact between electrode and soil reduction resulting in lower electro-osmotic reinforcement efficiency in the later period of electro-osmotic.Electrochemical reaction of electro-osmotic process to produce hydroxide colloid,considering adding to chemical substances react with the soil to further enhance the strength of the soil.In order to be more economical and environmentally friendly,the author carried out low-volume lime electrochemical reinforcement tests.The mechanism of lime treatment for soil involves cation exchange,which leads to the flocculation and agglomeration.Five representative laboratory tests一an electro-osmotic test and four electrochemical tests with various proportions of lime—were performed on dredged marine clay.The objectives of this study are to investigate the effect of electrochemical treatment and to determine the optimum dose for optimal consolidation performance of dredged marine clay.The results show that a better consolidation effect was achieved in terms of current,temperature,and vane shear strength by using electrochemical treatment.The best results were observed for the electrochemical test using 4%lime content.In view of the problem of soil cracking during the process of electroosmotic reinforcement and the contact deviating between the electrode and the soil,the electroosmosis combined with surcharge preloading test is carried out at last.The objectives of this study are to investigate the effect of electroosmosis combined with surcharge preloading and to determine the optimum surcharge activation time for optimal consolidation performance of dredged marine clay.Four representative laboratory tests—an electro-osmotic test and three electroosmosis combined with surcharge preloading tests in various surcharge activation time in degree of consolidation—were performed on dredged marine clay.The results show that a better consolidation effect was achieved in terms of water drainage,effective voltage,and vane shear strength by using electroosmosis combined with surcharge preloading.The best results were observed for the test starting surcharge preloading when the degree of consolidation is 40%.In this paper,the above three foundation reinforcement methods would hope to have useful data support and theoretical guidance for engineering practice through the above three experimental studies. |
