Experimental Study On Reinforced Soft Clay Foundation By New Vacuum Preloading

At present,most of the reclamation land reclamation needs to be treated by vacuum preloading before it can be exploited.Although the vacuum preloading technology has been widely used in large area engineering practice,the conventional vacuum preloading still has the effect of drainage board blocking effect,serious degree of vacuum deepness decay,deep soil reinforcement effect,long construction time and foundation bearing capacity.So the existing vacuum preloading technology needs further improvement and innovation,so as to improve the treatment effect of the existing vacuum preloading treatment.In this paper,based on a large amount of literatures,combined with the Wenzhou coastal tideland reclamation project,the new vacuum preloading method is used to reinforce the silt-filled silt foundation to solve the existing blocking effect of vacuum preloading.Deep soil reinforcement effect is poor,the construction period is long and the bearing capacity of the foundation is low and so on,the main contents are as follows:Stage vacuum preloading and traditional vacuum preloading indoor comparison test.The maximum average settlement of the vacuum in stages is 176.4 mm.Compared with the traditional one-time vacuum the maximum settlement,an increase of 10 mm.The consolidation degree after vacuum strengthening is 89.09%,and the consolidation degree of the traditional one-time vacuum is 84.67%,which indicates that the vacuum can improve the consolidation effect of the soil.The SEM images show that the filter layer is formed around the drainage board,which greatly relieves the phenomenon of the muddy bolls on the surface,and verifies that the preliminary vacuum preloading can solve the blocking effect.The comparison experiment of multi-layer vacuum preloading and traditional vacuum preloading was carried out.The vacuum decay gradient of the three-layer vacuum pre-drainage drainage board is 5.2 kPa/m,and the decay gradient of the traditional single-layer drainage board vacuum is 12.8 kPa/m,and the vacuum attenuation is reduced.The reduction rate of water content after vacuum precompression test was 46.91%and that of single layer sand was 57.63%(22.85%higher than that of traditional monolayer).The reduction rate of water content was 55.71%(18.76%higher than that of traditional monolayer),and the reduction rate of water content after vacuum preloading test was 60.65%(compared with the single layer).Double layer sanding effect is superior to single-layer sand control,that is,the effect of three-layer drainage is better than double-layer drainage,far better than the traditional single-layer drainage vacuum preloading.The average strength of the whole soil is 23.6 kPa,which is 202.6%higher than that of the traditional single-layer drainage.Under the three-layer drainage layer,the soil reinforcement is uniform,and the reinforcement of the deep soil is obviously improved.To carry out pressurized vacuum preloading and traditional vacuum preload comparison field test.During the test,after settling,the supercharging zone began to pressurize and the subsequent settlement was produced.It was verified that the supercharged vacuum preloading had the effect on the traditional vacuum preloading.According to the measured pore water stress value,the cumulative value of pore water pressure at different soil layers can be calculated.Based on the comparison of the pore water pressure with time and depth,the area of pressurized vacuum preloading B.And the dissipation of pore water pressure in the traditional vacuum preloading zone(F zone)is 13.9 kPa?25.38 kPa.The pore water pressure dissipated along the depth of the basic show a gradual decrease of the law.The variation of vacuum degree in each area is basically the trend of gradual fluctuation in the early stage,and the vacuum degree gradually decreases along with the depth,and the attenuation is not great.Vacuum preloading area B board vacuum attenuation of 6 kPa?12 kPa,after the start of a reduction in pressure is caused by pressurization.After the test,the limit value of the bearing capacity of the foundation soil and the corresponding settlement,the two measuring points of the pressurized area are 70 kPa,23.54 mm;60 kPa,24.17 mm,meet the requirements of the commission.Compared with traditional vacuum preloading,supercharged vacuum preloading can improve the bearing capacity of foundation by 50%.