| Soft soil is widely distributed in China,especially in coastal areas of China.Large areas of marine soft soil are distributed.Such soft soil has poor geological characteristics such as high water content,high compressibility,low strength and high sensitivity.Therefore,the foundation treatment of soft soil It is a key issue in the field of soft soil research,which directly affects the development and safety of subsequent projects.Vacuum preloading method is a common method for soft soil foundation treatment.Strait-line vacuum preloading method is a new type of vacuum preloading method developed in recent years.It has the advantages of environmental protection,no pollution,short reinforcement period,economical reliability,etc.In recent years,it has been widely used especially in dealing with large-area soft soil foundations.Haiyan County is located in the Hangzhou Bay area and belongs to the typical marine sedimentary soft soil area.Based on the detailed analysis of the reinforcement mechanism of the strait-line vacuum preloading method,this paper relies on the ground treatment project of Shanshui Liuqi International Resort in Haiyan County,Zhejiang Province.Through the on-site design monitoring program and results arrangement,the variation law of land subsidence,stratified settlement,pore water pressure and vacuum degree with time in the reinforcement process is analyzed.The hyperbolic method,exponential curve method and grey system theory method are applied to the foundation reinforcement.The degree of consolidation is calculated,and the ground bearing capacity is verified by static load test.The calculation is combined with numerical simulation and compared with the measured values.The following conclusions are drawn:(1)The difference between the strait-line vacuum preloading method and the traditional vacuum preloading method is that the surface level drainage sand cushion layer is removed,and the plastic drainage board is directly connected with the main and secondary tubes to evacuate,which can improve the vacuum preloading energy efficiency and shorten the construction period.And on the basis of saving engineering costs,on this basis,the paper introduces in detail the design and monitoring scheme of the strait-line vacuum preloading method,and compares and selects the ground treatment scheme according to the soft soil properties of the project location;(2)Combined with the monitoring data analysis,the ground settlement is the largest when the vacuum is 10-15 days,and the ground settlement is up to 55mm/day.At this time,the vacuum reaches the design requirement of 80 kpa and remains stable,and the stratified sedimentation is analyzed.The settlement value still has the same regularity every day.It is considered that the straight-line vacuum preloading method has a relatively fast consolidation of the foundation soil in a short period of time,and the consolidation speed is relatively slow and maintains a gentle state after the vacuum degree is stabilized;(3)It can be concluded from the stratified settlement that the consolidation of the soil in the soft soil mainly occurs in the range of 3 to 18 m,the stratified settlement can reach 4 cm to 11 cm,and the settlement below 18 m is relatively small to 0 to 4 cm;(4)Using the hyperbolic method,exponential curve method and grey system theory method,the final settlement of the foundation is predicted by different samples,and the relative error of the exponential curve method is considered to be small,which is more suitable in the engineering of the area.Hyperbolic method The gray theory method has greater error than the former two methods,so the gray theory method can be used as a short-term settlement prediction with more practical significance;(5)Combined with Biot’s consolidation theory,the finite element numerical simulation software is used to simulate the settlement.It can be obtained that the calculated value is consistent with the measured data.The maximum settlement of the foundation occurs in the soil with a depth of 26 m or more,and the soil is deep below 26 m.The effect of reinforcement is small,and the horizontal displacement mainly occurs at a depth of more than 20 m.The vacuum transfer efficiency is very significant for the vacuum pre-compaction consolidation,and verifies the reason why the strait-line vacuum preloading method is more efficient,which can provide reference and experience for similar projects;... |
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