| With the deepening of China’s reform and development,the scope of urbanization is becoming wider and wider,and the construction land is becoming more and more scarce.Using vacuum preloading technology to treat dredged silt is an important way to solve the shortage of land resources.Because dredged sludge has the characteristics of high water content,high compressibility,high porosity and low permeability,it is usually treated by plastic drainage plate combined with vacuum preloading technology.The settlement of the foundation treated by this method is uneven,and the inclusion of plastic drainage board in the foundation is difficult to decompose,which causes great environmental pollution.Therefore,this paper proposes to use crop straw as straw drainage body and vacuum preloading technology to consolidate dredged sludge.On the one hand,crop straw is rich in resources in China and is mostly incinerated as waste;on the other hand,because straw is degradable,it can produce nutrients needed by plants and improve soil ecological function.In order to better study the feasibility and consolidation characteristics of straw drainage vacuum preloading treatment of dredged sludge with high water content,this paper carried out indoor large-scale model tests and reached the following conclusions:(1)The settlement rate and drainage rate of straw drainage body in the early stage of model test are higher than those of plastic drainage board,which is more suitable for rapid foundation treatment.However,although the accumulated settlement and water yield of plastic drainage plate model test are slightly more than that of straw drainage body,the uneven settlement of plastic drainage plate is more obvious and the siltation is more serious.(2)The bending of straw drainage body is far less than that of plastic drainage board.Straw drainage body itself has great anti-deformation ability and shrinkage performance.Compared with plastic drainage board,it has less bending degree and less friction with soil,and the phenomenon of "soil column" is not obvious.However,the bending situation of plastic drainage board is mainly wave-shaped,which has larger bending and greater friction with soil,forming a rigid connection around it,and the phenomenon of "soil column"is more obvious.Therefore,the shape of drainage is one of the important factors affecting the consolidation characteristics of soil.(3)The vacuum degree inside straw drainage body and plastic drainage board will be attenuated to a certain extent.Due to its own shrinkage characteristics,the straw drainage body bends slightly,so the vacuum degree is transmitted smoothly,and the vacuum degree is gradually attenuated with time.The plastic drainage board bends with the consolidation of soil,and the vacuum degree remains stable for a period of time,and then decreases sharply.Therefore,the large-scale model has certain influence on the transmission effect of vacuum degree.(4)After the vacuum preloading test of straw drainage,the soil strength decreases with the increase of water content.Because of the advantage of small bending,the soil strength decreases with the increase of depth and horizontal distance,showing a qualitative law.The law of water content increasing with depth and horizontal distance is the same.(5)The main components of straw fiber are cellulose,hemicellulose and lignin.In the process of vacuum preloading,straw will be degraded,and these three main components will be reduced.After straw degradation,carbon,nitrogen,phosphorus,potassium and other elements are produced in the soil,which are some nutrient elements needed by plants.Therefore,using straw as drainage body improves the economic benefits of the project,and accords with the strategy of environmental protection and sustainable development.Figure 66 Table 9 Reference 99... |
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