1、Overview of Soft Subgrade Treatment Abstract: The reinforcement of soft soil roadbed There are many ways, several to explain the reinforcement mechanism of the role, scope, and individual project example elaboration. New reinforcement materials and new technology development and utilization of soft
2、subgrade reinforcement played an important role to do with the simple description. When road works are often encountered in soft soil subgrade, the carrying capacity of the foundation have become increasingly demanding due to the development of highway, railway, natural soft ground is far from meeti
3、ng these high-grade structures are the foundation bearing force requirements. 1980s and 1990s, due to population expansion of land resources are becoming increasingly tense, soft soil subgrade reinforcement technology has made great progress, and economic conditions have improved, a variety of soft
4、soil reinforcement theory has been fully Application and verification of soft base reinforcement technology has made rapid progress in different areas are covered； to the 1990s, a variety of soft foundation treatment technology has been widely used in various road projects. Foundation in soft soil,
5、usually in soft new moon or under the state of the flow of new moon of the clay. Which is characterized by the natural water content, void ratio, compressibility factor, low strength and creep, thixotropy, and other special engineering geological properties, poor engineering geological conditions. S
6、election of soft soil roadbed application must be put forward practical measures. Soil, such as in the construction of the base of the embankment or bridge and culvert structures, optimum moisture content is not easy to grasp, is extremely difficult to achieve the required degree of compaction can n
7、ot meet the density requirements after the opening, often a roadbed instability or excessive settlement. Its obvious dangers, therefore prohibiting the use. Construction of embankment on soft ground, especially Bridge Approach, if not take effective measures for the reinforcement, it will have varyi
8、ng degrees of collapse slip or subsidence, resulting in road damage or is not working is known as the Bump. In general, in addition to ensure that the new subgrade Using density to reduce the settlement In addition, the total settlements of the foundations of the original ground must meet the basic
9、stability of the settlement roughly more than 80% of the total settlement amount, to allow resurfacing. Serious settlement of soft ground, not only to increase the amount of fill, and subsidence or horizontal displacement of the bridge near the filling, retaining walls, culverts, and even the techni
10、cal standards of the nearby residential, farmland, and the route will have a huge impact . To this end, according to the engineering properties of foundation soil, the selection of appropriate measures to deal with. After a long practice, the formation of roads, railways, various forms of soft groun
11、d, combined with a lot of construction companies many years of experience in construction and related experts and scholars discussed summarized as follows: A replacement cushion method When the thickness of the soft soil, soft soil below the subgrade surface within part or all of the excavation, the
12、n change to fill the greater intensity of soil or other stability, non-erosive materials (usually good water permeability in coarse sand) called Replacement Cushioning. This economical and practical method to deal with the height of 2 to 3m, if the thickness of the soft soil is too large, then using
13、 the replacement method will increase the disposable side and dug side content and increase the cost of the project. Replacement higher shear strength of soil, so as to achieve the goal of enhanced foundation bearing capacity to meet the requirements of the structures on the foundation. Reinforcemen
14、t Method Replacement, Stone Fill, cushion, COMPACTED silt several. Cushioning according to the different materials can be divided into the sand (gravel) cushion, gravel pads, fly ash cushion, the cushion of dry residue, soil (dust, ash) cushion. Representatives of sand cushion method and replacement
15、 method. Gravel cushion: when the embankment height is less than 2 times the limit height, soft soil layer is thin, the filling material is more difficult, or rainy season, construction, gravel (sand) cushion between the fill and the basement to set up a drainage face, so that the foundation by fill
16、ing load in the foundation soil pore water discharge speed to accelerate the consolidation to improve the bearing capacity of foundations, reduce sedimentation, to prevent the foundation of local shear deformation. Pay attention to controlling the filling speed, the materials used to clean coarse sa
17、nd with mud is not more than 5%, or maximum particle size less than 5cm natural gradation gravel. Replacement Method: water permeability material (gravel or crushed stone) in the soft soil thickness is not greater than 2m, filling replacement can reduce the compression to increase bearing capacity,
18、shear strength, and reduce the settlement to improve the dynamic characteristics accelerate soil consolidation by drainage. It is characterized by the construction process is simple, but the cost is relatively high. Stone Fill: When the soft soil or marsh soil located underwater, replace the soil co
19、nstruction difficulties, and the thickness is less than 3m, the surface without a hard shell, the substrate water content over liquid limit, embankment above the weight of the soft soil that can be squeezed out, drainage more difficult when using cast stone tablets (diameter generally less than 30cm
20、) to squeeze the deposition method. Start from the middle of the rubble, gradually extending to the sides, out of mud, to improve the subgrade strength. 2 deep compaction The use of blasting, compacting, extrusion and vibration and join the high shear strength of materials, etc., the foundation of d
21、eep soft soil density vibration and compaction of the foundation reinforcement method is called deep compaction. For soft soil thickness 3m thick soft soil reinforcement, distribution of a wide area of soft Reinforcement processing, has consolidated its depth is up to 30m. Vibration, squeezing groun
22、d Turkey body dense consolidation, and added with high shear strength of the pile material replacement of part of the soft soil of the three-phase (gas, liquid and solid phase) portion to form a composite foundation, to improve the shear strength of purpose. Main reinforcement methods: dynamic compaction, soil (or dust, fly ash plus lime) piles, sand piles, blasting, gravel pile (vibration and substitution method), lime piles,
