Comparison of Vacuum Surcharge Preloading Method and Surcharge Preloading Consolidation Method

Comparison of vacuum surcharge combined preloading method and surcharge preloading consolidation method Yu Jingyu combined preloading method compared with traditional surcharge preloading consolidation method, in the consolidation effect of subgrade soil, construction period, economic benefits and other aspects In contrast, the vacuum-loaded combined preloading method has obvious advantages over the surcharge preloading method. It has the advantages of fast filling speed, short construction period, strong stability, and good reinforcement effect, and it has a tendency to gradually replace it. .

1:A In recent years, highways have developed rapidly in China. During the construction of expressways, many problems have been encountered. Soft ground treatment is one of them. In the process of highway construction with soft foundations, soft ground treatment methods have a major impact on project quality and construction duration, and are directly related to various aspects of economic and social benefits. At present, the preloaded drainage consolidation method and the composite foundation reinforcement method are mainly used in the method of processing soft foundations. The vacuum-loaded combined preloading method is the second-generation expressway soft foundation treatment method that has been gradually implemented in recent years.

1 Engineering Geological Conditions The Beijing-Zhuhai Expressway Guangzhu Section is located in the plain area of ​​the Pearl River Delta of Guangdong Province. The terrain along the line is relatively flat and the water network is well developed. The surface below are all marine-continent intersecting silty soft soils, which have the common characteristics of soft soil layers in the Pearl River Delta region: high moisture content (greater than 60%), low strength (less than 15kPa), high compressibility (greater than 1.6MPa), soft soil thickness ( More than 30m deep soft soil causes slow drainage of the lower soft soil, long consolidation time, and large amount of soft soil deformation. The Guangzhou-Zhuhai section project started in August 1997 and required the opening of Macao before the return of Macao in 1999. The construction period was only over two years. How to scientifically and quickly fill it out has become the key to ensuring the successful completion of the project.

2The construction process of two types of construction methods briefly describes the surcharge preloading at 21K35+282: the embankment was refilled in February 1998, and the design elevation of the road surface was filled in mid-August 1998. The filling height 4im is in accordance with the planned construction plan. In May 1999, the unloading began for the construction of the road surface. At the road surface height 46, the coordinate values ​​in the Y'CZ' coordinate system of each pair were obtained. Table 1 shows the table of the pile position coordinates.

Table 3 Combination 5 Single Pile Top Axial Force Table kN The normal operation status is calculated according to combination 1 to combination 4. After trial calculation, combination 1 is the most unfavorable combination. According to the calculation results of the superstructure, the force transmitted to the arch foot is: the bending moment M = earth pressure after the frame is 1980kN. After calculation, the load acting on each root is: bending moment M. 257kN, axial force Pi see Table 2 As shown.

Table 2 Combination 1 Single Pile Top Axial Force Table kN The seismic state is calculated according to combination 5, and the combination 5 is calculated based on the upper structure. The force transmitted to the arch leg is: bending moment M = 920 kNm, axial force N = 4150 kN, shear force Q = 310 kN. The dynamic earth pressure behind the frame is 1081 kN. After calculation, the bearing capacity and strength are calculated based on the single top load acting on each root.

In addition to meeting the structural requirements, the design of the platform cap design of the pile cap has performed local compressive stress checking, bending resistance and shear strength checking.

5 Conclusion The reconstruction project of Shengli Bridge is under construction. The abutment design embodies the combination of practicability, sociality and appreciation, and fully considers the combination of new and old bridges, and meets the requirements of the hydrogeological structure of the bridge site.

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