The soft soil of the subgrade is mainly sedimentary silty silty clay, pond bottom or river bottom silt and silty soil, and the distribution characteristics of soft soil are mainly shallow soft soil treatment scheme and deep treatment scheme. The shallow soft soil is mainly distributed in the location of fish ponds and depression paddy fields, and the thickness of the soft soil is small and generally less than 3m, so the more economical shallow replacement method is adopted. For deep soft soil, the deep treatment of soft foundation is carried out by pre-pressing or plastic drainage board pre-pressing method. In the deep treatment of soft foundation, according to the thickness of the soft foundation, the deformation requirements, the height of the filling and the distribution characteristics of the structure, the plastic drainage board preloading method is selected in sections. For the general subgrade section with relatively small soft soil thickness and small deformation requirements, the stacking preloading method or plastic drainage board stacking preloading can be adopted.
The plastic drainage board stacking preload drainage consolidation method is mainly to increase the vertical drainage channel of the foundation, shorten the drainage path, accelerate the consolidation rate of the foundation and promote the growth of the strength of the foundation, improve the stability of the subgrade, and make most of the settlement completed in the construction period and preloading period in advance. The scheme is characterized by low cost, convenient and fast construction.
The plastic drainage board is required to be made of virgin materials, polyethylene and polypropylene, and the tongue-shaped tear strength of the core board should not be less than 20N, and the longitudinal water flow should not be less than 50cm3 s. SPB-B or SPB-C plastic drainage boards can be used. The plastic drainage plate plate should be provided with a device that can measure the depth, and the displacement sensor of the intubation head and the displacement sensor of the plastic drainage plate are generally used to detect the insertion depth of the intubation head and the return belt length of the drainage plate respectively, so as to determine the depth of the drainage plate.
Preparation for construction
Preparation for construction must be done before soft foundation treatment and subgrade filling. The general road section must be cleaned first, the site must be leveled, the topsoil, weeds and floating mud should be removed, and the longitudinal and horizontal drainage ditches should be excavated to remove the stagnant water, and the temporary drainage ditches should be done, and then dried and compacted.
Plastic drainage board laying
1. When the plastic drainage board is lofting, the plastic drainage board is arranged horizontally and longitudinally according to the route, and the distance between the plastic drainage plates is 1 meter, and attention is paid to the equilateral triangle layout.
2. During the construction of the plastic drainage board, the depth of the plastic drainage board should be controlled according to the application situation.
3. The construction of plastic drainage board should be carried out after laying the gravel cushion. The length of the hole left by the drainage board should be guaranteed to extend into the cushion not less than 05m。After the construction is completed, the exposed end of the drainage board can be bent and buried in the gravel cushion to level the cushion.
4. The plastic drainage board can be set by the inserting machine, and the plastic drainage board can be constructed by hammering method and vibration method.
5. During construction, the guide rail should be vertical, the steel casing should not be bent, and the permeable filter sleeve should not be torn and polluted; There should be reliable anchoring measures at the bottom of the drainage board to avoid bringing out the core board when pulling out the casing; The verticality should be controlled by theodolite or hammer when setting. During the construction process, the plastic drainage board should be ensured continuously. Measures should be taken to reduce the disturbance to the surrounding soil during construction.
6. The spacing and depth should be strictly controlled during construction, and if the plastic plate is brought more than 40cm during the extubation process, it should be reprinted. When the plastic plate needs to be lengthened, the connection method of flat lap in the water filter membrane should be adopted, and the lap length should be more than 20cm. After the drainage board is erected, a layer of gravel cushion should be laid immediately to prevent the aging of the board body due to long-term exposure to air.
7. It is strictly forbidden to lap the plastic drainage board.
8. The inspection and evaluation standards are specified in the Code for Construction and Quality Acceptance of Urban Road Engineering (CJJ1-2008).
**: Guangzhou Shengzhou Foundation Project***
Guangzhou Shengzhou Foundation Engineering has the national first-class qualification for professional contracting of foundation engineering, and is a company focusing on soft foundation treatment and construction. The company is equipped with a plate inserter, a pile mixer, an excavator, a vacuum equipment, a water engineering ship, and its own 10,000 square meters of plastic drainage board material production plant and equipment base to meet the construction needs of foundation treatment projects of various sizes. For more than 20 years, the company has accumulated rich construction experience and engineering cases in the construction of soft foundation treatment projects in airports, ports, docks, chemical industry, urban construction, municipal administration, roads and other fields, and its construction footprint covers more than 20 provinces, cities and regions across the country, as well as overseas regions in Southeast Asia and the Middle East.