1. Basic working principle
The reinforcement mechanism of the geogrid is the friction reinforcement mechanism and the cohesion-like mechanism. By laying the geogrid in the dam filler, the better tensile strength of the geogrid and the mosaic ability of the dam filler are increased. The friction between the soil and other materials diffuses the stress of the earth and rock mass, limits the lateral deformation of the earth and rock mass, enhances the stability of the earth and rock mass, and thus improves the overall strength of the dam.
2. Material use requirements
(1) Filling material Filling material is gravel soil (crushed stone content 20%), the clay particles are silty clay, and the gravel is block gravel excavated from the reservoir area. The maximum particle size should not be greater than 50mm. The building materials should be mixed with gravel and soil before filling, and the filling materials should be covered after preparation to keep the natural moisture content stable. It is forbidden to use bad soil such as cultivated soil or silt, and it is forbidden to directly use excavated materials for filling.
(2) Reinforced material
Reinforced materials are made of two-way adhesive welded geogrids. Reinforced materials should have a factory test report and a factory certificate, and technical indicators should be measured. Those that do not meet the design requirements shall not be used.
Construction methods and key points of construction technology
1. Rolling test
(1) Purpose of roller compaction test
Rolling compaction test is to carry out on-site filling and compaction test of the filling material according to the design and construction specifications under the existing engineering construction conditions. The main purpose is to determine the construction equipment and the number of rolling compaction, and determine the construction technology of the filling And measures, and formulate implementation rules for filling construction.
(2) Methods and steps of roller compaction test
①Test site layout
According to the rolling compaction plan, select level rolling, sample the dam area after passing the test as the base layer, mark three rectangular areas of 10mX4m with white gray on the site, and spread crushed stone on it for the rolling test.
②Rolling machine
YZ18JD vibration roller, ZL50 loader, P200 grader.
③Compression combination of rock pressure test
Layer thickness: take 50 ~ 60cm (according to the vertical spacing of the geogrid design (50cm) to control, to ensure that the layer thickness after rolling is less than or equal to the geogrid spacing); Rolling times: take 5 ~ 7 times; moisture Natural moisture content: driving speed: 2 km / h.
④ Pressure obstruction test
Divided into 3 test areas, according to different soil thickness and number of compaction passes, roller compaction is performed. After compaction in each area, 4 samples (one sample per 10m) are used for the test, and the sampling points are compacted according to different The number of passes is staggered.
4. Geogrid laying
(1) The geogrid should be laid on the leveled and compacted packing according to the design requirements, and must not overlap, not be missed, and should not be curled or bent. The hard corner filler on the surface should be manually selected before laying to avoid direct contact.
(2) The geogrid should be laid vertically perpendicular to the axis of the dam, temporarily fixed to the ground with U-shaped nails every 1.5 ~ 2m, and the ribs should be tightened (the tension should be maintained-) and then pressed with a small amount of fill, Make it smooth and accurate positioning, and adjust the real-time adjustment of the disturbance effect on the reinforcement after rolling.
(3) When a fold line or curve is formed on a plane in the longitudinal direction, the reinforced material provided at the corner must be laid on the designed grid, and after laying more than 5cm thick filler, then lay it on it. Pay attention to protecting the geogrid during the laying process to avoid being damaged, pushed up or displaced.
(2) Construction method of dam filling;
①Paving
In order to avoid damage to the geogrid caused by transport vehicles, the method of spreading materials is adopted, and the thickness of the soil is not greater than 55cm, and the layer thickness is controlled by a ruler. When unloading the soil, first pile up the soil along the axis of the dam, and push the soil to both sides by the loader to ensure that the geogrid is accurately positioned and not twisted. The warehouse surface is leveled with a grader, and the undulation difference after leveling does not exceed 5 cm.
②Rolling
After the paving of the filling material is leveled, the roller is used for static rolling, and then vibratory rolling is performed six times. The walking path of the roller should be parallel to the axis of the dam, and the rollers should be rolled successively from the slope of the dam to the dam. The overlapping width of the track is 1/3 of the width.
③Acceptance
After the rolling is completed, a sample test should be taken immediately, and the new material can be paved after passing the test. Before laying new material, the surface layer should be shaved. The dam body paving is stopped in the middle of compaction, the surface of the compacted layer should be filled with a protective layer, and then removed before resuming work.
6. Dam body slope protection
The side of the garbage dam reservoir area is covered with anti-seepage membrane. The slope on the outside of the reservoir is protected by M10 slurry block stone arch, and the bowl body is masonry. The stone masonry arch is protected by spraying grass seeds for greening, and the seed seeds are planted with roots suitable for growing on the slope, resistant to early, cold and barren grass to achieve the effect of evergreen seasons.
Quality control measures
(1) The construction site organizes the construction strictly in accordance with the design requirements and relevant specifications. All materials entering the site will be used after witnessing the sampling, to ensure that the construction quality of the process meets the requirements of the design and acceptance specifications, and the compaction test should be performed in time.
(2) It is forbidden for construction vehicles and construction machinery to drive or park on the paved geogrid. During construction, check the quality of the geogrid at any time and repair or replace it if any damage such as breakage or tear is found.
(3) There should be no concentration of oversized stones and crushed stones in the filling materials, and the oversized stones should be cleaned in time. For the joints between the dam body and the slope, and between the dam body and the structure, when the mechanical rolling is not in place, the artificial layer is used to tamping to ensure the quality of the backfill.
(4) Strictly control the water content of the filling material. When the low water content affects the quality of rolling, the dam surface can be properly sprinkled with water to increase the water content. For the high water content, the filling material is prohibited.
(5) When unfavorable phenomena such as smooth surface and shear failure occur in the filling working surface after rolling, the filling material in the corresponding area should be cleared and re-rolled.
(6) Check and test the thickness of the soil, the number of rolling times, and the degree of compaction on the dam surface in time. After each layer of rolling is completed, a group of samples is taken every 500m 'to ensure the accuracy and scientificity of the test data. , Authenticity.