1. Upstream horizontal bedding
In horizontal seepage control, workers require simple construction method, short construction time and low cost, and the common method to meet these requirements is cushion. This method can not only effectively reduce foundation leakage and prevent deformation of dam foundation and bank slope, but also increase seepage control effect according to reservoir siltation. Therefore, this method plays a very important role in seepage control.
Because clay blanket has water permeability, its anti-seepage effect will be affected to some extent. Therefore, people choose composite geotextile as anti-seepage material for bedding and clay as protection and support layer, which makes the anti-seepage effect more obvious and reduces the use of clay.
2. Curtain grouting
In vertical seepage control, in order to reduce seepage gradient and seepage loss, it is necessary to choose a method that can enhance the strength of bedrock and reduce its permeability, and curtain grouting meets these requirements well and naturally becomes a common seepage control measure. Before determining the grouting treatment, the staff must first make a reasonable selection of the geological conditions of bedrock, dam type, bearing capacity and other factors. The upper and lower pressures of grouting holes in small reservoirs are different. Under normal circumstances, the downward pressure of grouting holes in small reservoirs is greater than the upward pressure, generally increasing by 0.01MPa/m/m. ..
According to the geological evaluation and actual effect, the setting of grouting holes can be adjusted appropriately, including the number and depth of holes. In order to ensure the compactness of grouting, the pressure of grouting holes in the subsequent sequence is usually greater than that in the previous sequence, and the middle row is greater than that in the side row. In order to quickly reach the standard pressure value, grouting generally adopts a one-time pressurization method to achieve this goal. When grouting, sometimes the foundation has strong water permeability, so the method of gradually increasing pressure should be adopted to effectively control the diffusion radius of grout. Curtain grouting for dam foundation of small earth-rock dams is also commonly used by subsection grouting method. This method follows the principle of subsection grouting from top to bottom, and the contact section is grouted for the first time. It should be noted that the grouting plug should be 0.2~0.3m below the rock surface, and the length of the contact section should be less than 2m. When grouting the contact section and the subsequent section, the grouting plug shall be placed 0.5m above the bottom of each grouting section. When the grouting reaches the designed depth and the water permeability is below 5Lu, the final comprehensive recharge can be started.
After the grouting is completed about 14d, the quality of curtain grouting can be tested by water pressure test. According to the actual situation, the relevant staff will make detailed arrangements for inspection holes, including the number and direction of inspection holes. If the inspection results show that the quality of a hole section is unqualified, it must be grouted again until it meets the design requirements.
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