What Is the Basal Cistern?

The pool is a water storage facility constructed with naturally formed small potholes filled with water or artificial materials and having an anti-seepage effect.

pool

(I) Requirements for the design of the pool structure

In addition to the design of the water storage project, the design of the pool structure should also consider the following requirements:

1. Load combination: Do not consider seismic loads, only consider the dead weight, water pressure and earth pressure of the pool. For open pools, the load combination is full of water in the pool and there is no soil outside the pool; for closed pools, load combination is no water in the pool and there is soil outside the pool. During calculation, the bulk density of the masonry stone masonry and concrete is taken to be 2.4t / m. For underground pools, the backfill soil outside the pool wall requires tamping. When calculating the earth pressure, the bulk density of the fill is taken as 1.8t / m, and the internal friction angle is taken as 30 °.

2. The allowable foundation bearing capacity should be calculated according to the geological conditions. If the actual bearing capacity of the foundation fails to meet the design requirements or the foundation will produce uneven subsidence, effective foundation treatment measures must be taken before the pool can be built. The foundation of the bottom plate of the pool must have sufficient bearing capacity, be flat and dense, otherwise, gravel (or coarse sand) must be used to flatten and compact it.

3 The pool should be designed as standard as possible, or designed according to the relevant specifications according to Grade 5 buildings. The bottom and side walls of the pool can be made of mortar stone, plain concrete or reinforced concrete. Brickwork can also be used in areas where the coldest month average temperature is higher than 5 , but cement mortar should be used. When mortar is used at the bottom of the pool, the mortar shall be used for the masonry. The size of the pool mortar shall not be lower than M10, and the thickness shall be not less than 25cm. When using concrete, the mark should not be lower than C15, and the thickness should not be less than 10cm. The soil foundation should be tampered with a depth of not less than 40 cm. The size of the pool wall should be determined according to the standard design or calculated according to the specifications.

4 The foundation of the pond is very important, especially in the collapsible loess area, if there is a slight leakage, it will endanger the safety of the project. Therefore, the pool built on collapsible loess should give priority to the use of integrated reinforced concrete or plain concrete pool. When the foundation soil is weakly collapsible loess, the bottom of the pond should be tamped, and the depth of tamping should not be less than 50cm; if the foundation soil is medium and strong collapsible loess, the tamping depth should be increased, and pre-sinking should be adopted. Measures to deal with.

5. Ladder should be set in the pool. Sewage pipes should be set at the bottom of the pool. Desilting service holes should be set in the closed pool. Fences should be set in the open pool. The fence should have sufficient strength and a height of not less than 1.1m.

(Two) structural characteristics of the pool

1. Open circular pool

The open-type pool body is composed of a pool bottom and a pool wall. It is mostly a seasonal pool and does not have anti-freezing and anti-evaporation effects. The circular pool structure has good stress conditions. Under the same water storage capacity, the construction materials used are less expensive and the investment is less. The open-type circular mortar-stone masonry pool foundation bearing capacity is designed according to 10 t / m, the pool floor is C15 concrete, the thickness is 10 cm, and the pool wall is M7.5 mortar masonry. Its thickness is determined by standard design or relevant specifications according to the load conditions. , Table 2 lists the main size, engineering quantity and material consumption table of the open circular mortar stone pool for reference.

2. Open rectangular pool

The composition, ancillary facilities, and wall structure of a rectangular pool are basically the same as those of a circular pool, except that the circle is changed into a rectangle according to the terrain conditions. However, the structural conditions of rectangular pools are not as good as those of circular pools, and the corners are weak links, and precautionary measures need to be taken. When the water storage capacity is within 60m, its shape is approximately square. When the length-to-width ratio of the pool exceeds 3, a partition wall needs to be installed in the middle to prevent side pressure from losing the stability of the ambassador's side wall. A water outlet in the upper part of the partition wall can effectively settle the sediment. Figure 3-12 shows the structure of an open rectangular pool. The bottom of the pool is C19 concrete, 20cm thick, the columns are C19 reinforced concrete, the wall of the pool is 24cm thick masonry, M10 cement mortar is used for surface impermeable, 3cm thick, and the body of the pool. Concrete hollow slab for roof.

3.Closed round pool

Most of the enclosed pool body is located below the ground, which increases the anti-freezing and thermal insulation effect. The thickness of the thermal insulation and anti-freezing layer should be determined according to the local climate and the maximum depth of the frozen soil layer to ensure that the water in the pool does not freeze and frost. The structure of the closed pool is more complicated and the investment is increased. The top of the pool uses thin-shell concrete arches or rib arches to reduce the load and save investment. The value of the depth-diameter ratio of the closed cylindrical concrete pool in Gansu Province ranges from 1.2 to 1.8. The bottom of the pool is a reverse arch. The bottom of the pool is paved with 37 cm lime soil and 30 cm thick, and the concrete is poured on top of it by 10 cm. , 10cm thick, a layer of cement mortar is applied to the concrete surface to enhance the anti-seepage. The cover is prefabricated concrete with barbed wire, numbered C18. The pool neck is paved with brick cement mortar.

Rectangular pools are highly adaptable, and different terrain sizes and water storage requirements require different specifications and structural forms, with large changes in water storage capacity. The bottom of the closed rectangular pool is M7.5 cement mortar masonry, 40cm thick, on which C19 concrete is poured, 15cm thick, the wall of the pool is concrete, 15cm thick, the top cover is a hollow concrete slab, and the slag insulation layer is overlaid. The thickness is 1.0 m, the thickness of the soil layer is 30cm, and there are ladders and related auxiliary facilities.

(Three) mobile support pool

With the advancement of science and technology and the development of the domestic economy, the pools that require infrastructure can no longer meet the requirements of social and economic development. People have developed new bracket pools. These movable bracket pools can be used in temporary water places, such as exhibition hall In the animation water world such as stadiums, swimming pools, and squares, these pools are a combination of steel frame and screened polyether vinyl pvc cloth, so they are called bracket pools. The height is 60cm--150cm, and the length and width are in the range of 2x2m to 50x50m.