Trench method of construction of underground structures
When the trench method otkatyvaetsya pit and conventional methods the Future is being built underground structure.
After completion, the pit is filled with soil. When using this method provides the most favorable conditions for the placement of concrete, an arrangement of exterior waterproofing. Construction loads on the enclosing structure in this method of construction not exceeding! operational.
A disadvantage of the trench method is the need to reserve a considerable surface area for the contours of the constructed facility when satkoski walls of the pit for stable slope angles or bracing of the vertical walls. This fact generally limits the use of trench method depth of 5. 7 M.
Method of sunk well. Method of sunk well (Fig. 12.7, b) is that the enclosing walls of the underground structure in the form of a closed loop (circular, rectangular, etc.) are built on the surface of reinforced concrete or of prefabricated elements (blocks, panels) for a special design, called the knife. After erection of walls adequate for the start of the dive height is the extraction of the soil inside the well, which is accompanied by subsidence of the well under the forces of sobstvennogo. To reduce friction forces of the well on the ground outer diameter of the knife taken on 10. 30 cm larger than the diameter of the walls, it creates a gap between the ground and walls. In unstable soils, this gap is filled with thixotropic mud. If the weight of the well is insufficient to overcome the frictional forces that usually occurs when small in terms of size well, the top of the well prigruzhajut goods or by tension anchors, passing through vertical holes in the walls and anchored deeply in the soil. After lowering of the well to the desired depth gets its bottom – the bottom fence underground structures.
Lowering the well in flooded soils is usually done with a drawdown, and if the soil plavannya properties and poor yield, which threatens the lifting of the soil bottom in the process of lowering and precipitation of the surrounding surface around the well are lowered sheet or logrotate the fence, reaching down to the impermeable layer, or a clay protivorechit operational curtain. In such circumstances it is also possible immersion well with flooding of its interior space groundwater and underwater excavation, however, it reduces the weight of the well on the value of Archimedean forces weighing and creates difficulties when meeting the knife solid inclusions of boulders. Inevitable in the development of submarine underwater concreting of the bottom requires a large consumption of concrete. For these reasons, the dip of the flooded wells is rarely used.