Wide-area excavations, part 1



tmpb4ba-1Protection of a wide excavation: a) skarpami, b) a slope supported by stupas, c), d) support with braces, e), f) support with ties.

The walls of the excavation are protected against removal by making slopes or supporting the walls. In cases, when the execution of the slope is impossible due to the narrow space or the high level of groundwater - higher than the foundation level - it is necessary to support the walls of the excavations.

Deep and steep trenches should be supported from the inside, especially then, when the ground is not cohesive. If the trench is that deep, that even the hard grimi can be removed due to wetness, then it is also necessary to support the walls.

The following general rules should be followed when constructing supporting walls:

a) the support should be firm and firm,

b) the support structure should not interfere with the foundation works,

c) support structures and connections should be simple and easy to assemble and disassemble, in order to be able to use them for further works.

Figure a shows the excavation wall secured with buttresses, with the angle of inclination specified in point, while in figure b it is secured with a slope in the upper part and a supporting wall in the lower part.

The most frequently used trench wall supports are shown in Fig. B-f.

If the walls are not too high and the soils are as dry as possible, the wall can be made of piles at intervals 1,20-2,0 m at least in depth 1,0 m and horizontal formwork made of logs (rys.b).

Instead of driving the piles deep into the ground, the piles can be supported with braces (Lynx. b, d). Method d) it is used for greater depths and is more laborious than method c).

A prop with braces is usually used for excavations, where we have a lot of space. If the struts interfere with the performance of further construction works, a there is a site at ground level beyond the edge of the slope, it is best to use the supports shown in fig. e, f, where the upper part of the pile is anchored to the piles with steel bars - square timber or logs. For average soils, the length of the bolt is not much greater than the height of the trench wall.

Figure f gives the solution, with wooden anchors. A pavement for pedestrian traffic or material transport is laid on the horizontal logs, and for logs erected above ground level, approx. 1,20 m, railing boards were attached, preventing accidents from falling into a trench.