stabilization,foundation, material
If we want to make a cheaper foundation we must improve the foundation material. For example, many single-storey industrial buildings with heavily loaded floors have superstructures which easily protect against the weather and exert negligible loads on the foundations. When the subsoil is compressible, the floor may settle excessively, if a very costly standard foundation is not installed. Preloading the site with the purpose of inducing settling, before the structure is built, may permit construction of the floor directly on the; round. In preloading, a temporary fill of earth is placed over an area which is larger than the area of the proposed structure. The weight of the fill is determined by means of the analysis of the subsoil and the predicted degree of settling. So preloading permits to found many structures above loose sandy or silty soils and in marshy areas. Installation of settlement plates on the surface before the fill is placed allows making the observation of the rate and magnitude of settling. The settlement curves indicate when most of the settling has taken place, and then the temporary load can be removed. If settling under preloading will be too slow, it sometimes may be accelerated withstand drains which help to the outflow of water. a) Shoring Shoring may be required if the foundations of an existing structure are unsuitable or if they become dangerous because of adjacent construction or excavation. Shoring provides temporary support of a wall or column while adjacent construction or underpinning is in progress. If the foundation or a wall must be retained after settling, part of the wall may be removed, leaving short horizontal slots in which screw jacks may be introduced. The slots are then extended in short sections and additional jacks are introduced until all the upper part of the Wallis supported by jacks. The jacks are extended as necessary to keep the wall in position until the foundation is stabilized; then they are removed and the wall is restored tin sections. b) Underpinning Underpinning may be used to replace old foundations (usually below the earlier level) and is often required if adjacent excavation or a new structure will extend below the old foundation level. Pit underpinning is used if suitable support can be found below the existing footing beneath a wall. Small pits are excavated at spans are required. Steel is mostly used for very tall structures for intervals alongside the wall to a depth sufficient to give access to the unison of economy in construction and space. For example, in the underside of the footing. Then the earth is removed to new foundation system called box frame construction, each unit is composed of two depths beneath the part of the footing and is replaced by concrete. The walls bearing a slab (the other two walls enclosing the unit are operation is repeated in different sections until all the wall is nun bearing screen walls). Provided with a new footing. When the load is transferred to the new foundation, it always causes settling. To avoid this, jacks are usually left in place, while the new concrete sets and shrinks.
