Engineering Preparation of Populated Areas
Engineering Preparation of Populated Areas
the set of engineering measures and structures used to develop territories for purposeful urban planning and to improve the health, hygienic, and microclimatic conditions of populated areas.
Problems of engineering preparation are essential both during the selection of sites for the construction of new cities and communities and during reconstruction and expansion of existing populated areas, since there is virtually no territory that is entirely suitable for urban construction in terms of natural conditions and is at the same time large enough. In most existing cities and communities the proportion of land that is entirely unsuitable or suitable only for restricted use averages 8–10 percent of the total populated area; engineering preparation makes possible the maximum reduction of the size of such unusable areas.
The type of engineering preparation measures taken depends on the natural conditions of the area being developed (terrain, soil, and the extent of submerged and swampy land), taking into account the planned layout of the area. In some cases engineering preparation measures determine the architectural and planning structure and spatial composition of populated areas. For example, the filling of areas on the coast of the Gulf of Finland in Leningrad created an additional opportunity for construction on two shallow-water sectors of about 400 hectares (ha) and 200 ha along the shore of the gulf. This measure gave the city a broad opening toward the sea.
Three types of engineering preparation measures are distinguished, depending on their complexity and the size of the expenditures for them:
(1) Measures that are essential on some scale in virtually all places. Such measures include the grading of the area, the arrangement of surface runoff and elimination of stagnant waters, and in many cases the regulation of streams, the creation and redesign of bodies of water, the installation of shore reinforcement works, and the restoration of shorelines. The expenditures for these measures are usually about 1–2 percent of the total cost of urban construction.
(2) Measures that are widespread, including lowering the level of groundwater, protection of an area from flooding and a rise in groundwater, the assimilation of ravines, combating karst phenomena and landslides, and restoration of areas harmed by human activity (for example, as a result of mining). The cost of this work averages 2.5–5.0 percent of the total cost of urban construction.
(3) Measures for the reclamation of areas with exceptionally unfavorable natural conditions, such as a deep peat bog over a large area, on which a complex group of engineering preparation jobs must be performed (deep drainage, massive peat removal, filling in areas with large quantities of earth, and so on); engineering preparation of areas composed of sunken soils; and the protection of areas against mud and rock slides. The reclamation of land in seismic areas and regions of permafrost soils is particularly difficult. Expenditures for engineering preparation of such areas are up to 10 percent of the total cost of urban construction.
One of the basic, virtually universal steps in engineering preparation is grading, which involves the preparation of the natural terrain for the placement of buildings and structures, the provision of transportation links, and the organization of surface runoff by cutting, filling, and the moderation of slopes. The requirement for the greatest possible preservation of the natural terrain is usually followed during grading. The volume of work during grading is 800–1,500 m3/ha for partial transformation of gentle terrain, with a slope of 0.5 to 10 percent; for hilly terrain it reaches 3,000 m3/ha. Grading is usually done by earthmoving equipment. When moving earth masses of more than 1 million cu m, the hydromechanical method is most efficient, and when the volume exceeds 1.5 million cu m, explosive excavation is most efficient.
An open, closed, or mixed drainage network is combined with grading to organize surface runoff of precipitation.
A common engineering preparation measure that is particularly important for urban construction is protection against flooding, which is done by raising the ground level (by filling and aggradation), by building dikes, and by lowering the water level by building reservoirs or creating overflow channels, mainly on small rivers. In practice the measures are used together rather than separately. For example, the filling of areas (as compared to building dikes) ensures access to bodies of water, but it is impossible in built-up areas. When protecting an area against flooding, steps should ordinarily be taken to protect it against a rise in the level of groundwater caused by a rise in the water table in a river or reservoir. Such protection is achieved by installing horizontal shore drainage, a system of vertical drainage wells, or a combination of both. Provision is also made for lowering the groundwater level in areas where a rise is possible, for example, during construction.
A complex but essential type of engineering preparation is the restoration of damaged areas, whose number is increasing constantly as a result of production and urban construction activity. Damaged areas may be restored for housing, industrial, or other construction and for recreation areas (with the creation of bodies of water). Specifically, areas damaged during the extraction of mineral products are restored by filling in gaps with mine rock, stockpiling rock in excavated areas of quarries, and leveling out heaps of stripping debris or mine rock. As a whole, measures for engineering preparation of the sites of populated points are an inseparable part of urban construction.
REFERENCESOsnovy sovetskogo gradostroiteVstva, vol. 3. Moscow, 1967.
SlroiteTnye normy ipravila, part 2, sec. K, ch. 2: “Planirovka i zastroika naselennykh mest: Normy proektirovaniia.” Moscow, 1967.
N. IA. BURLAKOV and I. V. LAZAREVA