Azizdzhan fazilovich babadjanov
§2.5. Technogenic factors contributing to the formation and development of the process of flooding and drainage
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§2.5. Technogenic factors contributing to the formation and development of the process of flooding and drainageResearch on man-made factors contributing to the formation and development of the process of flooding were studied mainly in the territory of the city of Karshi and adjacent territories - this is the process of raising the level of groundwater above a certain critical position (1.0 - 1.5 m), as well as the formation of perched water along irrigation canals, industrial and civil structures or the emergence of a man-made aquifer, leading to a deterioration in the engineering and geological conditions of construction areas, irrigated and irrigated areas. Basically, the depth of the critical level is determined according to regulatory documents (SHNK 1.02.09-15, etc.), depending on the depth and type of foundations, the structures of the underground part of the structures, the properties of the foundation soils in the active aeration zone, the height of the capillary border. Critical depths for urbanized areas are assumed to be 3.0 - 4.0 m. The presence of poorly permeable rocks in the aeration zone, the close location of regional or local aquicludes, poor drainage of the territory, shallow groundwater level and other parameters determine the development of the flooding process. In addition, the development of the flooding process is associated with the emergence of new sources of groundwater supply, violation of the conditions for the natural discharge of groundwater. Land flooding is expressed in an increase in the level of groundwater to a critical level: groundwater appears in the basements of buildings and structures. The processes of flooding of the central, southwestern and southern parts of the city of Karshi are manifested in the territory of the military camp, the regional trauma hospital, the village. Shibaeva and pos. Machine operators, in the area of the airport and railway station, where the groundwater level lies at depths of 1.0 to 2.0 m, on average - 1.5 m in the non-vegetation period, and in the vegetation level is 0.7-1.0 m , which creates an unfavorable environment on 15% of the city area. On the territory of the city of Karshi, technogenic factors contributing to the formation and development of the flooding process are the following: 1 - technogenic leaks from water-bearing communications (underground water supply, heat supply, sewerage system, facilities that intensively use drinking or industrial water), ponds, irrigation canals, settling tanks , reservoirs due to poor organization of surface runoff in built-up and developed areas; 2 - barrage (occurs as a result of complete or partial blocking of the aquifer by an underground structure) effect during the construction of buried underground structures (underpasses, basements, underground garages, etc.) and multi-storey administrative and residential buildings, backfilling of ravines and low areas with poor filtering material or technogenic soils, arrangement of pile fields during construction, moisture condensation under the foundations of buildings and structures; 3 - engineering and planning work related to construction and hydro-reclamation measures, and blind concreting of the sides of canals and rivers that serve as natural drains. The main technogenic factors influencing the groundwater regime in the city of Karshi are: water supply to irrigated fields, infiltration of surface water from main canals, ditches , collector-drainage runoff, withdrawal of groundwater for various purposes. The consequences of flooding are predetermined by the engineering and geological conditions of the city of Karshi and adjacent territories. Engineering-geological conditions of the area are characterized in detail by E.V. Mavlyanov, K.P. Pulatov, Yu. Irgashev and others [54; With. 50-57, 72; 95-p.] on the basis of complex studies when surveying the study area at a scale of 1:50000. According to the results of the analysis of the dissertator's previous and personal studies, the territory of the study area is represented by alluvial and proluvial plains. The alluvial plain is confined to the first and second floodplain terraces and is traced in a narrow strip along the Kashkadarya riverbed, reaches a width of 0.5 km near the village of Hilal and then gradually expands to 40 km. The alluvial-proluvial plain is confined to the third terrace above the floodplain of the Kashkadarya River and can be traced along the periphery of the alluvial plain. Absolute marks range from 400 to 280 m, the general slope is to the northwest. The surface is composed of alluvial loams, sandy loams and sands of the Amudarya complex, and alluvial-proluvial sandy rocks of the Sukaita complex [57;278-p.]. The area of predominant development of alluvial-deltaic loamy-sandy deposits of the Amudarya complex occupies a flat plain of the modern delta of the Kashkadarya River. The absolute marks of the surface are 400–230 m, the general slope of the surface is from east to west and northwest. The surface is composed of alluvial-delta deposits, represented from the surface by intercalation of dense loam and brownish-gray sandy loam, 4–6 m thick. Below, they are represented by inequigranular sands containing a large amount of gravel and, rarely, pebbles. The thickness of inequigranular sands reaches 20–35 m. The total thickness of the alluvial-delta deposits of the Amudarya Formation is 20–40 m. The alluvial deposits of the Amudarya complex are underlain by alluvial-proluvial loamy-sandy rocks of the Sukaita complex in the central and western parts of the study area, and in the northwestern part by the Guzar Formation of the Upper Neogene. According to the granulometric composition, alluvial loams are characterized by a high content of silt particles. Filtration coefficients of loess-like sandy loams in the aeration zone, according to experimental water pouring into pits, range from 0.32 to 1.8 m/day, loam - from 0.17 to 0.36 m/day, sand - from 3.6 to 11.75 m/day. The coefficients of relative subsidence of loess-like sandy loams and loams range from 0 to 0.006 and are considered practically not subsidence. The territory of predominant development of the proluvial loess of the Karnab complex on sandy-clay deposits of the Upper Neogene occupies the eastern part of the described area. The absolute marks are 460–350 m with a general slope of the surface to the northwest and west. This region is incised by large erosional hollows running in the northwestern and western directions. Relative deepenings - 8–16 m. In the northern part of the region, at the latitude of the villages Mulaly - Karabair, the width of the proluvial plain is the greatest, and near the village of Khanabad it narrows significantly. The rocks that make up the described plain are characterized by the predominant development of homogeneous silty sandy loams and loams, the granulometric composition, structure and color of which are very uniform. The granulometric composition of sandy loams is dominated by particles with a size of 0.05–0.01 mm - they make up 5%. A well in the area of the Mulla-Kuvat village reveals a homogeneous layer of silty loam to a depth of 130.0 m, the color of which is light gray with a yellowish tint to a depth of 28.0 m, below it turns into dark gray and yellowish gray. On the left bank of the Kashkadarya River, the structure of the proluvial plain differs in places by alternating loam, sandy loam and sand. Such a structure is typical for areas where ancient irrigation canals passed. The granulometric composition of the loess rocks of the Karnab complex, which make up the proluvial plains, is characterized by the uniformity of silty fractions from 34 to 95%, on average from 64 to 78%. The content of the clay fraction varies from 3 to 18%, more often from 64 to 78%. The content of the clay fraction is from 6 to 58%, on average - from 15 to 36%. The carbonate content and the content of easily soluble salts in the proluvial loess rocks of the Karnab complex range from 18 to 47%, averaging 26.8%, and at a depth of 4.0 m it is 71.5%. The mineralogical composition of the described deposits is characterized by the predominance of light fraction minerals: quartz, feldspar, mica group (muscovite, biotite) - from 4 to 18.5%, on average - 8.8%. The content of sand in soils prevails over the content of sandy loam and reaches 18.5%. The heavy fraction minerals are dominated by hornblende, epidote, limonite-hematite, and magnetite-ilmenite. Content of hornblende in proluvial loess rocks from 2.0 to 22.2%, on average - 10.2%; limonite-hematite - from 14.1 to 50.5%, on average - 18.2%; magnetite-ilmenite - from 4 to 9.9%, on average - 6.5%. In general, the mineralogical composition of these deposits does not change in depth and area. The degree of salinity of the proluvial loess is less than 0.3%; in the presence of chlorine, from 0.01 to 0.1%; in the presence of a dense residue, 0.3–1; in the presence of chlorine, less than 0.01%. From a depth of 1–2 m and below, they pass into medium and highly saline. The nature of salinity is sulfate with a high content of chlorides and calcium. The change in the moisture content of rocks, other things being equal, depends on the granulometric composition. The more clay fractions, the more moisture. Thus, the moisture content of loams varies from 2.3 to 32.8%, on average - 12%; sandy loam - 1.3–28.1%, on average - 10.5%; sands - from 4.3 to 11.3%, on average - 8.05%. An analysis of the moisture content of the soils of the described plain leads to the conclusion that with the transition to more coarse-grained soils, the natural moisture content decreases. The upper limit of plasticity of proluvial loess soils varies in the range of 1.6–38%, the lower limit is 1.3–40%. Plasticity - from 1 to 24%. The maximum molecular moisture capacity in the described deposits varies from 8 to 19%. In sandy loams, it ranges from 8 to 19%, on average - 12.5%, in loams - from 15 to 19%, on average - 16.6%. The density of soil particles of various components of the proluvial loess rocks of the Karnab complex is 2.68–2.78 t/m 3 . Soil density at natural moisture ranges from 1.35 to 2.04 g/cm 3 , in a dry state - from 1.28 to 1.79 g/cm 3 . The porosity of proluvial loess soils varies from 32 to 55%. The change in soil porosity with depth depends on the genesis, age and lithological composition of the rocks. Changes in porosity in the vertical section of rocks are uneven. The rate and nature of the soaking of the proluvial loess rocks of the Karnabian complex varies from 44 to 15 minutes. The nature of soaking is lumpy. The process of soaking occurs through the disintegration of soils into macroaggregates, which form a dusty-cloddy mass. The value of the filtration coefficient of rocks in the aeration zone ranges from 0.5 to 1.5 m/day. Of the modern geological and engineering-geological processes in the city of Karshi and adjacent areas, seismicity, erosion, waterlogging, flooding, soil salinity, subsidence in loess-like soils, etc. are developing. [four; With. 233-235, 5;208-s.] . According to the intensity of seismicity and in accordance with Appendix 1. KM K 2.01.03-96, the study 5 area belongs to the area with an earthquake intensity of 7 points with a frequency of 1 time in 1000 years. Erosion phenomena are fixed in the form of washing away of the banks and the channel by water flows. Of the erosion processes in this area, bottom and lateral erosion are noted, as a result of which the banks of the Kashkadarya River and irrigation canals are processed. Bogging occurs when territories are flooded, when an increase in the level of groundwater leads to the formation and long-term existence of a free water surface in a certain area. Swamping processes are observed only in the southwestern part of the territory (settlement Miriman) behind the Karshi main canal, from the northern and western outskirts of the locomotive depot to the railway station and appear during spring precipitation. When groundwater occurs close to the surface (less than 1–3 m), intense soil salinization occurs due to evaporation. As a result of irrigation and infiltration, saline areas are washed away from canals and collectors. Polluted waters mix with groundwater, resulting in an increase in mineralization and the concentration of sulfates in groundwater. Such mismanagement leads to salinization of soils, the value of dry residue according to the chemical analysis of water extract varies from 650.0 to 7024.0 mg/kg. The content of SO 4 - 2 ions varies from 650 to 14560.0 mg / kg, HCO 3 - from 205.7 to 8376.1 mg/kg, C l - ions - from 84.0 to 2100.0 mg/kg. According to the content of SO 4 -2 ions , soils are rated mainly as highly aggressive to concrete on sulfate-resistant cements according to GOST 22266-2013, and according to the content of C l ‑ions and SO 4 -2 ions - as highly aggressive to reinforced concrete structures . The corrosive aggressiveness of soils in relation to carbon steel is generally high, in isolated cases - medium and low . Loess-like clayey soils that make up the study area have subsidence properties, which, as a rule, are developed in the upper part of the section above the groundwater level. The type of soil conditions for subsidence, according to KMK 2.02.01-98 6, is I (first), and in the area where groundwater occurs at depths of more than 5.0 m - II (second). According to the results of compression studies, medium subsidence territories with a subsidence value of 0.5 to 1.0 m are noted in the described area. Such territories are found in the watershed areas of hills and a flat proluvial plain, where the thickness of the subsidence layer is 18–35 m. Low subsidence territories include the central part of the flat proluvial plain, as well as predominantly elevated areas and gentle slopes of the proluvial plains, where the subsidence thickness is 8–20 m, the subsidence value is from 0.015 to 0.5 m. from 0.05 to 0.15 m are the western and southwestern parts of the proluvial flat plain and the slopes of large valley-like hollows, where the groundwater level lies at shallow depths - within 8–15 m. The southern, southwestern and western parts of the described The district belongs to a practically non-subsidence territory, where the groundwater level lies at a depth of 1–5 m [41; With. 126-130]. Technogenic formations were unearthed in the study area - redeposited bulk sandy-loamy soils with a high content of household and construction debris, as well as irrigation loams gray, silty, humified, heterogeneous in density and deposits of cemeteries. The thickness of technogenic formations is from 0.2 to 3.0 m, and at some points - 7.0–8.0 m. Based on the geological and geomorphological structure and hydrogeological conditions, and also , according to GOST 25100-2011 7, the soils developed in the study area belong to the dispersed class, in which two groups are distinguished: coherent sedimentary and incoherent sedimentary. Cohesive sedimentary soils are polymineral in type and clayey in appearance. According to the quantitative indicators of the material composition, properties and structure, the exposed stratum of clayey soils is represented by sandy loams, loams and, less often, clays. From the surface, they are modified into a soil-vegetative layer - sandy loam and loam with the content of plant roots 0.2–0.5 m thick. Non-cohesive sedimentary soils are polymineral in type, sandy in appearance. Sandy soils are represented by different-grained sands - from silty to gravelly. Based on the lithological structure and physical and mechanical properties of soils, six engineering-geological layers (IGL) are distinguished in the 0-26 meter thickness (Fig. 2.6). Figure. 2.6 . _ Identification of engineering-geological layers by section First engineering-geological layer ( IG S-1) includes technogenic soils, redeposited sandy loams and loams with the inclusion of household and construction debris, irrigation loams and sandy loams, silty, humified, heterogeneous in composition and density, from low-moisture to wet, from hard to soft-plastic. The soils occur in the upper part of the section, above the groundwater level. Soils are highly porous, extreme and standard values of indicators of physical and mechanical properties of soils IG C - 1 are given in table. 2. Table 2. Extreme values of soil characteristics IG S-1
The second engineering-geological layer (IG S - 2) combines sandy loams and loams pale, grayish-brown, light brown and brown, of natural composition, loess-like, macroporous, with the inclusion of carbonate nodules, with veinlets of gypsum up to 10%, with a single inclusion of pebbles , with traces of ferruginization, low-moisture and wet, from hard to plastic, subsidence under additional loads and non-subsidence under natural pressure. The soils of IG S -2 lie in the upper part of the section above the groundwater level . In table. 3 shows all the extreme and standard values of the indicators of the physical and mechanical properties of soils IG S -2. Table 3 Extreme and standard values of soil characteristics IG S - 2
The third engineering-geological layer (IGS - 3) combines sandy loam and loam with the inclusion of carbonate nodules and gypsum up to 10%. Water-saturated, from solid to fluid, lying below the groundwater level and in the zone of variable moisture, non-subsidence. According to static sounding data, weak soils of IG S -3 are characterized by cone sinking resistance Р q c = 6.7-19.0 kgf/cm² (0.67-1.9 MPa). The standard value of P q c \u003d 13 kgf / cm² (1.3 MPa). In table. 4 shows all the extreme and standard values of the indicators of the physical and mechanical properties of soils IG S - 3. Table 4 Extreme and standard values of soil characteristics IG S - 3
The fourth engineering-geological layer (IG S - 4) includes heavy loams and loess-like clays, macroporous, with inclusions of carbonate concretions, with veins of gypsum up to 10%, low-moisture and moist, from hard to hard-plastic, subsidence under additional loads and non-subsidence under natural pressure. In table. 5 shows all the extreme and standard values of the physical and mechanical properties of soils IG S - 4. Table 5 Extreme and standard values of soil characteristics IG S - 4
The fifth engineering-geological layer (IGS - 5) combines heavy loams and loess-like clays, low-porosity with the inclusion of carbonate nodules and gypsum up to 10%, water-saturated, from solid to fluid-plastic, occurring below the groundwater level and in the zone of variable moisture, non-subsidence. In table. 6. All extreme and normative values of indicators of physical and mechanical properties of soils IG S - 5 are given. The sixth engineering-geological element (IGS- 6 ) combines gray and yellowish-gray sands, from silty to gravelly, in places with the inclusion of small pebbles, dense and medium in density, from low-moisture to water-saturated. The exposed thickness of the sands is 0.4–5.8 m, and in some workings it is 6.1–9.0 m. Table 6
The granulometric composition is dominated by sands of medium size with a fraction content of more than 0.25 mm - 51.1–68.2% and silty with a content of fractions larger than 0.1 mm - 33.6–68.4%. The main indicators characterizing the physical and mechanical properties of sandy soils IG C -6 are given in Table. 2.8. Table 2.8 Extreme values of soil characteristics IG S - 6
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