The vertical arrangement is an important part of the general layout design of the substation. The main tasks are: transforming the natural terrain of the construction site, and planning the design of the ground elevation of the site in a straight direction. Choose the appropriate site elevation and slope. The modified site can adapt to and meet the substation electrical equipment layout, the construction needs of various structures, facilitate the rapid elimination of ground rain, and meet the electrical production process, transportation roads and underground Pipeline laying requirements, for the construction of the foundation of the building and the buried depth of underground pipelines can make full use of good engineering geology to create favorable conditions, while stressing the earthwork and artificial support, slope protection engineering minimum, filling and balancing the balance. To save investment, speed up the project The purpose of the project construction progress.
Second, the design content
The main design content of the vertical layout has the following aspects:
1) Consider the impact of flood water level or inland water level on the site and the corresponding flood control treatment plan, so that the site is not affected by the flood level or the inland water level.
2) Consider the elevation and slope of the inbound road and the road inside the station to meet the requirements of process layout, transportation and operation and maintenance.
3) According to the natural terrain conditions, determine a reasonable orientation (flat slope, step, hybrid).
4) Determine the reasonable drainage method of the site area, so that the ground rain can be quickly eliminated.
5) Determine the reasonable elevation of the design level of the site area, so that the amount of earth and stone works is the least.
Third, the vertical arrangement
In the vertical layout design, factors such as flood water level, natural topography, process requirements, general layout of the station area, transportation, rainwater discharge, and soil (stone) work volume should be considered. There are generally three vertical arrangements: flat, stepped, and hybrid. The three vertical layouts have their own characteristics:
1) Flat slope vertical arrangement. The transportation links between different sites and the equipment hoisting and maintenance are convenient. This arrangement is most common in flat areas, but in areas with large changes in natural topography, soil (stone), retaining walls, slope protection and land use. Large area.
2) Stepped vertical arrangement. When the natural terrain slope of the station area is 5%-8%, and the original terrain has obvious slope, the vertical arrangement of the station area should adopt a stepped arrangement. The stepped arrangement is conducive to saving the amount of earth (stone) work and the area of ​​the land. However, the retaining wall is required at the junction of the station. The transportation links and pipeline laying conditions are poor, and the lifting and overhaul of the equipment in the power distribution equipment site is inconvenient.
3) Hybrid vertical arrangement. The hybrid arrangement is divided into a flat slope + slope arrangement and a flat slope + step arrangement. The hybrid type can effectively save the amount of earthwork and the area of ​​land used, and the transportation between different sites is convenient, and the hoisting and maintenance of the pipeline laying and distribution equipment are convenient.
The stepped and hybrid vertical arrangement should meet the layout requirements of the process and the construction of the station area, which is convenient for operation, maintenance, installation of various transportation and trenches, and maintain the original terrain as much as possible.
In the plain area, the terrain is relatively flat, and the vertical arrangement generally adopts a flat slope layout. In the mountainous area, the natural topography changes greatly. Considering factors such as soil (stone) side, retaining wall and slope protection engineering, the vertical arrangement can be Consider a stepped or hybrid arrangement.
In the case of large changes in natural topography, the stepped arrangement is more economical than the flat-sloping arrangement of earth (stone).
It should be noted that the stepwise vertical arrangement focuses on the division of the steps and the determination of the step height difference. The division of the steps follows the following principles.
1) According to the production area, it is convenient to produce, transport and pipeline. For substations, it is generally divided into 2-3 steps according to the outdoor power distribution equipment site.
2) The vertical axis of the step is arranged in accordance with the contour line. The connection between the steps should pay attention to whether the geological conditions meet the requirements. For the substation, the incoming and outgoing lines should be respectively located in the same elevation step to meet the electrical installation. And running safely.
3) The number, width and height of the order should be appropriate. In the stepped arrangement, the width and height of the step are important factors in determining the amount of earth and the overall economic benefit of the site. For the determination of the width and height of the step, the method of combining qualitative and quantitative is to balance the balance of the excavation and the minimum amount of earth. To find the height and width of the steps that meet the requirements of specifications and experience, while at the same time balancing the fill and excavation and minimizing the total amount of earth.
The hybrid vertical arrangement can effectively reduce the amount of soil (stone), retaining wall and slope protection in the station area, reduce the land acquisition area outside the station, thereby reducing the project cost, reducing the impact of the station construction on the surrounding environment, and building resource conservation. The type and environment-friendly substation has good economic practice significance.
Fourth, the layout requirements
4.1 General provisions
4.1.1 The design elevation of the station area of ​​the substation shall be determined according to the voltage level of the substation. The flood level is a prerequisite for determining the design elevation of the substation site. 220kV hub substation and substation of 220kV or above voltage level, the site design elevation of the station area should be higher than the flood water level with the frequency of 1% (recurring period, the same below) or the historical highest inland water level; the design elevation of the substation station area of ​​other voltage levels It should be higher than the flood water level with a frequency of 2% or the highest water level in history. When the site design elevation of the station area cannot meet the above requirements, the following three different measures can be taken to distinguish different situations:
1) When measures are taken on the elevation of the site, the design elevation of the site shall not be lower than the flood water level or the highest water level in history.
2) When flood control or flood control measures are taken for the station area, the elevation of flood control or flood control facilities should be higher than the above flood level or the highest level of the highest internal water level of 0.5m.
3) Take reliable measures to ensure that the main equipment base and the indoor floor of the production building are not lower than the above high water level. In substations affected by wind and waves along rivers, rivers, lakes and seas, the elevation of flood control facilities should also consider the high wind speed of 2% and the safety super high of 0.5m.
In the vertical design of the substation, when the station site does not meet the flood water level or the inland water level requirement, the purchased land (stone) square height site plan is generally adopted, or the flood control (canal) plan is modified around the site.
4.1.2 The design elevation of the site in the substation station should be higher or higher than the natural ground outside the station to meet the drainage requirements of the site.
4.1.3 The vertical arrangement of the station area should make rational use of natural topography. According to the process requirements, the general layout pattern of the station area, transportation, rainwater discharge direction, drainage point, earth (stone) balance, etc., the vertical arrangement should be determined according to local conditions. Form, minimize the amount of work for slope land, site leveling (stone), retaining wall and slope protection, and make the drainage path of the site short and smooth.
1) The vertical arrangement of the station area should generally consider the internal and external station (including the pit road, the residual soil of the foundation, the flood control facilities, etc.). Under the premise of comprehensively balancing the earth fill (stone), it is advisable to level the soil in the station area ( Stone) The smallest amount.
2) The vertical arrangement of substations in mountainous and hilly areas should make rational use of the terrain on the premise of meeting the requirements of the process, and adopt a stepped arrangement as appropriate to avoid deep excavation and ensure the stability of the slope.
4.1.4 Substation located in the expansive soil area, the vertical design should maintain natural topography to avoid large excavation and filling; the substation located in the mountain front slope zone of the collapsible loess area should be arranged along the natural contour line as much as possible. The thickness of the fill should not be too large.
4.1.5 The vertical arrangement of the expansion and reconstruction substation shall be coordinated with the vertical arrangement of the original station area and make full use of the original drainage facilities.
4.2 Determination of design elevation
4.2.1 The indoor floor of the substation building shall be comprehensively determined according to the vertical arrangement form of the station area, the process requirements, the site drainage and the soil quality conditions.
1) The indoor floor of the building should be no less than 0.3m from the outdoor floor.
2) In the collapsible loess area, the indoor floor of the multi-storey building should be 0.45m higher than the outdoor floor.
4.2.2 Site design The comprehensive slope should be comprehensively determined according to factors such as natural topography, process layout (mainly in the form of outdoor power distribution devices), soil conditions, drainage methods and road longitudinal slopes, preferably 0.5% to 2%, with reliable drainage measures. It may be less than 0.5% but should be greater than 0.3%. The local maximum slope should not be greater than 6%, and anti-scouring measures should be taken when necessary. The slope of the site design of the outdoor power distribution device parallel to the busbar should not be greater than 1%.
4.2.3 The elevation of the road junction point inside and outside the station should be determined to facilitate driving and drainage. The elevation of the pavement at the entrance and exit of the station area should be higher than the elevation of the pavement outside the station. Otherwise, there should be measures to prevent rainwater from flowing into the station.
4. 3 slopes and retaining walls
4.3.1 When the natural terrain slope of the station area is above 5%~8%, and the original terrain has obvious slope, the vertical arrangement of the station area should adopt a stepped arrangement (the large substation site area is large, the lower limit should be taken, otherwise Upper limit).
4.3.2 The division of the steps shall meet the layout requirements of the process and the building (structure), which is convenient for operation, maintenance, equipment transportation and pipe trenching, and maintain the original terrain as much as possible. The long sides of the steps should be arranged parallel to the natural contours, and the number of steps should be reduced.
4.3.3 The slope of the slope should be determined according to the natural stable inclination angle of the rock and soil. The slope surface should be treated as a protective surface, and the slope should be provided with drainage ditch; the back wall of the retaining wall should be well protected against drainage, and should be set at the water inlet side of the drain hole. Filter layer or filter bag. The height of the retaining wall located in the expansive soil area should not exceed 3m.
4.3.4 The distance from the top of the slope to the building (construction) should consider the influence of the foundation side pressure of the building (structure) on the slope and retaining wall. For a building located on the top of a stable soil slope, when the length of the base bottom surface perpendicular to the top line of the slope is less than or equal to 3 m, the horizontal distance a from the outer edge line of the base bottom to the top of the slope (see Figure 4) shall be consistent with The requirements of 4−1) and (4 −2), but not less than 2.5m.
When the horizontal distance from the outer edge line to the top of the base does not meet the requirements of equations (4−1) and (4−2), the basis can be determined according to the basic pressure of the base according to the provisions of GB 50007 “Code for Design of Building Foundationsâ€. The distance from the edge of the top of the slope and the depth of the foundation. When the slope angle is greater than 45° and the slope height is greater than 8m, the slope stability shall be checked according to the provisions in GB 50007 “Code for Design of Building Foundationsâ€. The distance from the top of the slope to the building (construction) should consider the requirements of process layout, transportation, and cable shaft. The minimum width shall meet the stability requirements of the building's scattered water, excavation basement to slope or retaining wall, and the arrangement of the drainage open channel, and shall not be less than 2m. The net distance between the outer wall of the building (construction) and the supporting structure of the foot in the expansive soil area shall not be less than 3m. The horizontal distance from the outer edge line of the bottom wall of the fill area to the top line of the slope can be 1.5m~2m.
4.3.5 between the slope foot and the rain water ditch, for sand, loess, easily weathered rock or other bad soil, a clear trench platform should be set, the width should be 0.4m~1.0m, if the slope height is less than 1m or For reinforcement, there is no platform.
4.3.6 The allowable value of site excavation slope rate shall be determined according to the geological conditions and design slope height described in the engineering geological survey report.
1) The allowable value of the slope rate of the excavation slope should be determined according to the experience and according to the principle of engineering analogy and the slope value of the existing stable slope. When there is no experience, the soil is evenly homogeneous, the groundwater is poor, there are no bad geological phenomena and the geological environment conditions are simple, it can be determined by the following table (Table 4.3.6−1).
2) Under the condition that the slope maintains overall stability, the allowable slope rate of rock slope excavation should be determined according to the actual experience and according to the principle of engineering analogy and the slope value of the existing stable slope. For rock slopes without a cambered weak structural surface, the allowable slope rate can be determined by the following table (Table 4.3.6−1).
4.3.7 The allowable value of the slope of the compacted fill in the filling area shall be determined according to the thickness, the nature of the packing and other factors, combined with the regional experience, as determined by the values ​​in the table below.
4.3.8 The allowable slope value of the following slopes shall be determined by stability analysis calculation:
1) The slope with a slope height exceeding the range of Table 4.3.6−1 and Table 4.3.6−2.
2) A softer slope.
3) A slope with a large load near the edge of the top of the slope.
4) The groundwater is relatively developed or has a rocky slope with a softened structural surface.
5) Slopes with poor geological conditions under the slope.
4.3.9 When there are accumulated wetlands, groundwater seepage or groundwater outcrops on the surface of the slope, corresponding drainage measures should be set according to the actual situation.
4.4 Site drainage
4.4.1 The drainage of the site should be based on the terrain of the station area, the rainfall of the area, the type of soil, the vertical direction of the station and the layout of the road, and the drainage method should be reasonably selected. It is advisable to use natural ground seepage drainage, rainwater open ditch, dark ditch (pipe) or mixed drainage. the way.
4.4.2 The drainage of the outdoor power distribution equipment should be unblocked. For the rainwater intercepted by the cable trenches and patrol trails above the ground, it is advisable to use the drainage aqueduct or set the gully and lay the rainwater channel to eliminate it.
4.4.3 When draining rainwater gully, the drainage ditch should be arranged along the road, and the cross should be reduced. When it is necessary to cross, it should be orthogonal. The cross angle should not be less than 45° when oblique. Minggou should be used as a face treatment. The section and form of the open trench should be determined according to the hydraulic calculation. The starting point of the open trench should not be less than 0.2m, and the longitudinal slope of the open trench should be consistent with the longitudinal slope of the road and should not be less than 0.3%, and the collapsible loess area should not be less than 0.5%. When the longitudinal slope of the open channel is large, a drop or rapid flow trough should be set, and its position should not be set at the bend of the open ditch.
4.4.4 When using the rainwater submerged drainage system, the gully should be located in the concentrated area of ​​the catchment. The form, quantity and arrangement of the gully should be based on the flow within the catchment area, the discharge capacity of the gully, the longitudinal slope of the road, and the pavement. Factors such as the type are determined. The distance between the gullies should be 20m~50m. When the longitudinal slope of the road is greater than 2%, the distance between the gullies can be greater than 50m. When the intersection is the lowest elevation, the gully should be added.
4.4.5 When partial drainage is used, only sufficient drainage holes should be left in the lower part of the drainage side wall, and the drainage hole should be provided with a protective net. In the rainy area, there should be proper drainage and anti-scouring on the outside of the station with the drainage hole. facility.
4.4.6 The retaining wall or slope top of the mountain substation shall be provided with intercepting ditch or flood ditches as required (see the figure below). The distance from the intercepting ditch to the top of the slope should not be less than 2m. When the soil is good, the slope is low or the intercepting ditch is strengthened, the distance can be appropriately reduced. The intercepting ditch should not cross the station area.
4.4.7 When there is a catchment area in the excavation area, a water intercepting ditch should be provided at the foot of the slope.
4.4.8 Rainwater in the station area should be discharged by self-flow. When unconditional self-flow, the rainwater pump room should be equipped with strong drainage.
4.5 soil (stone) side project
4.5.1 The soil (stone) volume of the station area should reach the basic balance of the total amount of excavation and filling. The contents include: the site leveling of the station area, the foundation of the building (structure) and the residual soil of the underground facilities, the road inside and outside the station, The amount of earth (stone) work such as flood control facilities. When the inbound road is long, you should first consider your own earthwork balance and try to avoid and reduce the secondary reversal of the earth. When the soil (stone) quantity of the station area is not balanced by the conditions, a reasonable spoil or borrowing site should be selected, and the possibility of reclaiming the land should be considered. For substations in mountainous and hilly areas, the proportion of earth and stone should be separately listed and listed when earth and stone are present.
4.5.2 The surface soil treatment of the site in the station area shall meet the following requirements:
1) The surface soil of the station area is cultivated soil or silt. When the organic matter content is more than 5%, it must be excavated before backfilling. The surface soil of this layer should be piled up in a centralized manner, covering the surface of the station area for greening or reclaiming land, which can be included in the amount of earthwork.
2) When the soil quality of the surface of the filling area is good and the organic matter content is less than 5%, the surface soil should be compacted (夯) and then backfilled.
4.5.3 The quality of the leveling filler shall comply with the relevant specifications. The filling shall be layered and compacted, the layer thickness shall be about 300mm, and the field level compaction coefficient shall not be less than 0.94. For collapsible loess sites, the site should be leveled within 6m around the building. When filling, the layer should be layered (or pressed), the compaction coefficient should not be less than 0.95; when it is cut, the self-weight collapsible loess For the site, the surface 夯 (or pressure) should be set to 150mm ~ 300mm thick lime soil surface layer, the compaction coefficient should not be less than 0.95.
4.5.4 Site leveling area When the retaining wall is used as the wall foundation, the fence of the station area shall be bounded; when the slope is set outside the station, it shall be leveled to the top of the excavation slope and the foot of the fill slope.
4.5.5 The earth (stone) square excavation should consider the loose coefficient, and the looseness coefficient should be determined by field test.
4.5.6 Earthwork fill should consider the compression coefficient of the ground surface of the site after compaction, the calculated thickness is generally 300mm ~ 500mm, the compression factor should be determined by field test.
4.5.7 In the collapsible loess area, the filling should consider the compression coefficient after compaction of loess, which can be determined according to field test or engineering experience.
4.6 pit stop road
The natural topography of the site where the site is located has a great impact on the construction of the inbound road. The substation's inbound road should meet the requirements of slope and large-turn transportation turning radius. The minimum turning radius of the general area is not less than 15m, and the mountainous hill is 30m. The micro hill is 100m. The maximum limit longitudinal slope should be able to meet the climbing requirements for large-scale equipment transportation, generally 6%. In the mountain and heavy hill areas, the maximum longitudinal slope of the four-level factory road can be increased by 1%, and the maximum allowable longitudinal slope is 10%.
In the plain area, the impact of the inbound road on the design elevation of the station area is weak, the longitudinal slope of the inbound road is generally flat; the mountainous and hilly terrain has a greater impact, and the turning radius and longitudinal slope of the inbound road directly affect the progress. The length of the station road, the final location of the station site, and the design elevation of the station site. If the terrain of the site is changed greatly and the pre-requisite factors for the flood level are excluded, the location of the substation site and the design elevation of the site site may depend on the inbound road, taking into account the maximum allowable longitudinal slope of the inbound road. Factor, substation will therefore be unable to determine the site design elevation according to the principle of basic balance of digging and filling.
In the actual project, if the substation can only determine the design elevation of the site area according to the maximum allowable longitudinal slope, it may lead to corresponding increase in the total soil (stone) side, retaining wall and slope protection engineering area and land acquisition area of ​​the substation. As a result, the proportion of civil construction costs of the entire substation is relatively large, and the project investment is increased. In mountainous and hilly areas with complex terrain, the site selection should fully consider the allowable slope of the inbound roads, and avoid the subversion of the allowed slope problems due to the pitted roads. The site situation has caused unnecessary waste of manpower and material resources.
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