An extended foundation and construction method for a wind power tower in collapsible loess sites

Abstract

The present invention belongs to the technical field of foundation, and in particular, relates to an extended foundation for a wind turbine tower in a collapsible loess site and a construction method. The present invention is composed of a composite foundation cushion layer arranged on the upper surface of the bottom of a foundation pit, a wind turbine tower foundation connected to the composite foundation cushion layer, and a first backfill soil, hidden scattered water, a second backfill soil and a surface covering soil layer arranged in sequence from bottom to top around the wind turbine tower foundation. The present invention performs multiple waterproofing protections on the foundation in a large range, reduces the possibility of foundation immersion, reduces resource consumption, and reduces the investment in the foundation of the wind turbine tower. The present invention eliminates the factors of collapsibility through multiple waterproofing, and is safe and economical. The present invention restores the surface and protects the environment. The present invention uses local materials, makes full use of materials, and saves resources. The present invention destroys the original structure of loess through compaction piles arranged in a triangular shape at the bottom of the foundation pit, eliminates or partially eliminates the collapsibility of the foundation, and improves the bearing capacity of the foundation.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation, and in particular relates to an extended foundation for a wind power tower in a collapsible loess site and a construction method thereof. Background Art

[0002] When collapsible loess is soaked in water under a certain pressure, the soil structure is quickly destroyed and significant and uneven additional subsidence occurs. Loess that collapses when soaked in water under the pressure of its own weight is called self-weight collapsible loess. The tower of a wind turbine built in such a collapsible loess area should implement the principles of safety, applicability, economic rationality, environmental protection, and resource conservation, carry out foundation treatment, adopt appropriate foundation forms and waterproofing measures, and take into account ecological and environmental protection. This is a difficult problem to solve.

[0003] The foundation of wind turbine towers generally adopts reinforced concrete extended foundation or pile foundation according to the geological conditions. Initial construction experience has been gained by building wind farms in collapsible loess sites. However, the foundation treatment and foundation structure of wind turbine towers are not yet mature. In collapsible loess sites, especially when the self-weight collapsible soil layer is thick, pile foundations are generally used to penetrate the collapsible loess layer. The foundation piles must not only bear the load of the upper wind turbine tower, but also consider the downward tension caused by the negative friction resistance of the loess that may collapse due to its own weight. The piles are long, the construction materials are consumed, the economic effect is poor, and the resources are not fully utilized. In order to prevent the adverse effects of the self-weight collapse of the loess foundation caused by the infiltration of surface rainwater on the foundation, a certain range of the surface around the wind turbine tower is set up with concrete or geotextiles and other materials. Plants cannot grow in a considerable range around the wind foundation, affecting ecological protection. Summary of the invention

[0004] The present invention provides an extended foundation for a wind turbine tower in a collapsible loess site and a construction method. One purpose is to provide an extended foundation for a wind turbine tower in a collapsible loess site that can eliminate or partially eliminate the collapsibility and improve the bearing capacity of the foundation; the second purpose is to provide an extended foundation for a wind turbine tower in a collapsible loess site that can effectively reduce the possibility of foundation flooding through waterproofing measures, thereby reducing resource consumption and reducing the investment in the foundation of the wind turbine tower; the third purpose is to provide an extended foundation for a wind turbine tower in a collapsible loess site that can change the existing surface waterproofing method, restore the surface after the foundation construction is completed, adapt to plant growth, and reduce the impact of the wind turbine tower construction on the local fragile ecological environment.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A wind turbine tower extension foundation on a collapsible loess site comprises at least a foundation pit, and also includes a wind turbine tower foundation, a second backfill soil, hidden drainage, a first backfill soil and a composite foundation cushion layer; the composite foundation cushion layer is arranged on the upper surface of the pit bottom; the wind turbine tower foundation is connected to the composite foundation cushion layer; the first backfill soil, hidden drainage and second backfill soil are arranged in sequence from bottom to top around the wind turbine tower foundation; the upper surface of the bottom bearing platform of the wind turbine tower foundation has an outward and downward slope.

[0007] The wind turbine tower foundation is a reinforced concrete integrated structure composed of a short cylinder, a frustum and a small cylinder from bottom to top; the upper surface of the hidden water spill is flush with the bottom edge of the frustum, and a gap is provided between the hidden water spill and the wind turbine tower foundation; a gap is provided between the edge of the short cylinder and the edge of the bottom of the foundation pit.

[0008] The bottom edge of the foundation pit is circular, and the slope ratio of the foundation pit is 1:0.5; the composite foundation cushion layer and the foundation bottom of the generator tower foundation are concentric circles.

[0009] It also includes compaction piles; the compaction piles are placed at the bottom of the foundation pit.

[0010] A plurality of compaction piles are provided, and three adjacent compaction piles are located at the three vertices of an equilateral triangle; the compaction piles are densely arranged at the edge of the foundation pit bottom; the spacing between the compaction piles densely arranged at the edge of the foundation pit bottom is half of the spacing between the compaction piles arranged at the center of the foundation pit bottom; the compaction pile body material is lime soil or cement soil.

[0011] The material used for the composite foundation cushion is lime soil or cement soil, and its compaction coefficient is not less than 0.97; the first backfill soil is lime soil or cement soil, and its compaction coefficient is not less than 0.95; the second backfill soil has a compaction coefficient of not less than 0.95 and a dry density of not less than 18kN / m 3 of plain soil.

[0012] The dark scattered water is cast by C10 plain concrete, and the thickness of the dark scattered water is 90-200mm; expansion joints are arranged at intervals along the dark scattered water, and the upper surface of the dark scattered water has an outward and downward slope.

[0013] The upper surfaces of the first backfill soil and the second backfill soil both have a slope toward the outside of the foundation.

[0014] A surface covering soil layer is laid on the second backfill soil.

[0015] A construction method for an extended foundation of a wind power tower in a collapsible loess site comprises the following steps:

[0016] Step 1: Excavation of foundation pit

[0017] Excavate the foundation pit with a slope ratio of 1:0.5 from the foundation pit to the bottom of the foundation, and preserve the surface soil layer;

[0018] Step 2: Compaction pile construction

[0019] The compaction piles are constructed at the bottom of the foundation pit; the compaction piles are arranged in a triangle at the center of the foundation pit bottom, and are arranged in a ring between the edge of the foundation pit bottom and the compaction piles arranged in a triangle; the spacing between the compaction piles arranged in a ring is half of the spacing between the compaction piles arranged in a triangle;

[0020] Step 3: Layered compaction and laying of composite foundation cushion

[0021] After removing the soil layer of preset thickness from the top of the compaction pile, compact it layer by layer with lime soil or cement soil with a compaction coefficient of not less than 0.97;

[0022] Step 4: Construction of wind turbine tower foundation

[0023] After step 3 is completed, the wind turbine tower foundation is constructed on the composite foundation cushion layer;

[0024] Step 5: First backfill

[0025] After step 4 is completed, the first backfill soil with lime soil or cement soil and a compaction coefficient of not less than 0.95 is backfilled in layers around the wind turbine tower foundation and compacted to the dark water height; the upper surface of the first backfill soil has a slope toward the outside of the foundation;

[0026] Step 6: Construction of hidden water

[0027] After step 5 is completed, dark scattered water is poured on the upper surface of the first backfill soil; the upper surface of the dark scattered water is flush with the bottom edge of the cone of the wind turbine tower foundation and has an outward downward slope; a gap is set between the dark scattered water and the wind turbine tower foundation, and expansion joints are set at intervals along the dark scattered water; the gap and expansion joint are filled with caulking agent;

[0028] Step 7: Second backfill

[0029] After step 6 is completed, the second backfill soil is compacted layer by layer from the top of the hidden water to the position 0.8m to 1.0m from the top of the foundation pit; and the top surface of the compacted soil layer has a slope toward the outside of the foundation;

[0030] Step 8: Backfilling of topsoil

[0031] After step seven is completed, the surface soil preserved during excavation is used to backfill above the compacted second backfill soil to restore the natural surface and revegetate.

[0032] Beneficial effects:

[0033] 1. The present invention simultaneously adopts foundation treatment measures and waterproof measures. The rammed soil below the surface soil is used as the first waterproof and drainage measure, and the outward and downward slope of the upper surface of the wind turbine tower foundation pedestal is used in combination with hidden water dispersion as the second waterproof and drainage measure. The backfill of ash soil or cement soil around the wind turbine tower foundation is used as the third waterproof measure. The ash soil or cement soil cushion layer under the wind turbine tower foundation and on the top of the compaction pile is used as the fourth waterproof measure, and the compaction piles densely arranged around it serve as the fifth waterproof measure. Multi-layer waterproof protection is performed on the foundation over a large range, which reduces the possibility of foundation flooding, reduces resource consumption, and reduces the investment in the foundation of the wind turbine tower. The present invention eliminates subsidence through multi-layer waterproofing, which is safe and economical.

[0034] 2. The present invention restores the ground surface and protects the environment. The present invention adopts a waterproofing method combining the wind turbine tower foundation and dark scattered water, which changes the existing method of waterproofing the ground surface. After the foundation construction is completed, the surface soil is used to restore the ground surface to adapt to plant growth and reduce the impact of wind turbine tower construction on the fragile ecological environment.

[0035] 3. The present invention uses local materials, fully utilizes materials, and saves resources. The present invention utilizes the outwardly inclined shape of the wind turbine tower foundation for waterproofing and drainage. Creatively uses hidden scattered water to receive drainage from the top surface of the wind turbine tower foundation. The existing foundation is used as the rammed soil with a counterweight setting, which has a certain waterproof property, and the excavated soil from the foundation pit is used as the source of the compacted pile, plain soil and gray soil rammed soil waterproofing material. The surface soil preserved during excavation is also used as the material for restoring the surface, so as to facilitate vegetation reconstruction.

[0036] 4. The present invention destroys the original structure of loess through compaction piles arranged in a triangular shape at the bottom of the foundation pit, eliminates or partially eliminates the collapsibility of the foundation, and improves the bearing capacity of the foundation.

[0037] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 It is a cross-sectional schematic diagram of the present invention;

[0040] Figure 2 It is a schematic plan view of the compaction pile layout of the present invention.

[0041] In the figure: 1- wind turbine tower foundation; 2- surface soil layer; 3- second backfill soil; 4- foundation pit slope; 5- hidden water; 6- first backfill soil; 7- composite foundation cushion layer; 8- asphalt mortar caulking; 9- foundation pit bottom; 10- compaction piles; 11- natural surface. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Embodiment 1:

[0044] according to Figure 1 The wind turbine tower extension foundation for a collapsible loess site shown in the figure comprises at least a foundation pit, and also comprises a wind turbine tower foundation 1, a second backfill soil 3, hidden water dispersion 5, a first backfill soil 6 and a composite foundation cushion layer 7; the composite foundation cushion layer 7 is arranged on the upper surface of a pit bottom 9 of the foundation pit; the wind turbine tower foundation 1 is connected to the composite foundation cushion layer 7; the first backfill soil 6, hidden water dispersion 5 and the second backfill soil 3 are arranged in sequence from bottom to top around the wind turbine tower foundation 1; the upper surface of the bottom bearing platform of the wind turbine tower foundation 1 has an outward and downward slope.

[0045] In actual use, first, the foundation pit is excavated to a preset height, and the composite foundation cushion layer 7 is laid in layers at the bottom of the foundation pit 9 and compacted. Then, the reinforced concrete foundation of the wind turbine tower foundation 1 is constructed. Then, the foundation pit around the wind turbine tower foundation 1 is backfilled with the first backfill soil 6, and the upper surface of the first backfill soil 6 has a slope of 4 to 7% toward the outside of the foundation. Concrete water 5 is poured on the first backfill soil 6, and the dark water 5 can be made of C10 plain concrete with a thickness of 100mm. The dark water 5 is annular. The top surface of the dark water 5 is flush with the upper surface edge of the bottom pedestal of the wind turbine tower foundation 1. The dark water 5 has expansion joints with the wind turbine tower foundation 1 and the dark water lining, and the joints are all caulked with asphalt mastic. Then, the second backfill soil 3 of the foundation pit is backfilled in layers on the dark water 5 and compacted.

[0046] The technical solution of the present invention uses the compacted second backfill soil 3 as the first waterproof and drainage measure, utilizes the outward and downward slope of the upper surface of the foundation of the wind turbine tower foundation 1 in combination with the hidden water dispersion 5 as the second waterproof and drainage measure, uses the first backfill soil 6 backfilled around the wind turbine tower foundation 1 as the third waterproof measure, and the composite foundation cushion layer 7 under the wind turbine tower foundation 1 as the fourth waterproof measure. Multiple waterproof protections are performed on the foundation in a larger range, which reduces the possibility of foundation flooding, reduces resource consumption, and reduces the investment in the foundation of the wind turbine tower.

[0047] The present invention uses hidden scattered water to receive drainage from the top surface of the wind turbine tower foundation 1. In specific applications, the existing foundation is fully utilized as the rammed soil set as the counterweight, which has a certain waterproof property, and the excavated soil from the foundation pit is used as the source of the backfill rammed soil waterproof material, which uses local materials and saves costs.

[0048] Embodiment 2:

[0049] according to Figure 1 The wind turbine tower extension foundation for a collapsible loess site shown in the figure is different from the first embodiment in that: the wind turbine tower foundation 1 is a reinforced concrete integrated structure composed of a short cylinder, a frustum and a small cylinder from bottom to top; the upper surface of the hidden water spill 5 is flush with the bottom edge of the frustum, and a gap is provided between the hidden water spill 5 and the wind turbine tower foundation 1; a gap is provided between the edge of the short cylinder and the edge of the foundation pit bottom 9.

[0050] In actual use, the wind turbine tower foundation 1 adopts this technical solution, which can effectively drain the top surface of the wind turbine tower foundation 1. The frustum edge of the wind turbine tower foundation 1 is flush with the upper surface of the dark water diffuser 5, so that the water of the wind turbine tower foundation 1 is drained to the far end of the wind turbine tower foundation 1, effectively reducing the possibility of waterlogging of the foundation.

[0051] In specific applications, the gap between the hidden diffuser 5 and the wind turbine tower foundation 1 has a width of 10 mm and is caulked with asphalt mortar.

[0052] In specific applications, the cone of the wind turbine tower foundation 1 can be set with a slope of 4 to 7%, and the slope value can also be specifically set as needed to facilitate drainage.

[0053] Embodiment three:

[0054] according to Figure 1 The wind turbine tower extension foundation for a collapsible loess site shown is different from the first embodiment in that: the bottom edge of the foundation pit is circular, and the slope ratio of the foundation pit slope 4 is 1:0.5; the composite foundation cushion layer 7 and the foundation bottom of the generator tower foundation 1 are concentric circles.

[0055] In actual use, the foundation pit, the composite foundation cushion layer 7 and the generator tower foundation 1 adopt this technical solution, so that the generator tower foundation 1 is more stable and the uniform effect of foundation drainage is better guaranteed.

[0056] Embodiment 4:

[0057] according to Figure 1 and Figure 2 The wind turbine tower extension foundation for a collapsible loess site shown is different from the first embodiment in that it also includes compaction piles 10; the compaction piles 10 are placed at the bottom of the foundation pit 9.

[0058] Preferably, a plurality of the compaction piles 10 are arranged, and three adjacent compaction piles 10 are located at the three vertices of an equilateral triangle; the compaction piles 10 are densely arranged at the edge of the foundation pit bottom 9; the spacing between the compaction piles 10 densely arranged at the edge of the foundation pit bottom 9 is half of the spacing between the compaction piles 10 arranged at the center of the foundation pit bottom 9; the pile body material of the compaction piles 10 is lime soil or cement soil.

[0059] In actual use, whether to set up the compaction piles 10 can be determined according to the actual conditions of the collapsible loess layer at the construction site. When the collapsible loess layer is thick, compaction piles 10 can be added, otherwise, compaction piles 10 may not be set up.

[0060] The technical solution of arranging the compaction piles 10 densely around the compaction piles 10 arranged in a triangle at the center of the foundation pit bottom 9 serves as the fifth waterproofing function for the present invention, provides multiple waterproofing protections for the foundation in a larger range, reduces the possibility of foundation flooding, reduces resource consumption, and reduces the investment in the foundation of the wind turbine tower.

[0061] The pile body material of the compaction pile 10 is lime soil or cement soil, and the excavated soil from the foundation pit is used as the source of the waterproof material of the compaction pile 10, so that local materials are used to save resources.

[0062] The present invention destroys the original structure of loess by means of compaction piles 10 arranged in a triangular shape at the bottom of the foundation pit, thereby eliminating or partially eliminating the collapsibility of the foundation and improving the bearing capacity of the foundation.

[0063] Embodiment five:

[0064] according to Figure 1 The wind turbine tower expansion foundation in a collapsible loess site shown in the figure is different from the first embodiment in that: the material used for the composite foundation cushion layer 7 is lime soil or cement soil, and its compaction coefficient is not less than 0.97; the first backfill soil 6 is lime soil or cement soil, and its compaction coefficient is not less than 0.95; the second backfill soil 3 has a compaction coefficient of not less than 0.95 and a dry density of not less than 18kN / m 3 of plain soil.

[0065] In actual use, the excavated soil from the foundation pit is used as the source of the compacted soil material in the composite foundation cushion layer 7, the first backfill soil 6 and the second backfill soil 3. The soil material is taken from the excavated soil from the foundation pit and is locally sourced, which saves resources and reduces the investment in the foundation of the wind turbine tower.

[0066] Embodiment six:

[0067] according to Figure 1 The wind turbine tower extension foundation for a collapsible loess site shown in the figure is different from the first embodiment in that: the dark scattered water 5 is cast with C10 plain concrete, and the thickness of the dark scattered water 5 is 90 to 200 mm; expansion joints are arranged at intervals along the dark scattered water 5 in an annular direction, and the upper surface of the dark scattered water 5 has an outward and downward slope.

[0068] In actual use, the expansion joint has a width of 10 mm and is caulked with asphalt cement. The hidden water dispersion 5 adopts the technical solution to ensure the safety of the present invention under different temperature environments.

[0069] The thickness of the dark diffuser 5 and the outward and downward slope of the upper surface of the dark diffuser 5 can be set according to actual needs.

[0070] The upper surface of the hidden water spill 5 is arranged with an outward downward slope, so that the drainage effect to the far end of the foundation is better.

[0071] Embodiment seven:

[0072] according to Figure 1 The wind turbine tower extension foundation for a collapsible loess site shown is different from the first embodiment in that the upper surfaces of the first backfill soil 6 and the second backfill soil 3 both have a slope toward the outside of the foundation.

[0073] In actual use, the first backfill 6 and the second backfill 3 adopt this technical solution, so that the water on the wind turbine tower foundation 1 can be effectively drained to the far end of the wind turbine tower foundation 1, effectively reducing the possibility of foundation flooding.

[0074] The upper surfaces of the first backfill soil 6 and the second backfill soil 3 can have a slope of 4-7% toward the outside of the foundation, which can also be set according to actual needs.

[0075] Embodiment eight:

[0076] according to Figure 1 The wind power tower extension foundation for a collapsible loess site shown is different from the first embodiment in that a surface covering soil layer 2 is laid on the second backfill soil 3 .

[0077] In actual use, a surface covering layer 2 is laid on the second backfill soil 3. The source of the surface covering layer 2 is the surface soil preserved when the foundation pit is excavated. The natural surface 11 enables local plants to adapt quickly and grow rapidly, which is conducive to vegetation reconstruction and effectively reduces the impact of wind turbine tower construction on the fragile ecological environment.

[0078] Embodiment nine:

[0079] A construction method for an extended foundation of a wind power tower in a collapsible loess site comprises the following steps:

[0080] Step 1: Excavation of foundation pit

[0081] Excavate the foundation pit with a slope ratio of 1:0.5 to the foundation bottom surface, and preserve the surface soil layer;

[0082] Step 2: Compaction pile construction

[0083] The compaction piles 10 are arranged in a triangle at the center of the foundation pit bottom 9, and are arranged in a ring between the edge of the foundation pit bottom 9 and the compaction piles 10 arranged in a triangle. The spacing between the compaction piles 10 arranged in a ring is half of the spacing between the compaction piles 10 arranged in a triangle.

[0084] Step 3: Layered compaction and laying of composite foundation cushion 7

[0085] After removing the soil layer of preset thickness from the top of the compaction pile 10, compact it layer by layer with lime soil or cement soil with a compaction coefficient of not less than 0.97;

[0086] Step 4: Construction of wind turbine tower foundation 1

[0087] After step 3 is completed, the wind turbine tower foundation 1 is constructed on the composite foundation cushion layer 7;

[0088] Step 5: First backfill

[0089] After step 4 is completed, the first backfill soil 6 with lime soil or cement soil and a compaction coefficient of not less than 0.95 is backfilled in layers around the wind turbine tower foundation 1 and compacted to the height of the dark water 5; the upper surface of the first backfill soil 6 has a slope toward the outside of the foundation;

[0090] Step 6: Construction of dark scattered water 5

[0091] After step 5 is completed, a hidden water spill 5 is poured on the upper surface of the first backfill soil 6; the upper surface of the hidden water spill 5 is flush with the bottom edge of the cone of the wind turbine tower foundation 1 and the upper surface of the hidden water spill 5 has an outward downward slope; a gap is provided between the hidden water spill 5 and the wind turbine tower foundation 1, and expansion joints are provided at intervals along the hidden water spill 5; the gap and the expansion joint are filled with a caulking agent;

[0092] Step 7: Second backfill

[0093] After step 6 is completed, the second backfill soil 3 is compacted layer by layer from the top of the hidden water dispersion 5 to the position 0.8m to 1.0m from the top of the foundation pit; and the top surface of the compacted soil layer has a slope toward the outside of the foundation;

[0094] Step 8: Backfilling of topsoil

[0095] After step 7 is completed, the topsoil preserved during excavation is used to backfill above the compacted second backfill soil 3 to restore the natural surface and revegetate.

[0096] In actual use, the expanded foundation of the wind turbine tower in the collapsible loess site obtained by the present invention uses the rammed soil below the surface soil as the first waterproof and drainage measure, uses the outward and downward slope of the upper surface of the cap of the wind turbine tower foundation 1 combined with the hidden scattered water 5 as the second waterproof and drainage measure, and uses the second backfill soil 3 made of ash soil or cement soil as the material around the wind turbine tower foundation 1 as the third waterproof measure. The composite foundation cushion layer 7 under the wind turbine tower foundation 1 and on the top of the compaction pile is used as the fourth waterproof measure, and the compaction piles 10 arranged densely serve as the fifth waterproof. The foundation is protected by multiple waterproof layers in a large range, which reduces the possibility of foundation flooding, reduces resource consumption, and reduces the investment in the foundation of the wind turbine tower. The present invention eliminates wet collapse through multiple waterproof layers, which is safe and economical. The present invention restores the surface and protects the environment. The present invention adopts a waterproofing method combining a wind turbine tower foundation 1 and a hidden water dispersion 5, which changes the existing method of waterproofing on the surface. After the construction of the wind turbine tower foundation 1 is completed, the surface soil is used to restore the surface to adapt to plant growth and reduce the impact of wind turbine tower construction on the fragile ecological environment. The present invention uses local materials, makes full use of materials, and saves resources. The present invention uses the common outward-inclined shape of the upper part of the foundation for waterproofing and drainage. The hidden water dispersion 5 is creatively used to receive drainage from the top surface of the wind turbine tower foundation 1. The existing foundation is used as the rammed soil set as the counterweight, and the excavated soil of the foundation pit is used as the source of the compaction pile, plain soil and gray soil compaction soil waterproof material. The surface soil preserved during excavation is also used as the material for restoring the surface, so as to facilitate vegetation reconstruction. The present invention destroys the original structure of loess through the compaction piles arranged in a triangular shape at the bottom of the foundation pit, eliminates or partially eliminates the collapsibility of the foundation, and improves the bearing capacity of the foundation.

[0097] In specific applications, the excavated foundation pit bottom 9 is circular, which is more convenient for subsequent construction.

[0098] Embodiment ten:

[0099] A construction method for extended foundation of wind power tower in collapsible loess site

[0100] First, the foundation pit is excavated to a preset height. When the foundation pit is excavated, a soil layer with a thickness of about 1m on the top surface of the foundation pit is preserved. The bottom edge of the foundation pit is circular, and the slope of the foundation pit is 1:0.5. Then, the lime soil compaction pile 10 is constructed by the pipe sinking compaction method. The pile body material of the compaction pile 10 is lime soil or cement soil. The compaction piles 10 are arranged in a triangular shape at the bottom of the foundation pit. Three compaction pile rings are arranged between the compaction piles 10 arranged in a triangle at the bottom of the foundation pit and along the edge of the bottom of the foundation pit. The spacing between the compaction piles 10 in the compaction pile ring is half of the spacing between the compaction piles in the middle of the foundation pit. At the top of the compaction pile 10, after removing a 500mm thick soil layer, a composite foundation cushion layer 7 is laid. The material used for the composite foundation cushion layer 7 is 500mm thick lime soil or cement soil, and its compaction coefficient is not less than 0.97 and is compacted in layers. After that, reinforced concrete foundation construction is carried out. Then, the first backfill soil 6 of the foundation pit around the wind turbine tower foundation 1 is backfilled. The first backfill soil 6 is backfilled and compacted in layers with lime soil or cement soil to the height of the dark water 5, and the compaction coefficient is not less than 0.95. The upper surface of the first backfill soil 6 has a slope of 5% toward the outside of the foundation. The dark water 5 is poured on the upper surface of the first backfill soil 6; the dark water 5 is made of C10 plain concrete, 100mm thick. The dark water 5 is arranged in a ring shape. The upper surface of the dark water 5 is flush with the bottom edge of the cone of the wind turbine tower foundation 1, and the dark water 5 has a slope of 5% outward and downward, and the gap between the dark water 5 and the wind turbine tower foundation 1 is 10mm wide. A radial expansion joint is set every 6 to 10m along the circumference of the dark water 5, and the width of the joint is 10mm. The expansion joints on the dark water 5, the wind turbine tower foundation 1, and the dark water 5 are all caulked with asphalt mastic. Then the second backfill soil 3 of the foundation pit is backfilled. From the top of the hidden watershed 5 to the position about 0.8m to 1.0m from the top of the foundation pit, the soil is compacted layer by layer, and the compaction coefficient is not less than 0.95, and the dry density is not less than 18kN / m 3 The top surface of the compacted soil layer has a 5% slope toward the outside of the foundation. Finally, above the compacted fill, the surface soil preserved during excavation is used for backfilling to restore the natural surface and revegetate.

[0101] The spacing of the compaction piles 10 is determined by the properties of the collapsible coating and is designed in accordance with the specifications and after pile trials.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0103] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0104] In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0105] In the absence of conflicts, technicians in this field can combine the relevant technical features in the above examples according to actual conditions to achieve corresponding technical effects. The specific combinations are not described here one by one.

[0106] The above are only preferred embodiments of the present invention. The present invention will not be limited to the embodiments shown herein, but should conform to the widest scope consistent with the principles and novel features disclosed herein. Any simple modification, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An extended foundation for a wind power tower in a collapsible loess site, comprising at least a foundation pit, characterized in that: It also includes a wind turbine tower foundation (1), a second backfill soil (3), hidden water (5), a first backfill soil (6) and a composite foundation cushion layer (7); the composite foundation cushion layer (7) is arranged on the upper surface of a foundation pit bottom (9); the wind turbine tower foundation (1) is connected to the composite foundation cushion layer (7); the first backfill soil (6), hidden water (5) and the second backfill soil (3) are arranged in sequence from bottom to top around the wind turbine tower foundation (1); the upper surface of the bearing platform at the bottom of the wind turbine tower foundation (1) has an outward and downward slope; The wind turbine tower foundation (1) is a reinforced concrete integrated structure consisting of a short cylinder, a frustum, and a small cylinder in order from bottom to top; the upper surface of the hidden water diffuser (5) is flush with the bottom edge of the frustum, and a gap is provided between the hidden water diffuser (5) and the wind turbine tower foundation (1); a gap is provided between the edge of the short cylinder and the edge of the foundation pit bottom (9); The composite foundation cushion layer (7) is made of lime soil or cement soil, and its compaction coefficient is not less than 0.97; the first backfill soil (6) is lime soil or cement soil, and its compaction coefficient is not less than 0.95; the second backfill soil (3) is plain soil with a compaction coefficient of not less than 0.95 and a dry density of not less than 18 kN / m³; The hidden sprinkler (5) is cast with C10 plain concrete, and the thickness of the hidden sprinkler (5) is 90-200 mm. Expansion joints are arranged at intervals along the hidden sprinkler (5), and the upper surface of the hidden sprinkler (5) has an outward and downward slope.

2. The wind turbine tower extension foundation for collapsible loess sites according to claim 1, characterized in that: The bottom edge of the foundation pit is circular, and the slope ratio of the foundation pit side slope (4) is 1:0.5; the composite foundation cushion layer (7) and the foundation bottom of the wind turbine tower foundation (1) are concentric circles.

3. The wind turbine tower extension foundation for collapsible loess sites according to claim 1, characterized in that: It also includes compaction piles (10); the compaction piles (10) are placed at the lower part of the foundation pit bottom (9).

4. The wind turbine tower extension foundation for collapsible loess sites according to claim 3, characterized in that: A plurality of compaction piles (10) are provided, and three adjacent compaction piles (10) are located at three vertices of an equilateral triangle; the compaction piles (10) are densely arranged at the edge of the foundation pit bottom (9); the spacing between the compaction piles (10) densely arranged at the edge of the foundation pit bottom (9) is half the spacing between the compaction piles (10) arranged at the center of the foundation pit bottom (9); the compaction piles (10) are made of lime soil or cement soil.

5. The wind turbine tower extension foundation for collapsible loess sites according to claim 1, characterized in that: The upper surfaces of the first backfill soil (6) and the second backfill soil (3) both have a slope toward the outside of the foundation.

6. The wind turbine tower extension foundation for collapsible loess sites according to claim 1, characterized in that: A surface covering soil layer (2) is laid on the second backfill soil (3).

7. A construction method for an extended foundation of a wind power tower in a collapsible loess site, characterized in that: The following steps are included Step 1: Excavation of foundation pit Excavate the foundation pit side slope (4) with a slope ratio of 1:0.5 from the foundation pit to the foundation bottom surface height, and preserve the surface soil layer; Step 2: Compaction pile construction The compaction piles (10) are constructed at the bottom of the foundation pit (9); the compaction piles (10) are arranged in a triangular shape at the center of the foundation pit bottom (9), and are arranged in a ring shape between the edge of the foundation pit bottom (9) and the compaction piles (10) arranged in a triangular shape; the spacing between the compaction piles (10) arranged in a ring shape is half the spacing between the compaction piles (10) arranged in a triangular shape; Step 3: Layered compaction and laying of composite foundation cushion (7) After removing a soil layer of a preset thickness from the top of the compaction pile (10), the soil is compacted layer by layer using lime soil or cement soil with a compaction coefficient of not less than 0.97; Step 4: Construction of wind turbine tower foundation (1) After step 3 is completed, the wind turbine tower foundation (1) is constructed on the composite foundation cushion layer (7); Step 5: First backfill After step 4 is completed, the first backfill soil (6) with a compaction coefficient of not less than 0.95 is backfilled in layers around the wind turbine tower foundation (1) and compacted to the height of the dark water spill (5); the upper surface of the first backfill soil (6) has a slope toward the outside of the foundation; Step 6: Construction of hidden water (5) After step 5 is completed, a hidden water spill (5) is poured on the upper surface of the first backfill soil (6); the upper surface of the hidden water spill (5) is flush with the bottom edge of the cone of the wind turbine tower foundation (1) and the upper surface of the hidden water spill (5) has an outward downward slope; a gap is provided between the hidden water spill (5) and the wind turbine tower foundation (1), and expansion joints are provided at intervals along the hidden water spill (5); the gap and the expansion joint are filled with a caulking agent; Step 7: Second backfill After step 6 is completed, the second backfill soil (3) of the plain soil is compacted layer by layer from the top of the hidden water dispersion (5) to a position 0.8m to 1.0m from the top of the foundation pit; the top surface of the compacted plain soil layer has a slope toward the outside of the foundation; Step 8: Backfilling of topsoil After step 7 is completed, the topsoil preserved during excavation is used to backfill above the compacted second backfill soil (3) to restore the natural surface and revegetate.

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