A displacement type anti-floating pressure relief device

Abstract

A displacement-type anti-buoyancy pressure relief device includes a sleeve 1 fixed inside a foundation 6 at the bottom of a building, with an opening at the bottom of the sleeve 1; and a support 2 fixed inside the foundation soil layer below the foundation 6; a drain pipe 4 is also fixed inside the foundation 6, with the outlet end of the drain pipe 4 extending from the top of the foundation 6, and the drain end 40 of the drain pipe 4 passing through and extending into the sleeve 1; a displacement-type drain switch 3 is fixedly connected to the top of the support 2; a spring 30 is installed on the top of the displacement-type drain switch 3; the maximum extension of the spring 30 is adjustable; a spring top plate 31 is fixedly connected to the top of the spring 30; the spring top plate 31 corresponds vertically to the drain end 40 of the drain pipe 4; and when the spring top plate 31 abuts against the inlet end of the drain pipe 4, it blocks the drain end 40 of the drain pipe 4.

Description

Technical Field

[0001] This utility model relates to the field of underground construction technology, specifically to a displacement-type anti-buoyancy pressure relief device. Background Technology

[0002] Underground structures, when exposed to groundwater, experience buoyancy. If this buoyancy exceeds the sum of the structure's own weight and counterweight, it can cause the structure to rise and damage it. Therefore, underground engineering projects employ measures such as increasing counterweight and installing anti-buoyancy anchors to resist buoyancy, based on a predetermined anti-buoyancy design water level. Some methods involve drainage and pressure relief, where pressure is released when it exceeds a certain limit to control buoyancy and ensure structural safety. The "drainage and pressure relief method" uses pressure as the control indicator; simultaneously, to prevent soil loss, filter cloths and other measures are used to prevent soil particles from being carried away by the water flow. The applicant previously applied for patent number ZL 2022 22034114.0, which disclosed a control system for anti-buoyancy deformation of underground structures under conditions of excessive buoyancy, controlling structural deformation under such conditions.

[0003] The principle behind the above structure is that, in extreme situations, when the water level rises and the buoyancy of the water causes elastic deformation of the underground building structure, a cavity is formed between the raft foundation pad and the foundation. The cavity is filled with groundwater, and the drainage pipe is raised with the main body to drain the water from the underground cavity between the foundation and the ground. In other words, drainage is carried out immediately when the water level rises.

[0004] When the applicant submitted the above application, it was in the conceptual stage. In actual use, the following problems were found: When the building has just risen, the height of the cavity is relatively low. The flow rate (Q) per unit time = flow velocity (v) × area (A). The flow rate of groundwater seeping out of the soil layer is constant. The low height of the cavity results in a small cross-sectional area of ​​the channel (cavity) through which water flows to the drainage pipe, which leads to a large water velocity in the cavity. The large water velocity causes the silt in the foundation to be washed away by the water flow, resulting in soil loss on the one hand and the drainage pipe is more prone to blockage on the other hand.

[0005] Based on the above problems, improvements are needed. On the one hand, the drainage pipes need to be improved so that drainage does not start immediately when the building floats up, but rather starts when the building floats to a specific height according to the designer's design. On the other hand, how to determine the specific height at which the building floats up when drainage begins, so that the cross-sectional area of ​​the channel (cavity) is sufficient to reduce the flow velocity v to a level that does not excessively carry away sediment, are the two technical problems that this utility model aims to solve. Utility Model Content

[0006] To address the issue of drainage pipes being able to drain water when a building floats to a specific height according to the designer's design, this utility model provides a displacement-type anti-buoyancy pressure relief device.

[0007] The purpose of this utility model is achieved in the following manner: a displacement-type anti-buoyancy pressure relief device includes a sleeve 1 fixed in the foundation 6 at the bottom of the building, with an opening at the bottom of the sleeve 1; and a support 2 fixed in the foundation soil layer below the foundation 6; a drain pipe 4 is also fixed in the foundation 6, with the outlet end of the drain pipe 4 extending from the top of the foundation 6, and the drain end 40 of the drain pipe 4 passing through and extending into the sleeve 1; a displacement-type drain switch 3 is fixedly connected to the top of the support 2; a spring 30 is provided on the top of the displacement-type drain switch 3; the maximum extension of the spring 30 is adjustable; a spring top plate 31 is fixedly connected to the top of the spring 30; the spring top plate 31 corresponds vertically to the drain end 40 of the drain pipe 4; and when the spring top plate 31 abuts against the inlet end of the drain pipe 4, it blocks the drain end 40 of the drain pipe 4.

[0008] Furthermore, the displacement-type drain switch 3 includes an upper support 22 and an elastic element that can be detachably connected to the upper support 22; the upper support 22 includes at least one vertical steel plate 23 fixedly connected to the bracket 2, and a horizontal steel plate 25 fixedly connected to the top of the vertical steel plate 23; the elastic element includes a spring base plate 26 abutting against the top of the horizontal steel plate 25, the bottom end of the spring 30 fixedly connected to the top of the spring base plate 26, a spring top plate 31 fixedly connected to the top of the spring 30, a leak-proof gasket 32 ​​fixedly connected to the top of the spring top plate 31, and a screw 33 fixedly connected to the bottom of the spring top plate 31. The screw 33 passes downward through the spring base plate 26 and the horizontal steel plate 25 in sequence, and is threaded with an adjusting nut 34, so that the maximum elongation of the spring 30 can be adjusted by adjusting the position of the adjusting nut 34 on the screw 33 and the limiting cooperation with the bottom of the horizontal steel plate 25.

[0009] Furthermore, the detachable connection between the upper support 22 and the elastic element means that: the horizontal steel plate 25 extends from the middle to the side with a horizontal opening slot 24, the screw 33 between the spring base plate 26 and the adjusting nut 34 is inserted into the upper support 22 through the horizontal opening slot 24, at least one limiting steel ball 27 is fixedly connected to the bottom of the spring base plate 26, and the top of the horizontal steel plate 25 is provided with a hole 29 that cooperates with the limiting steel ball 27 for positioning.

[0010] Furthermore, a covering structure 5 is provided within the foundation soil layer, covering the support 2. The covering structure 5 includes a fragmented layer 13 in contact with the foundation soil layer. A permeable geotextile 12 is provided between the fragmented layer 13 and the foundation soil for limiting the movement. A stainless steel grid 14 is provided within the fragmented layer 13 for limiting the movement. The stainless steel grid 14 is arranged around the support 2.

[0011] Furthermore, a reinforced concrete layer is provided at the bottom of the fragment layer 13. The permeable geotextile 12 and the stainless steel grid 14 are fixedly connected to the reinforced concrete layer. The reinforced concrete layer includes a concrete slab 11 and a steel mesh 10 encased within the concrete slab 11. Several water inlet holes are provided on the support 2. Several reserved steel bar holes 17 are provided at the bottom of the support 2. The bottom of the support 2 is embedded in the concrete slab 11, and the steel bars that make up the steel mesh 10 pass through the reserved steel bar holes 17.

[0012] Furthermore, a circular ring 44 for building surface layer is fixed on the foundation 6 at the top of the sleeve 1, a flange 41 is fixedly connected to the top of the sleeve 1, a blind plate 42 is fixedly connected to the top of the flange 41 by screws 43, and a water-stop steel plate 39 is fixedly connected to the outer periphery of the sleeve 1; a waterproof pad 7 is fixed to the bottom of the foundation 6, the waterproof pad 7 separates from the foundation soil layer when the building floats, a cover plate 36 surrounding the sleeve 1 is fixedly connected to the bottom of the waterproof pad 7, and two layers of studs 38 are fixed in a circumferential array along the outer periphery of the bottom of the sleeve 1, and the cover plate 36 is clamped between the two layers of studs 38.

[0013] Furthermore, the first pressure-resistant steel block 20 is fixedly connected to the outer periphery of the support 2, and the second pressure-resistant steel block 37 is fixedly connected to the inner wall of the sleeve 1. When the building does not float, the first pressure-resistant steel block 20 and the second pressure-resistant steel block 37 abut against each other.

[0014] Furthermore, the limit value for the upward deformation of the building is Smax; the difference between the height of the drainage end 40 when the building is not uplifted and the height when the drainage end 40 separates from the spring top plate 31 and begins to drain is the upward pressure relief value S, and the initial value for upward deformation pressure relief is Smin, Smin≤S<Smax, where Smin=(K·i·A' / C·v'), where K is the soil permeability coefficient of the foundation soil layer, i is the hydraulic gradient, A' is the area borne by the equipment, C is the perimeter of the area enclosed by the junction of the fragment layer 13 and the foundation soil, and v' is the non-scouring flow velocity determined according to the soil properties of the foundation soil.

[0015] Compared to existing technologies, this utility model features a displacement-type drainage switch with adjustable maximum elongation that works in conjunction with the drainage pipe. The displacement of the drainage pipe from the displacement-type drainage switch can be preset. If the displacement is below the preset displacement, no pressure is released; if the displacement exceeds the preset displacement, pressure is released. This effectively combines displacement and pressure release, eliminating the need for drainage when the building is just floating. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the displacement-type pressure relief device during drainage;

[0017] Figure 2 This is a schematic diagram of the covering structure;

[0018] Figure 3 This is a schematic diagram of the support structure;

[0019] Figure 4 This is a structural schematic diagram of the elastic element of a displacement-type drain switch;

[0020] Figure 5 This is a schematic diagram of the structure of the support part of the displacement type drain switch;

[0021] Figure 6 This is a schematic diagram of the sleeve structure;

[0022] Figure 7 This is a schematic diagram of the critical state of a building's upward deformation before pressure is released;

[0023] Figure 8 This is a schematic diagram of the building in a deformed state before it floats up;

[0024] Figure 9 This is a schematic diagram of the status of a displacement-type drain switch, in which... Figure 9 .1 corresponds to Figure 8 The state; in which Figure 9 .2 corresponds to Figure 7 The state; in which Figure 9 .3 corresponds Figure 1 The state.

[0025] The components include: sleeve 1, bracket 2, displacement-type drainage switch 3, drainage pipe 4, covering structure 5, concrete foundation (raft slab) 6, cushion layer and waterproof layer 7, water cake 8, steel mesh 10, concrete slab 11, permeable geotextile 12, fragment layer 13, stainless steel grid 14, round steel pipe 15, base 16, reserved steel bar hole 17, rectangular hole 18, round hole 19, first compressive strength steel block 20, limiting strip 21, and upper support 2. 2. Vertical steel plate 23. Horizontal opening slot 24. Horizontal steel plate 25. Spring base plate 26. Limiting steel ball 27. Round hole 28. Hole 29. Spring 30. Spring top plate 31. Leak-proof gasket 32. Screw 33. Adjusting nut 34. Round steel pipe 35. Cover plate 36. Second pressure-resistant steel block 37. Stud 38. Water-stop steel plate 39. Drainage end 40. Flange 41. Blind plate 42. Screw 43. Ring for building surface layer 44. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In this invention, unless otherwise explicitly specified and limited, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.

[0028] As attached Figure 1 As shown, a displacement-type anti-buoyancy pressure relief device includes a sleeve 1 fixed within a foundation 6 at the bottom of a building. The foundation 6 is a concrete foundation or raft foundation. The sleeve 1 is preferably a steel cylinder structure with an opening at the bottom. A support 2 is fixed within the foundation soil layer below the foundation 6. A drainage pipe 4 is also fixed within the foundation 6. The outlet end of the drainage pipe 4 extends from the top of the foundation 6 and is connected to a corresponding drainage ditch. The drainage end 40 of the drainage pipe 4 passes through and extends into the sleeve 1, preferably with its opening facing downwards. A displacement-type drainage switch 3 is fixedly connected to the top of the support 2. Figure 4 As shown, a spring 30 is provided on the top of the displacement type drain switch 3. The maximum extension of the spring 30 is adjustable. A spring top plate 31 is fixedly connected to the top of the spring 30. The spring top plate 31 corresponds vertically to the drain end 40 of the drain pipe 4. When the spring top plate 31 abuts against the water inlet end of the drain pipe 4, it blocks the drain end 40 of the drain pipe 4.

[0029] Sleeve 1 and drain pipe 4 are integrated with the foundation raft 6. They rise and fall together when the building floats and deforms, and smoothly discharge water during pressure relief and drainage. The diameter of the drain pipe is selected according to the drainage volume.

[0030] Further details are attached. Figure 4-5As shown, the displacement-type drain switch 3 includes an upper support 22 and an elastic element detachably connected to the upper support 22; the upper support 22 includes at least one vertical steel plate 23, preferably two, fixedly connected to the bracket 2, and welded to the bracket 2, with a horizontal steel plate 25 welded and fixedly connected to the top of the vertical steel plate 23; the elastic element includes a spring base plate 26 abutting against the top of the horizontal steel plate 25, the bottom end of the spring 30 fixedly connected to the top of the spring base plate 26, a spring top plate 31 fixedly connected to the top of the spring 30, a leak-proof gasket 32 ​​fixedly connected to the top of the spring top plate 31, the leak-proof gasket 32 ​​preferably being made of soft, waterproof rubber, and a screw 33 fixedly connected to the bottom of the spring top plate 31. The screw 33 is located inside the spring 30. The screw 33 passes downward through the spring base plate 26 and the horizontal steel plate 25 in sequence, and is threadedly connected to the adjusting nut 34. The position of the adjusting nut 34 on the screw 33 and its limiting cooperation with the bottom of the horizontal steel plate 25 are adjusted. Preferably, a washer is fixed on the top of the adjusting nut 34 and placed between the adjusting nut 34 and the bottom of the horizontal steel plate 25 to adjust the maximum elongation of the spring 30. For example, by turning the adjusting nut 34 upward, the spring 30 is further compressed, reducing the maximum elongation of the spring 30, that is, reducing the maximum height of the spring top plate 31. At this maximum height, the drain end 40 of the drain pipe 4 can be separated from the spring top plate 31.

[0031] The displacement-type drainage switch 3 closes and does not drain water until the building's upward deformation reaches the initial pressure relief value. Once this value is exceeded, it opens and drains water. When closed, it seals off water leakage using a waterproof gasket 32 ​​and appropriate pressure (spring 30 stiffness and displacement). The position of the adjusting nut 34 on the screw 33 controls the extension and retraction of the spring 30, thus achieving the displacement-type switch. Preferably, after installation, the extension and retraction of the spring 30 (the nut's positioning) equals the "initial pressure relief value Smin" (see below for details).

[0032] Furthermore, the detachable connection between the upper support (22) and the elastic element means that: the horizontal steel plate 25 extends a horizontal opening groove 24 from the middle to the side, the groove width is greater than or equal to the diameter of the screw 33, the screw 33 between the spring base plate 26 and the adjusting nut 34 is inserted into the middle of the upper support 22 through the horizontal opening groove 24, at least two limiting steel balls 27 are fixedly connected to the bottom of the spring base plate 26, and the top of the horizontal steel plate 25 is provided with holes 29 that cooperate with the limiting steel balls 27 for positioning, so that the elastic element can be separated and adjusted.

[0033] Further details are attached. Figure 2As shown, a covering structure 5 is installed within the foundation soil layer, covering the support 2. The covering structure 5 includes a fragmented layer 13 in contact with the foundation soil layer. The fragmented layer 13 is preferably composed of materials such as sand and gravel, which are less likely to be carried away by water flow compared to the foundation soil. A permeable geotextile 12 is installed between the fragmented layer 13 and the foundation soil to limit the loss of undisturbed soil. A stainless steel grid 14 is installed within the fragmented layer 13 to limit the flow of fragments. The stainless steel grid 14 is installed around the support 2, and sufficient gaps are left between the stainless steel grid 14 and the support 2 to form a water-retaining cavity; that is, the fragmented layer 13 is covered by the stainless steel grid 14 and the support 2. The permeable geotextile 12 forms an annular cavity covering the structure, and this covering structure 5 is permeable to water. It is connected to the foundation soil through the covering structure 5. When the building floats and deforms, it remains stationary with the foundation soil, allowing the water cake 8 to form smoothly. The permeable geotextile 12, sand, gravel 13 and other materials prevent soil particles from being carried away by water. The grid 14 forms a cavity with water but no soil, which collects water and facilitates its smooth drainage. Preferably, the fragment layer 13, as shown in the figure, has a stepped / conical structure with a diameter that gradually decreases from the top to the bottom. The purpose of this setting is to increase the top range of the fragment layer 13. The advantages brought by this setting involve another important feature, which will be detailed later.

[0034] Furthermore, a reinforced concrete layer is provided at the bottom of the fragment layer 13. The bottom of the permeable geotextile 12 and the bottom of the stainless steel grid 14 are both fixedly connected to the reinforced concrete layer. The reinforced concrete layer includes a concrete slab 11 and a steel mesh 10 encased within the concrete slab 11, as shown in the attached figure. Figure 3 As shown, the support 2 preferably includes a round steel pipe 15 as the main body. The round steel pipe 15 is provided with a number of water inlet holes, preferably including a rectangular hole 18 at the bottom and a circular hole 19 in the middle. The bottom of the support 2 is provided with a number of reserved steel bar holes 17. The bottom of the support 2 is embedded in the concrete slab 11, and the steel bars that make up the steel mesh 10 pass through the reserved steel bar holes 17. During production, the steel mesh (truss) is set through the support 2 when it is constructed. When the concrete is poured, the concrete slurry covers the base 16 at the bottom of the round steel pipe 15 to form a stable integrated structure.

[0035] Further details are attached. Figure 6As shown, a circular ring 44 for building surface layer is fixed on the foundation 6 at the top of the sleeve 1 (the circular ring 44 can be replaced with an openable "manhole cover" according to the building decoration requirements). The circular ring 44 for building surface layer is located at the top of the foundation 6. A flange 41 is fixedly connected to the top of the sleeve 1. A blind plate 42 is fixedly connected to the top of the flange 41 by screws 43. A water-stop steel plate 39 is fixedly connected to the outer periphery of the sleeve 1 to prevent water from seeping upward from the outside of the sleeve 1. A waterproof pad 7 is fixed at the bottom of the foundation 6. When the building floats, the waterproof pad 7 separates from the foundation soil layer. The waterproof pad 7 and the feature of separation from the foundation soil layer are existing technologies. A cover plate 36 is fixedly connected to the bottom of the waterproof pad 7 and surrounds the sleeve 1. Two layers of studs 38 are fixed in a circumferential array along the outer periphery of the bottom of the sleeve 1. The cover plate 36 is clamped between the two layers of studs 38.

[0036] Furthermore, the first pressure-resistant steel block 20 is fixedly connected to the outer periphery of the support 2, and the second pressure-resistant steel block 37 is fixedly connected to the inner wall of the sleeve 1. When the building is not floating, the first pressure-resistant steel block 20 and the second pressure-resistant steel block 37 abut against each other, providing support when the building is not floating. Preferably, the outer periphery of the support 2 is fixedly connected to the limiting strip 21, which abuts against the inner wall of the sleeve 1, so that the sleeve 1 and the support 2 form a sliding fit to prevent the displacement type drainage switch 3 from shifting.

[0037] Furthermore, the limit value for the upward deformation of the building is Smax; the difference between the height of the drainage end 40 when the building is not uplifted and the height when the drainage end 40 separates from the spring top plate 31 and begins to drain is the upward pressure relief value S, and the initial value for upward deformation pressure relief is Smin, Smin≤S<Smax, where Smin=(K•i•A' / C•v'), where K is the soil permeability coefficient of the foundation soil layer, i is the hydraulic gradient, A' is the area borne by the equipment, C is the perimeter of the area enclosed by the junction of the fragment layer 13 and the foundation soil, and v' is the non-scouring flow velocity determined according to the soil properties of the foundation soil.

[0038] Relevant calculation principles or formulas:

[0039] Seepage flow rate per unit time: Q = K•i•A' (K: soil permeability coefficient, i: hydraulic gradient, A': area covered by equipment). The soil mechanics professional code provides a detailed explanation, which will not be elaborated here.

[0040] For the area A' borne by the equipment, if a 5000㎡ building uses only one anti-buoyancy pressure relief device, then A' is 5000㎡. If 10 anti-buoyancy pressure relief devices are evenly distributed, then A'≈500㎡. The actual area borne by each location varies depending on the location and needs to be confirmed according to the actual situation.

[0041] Non-scouring velocity v': The velocity of water flow that prevents sediment from being washed away is called the non-scouring velocity. For this anti-buoyancy and pressure relief technology, the non-scouring velocity is mainly related to the soil type, or rather, the characteristics of the soil. For example, silt and mud (particle size 0.005~0.05 mm), the non-scouring velocity is 0.09~0.13 m / s; fine sand (particle size 0.05~0.25 mm), the non-scouring velocity is 0.13~0.20 m / s; medium sand (particle size 0.25~1.0 mm), the non-scouring velocity is 0.2~0.35 m / s; coarse sand (particle size 1.0~2.5 mm), the non-scouring velocity is 0.35~0.40 m / s; medium gravel (particle size 5.0~10.0 mm), the non-scouring velocity is 0.50~0.60 m / s (refer to tables or calculate in "River Dynamics" and hydraulic calculation manuals).

[0042] Calculation of the initial value Smin for pressure relief during upward deformation:

[0043] Flow rate per unit time (Q) = Unflushed velocity (v') × Area (A)

[0044] Area (A) = Upward deformation value S × Perimeter of fragment layer C (13)

[0045] Area (A) is the area where water flows through the fragmented layer 13 and the original soil in the water cake 8. The water flows through the original soil at the fastest speed and is most likely to carry away the sediment of the original soil.

[0046] The above formula is particularly applicable to cases where the upper surface of the covering structure 5 is circular and the support 2 is located at the center of the circle.

[0047] At the edge of the covering structure of the displacement-type anti-buoyancy pressure relief device, i.e. the junction with the original soil, the initial value of the upward deformation pressure relief is determined based on the non-rushing velocity of the original soil. The selection of materials inside the covering structure is determined based on the non-rushing velocity of the material, including the determination of the diameter of the stainless steel grid mesh inside the covering structure.

[0048] The calculation of the diameter of the drainage pipe is based on the required flow rate and the principle of smooth discharge. The design code of "Water Supply and Drainage" contains detailed formulas and explanations, which will not be elaborated here.

[0049] When using this technology, it is recommended to increase the ductility of the building structure according to project needs, so that during the building's ascent, the failure mode of structural components is cracking first, rather than concrete crushing. Relevant content is available in building structural design codes and will not be elaborated further.

[0050] Definitions:

[0051] Uplift Deformation Limit Smax: Using existing elastoplastic finite element analysis software, relevant building information is input into the software to analyze the development of cracks caused by the building's uplift deformation. The uplift value is the value at which the crack size of structural components reaches the allowable value specified in the code (which can be found through national standards), or when individual components (e.g., 5%) exceed the allowable value. Generally, no repair or only simple repair is needed before use. This deformation value is called the non-destructive deformation limit of the structure, also known as the uplift deformation limit. The main influencing factors include: underground building area, length and width, column grid size, structural type, materials, etc. The value varies at different locations and is determined by design calculations, a complex process typically completed using existing building structural calculation software and handled by structural designers.

[0052] Initial value of upward deformation pressure relief, Smin: This term is a self-coined term proposed in this invention. It refers to the upward deformation value at the start of upward pressure relief drainage for a building. To ensure that the upward deformation of the building does not exceed the upward deformation limit, pressure relief drainage is performed in advance. During drainage, if the water flow velocity is greater than the soil's non-flushing velocity, soil particles will be carried away. To control the water flow velocity, an initial value for upward pressure relief drainage deformation is set. The determination of the initial value of upward deformation pressure relief is based on the principle that soil particles are not carried away. The main influencing factors include: the selection of displacement-type anti-buoyancy pressure relief devices (model, quantity, etc.), soil properties under geological conditions, and the design of the covering structure. The value varies at different locations and is determined by design calculations.

[0053] The working process of this invention:

[0054] Let me briefly describe the process of underground structure failure due to buoyancy. As the groundwater level gradually rises, the buoyancy increases. When the buoyancy exceeds the weight of the structure, the underground structure floats and deforms, and the foundation (raft slab) 6 separates from the foundation soil, forming a thin water cake 8. The upward displacement value is the same as the thickness of the water cake 8. As the water volume increases, the volume and thickness of the water cake gradually increase, and the amount of upward deformation of the structure increases. When the amount of upward deformation of the structure is within the elastic range, the structure will not be damaged. When it exceeds the elastic deformation and gradually enters the elastic-plastic state, cracks appear in the structure. The cracks grow from small to large (the deformation reaches the upward deformation limit Smax, and then exceeds the upward deformation limit Smax), and the structure enters the plastic state, gradually failing.

[0055] During its failure process, the rate of expansion of the water cake 8, or the rate at which its thickness increases, is related to factors such as the permeability coefficient of the foundation soil, the water head height, and the foundation area. For a single project, the maximum expansion rate is determined. Before the building's upward deformation enters the elasto-plastic stage, the water inside the water cake 8 is drained, ensuring that the drainage rate is greater than its expansion rate, thus guaranteeing the building's safety. The size and number of displacement-type anti-buoyancy pressure relief devices are determined based on factors such as the maximum expansion rate of the water cake 8. During drainage, the water inside the water cake flows towards the pressure relief device. The water flow velocity v is inversely proportional to the thickness of the water cake 8. Increasing the thickness reduces the water flow velocity. If the water flow velocity v is too high, exceeding the soil's non-scouring velocity v', soil particles are carried away. When this amount reaches a certain level, it affects the safety of the building later. Therefore, the water flow velocity must be controlled to be less than the soil's non-scouring velocity v'. The water flow velocity inside the water cake 8 can be controlled by controlling its thickness.

[0056] A design method for an anti-buoyancy pressure relief structure including the aforementioned displacement-type anti-buoyancy pressure relief device, the method comprising: designing and determining the number and location of displacement-type pressure relief devices based on the underground structure and geological conditions; calculating the building's upward deformation limit value Smax (or taking effective measures to increase structural ductility and increase Smax); and determining the initial upward deformation pressure relief value Smin corresponding to each displacement-type pressure relief device, ensuring that Smin < Smax, and that the difference between Smax and Smin is sufficient (enough to relieve pressure and drain water); when it is found that Smin > Smax or the values ​​are close (e.g., the difference is less than 20%) at a certain displacement-type anti-buoyancy pressure relief device, by increasing the value of the displacement-type anti-buoyancy pressure relief device... The density of displacement-type anti-buoyancy pressure relief devices near the location is reduced, the area A' borne by the equipment of the displacement-type anti-buoyancy pressure relief device is reduced, and / or the area enclosed by the fragment layer 13 is increased to increase the perimeter C, so that Smin is reduced to Smin < Smax and the difference requirement is met. The value of S is determined by Smin, so that S = Smin or S is greater than the value of Smin by 0~5mm, and S is guaranteed to be much smaller than Smax (for example, the difference is greater than 20%). According to the determined value of S, during actual installation, the position of the adjusting nut 34 on the screw 33 is adjusted to change the maximum elongation of the spring 30, so that after the drain pipe 4 is raised to a height S, it is separated from the spring top plate 31 and begins to drain.

[0057] The working process of this invention is as follows: Based on the underground structure and geological conditions, the number and location of displacement-type pressure relief devices are designed and determined to ensure that the building's upward deformation value S does not exceed the upward deformation limit Smax. Before the building undergoes upward deformation (e.g. Figure 8 , Figure 9 1) The displacement-type drainage switch 3 does not open and there is no leakage. As the buoyancy of the water increases, the building begins to slowly rise and deform. A water cake 8 forms between the foundation (raft) 6 and the foundation soil. The space enclosed by the stainless steel mesh 14 of the covering structure 5 is filled with water. When the building's rising deformation is small, the displacement-type drainage switch 3 does not open (e.g. Figure 7 , Figure 9 .2) After the building's upward deformation exceeds the initial value of the upward deformation relief Smin and reaches the upward deformation amount S, the displacement-type drainage switch opens (e.g. Figure 1 , Figure 9 3) Start depressurization and drainage. As the upward deformation S increases, the drainage outlet opening widens and the drainage volume increases until equilibrium is reached, ensuring that the upward deformation value S of the building does not exceed the upward deformation limit Smax. After the groundwater level drops, the water in the water cake 8 seeps back, and the upward deformation of the building returns to zero.

[0058] The circular ring 44 at the upper end of the sleeve 1, the flange blind plates 41 and 42, and the internal threaded holes and nuts 43 on the blind plates are all designed for later inspection, maintenance, and repair. During inspection, open the concrete or mortar or "manhole cover" inside the circular ring 44, unscrew the nut 43, insert the inspection rod through the nut hole 43, and check whether there is silt at the bottom. If so, remove the blind plate 42 and clean the silt at the bottom; or if the displacement-type drain switch 3 exceeds its service life, remove it, replace it, and then restore it.

[0059] This pressure relief device addresses durability issues and ensures its service life by increasing the wall thickness of ordinary steel, applying chemical corrosion protection, or using corrosion-resistant materials. Other equivalent materials may also be used.

[0060] Sleeve 1 and bracket 2 are not limited to being circular. Displacement type drain switch 3 is available in two types: detachable and non-detachable. When used only during the construction period, the non-detachable type can be selected. In the non-detachable type, the displacement type drain switch 3 and bracket 2 are integrated into one unit, which can further simplify the two.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several changes and improvements without departing from the overall concept of the present invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A displacement-type anti-buoyancy pressure relief device, characterized in that: Includes a sleeve (1) fixed in the foundation (6) at the bottom of the building, with an opening at the bottom of the sleeve (1); and a support (2) fixed in the foundation soil layer below the foundation (6); a drain pipe (4) is also fixed in the foundation (6), with the outlet end of the drain pipe (4) extending from the top of the foundation (6), and the drain end (40) of the drain pipe (4) passing through and extending into the sleeve (1). A displacement type drain switch (3) is fixedly connected to the top of the support (2), and a spring (30) is set on the top of the displacement type drain switch (3). The maximum extension of the spring (30) is adjustable, and a spring top plate (31) is fixedly connected to the top of the spring (30). The spring top plate (31) corresponds vertically to the drain end (40) of the drain pipe (4), and when the spring top plate (31) abuts against the inlet end of the drain pipe (4), it blocks the drain end (40) of the drain pipe (4).

2. The displacement-type anti-buoyancy pressure relief device as described in claim 1, characterized in that: The displacement type drain switch (3) includes an upper support (22) and an elastic element that can be detachably connected to the upper support (22); the upper support (22) includes at least one vertical steel plate (23) fixedly connected to the bracket (2), and a horizontal steel plate (25) fixedly connected to the top of the vertical steel plate (23); the elastic element includes a spring base plate (26) that abuts against the top of the horizontal steel plate (25), the bottom end of the spring (30) fixedly connected to the top of the spring base plate (26), the top of the spring (30) fixedly connected to the top of the spring top plate (31), the top of the spring top plate (31) fixedly connected to the top of the spring top plate (31), and a screw (33) fixedly connected to the bottom of the spring top plate (31). The screw (33) passes through the spring base plate (26) and the horizontal steel plate (25) in sequence and is threaded with an adjusting nut (34), so that the maximum elongation of the spring (30) can be adjusted by adjusting the position of the adjusting nut (34) on the screw (33) and the limiting cooperation with the bottom of the horizontal steel plate (25).

3. The displacement-type anti-buoyancy pressure relief device as described in claim 2, characterized in that: The upper support (22) and the elastic element can be separated and connected, meaning that: the horizontal steel plate (25) extends from the middle to the side with a horizontal opening groove (24), the screw (33) between the spring base plate (26) and the adjusting nut (34) is inserted into the upper support (22) through the horizontal opening groove (24), at least one limiting steel ball (27) is fixedly connected to the bottom of the spring base plate (26), and the top of the horizontal steel plate (25) is provided with a hole (29) that cooperates with the limiting steel ball (27) for positioning.

4. A displacement-type anti-buoyancy pressure relief device as described in claim 2, characterized in that: A covering structure (5) is set inside the foundation soil layer. The covering structure (5) covers the outside of the support (2). The covering structure (5) includes a fragment layer (13) that is in contact with the foundation soil layer. A permeable geotextile (12) is set between the fragment layer (13) and the foundation soil for limiting. A stainless steel grid mesh (14) is set inside the fragment layer (13) for limiting. The stainless steel grid mesh (14) is set around the outside of the support (2).

5. A displacement-type anti-buoyancy pressure relief device as described in claim 4, characterized in that: A reinforced concrete layer is set at the bottom of the fragment layer (13). The permeable geotextile (12) and stainless steel grid mesh (14) are fixedly connected to the reinforced concrete layer. The reinforced concrete layer includes a concrete slab (11) and a steel mesh (10) wrapped inside the concrete slab (11). Several water inlet holes are set on the support (2). Several reserved steel bar holes (17) are set at the bottom of the support (2). The bottom of the support (2) is embedded in the concrete slab (11), and the steel bars that make up the steel mesh (10) pass through the reserved steel bar holes (17).

6. The displacement-type anti-buoyancy pressure relief device as described in claim 5, characterized in that: A circular ring (44) for building surface layer is fixed on the foundation (6) at the top of the sleeve (1). A flange (41) is fixedly connected to the top of the sleeve (1). A blind plate (42) is fixedly connected to the top of the flange (41) by screws (43). A water-stop steel plate (39) is fixedly connected to the outer periphery of the sleeve (1). A waterproof pad (7) is fixed at the bottom of the foundation (6). When the building floats, the waterproof pad (7) separates from the foundation soil layer. A cover plate (36) surrounding the sleeve (1) is fixedly connected to the bottom of the waterproof pad (7). Two layers of studs (38) are fixed in a circumferential array along the outer periphery of the bottom of the sleeve (1). The cover plate (36) is clamped between the two layers of studs (38).

7. A displacement-type anti-buoyancy pressure relief device as described in claim 6, characterized in that: The first pressure-resistant steel block (20) is fixedly connected to the outer periphery of the support (2), and the second pressure-resistant steel block (37) is fixedly connected to the inner wall of the sleeve (1). When the building does not float, the first pressure-resistant steel block (20) and the second pressure-resistant steel block (37) abut against each other.

8. A displacement-type anti-buoyancy pressure relief device as described in claim 7, characterized in that: The limit value for the upward deformation of the building is Smax; the difference between the height of the drainage end (40) when the building is not uplifted and the height when the drainage end (40) separates from the spring top plate (31) and begins to drain is the upward pressure relief value S, the initial value for upward deformation pressure relief is Smin, Smin≤S<Smax, where Smin=(K·i·A' / C·v'), where K is the soil permeability coefficient of the foundation soil layer, i is the hydraulic gradient, A' is the area borne by the equipment, C is the perimeter of the area enclosed by the junction of the fragment layer (13) and the foundation soil, and v' is the non-flushing velocity determined according to the soil quality of the foundation soil.

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