Building groundwater passive maintenance-free anti-floating system and construction method

Abstract

The application discloses a kind of building groundwater passive maintenance-free anti-floating system and construction method, system includes being arranged in the building perimeter of fat groove, the fat groove is filled with water-permeable layer, water-stop geotextile and backfill layer from bottom to top in sequence, passive drainage pipe is equipped in the water-permeable layer, the passive drainage pipe is formed closed loop around the building perimeter, the passive drainage pipe has small hole for water permeation on, and passive drainage pipe has drainage slope, and outlet pipe is connected at the lowest point of drainage slope, outlet pipe is connected to predetermined discharge point;Fat groove is equipped with the dewatering well of bottom end extending to the structure bottom plate below of building, multiple are arranged along the circumference of fat groove in dewatering well, dewatering well is filled with water-permeable layer, and the upper end of dewatering well is located below passive drainage pipe.This application realizes the long-term, stable, maintenance-free anti-floating effect of structure, and the system has the advantages of simple construction, low cost, maintenance-free and the like.

Description

Technical Field

[0001] This invention relates to the technical field of building anti-buoyancy, and in particular to a passive, maintenance-free anti-buoyancy system for groundwater in buildings and its construction method. Background Technology

[0002] With the acceleration of urbanization in my country, underground space development is becoming increasingly widespread, with numerous deep-buried underground structures such as underground parking garages, subway stations, underground shopping malls, and underground equipment rooms being constructed. This has highlighted the growing problem of buoyancy resistance in underground structures. Traditional buoyancy resistance measures, such as anti-buoyancy anchors, anti-uplift piles, and ballast methods, while effectively resisting buoyancy, suffer from drawbacks such as complex construction, high costs, long construction periods, significant post-construction maintenance requirements, and susceptibility to groundwater corrosion. Active drainage and pressure reduction measures require operation, maintenance, and repair of the equipment, increasing management and operating costs, and the entire system is unlikely to reach the designed service life of the building. Summary of the Invention

[0003] This invention provides a passive, maintenance-free anti-buoyancy system and construction method for building groundwater. By utilizing the synergistic effect of the building's self-weight and the terrain elevation difference, a passive anti-buoyancy system with active pressure relief and continuous drainage is formed, fundamentally eliminating or significantly reducing the buoyancy acting on the structural base plate.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This invention discloses a passive, maintenance-free anti-buoyancy system for groundwater in buildings, comprising a trench surrounding the building. The trench is backfilled from bottom to top with a permeable layer, a waterproof geotextile, and a backfill layer. A passive drainage pipe is installed within the permeable layer, forming a closed loop around the building. The passive drainage pipe has small holes for water permeation and a drainage slope. An outlet pipe is connected at the lowest point of the drainage slope and is connected to a predetermined discharge point.

[0006] The trough is equipped with dewatering wells that extend to the bottom of the building's structural base. Multiple dewatering wells are spaced apart along the circumference of the trough. The dewatering wells are filled with a permeable layer, and the upper end of the dewatering wells is located below the passive drainage pipe.

[0007] A portion of the water below the structural base slab flows through the dewatering well and then into the passive drainage pipe via the drainage channel. Another portion flows through the drainage channel into the passive drainage pipe via the infiltration of the foundation itself. The passive drainage pipe, under the action of the drainage slope, discharges the water to the predetermined discharge point.

[0008] This invention discloses a passive, maintenance-free, anti-buoyancy system for building groundwater. Further, a drainage blind ditch distributed in a grid or ring pattern is provided on the base below the structural base plate. The drainage blind ditch has a drainage slope that allows water to flow into the drainage ditch. A filter layer is laid in the base and the drainage blind ditch. A permeable layer is provided on the drainage blind ditch and the base. A filter layer is laid on the bottom surface of the structural base plate on the permeable layer. Water below the base flows through the filter layer and the permeable layer and collects in the drainage blind ditch.

[0009] The present invention discloses a passive maintenance-free anti-buoyancy system for groundwater in buildings. Further, the sump is provided with a water collection well and a maintenance well, the bottom elevation of the water collection well and the maintenance well is below the passive drainage pipe, the top elevation of the well is the same as the ground elevation, and the passive drainage pipe is connected to the water collection well and the maintenance well.

[0010] The present invention discloses a passive, maintenance-free anti-buoyancy system for groundwater in buildings, wherein a one-way valve is installed at the outlet pipe.

[0011] The present invention discloses a passive, maintenance-free anti-buoyancy system for groundwater in buildings. Furthermore, the fertilizer tank is wrapped with non-solidified soil on the outside of the seepage layer.

[0012] The present invention discloses a construction method, comprising the following steps:

[0013] Step 1: Calculate the drainage flow rate of the anti-buoyancy system based on the scaled-down model:

[0014] A scaled-down model of the building's anti-buoyancy system is established, comprising a foundation pit simulation box, a water injection simulation box, a building simulation box, a passive drainage system, and a water injection system. The foundation pit simulation box contains a backfill layer. The water injection simulation box is located outside the foundation pit simulation box, forming a water injection cavity between them. The side walls of the foundation pit simulation box have permeable holes, and a pull-out water volume control plate is installed on its side walls to control the number of permeable holes blocked. The bottom of the building simulation box rests on the foundation pit simulation box. The bottom of the tank is filled with soil, and the foundation pit simulation tank and the building simulation tank are connected by a pressure sensor. There is a soil layer between the side walls of the foundation pit simulation tank and the building simulation tank. The passive drainage system is located in the soil layer between the side walls of the foundation pit simulation tank and the building simulation tank, and forms a closed loop in the foundation pit simulation tank. The passive drainage system has small holes for water permeation and a drainage slope. An outlet pipe is connected to the lowest point of the drainage slope and connected to an external metering tank. The water injection system is used to inject water into the water injection simulation tank.

[0015] The operation steps are as follows:

[0016] 1.1) Calculate the on-site water replenishment flow rate Q 补: Drill wells at representative locations in various directions within the site area, then conduct water level recovery tests after pumping, compile the water level recovery data, and derive the water replenishment rate Q. 试 Then, by comparing the ratio of the historical highest precipitation to the current year's precipitation, the final water replenishment rate Q can be obtained. 补 Q 补 =Q 试 ·(R 最 / R 今 ), R 最 This is the highest historical precipitation; R 今 This represents the annual precipitation.

[0017] 1.2) Obtain the drainage flow rate Q 排 Water is injected into the water injection simulation tank through the water injection system. During the water injection process, the outlet of the passive drainage system is sealed. After the water level reaches the experimental level, the seal on the outlet is opened, and drainage begins. The water injected into the pit simulation tank is discharged into the measuring bucket. During this process, the drainage flow rate Q needs to be recorded per unit time. 排 Simultaneously, the water injection system is used to replenish water at the final rate Q. 补 Refill the water-filling simulation tank with water;

[0018] Step 2: Calculate the height of groundwater level reduction based on drainage flow and water replenishment flow: Calculate the drainage volume per unit time based on drainage flow and water replenishment flow. The ratio of drainage volume to the floor area of ​​the building simulation box is the effective height of groundwater level reduction.

[0019] h 降 =(Q 排 -Q 补 )*d / A;

[0020] Q 排 Q represents the drainage flow rate; 补 d represents the final water replenishment rate; d represents the unit time; A represents the floor area of ​​the building simulation box.

[0021] Step 3: Calculation of Anti-buoyancy Stability Safety Factor: Calculate the anti-buoyancy stability safety factor. If it meets the standard, use the calculated slope of the passive drainage system and the conversion ratio to calculate the pipe diameter of the passive drainage system for the next construction step. If it does not meet the standard, adjust the drainage slope and pipe diameter of the passive drainage system, recalculate the drainage flow rate, and recalculate the anti-buoyancy stability safety factor until the anti-buoyancy stability safety factor passes the calculation.

[0022] Step 4: Remove debris from the sump, but retain the dewatering wells in the sump around the building; backfill the sump and dewatering wells with a permeable layer. When the permeable layer is backfilled to the bottom elevation of the passive drainage pipe, install the passive drainage pipe according to the design elevation and drainage slope; after installation, continue backfilling the permeable layer.

[0023] Step 5: Lay a waterproof geotextile on the permeable layer, and then carry out the backfill layer construction on the waterproof geotextile.

[0024] The construction method of this invention further includes a water injection system comprising a water supply tank, a water supply pump, a metering pump, and a water supply pipe. The water supply pump and the metering pump are respectively connected to the water injection simulation tank through the water supply pipe. During the experiment, water is first injected into the simulation tank through the water supply pump tank to the design elevation. Then, the water supply pump is turned off, and the water is replenished according to the final water replenishment rate Q through metering. 补 Refill the water-filled simulation tank with water.

[0025] In the construction method of the present invention, after the foundation pit is excavated to the design elevation, a drainage ditch is dug at the base, and one or more layers of geotextile are fully laid in the base and the drainage ditch as a filter layer. A permeable layer is laid in the base and the drainage ditch, and a filter layer is fully laid on the bottom surface of the base above the permeable layer.

[0026] In the construction method of this invention, a water collection well and a maintenance well are set in the fertilizer tank. The bottom elevation of the water collection well and the maintenance well is below the passive drainage pipe, and the top elevation is the same as the ground elevation. The passive drainage pipe is connected to the water collection well and the maintenance well.

[0027] In the construction method of this invention, when backfilling the permeable layer in the fertilizer trench, non-solidified soil is simultaneously placed outside the permeable layer for wrapping.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This application innovatively proposes the concept of "passive self-draining maintenance-free anti-buoyancy". By utilizing the synergistic effect of the building's self-weight and the terrain elevation difference, combined with a scientific drainage path design and a reliable filtration system, a passive anti-buoyancy system with active pressure relief and continuous drainage is formed. This fundamentally eliminates or significantly reduces the buoyancy acting on the structural base plate, achieving a long-term, stable, and maintenance-free anti-buoyancy effect for the structure. This system has the advantages of simple construction, low cost, and maintenance-free operation.

[0030] 2. Provide suitable design parameters for calculating and meeting anti-buoyancy requirements, so that the "passive self-draining maintenance-free anti-buoyancy" meets the anti-buoyancy requirements of the building;

[0031] 3. Passive self-drainage: It does not require external power equipment and relies on the natural pressure difference between groundwater and the water level inside the structure to achieve automatic drainage, which reduces energy consumption and operating costs;

[0032] 4. Strong drainage capacity: Through carefully designed drainage paths (such as gravel blind drains, permeable pipes, and seepage layers) and water collection well systems, an efficient and smooth drainage network is formed, which can quickly collect and discharge groundwater;

[0033] 5. Maintenance-free: The shell formed by non-solidified soil can effectively cover and protect the drainage system. The drainage system is specially designed with functions such as anti-clogging and anti-backflow, which reduces the amount of maintenance work and maintenance costs in the later stage.

[0034] 6. Good drainage effect: It can automatically adjust the drainage speed and drainage volume according to the changes in groundwater level, effectively lower the groundwater level, reduce the buoyancy of groundwater on underground structures, and improve the anti-buoyancy stability of underground structures;

[0035] 7. Permanent and temporary combination: During the construction phase, the blind drains and filter pipes of the passive self-draining maintenance-free anti-buoyancy system can be used for dewatering anti-buoyancy, and can also be combined with dewatering wells. Dewatering wells can also participate in permanent anti-buoyancy.

[0036] 8. Environmental protection and energy saving: It reduces the amount of building materials used in traditional anti-buoyancy methods, reduces the impact on the environment, and conforms to the development concept of green building;

[0037] 9. Applicable to all types of underground projects with an anti-buoyancy design water level within 6m of the foundation slab, especially suitable for projects with elevation differences. Generally, the slope difference should not be less than 0.3%, and the difference between the municipal drainage water level and the groundwater level should not be less than 0.5m. If the above conditions are not met, it can be used in combination with other anti-buoyancy measures.

[0038] The invention will now be further described with reference to the accompanying drawings. Attached Figure Description

[0039] Figure 1 This is a planar schematic diagram of the present invention;

[0040] Figure 2 for Figure 1 Sectional view of AA in the middle;

[0041] Figure 3 for Figure 1 Cross-sectional view of the middle section (BB);

[0042] Figure 4 for Figure 1 CC section view;

[0043] Figure 5 This is a schematic diagram showing the connection between a passive drainage pipe and a sump.

[0044] Figure 6 This is a schematic diagram of the scaled-down model of the present invention;

[0045] Figure 7 This is a planar schematic diagram of the scaled-down model of the present invention;

[0046] Figure 8 This is a cross-sectional schematic diagram of the scaled-down model of the present invention;

[0047] Figure 9 This is a schematic diagram of the water volume control plate installation structure of the present invention.

[0048] Figure label:

[0049] 1. Foundation pit simulation box; 2. Building simulation box; 3. Water injection simulation box; 4. Experimental table; 5. Water supply tank; 6. Metering pump; 7. Passive drainage system; 8. Drainage valve; 9. Pressure sensor; 10. Water volume control plate; 11. Water supply pump; 12. Backfill layer; 13. Metering bucket; 14. Water collection tank; 15. Slot structure; 16. Support beam; 17. Fertilizer trough; 18. Permeable layer; 19. Waterproof geotextile; 20. Backfill layer; 21. Passive drainage pipe; 22. Dewatering well; 23. Structural base plate; 24. Drainage blind ditch; 25. Filter layer; 26. Water collection well; 27. Inspection well; 28. Non-stabilized soil. Detailed Implementation

[0050] like Figures 1-5 As shown, this invention discloses a passive, maintenance-free anti-buoyancy system for building groundwater and its construction method. The system includes a trench 17 set around the perimeter of the building. The trench 17 is backfilled from bottom to top with a permeable layer 18, a waterproof geotextile 19, and a backfill layer 20. The permeable layer 18 is graded crushed stone. A passive drainage pipe 21 is installed in the permeable layer 18. The passive drainage pipe 21 forms a closed loop around the perimeter of the building. The passive drainage pipe 21 has small holes for water permeation and a drainage slope. An outlet pipe is connected at the lowest point of the drainage slope. A one-way valve is installed at the outlet pipe, and the outlet pipe is connected to a predetermined discharge point.

[0051] The trough 17 is provided with a dewatering well 22 extending to the bottom of the building's structural base 23. Multiple dewatering wells 22 are spaced apart along the circumference of the trough 17. The dewatering wells 22 are filled with a permeable layer 18. The upper end of the dewatering well 22 is located below the passive drainage pipe 21.

[0052] A portion of the water below the structural base slab 23 flows through the dewatering well 22 and the drainage channel 17 into the passive drainage pipe 21, while another portion flows through the drainage channel 17 into the passive drainage pipe 21 due to the infiltration of the base itself. The passive drainage pipe 21, under the action of the drainage slope, discharges the water to the predetermined discharge point.

[0053] Depending on the seepage rate of the foundation soil, drainage blind ditches 24 distributed in a grid or ring pattern can be provided on the foundation below the structural base slab 23. The drainage blind ditches 24 have a drainage slope that allows water to flow into the fertilizer trough 17. A filter layer 25 is laid in the foundation and the drainage blind ditches 24. A permeable layer 18 is provided on the drainage blind ditches 24 and the foundation. A filter layer 25 is laid on the bottom surface of the structural base slab 23 on the permeable layer 18. Water below the foundation flows through the filter layer 25 and the permeable layer 18 and collects in the drainage blind ditches 24.

[0054] The trough 17 is equipped with a water collection well 26 and a maintenance well 27. The bottom elevation of the water collection well 26 and the maintenance well 27 is below the passive drainage pipe 21, and the top elevation of the well is the same as the ground elevation. The passive drainage pipe 21 is connected to the water collection well 26 and the maintenance well 27.

[0055] The fertilizer trench 17 is surrounded by non-solidified soil 28 on the outside of the permeable layer 18.

[0056] Reference Figures 1-9 The construction method includes the following steps:

[0057] Step 1: Calculate the drainage flow rate of the anti-buoyancy system based on the scaled-down model:

[0058] The scaled-down model includes a foundation pit simulation box 1, a water injection simulation box 3, a building simulation box 2, a passive drainage system 7, and a water injection system.

[0059] In this embodiment of the application, the foundation pit simulation box 1 is a five-sided enclosed box made of transparent PVC thick material with an open top. The foundation pit simulation box 1 can be filled with soil and gravel with different permeability coefficients to simulate the foundation pit situation. The purpose of replacing soil and gravel is to simulate the different permeability of soil layers under various geological environments, and thus simulate the different effects of groundwater on the buoyancy of buildings. This item is variable C1 in this experiment.

[0060] A water injection simulation box 3 is installed on the outside of the foundation pit simulation box 1. The water injection simulation box 3 can be fixed to the foundation pit simulation box 1. A water injection cavity is formed between the side wall of the water injection simulation box 3 and the foundation pit simulation box 1. The water injection simulation box 3 is made of transparent PVC thick material. The side wall of the foundation pit simulation box 1 is provided with through water permeable holes. The diameter of the water permeable holes is 3mm in this embodiment. Water is injected into the foundation pit simulation box 1. Multiple sets of water permeable holes are arranged along the height direction of the foundation pit simulation box 1. Multiple water volume control plates 10 that can be pulled along their height direction are provided on the side wall of the foundation pit simulation box 1. Water can permeate into the foundation pit simulation box 1 through the water permeable holes. By adjusting the height of the water volume control plates 10, the amount and flow rate of water injected into the foundation pit simulation box 1 by the water injection simulation box 3 are controlled to simulate the changes and recharge of groundwater in the foundation pit of the building. This item is variable factor C2 of this test system. It simulates the groundwater level and recharge by different water injection volumes, and tests the buoyancy resistance of the building simulation box 2 under various water level conditions.

[0061] Specifically, a slot structure 15 is provided on the side wall of the foundation pit simulation box 1. The water volume control plate 10 is slidably disposed in the slot structure 15 along the height direction. The water volume control plate 10 is temporarily fixed to the side wall of the foundation pit simulation box 1 by a pin. Multiple sets of T-shaped structures are installed on the side wall of the foundation pit simulation box 1. The web end of the T-shaped structure is disposed on the foundation pit simulation box 1, and a slot structure 15 is formed between adjacent T-shaped structures.

[0062] The building simulation box 2 is a five-sided enclosed box made of thick transparent PVC material. Its bottom rests on the backfill layer 12 of the foundation pit simulation box 1. The building simulation box 2 and the foundation pit simulation box 1 are connected by connecting bolts and pressure sensors 9. In this embodiment, the pressure sensors 9 are respectively located at the four corners and the middle of the building simulation box 2. The pressure sensors 9 can display the buoyancy of the building simulation box 2 in real time, and reflect the drainage and buoyancy resistance and extreme working conditions of the entire passive maintenance-free anti-buoyancy system through variable factors.

[0063] A passive drainage system 7 is installed in the backfill soil between the side walls of the foundation pit simulation box 1 and the building simulation box 2, forming a closed loop within the foundation pit simulation box 1. The passive drainage system 7 includes a drainage simulation pipe made of 50mm diameter PPR pipe with 3mm diameter holes arranged in a quincunx pattern at 20mm intervals. The drainage simulation pipe is laid with a 0.5% slope, and an outlet pipe is located at the corner with the lowest slope. The outlet pipe passes through the side walls of the foundation pit simulation box 1 and the water injection simulation box 3 and connects to an external metering tank 13, allowing water to flow into the metering tank 13 for drainage volume measurement. Under the pressure of the building simulation box 2 and the backfill soil, the water injected into the foundation pit simulation box 1 is forced into the drainage simulation pipe. Due to the drainage slope, the water flows through the outlet pipe into the metering tank 13, achieving the purpose of drainage and pressure reduction. The drainage volume is measured using the metering tank 13.

[0064] The water injection system is used to inject water into the water injection simulation tank 3 and adjust the water volume. It includes a water supply tank 5, a water supply pump 11, a metering pump 6, and a water supply pipe. The water supply pump 11 and the water supply pump are connected to the water injection simulation tank 3 through the water supply pipe. Before the water injection system experiment, the outlet of the passive drainage system 7 needs to be sealed. After the water supply pump 11 draws water from the water supply tank 5 to the specified water level in the water injection simulation tank 3, the water supply is stopped, and the outlet is opened to start the experiment. Subsequently, the metering pump 6 is used to precisely control the water replenishment during the experiment. This is the variable factor C3 of this experimental system. By measuring the water supply volume of the metering pump 6, the drainage situation of the passive drainage system 7 and the changes in buoyancy received by the building under different rainfall conditions or different underground leakage conditions are simulated.

[0065] The experimental simulation box system, consisting of water injection simulation box 3, foundation pit simulation box 1 and building simulation box 2, is installed on the experimental platform 4. The experimental platform 4 integrates the switch control system of water injection pump and metering pump 6.

[0066] The experimental platform 4 also integrates the switch and display panel of the pressure sensor 9, which is used to observe the pressure value of the pressure sensor 9 in real time.

[0067] A drain valve 8 is installed at the bottom of the foundation pit simulation box 1. The drain valve 8 is connected to the water collection tank 14 through a water pipe. After the experiment is completed, the water is drained into the water collection tank 14.

[0068] A supporting beam 16 is provided between the side walls of the foundation pit simulation box 1 and the water injection simulation box 3 to support the foundation pit simulation box 1 and prevent it from deforming.

[0069] The operation steps are as follows:

[0070] 1.1) Calculate the on-site water replenishment flow rate Q 补 : Drill wells at representative locations in various directions within the site area, then conduct water level recovery tests after pumping, compile the water level recovery data, and derive the water replenishment rate Q. 试 Then, by comparing the ratio of the historical highest precipitation to the current year's precipitation, the final water replenishment rate Q can be obtained. 补 Q 补 =Q 试 ·(R 最 / R 今 ), R 最 This is the highest historical precipitation; R 今 This represents the annual precipitation.

[0071] 1.2) Obtain the drainage flow rate Q 排 Water is injected into the water injection simulation tank using a water pump. During the injection process, the outlet of the passive drainage system is sealed. After the water level reaches the experimental level, the seal on the outlet is opened, and drainage begins. The water in the foundation pit simulation tank is discharged into a measuring container. The drainage flow rate Q needs to be recorded per unit time during this process. 排 Meanwhile, the metering pump operates according to the final water replenishment rate Q. 补 Refill the water-filled simulation tank with water.

[0072] Step 2: Calculate the height of groundwater level reduction based on drainage flow and water replenishment flow: Calculate the drainage volume per unit time based on drainage flow and water replenishment flow. The ratio of drainage volume to the floor area of ​​the building simulation box is the effective height of groundwater level reduction.

[0073] h 降 =(Q 排 -Q 补 )*d / A;

[0074] Q 排 Q represents the drainage flow rate; 补 d represents the final water replenishment rate; d represents the unit time; and A represents the floor area of ​​the building simulation box.

[0075] Step 3: Calculation of the safety factor for anti-buoyancy stability:

[0076] The anti-buoyancy stability safety factor Kw = (structural self-weight G + resistance provided by anti-uplift piles / anchors R) / buoyancy force Nw ≥ the stability safety factor required by the standard.

[0077] Kw: Anti-buoyancy stability safety factor; G: Structural self-weight; R: When the structural self-weight is insufficient, the additional resistance provided by anti-uplift piles or anti-buoyancy anchors; Nw: Groundwater buoyancy, determined by the anti-buoyancy design water level, calculated as Nw = ρg * h * A, where ρ is the density of water, g is the gravitational acceleration, h is the height of the water level from the base, and A is the base area.

[0078] Based on the above calculations, determine whether the anti-buoyancy stability safety factor meets the standard. If it does, use the calculated slope and the conversion ratio to calculate the diameter of the passive drainage pipe and proceed to the next step of construction. If it does not meet the standard, adjust the slope and pipe diameter, recalculate the drainage flow rate, and recalculate the anti-buoyancy stability safety factor until the anti-buoyancy stability safety factor passes the verification.

[0079] Step 4: After the foundation pit is excavated to the design elevation, a drainage ditch is dug according to the design slope (i≥0.5%). Then, the loose soil, debris and water in the foundation are removed, and the foundation is compacted to ensure that it is flat, firm and without obvious undulations, and to avoid local water accumulation or stress concentration.

[0080] Step 5: Lay one or more layers of geotextile as a filter layer in the base and blind drain. The overlap width of the geotextile should not be less than 200mm. The joints should be sewn or heat-bonded to ensure continuity and filtration effect. The geotextile should be laid flat, without wrinkles or damage, and completely cover the seepage layer to prevent fine particles from seeping in and clogging during subsequent construction.

[0081] Step Six: A permeable layer, consisting of graded crushed stone, is laid within the base and drainage blind ditch. The drainage blind ditch is fully filled with this permeable layer. The thickness of the permeable layer on the base is 200-300mm, laid in layers, each layer not exceeding 150mm in thickness. A plate vibrator or manual compaction is used to ensure uniform density, avoid gaps, and guarantee good overall permeability and load-bearing capacity of the entire permeable layer. The spacing and dimensions of the blind ditches are determined based on hydrogeological conditions and drainage volume calculations, arranged in a grid or ring pattern to collect surrounding seepage.

[0082] Step 7: Lay one or more layers of geotextile on top of the permeable layer and on the bottom of the base to form a filter layer to prevent concrete slurry or fine particles from seeping in and clogging the surface during subsequent construction.

[0083] Step 8: Conduct a water seepage system test below the structural base slab. Observe the working condition of the drainage blind ditch and seepage layer by injecting water to ensure that the seepage path is smooth before proceeding with the construction of the structural base slab and exterior walls.

[0084] Step 9: Remove debris, loose soil, and standing water from the fertilizer trench, ensuring the bottom and sidewalls are flat and firm. Retain the dewatering wells within the trench around the building, extending 4-5 meters below the structural foundation and 1.0 meter above the trench bottom elevation.

[0085] Step 10: Backfill the fertilizer trench with a permeable layer, which is graded crushed stone. Backfilling should be done in layers. When backfilling in layers, non-stabilized soil should be placed around the permeable layer for wrapping.

[0086] When the permeable layer is backfilled to the bottom elevation of the passive drainage pipe, the passive drainage pipe is installed according to the design elevation and drainage slope. After installation, backfilling continues to a position 1m above the passive drainage pipe.

[0087] Step 11: Install sump and inspection wells. Sump and inspection wells should be installed within the pit. The bottom elevation of the sump and inspection wells should be 1m below the passive drainage pipe, and the top elevation should be the same as the ground level. Inspection wells should be installed at the outlet pipe and at the corners of the pit. The spacing between the sump and inspection wells should meet the requirements for water collection and maintenance. The inspection wells are mainly used for drainage system maintenance in extreme situations.

[0088] The passive drainage pipe is connected to the sump and inspection well, and the well pipe adopts a socket connection.

[0089] Step 12: Install a check valve at the outlet pipe to ensure that the drainage flows in only one direction. The outlet pipe is connected to the designated discharge point, which can be a municipal stormwater or sewage network, a nearby natural water body such as a river or canal (with permission), or a stormwater storage tank. The drainage outlet should be higher than the highest flood level, and a backup outlet should be provided to prevent backflow.

[0090] Step 13: Before backfilling the earthwork, test the drainage system in the trench by injecting water into the collection well, observing the drainage situation, and checking whether the drainage system is unobstructed and whether the one-way valve is working properly.

[0091] Step Fourteen: After the test is completed, continue to backfill the permeable layer to the design height, and lay the waterproof geotextile with the vertical surface turned up 500mm.

[0092] Step 15: Carry out the backfill layer construction. The backfill layer can be lime-soil or fluidized solidified soil.

[0093] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A passive, maintenance-free anti-buoyancy system for groundwater in buildings, characterized in that, The system includes a drainage trench (17) set around the perimeter of the building. The drainage trench (17) is backfilled from bottom to top with a permeable layer (18), a waterproof geotextile (19), and a backfill layer (20). A passive drainage pipe (21) is provided in the permeable layer (18). The passive drainage pipe (21) forms a closed loop around the perimeter of the building. The passive drainage pipe (21) has small holes for water permeation and a drainage slope. An outlet pipe is connected to the lowest point of the drainage slope and is connected to a predetermined discharge point. The trough (17) is provided with a dewatering well (22) extending to the bottom of the building’s structural base plate (23). Multiple dewatering wells (22) are spaced apart along the circumference of the trough (17). The dewatering wells (22) are filled with a permeable layer (18). The upper end of the dewatering wells (22) is located below the passive drainage pipe (21). A portion of the water below the structural base plate (23) flows through the dewatering well (22) and then through the trough (17) into the passive drainage pipe (21), while another portion flows through the trough (17) into the passive drainage pipe (21) under the infiltration of the base itself. The passive drainage pipe (21) discharges the water to the predetermined discharge point under the action of the drainage slope. The base below the structural base plate (23) is provided with drainage blind ditches (24) distributed in a grid or ring pattern. The drainage blind ditches (24) have a drainage slope that allows water to flow into the fertilizer tank (17). A filter layer (25) is laid in the base and the drainage blind ditches (24). A permeable layer (18) is provided on the drainage blind ditches (24) and the base. A filter layer (25) is laid on the bottom surface of the structural base plate (23) on the permeable layer (18). Water below the base is collected into the drainage blind ditches (24) through the filter layer (25) and the permeable layer (18).

2. The passive, maintenance-free anti-buoyancy system for building groundwater according to claim 1, characterized in that, The fertilizer tank (17) is equipped with a water collection well (26) and a maintenance well (27). The bottom elevation of the water collection well (26) and the maintenance well (27) is below the passive drainage pipe (21), and the top elevation of the well is the same as the ground elevation. The passive drainage pipe (21) is connected to the water collection well (26) and the maintenance well (27).

3. The passive, maintenance-free anti-buoyancy system for building groundwater according to claim 1, characterized in that, A check valve is installed at the outlet pipe.

4. A passive, maintenance-free anti-buoyancy system for building groundwater according to claim 1, characterized in that, The fertilizer tank (17) is wrapped with non-solidified soil (28) outside the permeable layer (18).

5. A construction method for a passive, maintenance-free anti-buoyancy system for groundwater in buildings as described in any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Calculate the drainage flow rate of the anti-buoyancy system based on the scaled-down model: A scaled-down model of the building's anti-buoyancy system is established, comprising a foundation pit simulation box, a water injection simulation box, a building simulation box, a passive drainage system, and a water injection system. The foundation pit simulation box contains a backfill layer. The water injection simulation box is located outside the foundation pit simulation box, forming a water injection cavity between them. The side walls of the foundation pit simulation box have permeable holes, and a pull-out water volume control plate is installed on its side walls to control the number of permeable holes blocked. The bottom of the building simulation box rests on the foundation pit simulation box. The bottom of the tank is filled with soil, and the foundation pit simulation tank and the building simulation tank are connected by a pressure sensor. There is a soil layer between the side walls of the foundation pit simulation tank and the building simulation tank. The passive drainage system is located in the soil layer between the side walls of the foundation pit simulation tank and the building simulation tank, and forms a closed loop in the foundation pit simulation tank. The passive drainage system has small holes for water permeation and a drainage slope. An outlet pipe is connected to the lowest point of the drainage slope and connected to an external metering tank. The water injection system is used to inject water into the water injection simulation tank. The operation steps are as follows: Calculate the on-site water supply flow rate Q 补 : Drill wells at representative locations in various directions within the site area, then conduct water level recovery tests after pumping, compile the water level recovery data, and derive the water replenishment rate Q. 试 Then, by comparing the ratio of the historical highest precipitation to the current year's precipitation, the final water replenishment rate Q can be obtained. 补 Q 补 =Q 试 ·(R 最 / R 今 ), R 最 This is the highest historical precipitation; R 今 This represents the annual precipitation. Obtain the drainage flow rate Q 排 Water is injected into the water injection simulation tank through the water injection system. During the water injection process, the outlet of the passive drainage system is sealed. After the water level reaches the experimental level, the seal on the outlet is opened, and drainage begins. The water injected into the pit simulation tank is discharged into the measuring bucket. During this process, the drainage flow rate Q needs to be recorded per unit time. 排 Simultaneously, the water injection system is used to replenish water at the final rate Q. 补 Refill the water-filled simulation tank with water; Step 2: Calculate the height of groundwater level reduction based on drainage flow and water replenishment flow: Calculate the drainage volume per unit time based on drainage flow and water replenishment flow. The ratio of drainage volume to the floor area of ​​the building simulation box is the effective height of groundwater level reduction. h 降 =(Q 排 -Q 补 )·d / A; Q 排 Q represents the drainage flow rate; 补 d represents the final water replenishment rate; d represents the unit time; A represents the floor area of ​​the building simulation box. Step 3: Calculation of Anti-buoyancy Stability Safety Factor: Calculate the anti-buoyancy stability safety factor. If it meets the standard, use the calculated slope of the passive drainage system and the conversion ratio to calculate the pipe diameter of the passive drainage system for the next construction step. If it does not meet the standard, adjust the drainage slope and pipe diameter of the passive drainage system, recalculate the drainage flow rate, and recalculate the anti-buoyancy stability safety factor until the anti-buoyancy stability safety factor passes the calculation. Step 4: Remove debris from the sump, but retain the dewatering wells in the sump around the building; backfill the sump and dewatering wells with a permeable layer. When the permeable layer is backfilled to the bottom elevation of the passive drainage pipe, install the passive drainage pipe according to the design elevation and drainage slope; after installation, continue backfilling the permeable layer. Step 5: Lay a waterproof geotextile on the permeable layer, and then carry out the backfill layer construction on the waterproof geotextile.

6. The construction method according to claim 5, characterized in that, The water injection system includes a water supply tank, a water supply pump, a metering pump, and water supply pipes. The water supply pump and the metering pump are connected to the water injection simulation tank through the water supply pipes. During the experiment, water is first injected into the water injection simulation tank to the design elevation using the water supply pump. Then, the water supply pump is turned off, and the water is replenished by the metering pump according to the final water replenishment rate Q. 补 Refill the water-filled simulation tank with water.

7. The construction method according to claim 5, characterized in that, After the foundation pit is excavated to the design elevation, a drainage ditch is dug at the base. One or more layers of geotextile are laid as a filter layer in the base and the drainage ditch. A permeable layer is laid in the base and the drainage ditch. A filter layer is laid on top of the permeable layer and on the bottom surface of the base.

8. The construction method according to claim 5, characterized in that, A water collection well and a maintenance well are installed inside the fertilizer tank. The bottom elevation of the water collection well and the maintenance well is below the passive drainage pipe, and the top elevation is the same as the ground elevation. The passive drainage pipe is connected to the water collection well and the maintenance well.

9. The construction method according to claim 5, characterized in that, When backfilling the permeable layer into the fertilizer trench, non-solidified soil should be placed around the permeable layer at the same time.

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