Passive maintenance-free anti-floating system for building underground water and construction method

Abstract

The invention discloses a building underground water passive maintenance-free anti-floating system and a construction method.The system comprises a fertilizer groove formed in the periphery of a building, a water seepage layer, waterproof geotechnical cloth and a backfilling layer are sequentially backfilled in the fertilizer groove from bottom to top, and a passive drainage pipe is arranged in the water seepage layer; the passive drainage pipe forms a closed loop around the periphery of the building, small holes for water permeation are formed in the passive drainage pipe, the passive drainage pipe has a drainage slope, an outlet pipeline is connected to the lowest point of the drainage slope, and the outlet pipeline is connected to a preset drainage point; a plurality of dewatering wells with the bottom ends extending to the position below a structural bottom plate of the building are arranged in the fertilizer groove in the circumferential direction of the fertilizer groove at intervals, the dewatering wells are filled with water seepage layers, and the upper ends of the dewatering wells are located below the passive drainage pipe. The anti-floating system achieves the long-term, stable and maintenance-free anti-floating effect of the structure, and has the advantages of being easy and convenient to construct, low in cost, free of maintenance and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building anti-floating, in particular to a building groundwater passive maintenance-free anti-floating system and construction method. BACKGROUND

[0002] With the acceleration of urbanization process in China, underground space development is increasingly widespread, and deep underground structures such as underground garages, subway stations, underground shopping malls, and underground equipment rooms are being built in large numbers. The problem of anti-floating of underground structures is becoming increasingly prominent. Traditional anti-floating measures such as anti-floating anchor rods, uplift piles, and weight pressing methods can effectively resist buoyancy, but have the disadvantages of complex construction, high cost, long construction period, high maintenance requirements, and susceptibility to groundwater corrosion. Active water drainage and pressure reduction measures require operation and maintenance of the equipment, increasing the management and operation cost, and the entire system is difficult to achieve the design service life of the building. SUMMARY

[0003] The present application provides a building groundwater passive maintenance-free anti-floating system and construction method, which utilizes the synergistic effect of building self-weight and topographic elevation difference to form a passive anti-floating system with active pressure relief and continuous drainage, thereby fundamentally eliminating or significantly reducing the buoyancy acting on the structure bottom plate.

[0004] To solve the above technical problems, the present application adopts the following technical solutions: The present application provides a building groundwater passive maintenance-free anti-floating system, which includes a trench arranged around the building. The trench is backfilled with a water permeable layer, a water-resistant geotextile, and a backfill layer from bottom to top. A passive drainage pipe is arranged in the water permeable layer. The passive drainage pipe forms a closed loop around the building. The passive drainage pipe has small holes for water permeation. The passive drainage pipe has a drainage slope, and an outlet pipe is connected to the lowest point of the drainage slope. The outlet pipe is connected to a predetermined discharge point. A dewatering well is arranged in the trench, with its bottom end extending below the structure bottom plate of the building. Multiple dewatering wells are arranged along the circumference of the trench. The dewatering wells are filled with a water permeable layer. The upper end of the dewatering well is located below the passive drainage pipe. A portion of the water below the structure bottom plate passes through the dewatering well and flows into the passive drainage pipe through the trench. Another portion of the water flows into the passive drainage pipe through the trench under the permeation of the base itself. The passive drainage pipe drains the water to the predetermined discharge point under the action of the drainage slope.

[0005] The application discloses a passive maintenance-free anti-floating system for underground water of a building, and further, a drainage blind ditch in a grid or ring shape is arranged on a foundation below a structural bottom plate, the drainage blind ditch has a drainage slope for collecting water into a fat groove; a filter layer is arranged in the foundation and the drainage blind ditch, a water permeation layer is arranged on the foundation and the drainage blind ditch, and a filter layer is arranged on the bottom surface of the structural bottom plate above the water permeation layer; water below the foundation is collected into the drainage blind ditch through the filter layer and the water permeation layer.

[0006] The application discloses a passive maintenance-free anti-floating system for underground water of a building, and further, a water collecting well and a maintenance well are arranged in the fat groove respectively, the bottom elevation of the water collecting well and the maintenance well is below the passive drainage pipe, the top elevation of the water collecting well and the maintenance well is the same as the ground elevation, and the passive drainage pipe is connected with the water collecting well and the maintenance well.

[0007] The application discloses a passive maintenance-free anti-floating system for underground water of a building, and further, a one-way valve is arranged at the outlet pipeline.

[0008] The application discloses a passive maintenance-free anti-floating system for underground water of a building, and further, the fat groove is wrapped with non-solidified soil outside the water permeation layer.

[0009] The application discloses a construction method, which comprises the following steps. Step one: calculating the drainage flow of the anti-floating system based on a scale model: A scale model is established based on the anti-floating system of the building, the scale model comprises a foundation pit simulation box, a water injection simulation box, a building simulation box, a passive drainage system and a water injection system, the inside of the foundation pit simulation box is provided with a filling layer; the water injection simulation box is arranged outside the foundation pit simulation box, a water injection cavity is formed between the water injection simulation box and the foundation pit simulation box, a water permeation hole is formed in the side wall of the foundation pit simulation box, a water amount control plate is arranged on the side wall of the foundation pit simulation box in a height direction and can be pulled out, and the water amount control plate is used for controlling the number of blocked water permeation holes; the bottom of the building simulation box is located on the filling layer at the bottom of the foundation pit simulation box, and the foundation pit simulation box and the building simulation box are connected through a pressure sensor, and a filling layer is arranged between the side walls of the foundation pit simulation box and the building simulation box; the passive drainage system is arranged in the filling layer between the side walls of the foundation pit simulation box and the building simulation box, forms a closed loop in the foundation pit simulation box, has small holes for water permeation, has a drainage slope, and has an outlet pipeline connected to the lowest point of the drainage slope, and the outlet pipeline is connected with an external measuring barrel; the water injection system is used for injecting water into the water injection simulation box. The operation steps are as follows: 1.1) calculating the on-site water supplement flow Q 补 : wells are drilled at representative positions in each direction in the field area, then water is pumped out and water level recovery test is conducted, water level recovery data is sorted out, and the water supplement rate Q is obtained 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. 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; 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 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. 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; 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; 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; 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. 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; 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. 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; 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.

[0015] The invention will now be further described with reference to the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a planar schematic diagram of the present invention; Figure 2 for Figure 1 Sectional view of AA in the middle; Figure 3 for Figure 1 Cross-sectional view of the middle section (BB); Figure 4 for Figure 1 CC section view; Figure 5 This is a schematic diagram showing the connection between a passive drainage pipe and a sump. Figure 6 This is a schematic diagram of the scaled-down model of the present invention; Figure 7 This is a planar schematic diagram of the scaled-down model of the present invention; Figure 8 This is a cross-sectional schematic diagram of the scaled-down model of the present invention; Figure 9 This is a schematic diagram of the water volume control plate installation structure of the present invention.

[0017] Figure label: 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

[0018] like Figures 1-5 As shown, this invention discloses a passive, maintenance-free anti-buoyancy system for groundwater in buildings 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] The fertilizer trench 17 is surrounded by non-solidified soil 28 on the outside of the permeable layer 18.

[0024] Reference Figures 1-9 The construction method includes the following steps: Step 1: Calculate the drainage flow rate of the anti-buoyancy system based on the scaled-down model: 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The operation steps are as follows: 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.

[0036] 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.

[0037] 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.

[0038] 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; and A represents the floor area of ​​the building simulation box.

[0039] Step 3: Calculation of the safety factor for anti-buoyancy stability: 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] The passive drainage pipe is connected to the sump and inspection well, and the well pipe adopts a socket connection.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] Step 15: Carry out the backfill layer construction. The backfill layer can be lime-soil or fluidized solidified soil.

[0056] 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-floating system for building groundwater, characterized in that, The application relates to a structure for draining water from the foundation of a building, which comprises a trench (17) arranged around the building, wherein a water-permeable layer (18) and a water-impermeable geotextile (19) are sequentially backfilled in the trench (17) from bottom to top, a passive drainage pipe (21) is arranged in the water-permeable layer (18), the passive drainage pipe (21) forms a closed loop around the building, the passive drainage pipe (21) has small holes for water permeation, the passive drainage pipe (21) has a water drainage slope, and an outlet pipe is connected to the lowest point of the water drainage slope and connected to a predetermined drainage point. A plurality of dewatering wells (22) are arranged in the trench (17) along the circumference of the trench (17), the dewatering wells (22) are arranged below the structural bottom plate (23) of the building, the dewatering wells (22) are filled with the water-permeable layer (18), and the upper ends of the dewatering wells (22) are located below the passive drainage pipe (21). Part of the water below the structural bottom plate (23) is collected into the passive drainage pipe (21) through the trench (17) via the dewatering wells (22), and part of the water is collected into the passive drainage pipe (21) through the trench (17) under the permeation of the foundation itself; the passive drainage pipe (21) drains the water to the predetermined drainage point under the action of the water drainage slope.

2. A passive, maintenance-free anti-floating system for building groundwater according to claim 1, characterized in that, The foundation below the structural bottom plate (23) is provided with a grid-shaped or ring-shaped drainage blind ditch (24), the drainage blind ditch (24) has a water drainage slope for collecting water into the trench (17); a filter layer (25) is arranged in the foundation and the drainage blind ditch (24), the drainage blind ditch (24) and the foundation are provided with the water-permeable layer (18), the filter layer (25) is arranged on the bottom surface of the structural bottom plate (23) on the water-permeable layer (18), and the water below the foundation is collected into the drainage blind ditch (24) through the filter layer (25) and the water-permeable layer (18).

3. A passive, maintenance-free anti-floating system for building groundwater according to claim 1, characterized in that, The trench (17) is respectively provided with a water collecting well (26) and a maintenance well (27), the bottom elevation of the water collecting well (26) and the maintenance well (27) is lower than the passive drainage pipe (21), the top elevation of the water collecting well (26) and the maintenance well (27) is the same as the ground elevation, and the passive drainage pipe (21) is connected with the water collecting well (26) and the maintenance well (27).

4. A passive, maintenance-free anti-floating system for building groundwater according to claim 1, characterized in that, A one-way valve is arranged at the outlet pipe.

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

6. A method of constructing a passive, maintenance-free anti-floating system for groundwater of a building according to any one of claims 1 to 5, characterized in that, The application further discloses a method for calculating the water drainage flow of the anti-floating system based on the scale model. Step one: calculating the water drainage flow of the anti-floating system based on the scale model. The application discloses a model based on a building anti-floating system, which comprises a foundation pit simulation box, a water injection simulation box, a building simulation box, a passive drainage system and a water injection system. The operation steps are as follows: Calculate the field water replenishment flow Q 补 : Select representative parts in each direction in the field area, then conduct water level recovery test after pumping, organize water level recovery data, and obtain the water replenishment rate Q 试 , and then compare the ratio of the highest historical precipitation to the current year's precipitation to obtain the final water replenishment rate Q 补 , Q 补 = Q 试 ·(R 最 / R 今 ), R 最 is the highest historical precipitation; R 今 is the current year's precipitation; Obtaining the drainage flow rate Q 排 : Water is injected into the water injection simulation box through the water injection system. The outlet of the passive drainage system is blocked during the water injection process. After the water injection reaches the experimental water level, the blockage of the outlet is opened, and the drainage begins. The water in the foundation pit simulation box is drained into the measuring barrel. The drainage flow rate Q needs to be recorded in the unit time during the process 排 , and the final water replenishment speed Q 补 is injected into the water injection simulation box through the water injection system; Step two: calculating the height of lowering the underground water level based on the drainage flow and the water supplement flow: the drainage flow in unit time is calculated according to the drainage flow and the water supplement flow, and the ratio of the drainage flow to the building simulation box area is the effective height of lowering the underground water level; h 降 = (Q 排 -Q 补 ) * d / A; Q 排 Q is the flow rate of the drain; Q 补 Q is the final makeup rate; d is the unit of time; A is the floor area of the building mockup. Step three: checking the anti-floating stability safety factor: the anti-floating stability safety factor is checked, if the factor meets the standard, the slope of the passive drainage system is calculated, the pipe diameter of the passive drainage system is calculated by conversion, and the next construction is carried out; if the factor does not meet the standard, the drainage slope and the pipe diameter of the passive drainage system are adjusted, the drainage flow is recalculated, the anti-floating stability safety factor is checked again, and the adjustment is repeated until the anti-floating stability safety factor passes the check; Step four: removing the sundries in the fat groove, and reserving the dewatering wells in the fat groove around the building; the seepage layer is backfilled in the fat groove and the dewatering well, when the seepage layer is backfilled to the bottom elevation of the passive drainage pipe, the passive drainage pipe is installed according to the design elevation and the drainage slope; after the installation is completed, the seepage layer is continuously backfilled; Step five: laying the waterproof geotextile on the seepage layer, and carrying out the backfill layer construction on the waterproof geotextile.

7. The construction method according to claim 6, characterized in that, The water injection system comprises 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 connected to the water injection simulation tank through the water supply pipe respectively; during the experiment, water is first injected into the water injection simulation tank through the water supply pump tank to the designed elevation, then the water supply pump is closed, and water is injected into the water injection simulation tank according to the final water supplement speed Q 补 by metering.

8. The construction method according to claim 6, characterized in that, After the foundation pit is excavated to the design elevation, the drainage blind ditch is excavated on the foundation bottom, one or more layers of geotextile are fully laid on the foundation bottom and the blind ditch as the filter layer, and the seepage layer is laid on the filter layer.

9. The construction method according to claim 6, characterized in that, The water collecting well and the maintenance well are arranged in the fat groove, the bottom elevation of the water collecting well and the maintenance well is lower than that of the passive drainage pipe, the top elevation is the same as the ground elevation, and the passive drainage pipe is connected with the water collecting well and the maintenance well.

10. The construction method according to claim 6, characterized in that, When the seepage layer is backfilled in the fat groove, the non-solidified soil is synchronously arranged outside the seepage layer for wrapping.

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