Foundation pit backfilling structure and anti-floating and anti-seepage system

Abstract

The invention discloses a foundation pit backfilling structure and an anti-floating impervious system, and relates to the technical field of building construction.The foundation pit backfilling structure comprises a foundation pit, the foundation pit comprises an impervious area, a structural area and an anti-floating area which are arranged from bottom to top, and the anti-floating area comprises a drainage layer, a water-resisting layer, a capillary network layer and an anti-floating layer which are arranged from bottom to top; the anti-floating layer is filled with aggregate used for forming pores, and the capillary network layer and the drainage layer are used for being communicated with an external water storage structure. The anti-floating and anti-seepage system comprises a drainage system and the foundation pit backfilling structure, the drainage system comprises a water collecting well, a water level sensor, a pressure sensor, water pumping equipment and a remote control terminal, and the water pumping equipment comprises a first drainage pump and a second drainage pump. The aggregate can form a plurality of pores, the density of the anti-floating layer can be reduced, underground water in the lateral direction of the foundation pit can be rapidly discharged into the capillary network layer and then discharged, the influence of buoyancy on the backfill structure is eliminated, and the technical effect of improving the building safety is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building construction, in particular to a foundation pit backfill structure and anti-floating and anti-seepage system. BACKGROUND

[0002] In the field of building engineering, foundation pit backfill is a key link in foundation construction, and its quality directly affects the stability and long-term safety of the upper structure. However, in this process, it often faces the negative impact of underground water. When the underground water level is high, during or after the backfill construction, the underground water will generate a huge upward floating force under the pressure of the soil layer. This floating force acts on the backfill material (such as plain soil, lime soil or graded sand, etc.) in the foundation pit, which may cause uneven floating of the filler layer, resulting in ground subsidence and cracking, or even push up the entire foundation slab, causing serious structural safety problems, and posing a great threat to the overall safety of subsequent construction and buildings.

[0003] To deal with this technical problem, the most common method in the prior art is to set a heavy weight pressure zone at the bottom of the foundation pit or in the backfill body. Specifically, a large amount of reinforced concrete counterweight block is usually used, or high-density materials (such as barite concrete, iron ore, etc.) are used for replacement and laying, so as to balance and offset the floating force of underground water through its huge self-weight. However, this traditional "anti-floating by weight" method is a kind of "passive resistance" and "forced offset" strategy, which does not fundamentally eliminate or weaken the floating force itself. This method acknowledges and accepts the objective existence of the floating force, and only tries to "suppress" it with a larger weight. Once the design counterweight is insufficient or the underground water level is abnormally high, resulting in a floating force exceeding the preset value, the anti-floating measure will fail, and the safety hazard cannot be completely eliminated.

[0004] Therefore, there is an urgent need for a foundation pit backfill structure and anti-floating and anti-seepage system with higher safety. SUMMARY

[0005] The purpose of the present application is to provide a foundation pit backfill structure and anti-floating and anti-seepage system, which can offset the floating force through the aggregate filling of the anti-floating zone, and quickly drain the underground water through the capillary network layer and the drainage layer, thereby avoiding the problem of floating force on the backfill structure and improving the safety of the building.

[0006] To achieve the above purpose, the present application provides the following solutions: The present application provides a foundation pit backfill structure, comprising: a foundation pit, the foundation pit comprising an anti-seepage zone, a structure zone and an anti-floating zone arranged from bottom to top, the anti-floating zone comprising a drainage layer, a water-resisting layer, a capillary network layer and an anti-floating layer arranged from bottom to top, the anti-floating layer being filled with aggregate for forming pores, and the capillary network layer and the drainage layer being used to communicate with an external water storage structure.

[0007] Preferably, the aggregate includes closed-cell ceramsite and foamed glass microspheres.

[0008] Preferably, the anti-buoyancy layer is filled with a water-repellent agent.

[0009] Preferably, the drainage layer includes a permeable filler layer and a drainage ditch. The permeable filler layer is located below the waterproof layer, and the drainage ditch is located below the permeable filler layer. The drainage ditch is used to connect to an external water storage structure.

[0010] Preferably, the permeable filler layer is a permeable sand layer, and the waterproof layer is a concrete layer.

[0011] Preferably, it also includes a serrated groove, which is disposed on the outer wall of the underground structure sidewall and is fitted with the anti-seepage zone and the structural zone.

[0012] Preferably, it also includes a permeable geogrid, which is pressed between the serrated trench and the impermeable zone and the structural zone.

[0013] Preferably, the waterproof layer and the drainage layer extend to the underside of the underground structure's base slab.

[0014] Preferably, the impermeable zone comprises nano-silica sol and bentonite, and the structural zone comprises cement-based curing agent and steel slag powder.

[0015] The present invention also provides an anti-buoyancy and anti-seepage system, characterized in that it includes a drainage system and the above-mentioned foundation pit backfill structure, wherein the drainage system includes: The water collection well is connected to the outlet of the drainage layer and the outlet of the anti-buoyancy layer, respectively, and the bottom surface of the water collection well is lower than the drainage layer. A water level sensor, wherein the water level sensor is disposed at a preset depth within the water collection well; A pressure sensor, wherein the pressure sensor is disposed within the capillary network layer; A water pumping device, comprising a first drainage pump and a second drainage pump, wherein the inlet of the first drainage pump is connected to a first pumping pipe extending into the water collection well, the outlet of the first drainage pump is connected to a drainage pipeline, the inlet of the second drainage pump is connected to the drainage outlet of the capillary network through a second pumping pipe, and the outlet of the second drainage pump is connected to the drainage pipeline. The system also includes a remote control terminal, and the first drainage pump, the water level sensor, the second drainage pump, and the pressure sensor are all communicatively connected to the remote control terminal.

[0016] The present invention achieves the following technical effects compared to the prior art: In this invention, the anti-buoyancy layer inside the foundation pit is filled with aggregate. The aggregate fills the pit with many pores. The presence of these pores prevents the anti-buoyancy layer from forming a complete, sealed surface to withstand all the water pressure. Groundwater from the side of the foundation pit can freely enter the layer, preventing the water pressure from accumulating into a huge upward thrust. Furthermore, the capillary network layer can drain the water that has entered the pores between the aggregates from the foundation pit. At the same time, the drainage layer can discharge the groundwater on the lower side of the foundation pit to an external water storage structure. This avoids the groundwater at the bottom of the foundation pit from generating buoyancy on the backfill structure due to underground stress, fundamentally eliminating the impact of buoyancy on the backfill structure and achieving the technical effect of improving building safety. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the anti-buoyancy and anti-seepage system (including the foundation pit backfill structure) in an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached diagram: 1. Impermeable zone; 2. Structural zone; 3. Water-resistant layer; 4. Capillary network layer; 5. Anti-buoyancy layer; 6. Permeable filler layer; 7. Drainage ditch; 8. Serrated trench; 9. Water collection well; 10. Drainage system. Detailed Implementation

[0020] 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.

[0021] The purpose of this invention is to provide a foundation pit backfill structure and an anti-buoyancy and anti-seepage system to solve the problems existing in the prior art. By using a capillary network layer and an anti-buoyancy layer, the influence of buoyancy on the backfill structure is eliminated, thereby improving the safety of the building.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1 Please refer to Figure 1As shown, this embodiment provides a foundation pit backfill structure, including: a foundation pit, which includes, from bottom to top, an impermeable zone 1 (top layer), a structural zone 2 (middle layer), and an anti-buoyancy zone (bottom layer). The impermeable zone 1 (top layer) is used to prevent rainwater from seeping down. The structural zone 2 (middle layer) provides structural strength for the foundation pit backfill structure, ensuring bearing capacity. The anti-buoyancy zone includes, from bottom to top, a drainage layer, a waterproof layer 3, a capillary network layer 4, and an anti-buoyancy layer 5. The capillary network layer 4 contains a capillary drainage network, and the capillary network layer 4 (capillary drainage network) and the drainage layer are used to connect to an external water storage structure. The anti-buoyancy layer 5 is filled with aggregate, which is used to form pores within the anti-buoyancy layer 5 and reduce density.

[0024] Its working principle is as follows: The anti-buoyancy layer 5 is filled with aggregate, which forms pores between the aggregate. The presence of these pores allows water from the soil on the side of the foundation pit to freely enter the anti-buoyancy layer 5 under the stress of the underground soil and quickly flow into the capillary network layer 4. This water is then rapidly discharged from the foundation pit through the capillary drainage network, eliminating buoyancy and preventing the accumulation of large amounts of buoyancy at the anti-buoyancy layer 5, which could cause the foundation pit to float or tilt. Simultaneously, the drainage layer at the bottom of the foundation pit guides the groundwater below the pit to an external water storage structure, preventing the groundwater below the pit from generating upward buoyancy on the backfill structure under stress. This fundamentally prevents the formation and accumulation of buoyancy, eliminating its impact on the backfill structure and achieving the technical effect of improving building safety.

[0025] In one embodiment, the surface of the capillary network layer 4 is covered with a permeable geotextile, that is, the upper surface of the capillary drainage network is covered with a permeable geotextile, which can filter silt and prevent the capillary drainage network from becoming clogged.

[0026] In one embodiment, lightweight aggregates such as closed-cell ceramsite or foamed glass microspheres can be used. Heavier aggregates such as crushed stone can also be used. However, lightweight aggregates are preferred because they reduce the self-weight of the backfill structure and counteract the buoyancy of groundwater. For example, the density of closed-cell ceramsite is typically around 300 kg / m³. 3~ 800kg / m 3 The density of foamed glass microspheres is as low as 100 kg / m³. 3 ~300kg / m 3 Crushed stone materials have a density as high as 1600 kg / m³. 3 ~2000kg / m 3Not only do they fail to counteract buoyancy, but their own weight may also increase the structural load. Lightweight aggregates achieve a negative buoyancy effect by reducing density, an active anti-buoyancy mechanism that heavier aggregates such as crushed stone cannot achieve. At the same time, lightweight aggregates are mostly industrial waste or recycled materials, meeting green building requirements. Their closed-cell structure is corrosion-resistant and non-degradable, maintaining density and anti-buoyancy performance for a long time. Crushed stone materials, on the other hand, are obtained through mountain mining, damaging the ecology and consuming high energy during transportation. They cannot achieve resource recycling, and may also undergo aggregate dissolution or chemical erosion in groundwater environments, leading to increased porosity and reduced anti-buoyancy performance.

[0027] In one embodiment, the anti-buoyancy layer 5 is filled with a water-repellent agent, and a hydrophobic layer is formed by adding the water-repellent agent to counteract the buoyancy of groundwater, so that water in the lateral soil of the foundation pit can preferentially enter the capillary network layer 4, thereby accelerating the outflow of groundwater in the lateral soil.

[0028] In one embodiment, the drainage layer includes a permeable filler layer 6 and a drainage ditch 7. The permeable filler layer 6 is located below the impermeable layer 3, and the drainage ditch 7 is located below the permeable filler layer 6, serving to connect to an external water storage structure. The impermeable layer 3 isolates the drainage layer from the anti-buoyancy layer 5, preventing water exchange between them and ensuring the independence of their respective drainage processes. The permeable filler layer contains numerous interconnected pores, forming an efficient underground drainage network. When the groundwater level rises and water pressure increases, groundwater preferentially flows into this permeable layer instead of directly pushing upwards against the impermeable layer 3. The permeable filler layer 6 is connected to the drainage ditch 7, allowing water flowing into it to enter the ditch 7, which then rapidly drains the water. Preferably, the permeable filler layer 6 can be directly connected to the external water storage structure, improving drainage efficiency through a dual-path drainage system using the permeable filler layer and the drainage ditch 7.

[0029] In one embodiment, the permeable filler layer 6 is a permeable sand layer.

[0030] In one embodiment, the waterproof layer 3 is a concrete layer. Preferably, the surface of the concrete layer is coated with a waterproof coating.

[0031] In one embodiment, the impermeable zone 1 includes nano-silica sol and bentonite, which can form a dense impermeable layer to prevent rainwater or domestic wastewater from seeping into the foundation pit.

[0032] In one embodiment, the structural zone 2 includes a cement-based curing agent and steel slag powder. The structural zone 2 with added cement-based curing agent and steel slag powder has higher strength, ensuring the bearing capacity of the backfill structure in the foundation pit.

[0033] In one embodiment, the foundation pit backfill structure also includes a sawtooth trench 8, which is set on the outer wall of the underground structure sidewall. The sawtooth trench 8 is fitted with the anti-seepage zone 1 and the structural zone 2. By setting the sawtooth trench 8, the connection strength between the anti-seepage zone 1 and the underground structure sidewall, and between the structural zone 2 and the underground structure sidewall is enhanced, further ensuring the bearing capacity of the backfill structure.

[0034] In one embodiment, a permeable geogrid is also included. The permeable geogrid is pressed between the serrated trench 8 and the impermeable zone 1 and the structural zone 2. The permeable geogrid can increase the mechanical interlocking force between the underground structure sidewall and the foundation pit, preventing the backfill structure of the foundation pit from slipping. At the same time, the permeable geogrid has a drainage channel function, which can eliminate the pore water pressure between the interfaces and improve the stability of the backfill structure of the foundation pit.

[0035] In one embodiment, the waterproof layer 3 and the drainage layer extend to the underside of the underground structure's base slab. This arrangement effectively prevents groundwater from exerting buoyancy on the base slab. Preferably, the drainage ditch 7 also extends to the underside of the underground structure's base slab.

[0036] In one embodiment, drainage pipes are installed inside the drainage ditch 7.

[0037] Example 2 refer to Figure 1 As shown, this embodiment provides an anti-buoyancy and anti-seepage system, including a drainage system and the foundation pit backfill structure in Embodiment 1. The drainage system includes a collection well 9, a water level sensor, a pressure sensor, a pumping device 10, and a remote control terminal. The outlets of the drainage layer and the anti-buoyancy layer 5 are respectively connected to the collection well 9. The bottom surface of the collection well 9 is lower than the drainage layer, and the water level sensor is set at a preset depth inside the collection well 9. The pressure sensor is set inside the capillary network layer 4. The pumping device 10 includes a first drainage pump and a second drainage pump. The inlet of the first drainage pump is connected to a first pumping pipe extending into the collection well 9, and the outlet of the first drainage pump is connected to the drainage pipeline. The inlet of the second drainage pump is connected to the drainage outlet of the capillary network through a second pumping pipe, and the outlet of the second drainage pump is connected to the drainage pipeline. The water level sensor, the first drainage pump, the second drainage pump, and the pressure sensor are all communicatively connected to the remote control terminal.

[0038] The working principle is as follows: water entering the drainage layer and the anti-buoyancy layer 5 can enter the water collection well 9 under the action of pressure and gravity. The water level sensor can monitor the liquid level in the water collection well 9. When the liquid level in the water collection well 9 reaches the preset height, the water level sensor transmits the signal to the remote control terminal. The remote control terminal then controls the first drainage pump to start, actively pumping out the water in the water collection well 9 and discharging it to the outside of the foundation pit through the drainage pipeline. When the inflow rate of capillary network layer 4 exceeds the outflow rate, the water accumulation in the capillary network will gradually increase. This increase in water accumulation will raise the pressure in capillary network layer 4. The pressure sensor can monitor the pressure in capillary network layer 4 and transmit the pressure information back to the remote control terminal. When the pressure in capillary network layer 4 reaches a certain level, the remote control terminal controls the second drainage pump to start. The second drainage pump can pump out the water in capillary network layer 4, allowing the water in capillary network layer 4 to be discharged quickly. The pressure in capillary network layer 4 is equivalent to buoyancy for the upper backfill structure. This setting method can ensure that the upper backfill structure is not affected by buoyancy.

[0039] Pressure sensors monitor water pressure changes in the pipeline network in real time and transmit the data to a remote control terminal via remote signals (such as the Internet of Things). This provides early warning of abnormal buoyancy. The capillary network layer 4 is connected to the collection well 9, which automatically starts the second drainage pump, achieving integrated "monitoring-drainage-anti-buoyancy". The collection well 9 is located below the permeable sand layer. A drainage ditch 7 is dug between the collection well 9 and the underground structure. The drainage ditch 7 passes through the permeable sand layer and connects to the collection well 9. Water level sensors monitor water level changes in the collection well 9 in real time, and the remote control terminal automatically adjusts the working status of the first drainage pump according to the water level.

[0040] In one embodiment, the backfill structure is made of fluidized solidified soil material, which can solve the drawbacks of traditional backfill materials and greatly increase economic and environmental benefits.

[0041] In one embodiment, the anti-buoyancy and anti-seepage system includes the following steps during manufacturing: S1. During the backfilling construction of the foundation pit, the bottom and side surfaces of the foundation pit are cleaned. The underground structure sidewall is installed on the side where the foundation pit is connected to the building. The underground structure sidewall is provided with a sawtooth groove 8 and equipped with a permeable geogrid. A concrete layer and a permeable sand layer are set at the bottom of the underground structure slab. S2. Locate the drainage ditch 7 and the collection well 9 under the permeable sand layer. Set up the collection well 9 in the internal space of the wall connecting the foundation pit and the building to ensure effective drainage of the underground structure. The collection well 9 has a concave structure. The drainage ditch 7 is under the permeable sand layer and runs through the foundation pit and the collection well 9. The drainage ditch 7 is dug between the collection well 9 and the underground structure and a drainage pipe is laid. The drainage pipe passes through the underground structure and connects with the collection well 9. S4, the capillary network layer 4 is connected to a main pipeline, which extends separately into the collection well 9. Pressure sensors are installed in the capillary network layer 4. The pressure sensors detect the water level pressure in the anti-seepage layer and upload the data to the remote control terminal. Permeable geotextile is laid on top of the capillary network layer 4. S5: Install a water level sensor in the water collection well 9; S6. Backfill the foundation pit and trench. Dynamically adjust the material composition according to the stress characteristics (compression, shear, and impermeability) of the backfill location to form a fluidized solidified soil system with differentiated proportions in different layers and zones: Lightweight aggregate (such as closed-cell ceramsite or foamed glass microspheres) is added to the anti-buoyancy layer 5 to reduce density, and a water-repellent agent is added to form a hydrophobic layer to counteract the buoyancy of groundwater; High-strength formula (cement-based curing agent + steel slag powder) is used in structural zone 2 to ensure bearing capacity; Nano-silica sol and bentonite are added to impermeable zone 1 to form a dense impermeable layer.

[0042] S7: The water level of the collection well 9 is monitored in real time by a water level sensor. The remote control terminal automatically adjusts the working status of the first drainage pump according to the water level. The water pressure of the capillary network layer 4 is monitored by a pressure sensor. The remote control terminal automatically adjusts the working status of the second drainage pump according to the water pressure.

[0043] This anti-buoyancy and anti-seepage system improves the strength requirements of foundation pit and trench backfill. Simultaneously, the fluidized solidified soil material overcomes the shortcomings of traditional backfill materials, significantly increasing economic and environmental benefits. While addressing backfill strength requirements, it also achieves anti-buoyancy and anti-seepage effects on high-water-level underground soil layers, resolving issues such as insufficient bearing capacity and long-term durability in foundation pits and trenches with high water levels. This achieves a balance between the load-bearing capacity and anti-buoyancy and anti-seepage performance of the foundation pit and trench backfill structure.

[0044] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A foundation pit backfilling structure, characterized in that, The foundation pit includes an impermeable zone (1), a structural zone (2), and an anti-buoyancy zone arranged from bottom to top. The anti-buoyancy zone includes a drainage layer, a water-proof layer (3), a capillary network layer (4), and an anti-buoyancy layer (5) arranged from bottom to top. The anti-buoyancy layer (5) is filled with aggregate for forming pores. The capillary network layer (4) and the drainage layer are used to connect to the external water storage structure.

2. The foundation pit backfill structure according to claim 1, characterized in that, The aggregate includes closed-cell ceramsite or foamed glass microspheres.

3. The foundation pit backfill structure according to claim 1, characterized in that, The anti-buoyancy layer (5) is filled with a water-repellent agent.

4. The foundation pit backfill structure according to claim 1, characterized in that, The drainage layer includes a permeable filler layer (6) and a drainage ditch (7). The permeable filler layer (6) is located below the waterproof layer (3), and the drainage ditch (7) is located below the permeable filler layer (6). The drainage ditch (7) is used to connect to the external water storage structure.

5. The foundation pit backfill structure according to claim 4, characterized in that, The permeable filler layer (6) is a permeable sand layer, and the waterproof layer (3) is a concrete layer.

6. The foundation pit backfill structure according to claim 1, characterized in that, It also includes a sawtooth groove (8), which is set on the outer wall of the underground structure sidewall and is fitted with the anti-seepage zone (1) and the structural zone (2).

7. The foundation pit backfill structure according to claim 6, characterized in that, It also includes a permeable geogrid, which is pressed between the sawtooth trench (8) and the impermeable zone (1) and the structural zone (2).

8. The foundation pit backfill structure according to claim 1, characterized in that, The waterproof layer (3) and the drainage layer extend to the underside of the underground structure floor slab.

9. The foundation pit backfill structure according to claim 1, characterized in that, The impermeable zone (1) includes nano-silica sol and bentonite, and the structural zone (2) includes cement-based curing agent and steel slag powder.

10. An anti-buoyancy and anti-seepage system, characterized in that, Includes a drainage system and a foundation pit backfill structure as described in any one of claims 1-9, wherein the drainage system comprises: The water collection well (9) is connected to the outlet of the drainage layer and the outlet of the anti-buoyancy layer (5), respectively. The bottom surface of the water collection well (9) is lower than the drainage layer. A water level sensor is installed at a preset depth inside the water collection well (9); A pressure sensor is disposed within the capillary network layer (4); Pumping equipment (10) includes a first drainage pump and a second drainage pump. The inlet of the first drainage pump is connected to a first pumping pipe that extends into the water collection well (9). The outlet of the first drainage pump is connected to a drainage pipeline. The inlet of the second drainage pump is connected to the outlet of the capillary network through a second pumping pipe. The outlet of the second drainage pump is connected to the drainage pipeline. The system also includes a remote control terminal, and the first drainage pump, the water level sensor, the second drainage pump, and the pressure sensor are all communicatively connected to the remote control terminal.

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