A method for constructing a pit within a pit and for dewatering

Abstract

This invention discloses a pit-within-a-pit construction method and dewatering mechanism, comprising a construction method for fully weathered mixed granite. The upper end of the fully weathered mixed granite is provided with a sandy clay layer, and a fixing plate is installed inside the sandy clay layer. Engineering columns are installed inside the fully weathered mixed granite. The surface of the fully weathered mixed granite is provided with two steel wire mesh shotcrete layers, A and B. A drainage ditch is provided on the upper surface of the fully weathered mixed granite, and a safety railing is installed above the drainage ditch. A pit-within-a-pit foundation is provided in the middle of the fully weathered mixed granite. Foundation pit support is provided inside the fully weathered mixed granite. A brick formwork partition wall is provided on one side of the pit-within-a-pit foundation. A water ditch flow channel is provided at the bottom of the sand and gravel backfill layer. This method offers good economic benefits, lower costs, eliminates the need for sheet piles and other similar processes, and reduces the use of large machinery, making it particularly advantageous for deep foundation pit projects.

Description

Technical Field

[0001] This invention relates to the field of drainage construction, and more particularly to a pit-within-a-pit and a method for dewatering construction. Background Technology

[0002] Currently, first-tier cities are undergoing rapid renovation and upgrading, while urban land space is limited. Most new or renovated buildings are developing at higher elevations or deep underground. Coastal cities often encounter challenging geological conditions and high groundwater levels, making pit-within-pit excavation extremely difficult.

[0003] Excavation of pits within pits is a crucial step before the main construction of a project; failure to do so will significantly impact subsequent progress. With the increasing height of modern buildings, the depth of pits within pits is also increasing. Therefore, ensuring the smooth progress of the project while simultaneously guaranteeing construction safety and economic efficiency presents immense challenges.

[0004] To ensure the safety of pit-in-pit excavation and the smooth progress of pit-in-pit construction, a method for pit-in-pit excavation and its dewatering construction is invented. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a pit-within-a-pit and dewatering construction method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a pit-in-pit and dewatering construction method, including a construction method for fully weathered mixed granite, wherein a sandy clay layer is provided at the upper end of the fully weathered mixed granite, a fixing plate is provided inside the sandy clay layer, and an engineering column is installed inside the fully weathered mixed granite.

[0007] The surface of the completely weathered mixed granite is provided with a steel wire mesh shotcrete surface layer A and a steel wire mesh shotcrete surface layer B. A drainage ditch is provided on the upper surface of the completely weathered mixed granite, and a safety railing is installed above the drainage ditch. A pit-in-pit foundation is provided in the middle of the completely weathered mixed granite. The pit support is provided inside the completely weathered mixed granite. A brick formwork partition wall is provided on one side of the pit-in-pit foundation. A pit-in-pit steel column cantilever is provided at the bottom of the pit-in-pit foundation. A sand and gravel backfill layer is provided on the surface of the steel wire mesh shotcrete surface layer A and steel wire mesh shotcrete surface layer B. A water ditch flow channel is provided at the bottom of the sand and gravel backfill layer.

[0008] The steps of the construction method are as follows:

[0009] S1: Familiarize yourself with the geological survey report and drawings, analyze the relevant geological conditions and water level of the pit-in-pit location, and determine the geological section type of the location based on the geology and water level of the pit-in-pit, and preliminarily determine the excavation method and whether dewatering is required.

[0010] S2: Based on the geological cross-section type and groundwater level, first determine the depth and number of dewatering wells, and then determine the layout range of the dewatering wells in conjunction with the location of the surrounding foundation. When the groundwater level is high, it should be considered that the soil in the pit within the pit may be soaked for a long time, and direct excavation may affect the original foundation soil of the pit within the pit. Therefore, when excavating the pit within the pit, a certain amount of undisturbed soil should be maintained at the bottom slab or foundation, with a thickness of not less than 500mm, to ensure that the foundation soil is not disturbed during the excavation of the pit within the pit. The dewatering depth of the dewatering wells should ensure that the water level in the pit within the pit drops to 500-1000mm or more above the excavation surface;

[0011] S3: When the water level drops to 500-1000mm above the excavation surface, the excavation of the pit within the pit can be carried out. The excavation range and slope ratio should be determined according to the geological conditions. At the same time, a 300×300mm drainage ditch should be set up around the top of the pit to ensure that it can intercept water when there is rainfall or other water use.

[0012] S4: Construct the pit in sequence to the bottom of the pit, and set up a drainage ditch around the perimeter of the pit bottom. Reserve water collection wells at the four corners of the pit to further ensure smooth drainage of the pit in case the dewatering wells are blocked or the dewatering depth is insufficient.

[0013] S5: After the pit-within-a-pit excavation is completed, a reliable method of slope protection should be adopted, such as wire mesh and shotcrete.

[0014] S6: When the excavation reaches the bottom, the pit-within-a-pit construction and retaining wall construction shall begin. A 1m high concrete retaining wall can be set at the bottom, and a brick formwork of different thicknesses shall be set at the top according to the height. The brick formwork shall be constructed with lime-sand bricks. At the same time, the drainage ditch at the bottom shall be retained when the foundation layer is poured, and a water collection well shall be reserved for pumping.

[0015] S7: Backfilling, after the pit-within-the-pit retaining structure is stable, backfill with graded sand and gravel;

[0016] S8: Construction completed. Waterproofing, rebar tying, and other procedures will be carried out according to the construction sequence.

[0017] As a further description of the above technical solution:

[0018] The sandy clay layer is filled on top of the completely weathered mixed granite, and the fixing plate is fixedly installed inside the sandy clay layer. There are several fixing plates. The engineering column is fixedly installed inside the completely weathered mixed granite. There are several engineering columns.

[0019] As a further description of the above technical solution:

[0020] The steel wire mesh shotcrete surface layer A is fixedly connected to the inclined side of the completely weathered mixed granite, and the steel wire mesh shotcrete surface layer B is fixedly connected to the inclined side of the completely weathered mixed granite. The steel wire mesh shotcrete surface layer A and the steel wire mesh shotcrete surface layer B have the same dimensions.

[0021] As a further description of the above technical solution:

[0022] The drainage ditch is opened on the surface of the completely weathered mixed granite, the safety railing is fixedly connected to the top of the completely weathered mixed granite, and there are several safety railings. The pit-in-pit foundation is fixedly installed inside the completely weathered mixed granite.

[0023] As a further description of the above technical solution:

[0024] The foundation pit support is fixedly connected to the outside of the pit foundation, and the size of the foundation pit support is smaller than the size of the completely weathered mixed granite. The brick formwork partition wall is fixedly connected to both sides of the pit foundation, and the size of the brick formwork partition wall is larger than the size of the pit foundation.

[0025] As a further description of the above technical solution:

[0026] The steel column cantilever in the pit is connected through the interior of the completely weathered mixed granite, and the size of the steel column cantilever in the pit is smaller than the size of the completely weathered mixed granite.

[0027] As a further description of the above technical solution:

[0028] The sand and gravel backfill layer is fixedly connected to the surfaces of the wire mesh shotcrete surface layer A and the wire mesh shotcrete surface layer B. The sand and gravel backfill layer is triangular in shape. The water ditch flow channel is opened between the sand and gravel backfill layer and the completely weathered mixed granite. The water ditch flow channel is connected to the drainage ditch.

[0029] The present invention has the following beneficial effects:

[0030] In this invention, 1. it has good economic benefits and low cost, does not require the use of steel sheet piles and other processes, and reduces the use of large machinery in construction, making it more advantageous for deep foundation pit projects.

[0031] 2. High safety and greater convenience. By analyzing the geological conditions, appropriate construction methods can be adopted more accurately without the need for multiple tests. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of a pit-within-a-pit and dewatering construction method proposed in this invention;

[0033] Figure 2This is a cross-sectional view of the reinforcement method for a pit-within-a-pit and dewatering construction method proposed in this invention;

[0034] Figure 3 This is a schematic diagram of the foundation pit support for a pit-within-a-pit and dewatering construction method proposed in this invention.

[0035] Figure 4 This is a cross-sectional view of the brick formwork and support method for a pit-within-a-pit and dewatering construction method proposed in this invention.

[0036] Figure 5 This is a cross-sectional view of the slope excavation and reinforcement method for a pit-within-a-pit and dewatering construction method proposed in this invention.

[0037] Legend:

[0038] 1. Completely weathered mixed granite; 2. Sandy clay layer; 3. Fixing plate; 4. Engineering column; 5. Steel wire mesh shotcrete surface layer A; 6. Drainage ditch; 7. Safety railing; 8. Pit-in-pit foundation; 9. Pit support; 10. Steel wire mesh shotcrete surface layer B; 11. Brick formwork partition wall; 12. Cantilever steel structure column in pit; 13. Sand and gravel backfill layer; 14. Flow channel for drainage. Detailed Implementation

[0039] 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] Reference Figure 1-5 An embodiment of the present invention provides a method for constructing a pit within a pit and a dewatering system, comprising a fully weathered mixed granite 1 and a construction method, wherein a sandy clay layer 2 is provided at the upper end of the fully weathered mixed granite 1, a fixing plate 3 is provided inside the sandy clay layer 2, and an engineering column 4 is installed inside the fully weathered mixed granite 1.

[0042] The surface of the completely weathered mixed granite 1 is provided with a steel wire mesh shotcrete surface layer A5 and a steel wire mesh shotcrete surface layer B10. A drainage ditch 6 is provided on the upper surface of the completely weathered mixed granite 1. A safety railing 7 is installed above the drainage ditch 6. A pit-in-pit foundation 8 is provided in the middle of the completely weathered mixed granite 1. A foundation pit support 9 is provided inside the completely weathered mixed granite 1. A brick formwork partition wall 11 is provided on one side of the pit-in-pit foundation 8. A pit-in-pit steel column cantilever 12 is provided at the bottom of the pit-in-pit foundation 8. A sand and gravel backfill layer 13 is provided on the surface of the steel wire mesh shotcrete surface layer A5 and the steel wire mesh shotcrete surface layer B10. A water ditch flow channel 14 is provided at the bottom of the sand and gravel backfill layer 13.

[0043] In this invention, the sandy clay layer 2 is filled on top of the completely weathered mixed granite 1, the fixing plate 3 is fixedly installed inside the sandy clay layer 2, and there are several fixing plates 3. The engineering column 4 is fixedly installed inside the completely weathered mixed granite 1, and there are several engineering columns 4. By setting the engineering columns 4, the stability of the structure can be maintained and it will not easily collapse.

[0044] Furthermore, the steel wire mesh shotcrete surface layer A5 is fixedly connected to the inclined side of the completely weathered mixed granite 1, and the steel wire mesh shotcrete surface layer B10 is fixedly connected to the inclined side of the completely weathered mixed granite 1. The steel wire mesh shotcrete surface layer A5 and the steel wire mesh shotcrete surface layer B10 have the same dimensions.

[0045] Specifically, for the construction and protection of pit-within-pit structures, a 1m high concrete retaining wall can be set at the bottom, and a brick formwork of different thicknesses can be set on the top according to the height. The brick formwork must be constructed with lime-sand bricks. At the same time, the drainage ditch at the bottom should be retained when pouring the foundation layer, and a water collection well should be reserved.

[0046] Furthermore, the drainage ditch 6 is opened on the surface of the completely weathered mixed granite 1, the safety railing 7 is fixedly connected to the top of the completely weathered mixed granite 1, and there are several safety railings 7. The pit-in-pit support 8 is fixedly installed inside the completely weathered mixed granite 1. Through the setting of the drainage ditch 6, the water in the pit-in-pit can be diverted out.

[0047] Furthermore, the foundation pit support 9 is fixedly connected to the outside of the pit foundation 8, and the size of the foundation pit support 9 is smaller than the size of the completely weathered mixed granite 1. The brick formwork partition wall 11 is fixedly connected to both sides of the pit foundation 8, and the size of the brick formwork partition wall 11 is larger than the size of the pit foundation 8.

[0048] Furthermore, the steel column cantilever 12 in the pit is connected through the interior of the completely weathered mixed granite 1, and the size of the steel column cantilever 12 in the pit is smaller than the size of the completely weathered mixed granite 1.

[0049] Furthermore, the sand and gravel backfill layer 13 is fixedly connected to the surfaces of the wire mesh shotcrete surface layer A5 and the wire mesh shotcrete surface layer B10. The sand and gravel backfill layer 13 is triangular in shape. The water ditch flow channel 14 is opened between the sand and gravel backfill layer 13 and the completely weathered mixed granite 1. The water ditch flow channel 14 is connected to the drainage ditch 6.

[0050] Example 1: S1: Familiarize yourself with the geological survey report and drawings, analyze the relevant geological conditions and water level of the pit-in-pit location, and determine the geological section type of the location based on the geology and water level of the pit-in-pit, and preliminarily determine the excavation method and whether dewatering is required.

[0051] S2: Based on the geological cross-section type and groundwater level, first determine the depth and number of dewatering wells, and then determine the layout range of the dewatering wells in conjunction with the location of the surrounding foundation. When the groundwater level is high, it should be considered that the soil in the pit within the pit may be soaked for a long time, and direct excavation may affect the original foundation soil of the pit within the pit. Therefore, when excavating the pit within the pit, a certain amount of undisturbed soil should be maintained at the bottom slab or foundation, with a thickness of not less than 500mm, to ensure that the foundation soil is not disturbed during the excavation of the pit within the pit. The dewatering depth of the dewatering wells should ensure that the water level in the pit within the pit drops to 500-1000mm or more above the excavation surface;

[0052] S3: When the water level drops to 500-1000mm above the excavation surface, the excavation of the pit within the pit can be carried out. The excavation range and slope ratio should be determined according to the geological conditions. At the same time, a 300×300mm drainage ditch should be set up around the top of the pit to ensure that it can intercept water when there is rainfall or other water use.

[0053] S4: Construct the pit in sequence to the bottom of the pit, and set up a drainage ditch around the perimeter of the pit bottom. Reserve water collection wells at the four corners of the pit to further ensure smooth drainage of the pit in case the dewatering wells are blocked or the dewatering depth is insufficient.

[0054] S5: After the pit-within-a-pit excavation is completed, a reliable method of slope protection should be adopted, such as wire mesh and shotcrete.

[0055] S6: When the excavation reaches the bottom, the pit-within-a-pit construction and retaining wall construction shall begin. A 1m high concrete retaining wall can be set at the bottom, and a brick formwork of different thicknesses shall be set at the top according to the height. The brick formwork shall be constructed with lime-sand bricks. At the same time, the drainage ditch at the bottom shall be retained when the foundation layer is poured, and a water collection well shall be reserved for pumping.

[0056] S7: Backfilling, after the pit-within-the-pit retaining structure is stable, backfill with graded sand and gravel;

[0057] S8: Construction completed. Waterproofing, rebar tying, and other procedures will be carried out according to the construction sequence.

[0058] Example 2: Drainage ditch 6 is opened on the surface of the completely weathered mixed granite 1, safety railing 7 is fixedly connected to the top of the completely weathered mixed granite 1, and there are several safety railings 7. Pit-in-pit support 8 is fixedly installed inside the completely weathered mixed granite 1. Through the setting of drainage ditch 6, the water in the pit can be diverted out.

[0059] The foundation pit support 9 is fixedly connected to the outside of the pit foundation 8. The size of the foundation pit support 9 is smaller than the size of the completely weathered mixed granite 1. The brick formwork partition wall 11 is fixedly connected to both sides of the pit foundation 8. The size of the brick formwork partition wall 11 is larger than the size of the pit foundation 8.

[0060] It offers good economic benefits, lower costs, eliminates the need for sheet piles and other similar technologies, and reduces the use of large machinery, making it particularly advantageous for deep foundation pit projects.

[0061] It offers high safety and greater convenience and speed. By analyzing the geological conditions, appropriate construction methods can be adopted more accurately without the need for multiple tests.

[0062] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pit-within-a-pit construction method and dewatering method, comprising fully weathered mixed granite (1) and a construction method, characterized in that: The upper end of the completely weathered mixed granite (1) is provided with a sandy clay layer (2), the inside of the sandy clay layer (2) is provided with a fixing plate (3), and the inside of the completely weathered mixed granite (1) is provided with an engineering column (4). The surface of the completely weathered mixed granite (1) is provided with a steel wire mesh shotcrete surface layer A (5) and a steel wire mesh shotcrete surface layer B (10). The upper surface of the completely weathered mixed granite (1) is provided with a drainage ditch (6). A safety railing (7) is installed above the drainage ditch (6). A pit-in-pit foundation (8) is provided in the middle of the completely weathered mixed granite (1). The interior of the completely weathered mixed granite (1) is provided with a foundation pit support (9). A brick formwork partition wall (11) is provided on one side of the pit-in-pit foundation (8). A pit-in-pit steel column cantilever (12) is provided at the bottom of the pit-in-pit foundation (8). The surfaces of the steel wire mesh shotcrete surface layer A (5) and the steel wire mesh shotcrete surface layer B (10) are provided with a sand and gravel backfill layer (13). A water ditch flow channel (14) is provided at the bottom of the sand and gravel backfill layer (13). The steps of the construction method are as follows: S1: Familiarize yourself with the geological survey report and drawings, analyze the relevant geological conditions and water level of the pit-in-pit location, and determine the geological section type of the location based on the geology and water level of the pit-in-pit, and preliminarily determine the excavation method and whether dewatering is required. S2: Based on the geological section type and groundwater level, first determine the depth and number of dewatering wells, and then determine the layout range of dewatering wells in conjunction with the location of the surrounding foundation. When the groundwater level is high, it should be considered that the soil of the pit within the pit may be soaked for a long time. Direct excavation may affect the original foundation soil of the pit within the pit. Therefore, when excavating the pit within the pit, a certain amount of undisturbed soil should be maintained at the bottom slab or foundation, with a thickness of not less than 500mm, to ensure that the foundation soil is not disturbed when the pit within the pit is excavated. The dewatering depth of the dewatering wells should ensure that the water level in the pit within the pit drops to 500-1000mm or more above the excavation surface. S3: When the water level drops to 500-1000mm above the excavation surface, the excavation range and slope ratio of the excavated pit should be determined according to the geological conditions. At the same time, a 300×300mm drainage ditch should be set up around the top of the pit to ensure that it can intercept water when there is rainfall or other water use. S4: Construct the pit in sequence to the bottom of the pit, and set up a drainage ditch around the perimeter of the pit bottom. Reserve water collection wells at the four corners of the pit to further ensure smooth drainage of the pit in case the dewatering wells are blocked or the dewatering depth is insufficient. S5: After the pit-within-a-pit excavation is completed, a reliable slope protection method should be adopted, including wire mesh and shotcrete. S6: When the excavation reaches the bottom, the pit-within-a-pit construction and retaining wall shall be constructed. A 1m high concrete retaining wall shall be set at the bottom, and a brick formwork of different thicknesses shall be set at the top according to the height. The brick formwork shall be constructed with lime-sand bricks. At the same time, the drainage ditch at the bottom shall be retained when the foundation layer is poured, and a water collection well shall be reserved for pumping. S7: Backfilling, after the pit-within-the-pit retaining structure is stable, backfill with graded sand and gravel; S8: Construction completed. Waterproofing and rebar tying will be carried out according to the construction procedures.

2. The method for constructing a pit-within-a-pit and dewatering system according to claim 1, characterized in that: The sandy clay layer (2) is filled on top of the completely weathered mixed granite (1), the fixing plate (3) is fixedly installed inside the sandy clay layer (2), and the engineering column (4) is fixedly installed inside the completely weathered mixed granite (1).

3. The method for constructing a pit-within-a-pit and dewatering system according to claim 1, characterized in that: The steel wire mesh shotcrete surface layer A (5) is fixedly connected to the inclined side of the fully weathered mixed granite (1), and the steel wire mesh shotcrete surface layer B (10) is fixedly connected to the inclined side of the fully weathered mixed granite (1). The steel wire mesh shotcrete surface layer A (5) and the steel wire mesh shotcrete surface layer B (10) have the same size.

4. The method for constructing a pit-within-a-pit and dewatering system according to claim 1, characterized in that: The drainage ditch (6) is opened on the surface of the weathered mixed granite (1), the safety railing (7) is fixedly connected to the top of the weathered mixed granite (1), the number of the safety railing (7) is several, and the pit-in-pit support (8) is fixedly installed inside the weathered mixed granite (1).

5. The method for constructing a pit-within-a-pit and dewatering system according to claim 1, characterized in that: The foundation pit support (9) is fixedly connected to the outside of the pit foundation (8). The size of the foundation pit support (9) is smaller than the size of the completely weathered mixed granite (1). The brick formwork partition wall (11) is fixedly connected to both sides of the pit foundation (8). The size of the brick formwork partition wall (11) is larger than the size of the pit foundation (8).

6. The method for constructing a pit-within-a-pit and dewatering system according to claim 1, characterized in that: The steel column cantilever (12) in the pit is connected through the interior of the completely weathered mixed granite (1), and the size of the steel column cantilever (12) in the pit is smaller than the size of the completely weathered mixed granite (1).

7. The method for constructing a pit-within-a-pit and dewatering system according to claim 1, characterized in that: The sand and gravel backfill layer (13) is fixedly connected to the surface of the wire mesh shotcrete surface layer A (5) and the wire mesh shotcrete surface layer B (10). The sand and gravel backfill layer (13) is triangular in shape. The water ditch flow channel (14) is opened between the sand and gravel backfill layer (13) and the completely weathered mixed granite (1). The water ditch flow channel (14) is connected to the drainage ditch (6).

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