Foundation pit dewatering method based on rock strata geology

Abstract

The present invention discloses a method for dewatering a foundation pit in rock stratum geology, which divides the bottom of the foundation pit into a plurality of relatively independent water collection areas, and sets a seepage blind ditch in each area. A seepage well is set up or a seepage ditch is excavated at the water gushing point at the bottom of the foundation pit, and a dewatering well and a pumping well are set up outside the foundation pit at the water gushing point on the side wall of the foundation pit to carry out fixed-point dewatering in the foundation pit. The seepage ditch well is connected to the seepage blind ditch and is connected to the dewatering well and the pumping well outside the foundation pit through the connecting blind ditch, so as to realize efficient, fixed-point and precise dewatering inside and outside the foundation pit. The present invention solves the problem that the dewatering effect of the foundation pit in rock stratum geology is poor when using the traditional dewatering method.

Description

Technical Field

[0001] The invention relates to the technical field of building construction, and in particular to a foundation pit dewatering method for rock stratum geology. Background Art

[0002] At present, for deep foundation pit excavation and drainage construction such as open-cut subway stations, it is generally necessary to construct precipitation wells in advance outside the foundation pit, and carry out precipitation operations in advance before foundation pit excavation to ensure that the foundation pit excavation support and other construction processes are carried out under water-free conditions. However, under geological conditions dominated by rock strata, the rock stratum area is mainly in the form of bedrock fissure water, which has a relatively obvious characteristic of flowing only along the bedrock fissures. The rock strata with good integrity have poor permeability. Most precipitation wells cannot achieve effective precipitation effects, the utilization rate of precipitation wells is very low, and the precipitation effect is poor. Correspondingly, in areas where bedrock fissures are more developed, the bedrock fissure water is large, and the precipitation wells set according to conventional parameters nearby cannot meet its precipitation requirements. It is difficult to accurately construct precipitation wells on the bedrock fissures from the ground, resulting in the inability to perfectly match the precipitation well position, bedrock fissure water position, and fissure water volume. Not only can the precipitation effect not be achieved, but also it causes cost waste, construction delays and other losses.

[0003] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0004] In order to overcome the defects of the prior art, a method for dewatering a foundation pit in rock stratum geology is provided to solve the problem that the traditional dewatering method for the foundation pit in rock stratum geology has poor dewatering effect.

[0005] In order to achieve the above object, a method for dewatering a foundation pit in rock strata geology is provided, comprising the following steps:

[0006] During the excavation of the foundation pit in the rock stratum geology, a temporary water collection pit is opened on the excavation surface of the foundation pit and the water in the temporary water collection pit is collected in time to avoid water accumulation in the foundation pit;

[0007] After the foundation pit is excavated, the bottom of the foundation pit is divided into a plurality of partitions, and a grid-shaped blind seepage ditch is buried in each of the partitions;

[0008] Determine a first water inflow point on the bottom of the pit and a second water inflow point on the side wall of the foundation pit;

[0009] A seepage ditch well is opened at the location of the first water gushing point, the seepage ditch well is connected to the seepage blind ditch in the partition corresponding to the first water gushing point, the top elevation of the seepage ditch well is lower than the top elevation of the seepage blind ditch, and the seepage blind ditch and the seepage ditch well are arranged below the bottom plate of the foundation pit;

[0010] A pumping well and a drainage well are set outside the foundation pit. The drainage well is arranged opposite to the second water gushing point, and a plurality of seepage blind ditches in the partitions are connected to the pumping well or the drainage well.

[0011] Furthermore, the first water gushing point is in a strip shape, and the seepage ditch is a seepage ditch arranged along the length direction of the first water gushing point.

[0012] Furthermore, the first water gushing point is in a point shape, and the seepage ditch well is a seepage well arranged opposite to the first water gushing point.

[0013] Furthermore, the seepage blind ditch is connected to the pumping well or the precipitation well through a connecting blind ditch.

[0014] Furthermore, the top elevation of the connecting blind ditch is higher than the top elevation of the seepage ditch well and lower than the top elevation of the seepage blind ditch.

[0015] Furthermore, the seepage blind ditch comprises:

[0016] A blind ditch body is formed at the bottom of the foundation pit;

[0017] a water-permeable pipe, arranged in the blind ditch body; and

[0018] The gravel layer filled in the blind ditch body covers the permeable pipe.

[0019] Furthermore, the precipitation well and the pumping well respectively include:

[0020] a sandless pipe buried in the foundation below the bottom of the pit; and

[0021] A gravel layer is coated on the sand-free pipe.

[0022] The beneficial effect of the present invention is that the foundation pit dewatering method of the rock stratum geology of the present invention divides the bottom of the foundation pit into a plurality of relatively independent water collection areas, and a seepage blind ditch is set in each area. A seepage well is set up or a seepage ditch is excavated at the water gushing point at the bottom of the foundation pit, and a dewatering well and a pumping well are set up outside the foundation pit at the water gushing point on the side wall of the foundation pit to carry out fixed-point dewatering in the foundation pit. The seepage ditch well is connected to the seepage blind ditch and is connected to the dewatering well and the pumping well outside the foundation pit through the connecting blind ditch, so as to realize efficient, fixed-point and precise dewatering inside and outside the foundation pit.

[0023] The rock stratum geological foundation pit dewatering method of the present invention, through the rock stratum geological bedrock fissure water combined with the foundation pit inside and outside the dewatering construction method, can not only solve the problem of the rock stratum fissure water well point dewatering effect is not obvious, to ensure the overall safety of the foundation pit structure and the main bottom plate construction, but also can significantly reduce the project cost, speed up the pile speed of the lower hard rock stratum, save resources and improve work efficiency.

[0024] The rock stratum geological foundation pit dewatering method of the present invention makes full use of the characteristics of strong self-stability of rock strata and mainly based on bedrock fissure water. In the foundation pit excavation stage, an open drainage scheme is adopted. Under the premise of ensuring the safety of foundation pit excavation, drainage, excavation and support are carried out. The method reduces the construction difficulty and construction cost, does not increase the interference to the surrounding environment, and achieves the purpose of rapid construction, safe construction, economic and energy-saving.

[0025] The rock stratum geological foundation pit dewatering method of the present invention is suitable for fractured rock strata, and is suitable for dewatering work of deep foundation pits and related main structure construction under conditions of abundant groundwater during construction. It has good promotion and application prospects, thereby achieving the purpose of rapid construction, and can also prevent safety problems caused by untimely dewatering.

[0026] The rock stratum geological foundation pit dewatering method of the present invention conforms to the advanced concept of tool-based operation. While being able to ensure the design intent, it is easy to operate and reduces excessive manpower and machinery input, thereby improving the safety of deep foundation pit construction in rock stratum areas and increasing construction costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0028] Figures 1 to 3 Schematic diagram of the steps of the foundation pit dewatering method for rock strata geology according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0030] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] Reference Figures 1 to 3 As shown, the present invention provides a method for dewatering a foundation pit in rock strata geology, comprising the following steps:

[0032] S1: During the excavation of the foundation pit in rock strata geology, a temporary water collection pit 1 is opened on the excavation surface A of the foundation pit and the accumulated water in the temporary water collection pit 1 is collected in time to avoid the formation of water accumulation in the foundation pit.

[0033] S2: After the foundation pit is excavated, the bottom C of the foundation pit is divided into a plurality of partitions B, and a grid-shaped blind seepage ditch 4 is buried in each partition B.

[0034] S3: Determine the first water gushing point at the pit bottom C and the second water gushing point on the side wall of the foundation pit.

[0035] S4: A seepage ditch 5 is opened at the first water gushing point, and the seepage ditch 5 is connected to the seepage blind ditch 4 in the partition B corresponding to the first water gushing point. The top elevation of the seepage ditch 5 is lower than the top elevation of the seepage blind ditch 4. The seepage blind ditch 4 and the seepage ditch 5 are arranged below the bottom plate 3 of the foundation pit.

[0036] The first water gushing point is in strip shape, and the seepage ditch 5 is a seepage ditch arranged along the length direction of the first water gushing point.

[0037] The first water gushing point is in a point shape, and the seepage ditch well 5 is a seepage well arranged opposite to the first water gushing point.

[0038] S5: A pumping well 7 and a drainage well 8 are drilled outside the foundation pit. The drainage well 8 is arranged opposite to the second water gushing point, and the seepage blind ditches 4 in multiple partitions B are connected to the pumping well 7 or the drainage well 8.

[0039] The seepage blind ditch 4 is connected to the pumping well 7 or the drainage well 8 through the connecting blind ditch 6 .

[0040] The top elevation of the connecting blind ditch 6 is higher than the top elevation of the seepage ditch well 5 and lower than the top elevation of the seepage blind ditch 4 .

[0041] Specifically, the seepage blind ditch 4 includes: a blind ditch body, a permeable pipe and a gravel layer. The blind ditch body is formed at the bottom C of the foundation pit. The permeable pipe is arranged in the blind ditch body. The gravel layer filled in the blind ditch body covers the permeable pipe.

[0042] The dewatering well 8 and the pumping well 7 respectively include: a sandless pipe and a gravel layer. The sandless pipe is buried in the foundation below the pit bottom C. The gravel layer covers the sandless pipe.

[0043] The rock stratum geological foundation pit dewatering method of the present invention does not adopt the conventional dewatering scheme of the dewatering well outside the pit during the foundation pit excavation stage, but performs temporary dewatering construction by means of open drainage in the pit. After the foundation pit is fully excavated, the actual position of the bedrock fissure is determined by the water gushing point, and the seepage ditch well and the seepage blind ditch are used for dewatering, and the blind ditch is connected to discharge the groundwater into the dewatering well and the drainage well outside the pit. Finally, the dewatering well and the drainage well outside the foundation pit use water pumps to discharge the basement into the ground drainage system.

[0044] The rock stratum geological foundation pit dewatering method of the present invention divides the bottom of the foundation pit into a plurality of relatively independent seepage and drainage zones, and a seepage blind ditch is set in each zone, and the seepage blind ditches are interconnected to form a closed loop. For the first visible water gushing point at the bottom of the foundation pit, a seepage ditch well (seepage well or seepage ditch) is constructed separately, and the seepage well or seepage ditch is connected to the seepage blind ditch in the corresponding area. The function of the seepage ditch well is to collect residual water such as bedrock fissure water in the corresponding zone range. Among them, the function of the seepage well is to collect the larger first water gushing point at the concentrated point of the bedrock fissure; the function of the seepage ditch is to collect the accumulated water in the seepage blind ditch in this area, and connect it with the pumping well or dewatering well outside the pit.

[0045] The construction time of the seepage well in the foundation pit can be before the excavation of the foundation pit, during the excavation of the foundation pit, or after the excavation of the foundation pit is completed. The specific construction stage or construction location shall be reasonably determined according to the amount of seepage in the pit.

[0046] The seepage ditch within the bottom of the foundation pit is constructed after the entire foundation pit is excavated.

[0047] The pumping well or drainage well outside the foundation pit is constructed after the excavation of the foundation pit is completed.

[0048] After the foundation pit is excavated to the designed elevation of the pit bottom, the base is cleaned. If the drainage well constructed in the foundation pit during the excavation stage is still effective, it can continue to be retained as a seepage well at the bottom of the foundation pit. If it deviates from the location of the bedrock cracks and cannot effectively dewater, it can be demolished and relocated before construction can be carried out.

[0049] The seepage ditch well at the bottom of the foundation pit is connected to the pumping well or drainage well outside the foundation pit through a connecting blind pipe. The connecting blind pipe passes through the appropriate position between the piles of the retaining structure 2 (support piles) without affecting the normal use of the retaining structure. A water pump is installed in the pumping well or drainage well outside the foundation pit, so that the seepage water at the bottom of the pit or the bedrock fissure water is discharged to the municipal official website on the ground through the pumping well or drainage well outside the foundation pit, so as to achieve waterless operation in the foundation pit.

[0050] The setting principle and location of the pumping well or drainage well outside the foundation pit are determined according to the gushing points on the side walls of the foundation pit. Observe the water leakage at the bottom and side walls of the foundation pit, mark the gushing points and seepage points at the bottom and side walls of the foundation pit, and confirm the location of the bedrock fissures in combination with the geological survey report. If there are obvious gushing points on the side walls within this partition, it is judged that there are bedrock fissures outside the foundation pit, and a drainage well is directly constructed at the corresponding position outside the foundation pit. If there are no obvious leakage points on the side walls corresponding to this partition, it is judged that there are no obvious bedrock fissures in this area, and a pumping well can be drilled at an appropriate position outside the foundation pit in this area.

[0051] The construction methods of precipitation wells are basically the same as those of pumping wells, both of which use sandless pipes and crushed stone filling on the outside.

[0052] The function of the pumping well outside the foundation pit is to extract the water from the seepage blind ditch in the corresponding area of ​​the foundation pit from the outside of the foundation pit.

[0053] The function of the drainage well outside the foundation pit is not only to pump out the water from the seepage blind ditch in the corresponding area of ​​the foundation pit, but also to collect and pump out the water in the bedrock fissures outside the foundation pit and discharge it to the ground drainage system.

[0054] According to the size of the foundation pit and other types, every 20m to 30m is a water collection and drainage zone. A seepage blind ditch is excavated at the bottom of the foundation pit. The size of the seepage blind ditch is 0.5m×0.5m, and it can be adjusted according to the amount of seepage. A permeable blind pipe is laid in the seepage blind ditch, and permeable gravel is used to level the permeable blind pipe.

[0055] The seepage well is connected to the closed-loop seepage blind ditch. After the seepage blind ditch of each partition forms a closed loop, it is led to the pumping well or drainage well outside the foundation pit through the connecting blind pipe that connects the inside and outside, and the holes of appropriate size are drilled from the foundation pit retaining structure. The water is pumped to the ground drainage system through the high-power water pump in the pumping well or drainage well. Multiple drainage partition systems work together to achieve the purpose of drainage of the entire foundation pit, avoiding the emergency measures such as grooving in the structure and reserving drainage holes in traditional practices, and effectively ensuring the overall waterproof quality of the structure.

[0056] During the excavation of the foundation pit, open drainage (temporary sump or temporary sump) is used to drain water. A temporary sump (or temporary sump) is set up at regular intervals on the excavation surface of the foundation pit. The depth of the sump is 1.5-3m, which collects the bedrock fissure water in each area and is pumped out to the ground in time through a high-power water pump to avoid water accumulation in the foundation pit and affect the excavation of the foundation pit. Excavation is carried out by machinery in combination with manual labor. If necessary, loosening blasting, controlled blasting and other methods can be used for construction.

[0057] The seepage well at the bottom of the foundation pit can be drilled or dug manually, with a hole diameter of about 1m. The depth of the seepage well is determined by the amount of seepage at this location. After the well is excavated, it is filled with sandless pipes, permeable gravel, pebbles, etc., and connected to the main blind ditch in this section through a branch blind ditch.

[0058] After the drainage construction of the entire foundation pit or several sections of the drainage area is completed by the drainage method of the present invention, and after it is determined that there is no wet stain such as open water on the bottom of the foundation pit and the side wall, the main structure of the basement can be constructed. After that, the waterproof layer and structural layer of the basement floor, middle plate, side wall, and top plate are completed in layers and sections.

[0059] After the main structure of the basement is completed, anti-floating beams and other corresponding measures are constructed to complete the backfilling and compaction of the top slab. The pumps in the pumping wells outside the foundation pit or the drainage wells are closed in stages to complete the relevant procedures of deep foundation pit construction.

[0060] For the deep soil layer above the foundation pit and the shallow groundwater level, it is easy to cause collapse and sand flow during excavation in the soil layer. Temporary measures such as rotary jet piles, interlocking piles, grouting reinforcement, and temporary shallow precipitation wells can be installed in the soil layer to consolidate the soil and prevent sand flow, and prevent the loss of soil behind the retaining structure, so as to ensure the safety of excavation. A small amount of seepage water is allowed to enter the foundation pit, and it is also handled by open drainage in the pit.

[0061] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

Claims

1. A method for dewatering a foundation pit in rock strata geology, characterized in that: The following steps are involved: During the excavation of the foundation pit in the rock stratum geology, a temporary water collection pit is opened on the excavation surface of the foundation pit and the accumulated water in the temporary water collection pit is discharged in time to avoid the formation of water accumulation in the foundation pit; After the foundation pit is excavated, the bottom of the foundation pit is divided into a plurality of partitions, and a grid-shaped blind seepage ditch is buried in each of the partitions; Determine a first water inflow point on the bottom of the pit and a second water inflow point on the side wall of the foundation pit; A seepage ditch well is opened at the location of the first water gushing point, the seepage ditch well is connected to the seepage blind ditch in the partition corresponding to the first water gushing point, the top elevation of the seepage ditch well is lower than the top elevation of the seepage blind ditch, and the seepage blind ditch and the seepage ditch well are arranged below the bottom plate of the foundation pit; A pumping well and a drainage well are set outside the foundation pit, the drainage well is arranged opposite to the second water gushing point, and a plurality of blind drainage ditches in the partitions are connected to the pumping well or the drainage well; The seepage blind ditch is connected to the pumping well or the precipitation well through a connecting blind ditch; The top elevation of the connecting blind ditch is higher than the top elevation of the seepage ditch well and lower than the top elevation of the seepage blind ditch.

2. The method for dewatering a foundation pit in rock strata geology according to claim 1, characterized in that: The first water gushing point is in a strip shape, and the seepage ditch is a seepage ditch arranged along the length direction of the first water gushing point.

3. The method for dewatering a foundation pit in rock strata geology according to claim 1, characterized in that: The first water gushing point is in a point shape, and the seepage ditch well is a seepage well arranged opposite to the first water gushing point.

4. The method for dewatering a foundation pit in rock strata geology according to claim 1, characterized in that: The seepage blind ditch comprises: A blind ditch body is formed at the bottom of the foundation pit; a water-permeable pipe, arranged in the blind ditch body; and The gravel layer filled in the blind ditch body covers the permeable pipe.

5. The method for dewatering a foundation pit in rock strata geology according to claim 1, characterized in that: The precipitation well and the pumping well respectively include: a sandless pipe buried in the foundation below the bottom of the pit; and A gravel layer is coated on the sand-free pipe.

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