JP2023518992A - Method and grouting apparatus for determining safe thickness of sidewalls in karst areas in foundation pits - Google Patents

Abstract

A method and grouting apparatus for determining the safe thickness of the sidewalls of karst areas in foundation pits. Kind Code: A1 The present invention discloses a method for determining a safe thickness of a karst zone sidewall in a foundation pit, the length m of the karst zone sidewall affected by the karst zone and the length n of the karst zone. , determining the steel bearing capacity F1 of the foundation pit wall, the air pressure F2 and the water pressure F3 in the karst area, and the axial displacement, potential and safety the present invention further discloses a grouting device for karst areas in foundation pits, comprising a metal mesh, a waterstop, a grouting pipe, a lifting pipe and a one-way communication device, The present invention can quickly eliminate the risk of water eruption in the karst area in the foundation pit, solve the difficult problems such as difficult grout injection and backflow of karst water during construction, and can seal the karst area. which saves construction investment and ensures construction safety. [Selection diagram] Fig. 1

Description

The present invention relates to the field of grouting in foundation pit construction, and more particularly to a method and grouting apparatus for determining the safe thickness of sidewalls in karst areas in foundation pits.

When excavating foundation pits in karst areas, the distribution of karst water is uneven and difficult to detect, which is easy to cause water injection accidents, and the specific distribution location and area of karst water cannot be detected during excavation In addition, if effective measures are not taken to protect the water outlet, the construction field will often be submerged, and the equipment will be damaged by impact, resulting in accidents involving equipment and workers, an increase in construction period, and an increase in construction investment. can cause problems.

The present invention solves the above technical problem by providing a method for determining the safe thickness of the karst area side walls in foundation pits.

The present invention provides a method for determining a safe thickness of a karst area sidewall in a foundation pit comprising the following steps.

S1: Determine the length m of the pit wall affected by the karst area, the length n of said karst area, the steel bearing capacity of the pit wall F ₁ , the air pressure F ₂ and the water pressure F ₃ in the karst area.

S2: Based on the elasto-plastic theory, calculate the axial displacement of the sidewall of the karst region, ie the following deformation rate:

where d is the safe thickness of the sidewall of the karst area.

S3: Calculate the sidewall potential of the karst area. A specific formula is as follows.

Here, W1 is the deformation potential of the water jet prevention layer, and W2 is the work due to the external force.

S4: Calculate the safe thickness of the sidewall of said karst area. A specific formula is as follows.

where E is the elastic modulus of the impermeable rock layer and μ is Poisson's ratio.

S5: Compare the calculated safe thickness of the side wall of the foundation pit in the karst area with the actual detection result, and determine the grouting method.

The present invention further provides a grouting apparatus for karst areas in foundation pits comprising a metal mesh, a waterstop, a grouting pipe, a lift pipe and a one-way communication device for conducting grout.

The metal mesh covers the water outlet of the karst area, the edge of the waterstop is fixedly connected to the edge of the water outlet of the karst area, and the waterstop completes the water outlet of the karst area. the metal mesh is between the water stop and the water outlet of the karst area;

the pumping pipe is used for extracting water in the karst area, one end passing through the metal mesh and the other end located in the karst area;

A side wall of the grout injection pipe is provided with a plurality of first connection ends with female threads,

The one-way communication device end is a second connection end provided with an external thread, the second connection end is screwed and sub-connected to the first connection end, and the one-way communication device connects the grout to the metal mesh. to form the sealing wall.

Further, the one-way communication device includes an outer member, an inner member, a spring and a base,

the second connecting end is provided at one end of the outer member, the outer member is hollow, and the outer member is sealingly connected to the base;

The internal member is provided inside the external member, one end of the internal member adjacent to the second connection end communicates with the outside, and the other end of the internal member is connected to the base via a spring,

Side walls of the outer member and the inner member are provided with a plurality of first grout outlets and a plurality of second grout outlets, respectively, and the inner member moves toward the base due to the pressure of the grout. By compressing the spring, the plurality of second grout outlets and the plurality of first grout outlets are superimposed to allow the grout to flow out.

Furthermore, it further includes a magnet for fixing the one-way communication device to the metal mesh, the magnet being fixedly connected to the outer wall of the one-way communication device.

Further comprising a pumping pipe for extracting water in the karst area, one end of the pumping pipe penetrates the metal mesh and is placed in the karst area.

Further, the outer diameter of the inner member is equal to the inner diameter of the outer member.

The other end of the external member is provided with a male thread, and the pedestal is provided with a female thread and is screwed and sub-connected to the other end of the external member.

Further, the spacing between the plurality of first grout outlets is equal to the spacing between the plurality of second grout outlets.

The present invention can quickly eliminate the risk of water spouting in the karst area in the foundation pit, and solves the difficult problems of conventional grout injection structures, such as difficult grout injection and backflow of karst water during construction. It can effectively realize the sealing of the karst area, the construction effect is high, the construction investment is saved, and the construction safety is ensured. By analyzing the relationship between each element and the safe thickness of the sidewall in the karst area, we provide a formula that can reasonably predict the safe thickness of the sidewall in the karst area, and provide a formula for the safe thickness of the sidewall in the karst area. You will be able to rationally deal with the water jet problem.

In order to describe the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly describes the drawings required for the description of the embodiments or the prior art and, of course, the following description The drawings are several examples of the present invention, and a person skilled in the art can conceive of other drawings based on these drawings without any creative effort.
FIG. 4 is a flow chart for determining the thickness of a sidewall of a karst area according to an embodiment of the present invention; FIG. 1 is a front view of a foundation pit and a karst area according to an embodiment of the present invention; FIG. 1 is a side view of a foundation pit and a karst area according to an embodiment of the invention; FIG. 1 is a schematic diagram of an application of an embodiment of the present invention to a foundation pit; FIG. Fig. 5 is an enlarged view of A in Fig. 4 of an embodiment of the present invention; Figure 3 is a perspective view of Figure 2 of an embodiment of the present invention; 1 is a schematic view of a combination of a grouting pipe and a one-way communication device according to an embodiment of the present invention; FIG. 1 is a structural schematic diagram of a grouting pipe according to an embodiment of the present invention; FIG. FIG. 4 is a structural schematic diagram of a one-way communication device according to an embodiment of the present invention;

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, hereinafter, with reference to the drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clear and complete. It goes without saying that the embodiments described and described are only some embodiments of the present invention rather than all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments in the present invention without creative work shall all fall within the scope of protection of the present invention.

Currently under construction to solve the problem that the distribution of water in the karst area 7 in the foundation pit 11 is uneven and difficult to detect, and if the thickness of the side wall of the karst area is too thin, water jets are likely to occur. In this case, the construction field is often submerged, the equipment is impacted and destroyed, and there is a possibility of causing adverse effects such as accidents for equipment and workers, an increase in the construction period, and an increase in construction investment. The present invention analyzes the relationship between each element and the safe thickness of the karst sidewall by constructing a calculation model of the safe thickness of the sidewall of the karst sidewall, and analyzes the relationship between the safe thickness of the sidewall of the karst sidewall. It provides a calculation formula that can reasonably predict the thickness, and can reasonably deal with the water ejection problem of the foundation pit in the karst area. Through mechanical analysis of unstable failure caused by water ejection in the karst area in the foundation pit, we will understand the characteristics including the water ejection process of the deep foundation pit in the covered karst area more comprehensively, and prevent effective treatment structures, etc. Measures can be taken to ensure safe excavation of foundation pits.

The catastrophic unstable area of the foundation pit is mainly concentrated in the karst area, and fractures radially to the periphery around the pressure-bearing position of the karst area. Depending on the size of the karst zone and the thickness of the sidewall of the karst zone, the plastic zone develops diffusely from the karst zone to the sidewall while the internal pressure of the karst zone increases, and the influence area of the plastic zone spreads outward. presents a quadrangular shape. By simplifying the profile cross-section of the karst area to a square, and further analyzing the catastrophe mechanism of the phenomenon, a mechanical model can be established as shown in FIGS. 1-3.

The present invention provides a method for determining the safe thickness of sidewalls in karst areas, which includes the following steps.

The side wall of the karst region constitutes a truncated pyramid body from countless thin cubes with a uniform thickness, the length m of the side wall of the foundation pit affected by the karst region, the length n of the karst region, the steel of the side wall of the foundation pit Determining the bearing force F1, the air pressure F2 and the water pressure F3 in the karst area, the pressure experienced by the karst area sidewall on the side of the foundation pit is F=F1+F2−F3, the karst area sidewall is an elastoplastic medium, Based on the elasto-plastic theory, calculate the axial displacement of the sidewall of the karst region, that is, the following deformation rate,

where d is the safe thickness of the sidewall of the karst area,

The boundary conditions are as follows.

The following is obtained from (1) and (2).

Using the law of conservation of energy, the potential of the side wall of the karst region is calculated, and the formula is as follows.

where W ₁ is the deformation potential of the sidewall of the karst area and is the sum of the bending deformation potential W ₁₁ and the intermediate strain potential W ₁₂ , i.e.

_W2 is work due to external forces, including work _W21 due to radial displacement and work _W22 due to axial outward displacement _,

Substituting (9) and (12) into (5),

where a ₁ , a ₂ , a ₃ are intermediate variables,

where x, y are intermediate variables,

Substituting (16) into (14), we obtain the following equation in matrix form,

In that case, fit the cusp catastrophe model,

Based on catastrophe theory, the equilibrium equations for the system are:

This makes it possible to determine the safe thickness of the sidewalls in the karst area to prevent water spurts.

As can be seen from equation (19), the safe thickness of the sidewall in the karst area depends on the elastic modulus of the impermeable rock layer, which is the elastic modulus of the sidewall in the karst area, Poisson's ratio, karst water pressure, steel support axial force, air pressure, Influenced by the dimensions of the foundation pit and the dimensions of the karst zone, the greater the modulus of elasticity of the sidewalls of the karst zone around the foundation pit, the smaller the minimum safe thickness. . The greater the excavation extent of the foundation pit and the size of the karst area, the greater the minimum safe thickness of the foundation pit.

According to the above analysis, the step S5 may also be a step of calculating a corresponding safe thickness according to the actual geological investigation conditions, and compared with the detected thickness, the safe thickness is If greater than the current detected thickness, take precautions by injecting grout using the following grouting equipment for karst areas in foundation pits.

The present invention further provides a grouting device for karst areas in foundation pits, as shown in FIGS. A metal mesh 3 covers the water outlet 7.1 of the karst area 7 and the edge of the stainless steel water stop 4 is attached via bolts 8 to the edge of the water outlet 7.1 of said karst area 7. Fixedly connected, said waterstop 4 does not completely cover the water outlet 7.1 of said karst area 7, and in order to prevent water outflow in the karst area, the top edge of the waterstop and the karst area , extending the grouting pipe 1 and the one-way communication device 5 into the karst area, said metal mesh 3 between said water stop plate 4 and the water outlet 7.1 of said karst area 7 , the metal mesh 3 is fixed to the water outlet 7.1 of the karst area 7 by pressing the water stop plate 4,

As shown in FIG. 8, one end of the grout injection pipe 1 is open for injecting grout inside, and a plurality of first connection ends 1-1 with internal threads are provided on the side wall of the grout injection pipe 1. be

As shown in FIG. 9, one end of the one-way communication device 5 is a second connecting end 5-1 provided with a male thread, and the second connecting end 5-1 is screwed to the first connecting end 1-1. The one-way communication device 5 is used to lead the grout to the metal mesh 3 to form a sealing wall.

Further, the one-way communication device 5 includes an outer member 5-2, an inner member 5-3, a spring 5-4 and a base 5-5, and the second connection end 5-1 is connected to the outer member 5-2. The external member 5-2 is provided at one end, the external member 5-2 is hollow, the other end of the external member 5-2 is provided with a male thread, the base 5-5 is provided with a female thread, and the external member 5- 2 to seal and detach the external member 5-2 for maintenance or replacement of the spring 5-4 inside the one-way communication device 5, and the internal member 5- 3 is provided inside the external member 5-2, one end of the internal member 5-3 close to the second connection end 5-1 communicates with the outside, and the other end of the internal member 5-3 is It is connected to the pedestal 5-5 via a spring 5-4, and a plurality of first grout discharge ports 5-2-1 and a plurality of A second grout discharge port 5-3-1 is provided, and the inner member 5-3 moves toward the base 5-5 under the pressure of the grout and simultaneously compresses the spring 5-4 to form a plurality of second grout outlets. The two grout outlets 5-3-1 and the plurality of first grout outlets 5-2-1 are overlapped, and the grout is discharged.

It further comprises a pumping pipe 2 for extracting water in the karst area, one end of said pumping pipe 2 penetrating said 3 and being placed in said karst area.

Specifically, as shown in FIG. 7, both the outer member 5-2 and the inner member 5-3 are stainless steel cylindrical barrel structures, and at the same time that grout is injected into the grouting pipe 1, The water in the karst area is extracted through the pumping pipe 2, so as not to affect the grouting adhesion to the metal mesh 3, the grouting being applied to the six first connecting ends 1- of the side wall of the grouting pipe 1. 1 into six one-way communication devices 5, and the inner member 5-3 in the one-way communication device 5 presses the spring 5-4 when receiving the pressure of the grout, and further two second grout discharges. The outlet 5-3-1 and the two first grout discharge ports 5-2-1 are superimposed, and the grout flows out from the first grout discharge ports 5-2-1 and is rapidly solidified near the metal net 3. , a magnet 9 is fixed on the outer wall of the outer member 5-2 so that the one-way communication device 5 can continuously inject grout in place, and the magnet 9 connects the one-way communication device 5 to the metal mesh 3. After the grout adheres to one area of the metal net 3, the injection of the grout is stopped. At this time, the internal member 5-3 is pressed by the spring 5-4 and returns. , the position of replacing the grouting pipe 3 and the one-way communication device 5 with the metal mesh 3, the entire metal mesh 3 and its adjacent areas are filled with grout and continuously and rapidly solidified to form a water outlet in the karst area 7. 7. It is only necessary to inject the grout until it forms a sealing wall that seals 1, and the maximum width of the whole device is greater than the maximum width of the metal mesh 3, so if the device is placed in the karst area, the metal mesh and set up the device, and finally, the remaining non-grouted area of the metal mesh 3 is small, and the other damaged areas are connected with wires to repair, and the five one-way communication devices 5 of them is removed and the grout is injected leaving only one one-way communication device 5, at which time the single one-way communication device 5 can be removed from the mesh.

Furthermore, in order to prevent grout from flowing out from the gap formed between the inner member 5-3 and the outer member 5-2 and damaging the device, the outer diameter of the inner member 5-3 is set to Equal to the inner diameter of the outer member 5-2.

Further, the plurality of first grout outlets 5-2-1 are arranged so that the grout flows out at the same time and the grout injection efficiency is improved. It is made equal to the interval between the plurality of second grout discharge ports 5-3-1.

Finally, it should be noted that the above embodiments are only for describing the technical solutions of the present invention, but not for limiting it. has been described in detail, but it is possible to modify the technical solutions described in each of the above-described embodiments, or equivalently replace some or all of the technical features thereof, and by these modifications or replacements, the corresponding technology It can be understood by those skilled in the art that the essence of the technical solution does not depart from the scope of the technical solution of each embodiment of the present invention.

Claims (8)

S1: Determining the length m of the foundation pit sidewall affected by the karst area, the length n of said karst area, the steel bearing capacity of the foundation pit sidewall F ₁ , the air pressure F ₂ and the water pressure F ₃ in the karst area. and,
S2: Based on the elasto-plastic theory, the axial displacement of the sidewall of the karst region, i.e. the following deformation

step where d is the safe thickness of the sidewall of the karst area;
S3: A step of calculating the potential of the sidewall of the karst area, the specific formula being:

where _W1 is the deformation potential of the anti-water jetting layer and _W2 is the work due to the external force;
S4: A step of calculating the safe thickness of the sidewall of the karst area, the specific formula being:

where E is the elastic modulus of the impervious rock layer and μ is the Poisson's ratio;
S5: Comparing the calculated safe thickness of the foundation pit sidewall in the karst area with the actual detection result, and determining the grouting method, the safe thickness of the sidewall in the karst area. how to determine the 2. The apparatus of claim 1, wherein the deformation rate boundary condition in said S2 is as follows.

comprising a metal mesh (3), a waterstop (4), a grouting pipe (1), a water pumping pipe (2) and a one-way communication device (5) for leading out the grout,
Said metal mesh (3) covers the water outlet (7.1) of the karst area (7), the edge of the waterstop (4) is the water outlet (7.1) of the karst area (7) said water stop (4) does not completely cover the water outlet (7.1) of said karst area (7) and said metal mesh (3) is connected to said stop between the water plate (4) and the water outlet (7.1) of said karst area (7),
said pumping pipe (2) is used to extract water in a karst area, said pumping pipe (2) penetrates said metal mesh (3) and is located in said karst area,
A plurality of first connection ends (1-1) are provided on the side wall of the grout injection pipe (1),
One end of the one-way communication device (5) is a second connection end (5-1), and the second connection end (5-1) is screwed to the first connection end (1-1). and said one-way communication device (5) is intended to lead grout into said metal mesh (3) to form a sealing wall sealing the water outlet (7.1) of said karst area (7). A grouting device for karst areas in foundation pits, characterized in that: The one-way communication device (5) includes an outer member (5-2), an inner member (5-3), a spring (5-4) and a base (5-5),
The second connecting end (5-1) is provided at one end of the external member (5-2), the external member (5-2) is hollow, and the external member (5-2) is the pedestal. (5-5) hermetically connected to
The internal member (5-3) is provided inside the external member (5-2), and one end of the internal member (5-3) adjacent to the second connection end (5-1) is externally Communicating, the other end of the internal member (5-3) is connected to the base (5-5) via a spring (5-4),
A plurality of first grout outlets (5-2-1) and a plurality of second grout outlets (5-3- 1) is provided, and the inner member (5-3) is moved toward the base (5-5) by the pressure of the grout and simultaneously compresses the spring (5-4) so that the plurality of second 4. The apparatus according to claim 3, characterized in that the grout outlet (5-3-1) and a plurality of first grout outlets (5-2-1) are overlapped to allow the grout to flow out. further comprising a magnet (9) for fixing said one-way communication device (5) to said metal mesh (3), said magnet (9) being fixedly connected to the outer wall of said one-way communication device (5); 4. Apparatus according to claim 3, characterized in that: A device according to claim 2, characterized in that the outer diameter of said inner member (5-3) is equal to the inner diameter of said outer member (5-2). A male thread is provided on the other end of the external member (5-2), and a female thread is provided on the pedestal (5-5) and is screwed and sub-connected to the other end of the external member (5-2). 6. Apparatus according to claim 5, characterized in that: 6. The apparatus according to claim 5, characterized in that the spacing of the plurality of first grout outlets (5-2-1) is equal to the spacing of the plurality of second grout outlets (5-3-1). .

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