Method and system for quickly judging whether recharge well of deep foundation pit containing confined aquifer is arranged or not

Abstract

The invention relates to the field of deep foundation pit recharge well arrangement, and discloses a method and system for rapidly judging whether a confined water layer-containing deep foundation pit recharge well is arranged or not, and the method comprises the following steps: S1, obtaining the water level drop depth of a to-be-arranged position of the recharge well based on a water pumping test and the actual horizontal distance from the to-be-arranged position of the recharge well to a water pumping well; s2, actual settlement of the to-be-arranged position of the recharge well is obtained according to the water level drop depth of the to-be-arranged position of the recharge well; and S3, whether the recharge well needs to be arranged at the to-be-arranged position of the recharge well or not is judged based on the actual settlement, obtained in the step S2, of the to-be-arranged position of the recharge well. According to the method, an effective calculation basis is provided, whether the recharge well needs to be arranged at any position on the periphery of the foundation pit in the foundation pit engineering can be rapidly judged, an accurate arrangement basis is provided, and resource waste caused by arrangement of the recharge well at an unnecessary position can be avoided.

Description

Technical Field

[0001] The invention relates to the field of deep foundation pit recharging well layout, and in particular to a method and system for quickly determining whether a deep foundation pit recharging well containing a confined water layer is laid. Background Art

[0002] Foundation pit dewatering will inevitably cause the surrounding groundwater level to drop, especially for deep foundation pits containing confined aquifers, where the amount of water pumped out is large, causing surrounding buildings (structures) and underground pipelines to be damaged to varying degrees due to uneven settlement. In order to eliminate this effect, recharge wells are often set up in the protection area. While the foundation pit is dewatered, the underground aquifer is recharged through the recharge wells outside the foundation pit to try to maintain the original water level of the building (structure) location, thereby effectively reducing the impact of precipitation.

[0003] Foundation pit recharge wells play an important role in protecting the surrounding environment of foundation pits, especially for buildings that need important protection. However, the current standards and specifications only provide qualitative regulations for the layout of recharge wells. For example, the "Construction Code for Building Foundation Engineering GB51004-2015" states that "when the groundwater level outside the foundation pit drops significantly and there are buildings (structures) or underground pipelines that need to be protected around the foundation pit, artificial groundwater recharge measures should be adopted", but there is no specific basis for the layout of recharge wells. In engineering, recharge wells are often laid around the foundation pit based on experience. For safety reasons, recharge wells will be laid when the foundation pit is pumped out and there are more important facilities around. They should be laid as much as possible without any calculation basis, which is undoubtedly a waste of resources. In response to this phenomenon, there is currently no effective calculation basis. Therefore, it is urgent to propose a rapid determination method for whether to lay recharge wells. Summary of the invention

[0004] Aiming at the lack of judgment basis on whether a recharge well is arranged in the prior art, the present invention provides a method and system for quickly judging whether a recharge well is arranged in a deep foundation pit containing a confined water layer.

[0005] In order to solve the above technical problems, the present invention is solved by the following technical solutions:

[0006] A method for quickly determining whether a recharging well is arranged in a deep foundation pit containing a confined water layer, comprising the following steps:

[0007] Step S1, obtaining the water level drop at the location where the recharging well is to be arranged based on the pumping test and the actual horizontal distance from the location where the recharging well is to be arranged to the pumping well;

[0008] Step S2, obtaining the actual settlement of the location where the recharging well is to be arranged according to the water level drop at the location where the recharging well is to be arranged;

[0009] Step S3: based on the actual settlement of the location where the reinjection well is to be arranged obtained in step S2, determine whether it is necessary to arrange a reinjection well at the location where the reinjection well is to be arranged.

[0010] Preferably, step S1 specifically includes the following steps:

[0011] Step S11: Obtain the pumping influence radius R and the pumping well radius r through a pumping test w and the water level drop in the pumping area S w ;

[0012] Step S12: Obtain the actual horizontal distance r from the location where the recharging well is to be laid to the pumping well, where

[0013] r=r1`+r2`+r3`+d;

[0014] Where r1' is the horizontal distance from the pumping well in the foundation pit to the inner edge of the ground-connected wall, r2' is the thickness of the ground-connected wall, r3' is the horizontal distance from the location of the recharging well to be laid to the outer edge of the ground-connected wall, and d is the seepage path distance of the water-stopping curtain.

[0015] Step S13, calculate the water level drop S' at the location where the recharging well is to be laid, the calculation formula is:

[0016]

[0017] Where S' is the water level drop at the location where the recharging well is to be laid, R is the pumping influence radius, and S w is the water level drop in the pumping area, r is the actual horizontal distance from the location of the recharging well to the pumping well, and r w It is the radius of the pumping well (the radius of the pumping well can be used for pumping tests; if it is a large-area precipitation calculation, the radius of the pumping area can be used).

[0018] Preferably, step S2 specifically includes obtaining the stratum deformation caused by precipitation according to the water level drop S', that is, the actual settlement S at the location where the recharging well is to be arranged,

[0019]

[0020] Among them, when the calculation point is above the initial groundwater level,

[0021] Δσ zi =0;

[0022] When the calculation point is located between the water level after precipitation and the initial groundwater level,

[0023] Δσ zi =γ w ·a0;

[0024] When the calculation point is below the water level after precipitation,

[0025] Δσ zi =γ w ·S′;

[0026] Where S is the ground deformation caused by precipitation, i.e., settlement; γ w is the density of water; Δσ zi is the additional effective stress at the midpoint of the i-th soil layer under the ground caused by precipitation; a0 is the vertical distance from the calculation point to the initial groundwater level; Δb i is the thickness of the i-th soil layer; E si is the compression modulus of the i-th soil layer.

[0027] Preferably, in step S3, the actual settlement at the location where the recharging well is to be arranged is compared with the foundation pit monitoring alarm value in the design specification, and whether to arrange the recharging well is determined according to the comparison result.

[0028] As a preferred method, the calculation formula of the pumping influence radius R is:

[0029]

[0030] Where S1 is the water level drop in observation hole 1, S2 is the water level drop in observation hole 2, r1 is the distance from observation hole 1 to the pumping well, and r2 is the distance from observation hole 2 to the pumping well.

[0031] As a preferred method, the calculation formula for the seepage path distance d of the water-stop curtain is:

[0032] d = Hh;

[0033] Where H is the depth of the water-stop curtain; h is the initial water level depth of the foundation pit.

[0034] A system for determining whether a recharging well is arranged in a deep foundation pit containing a confined water layer, comprising at least one processor and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the aforementioned method for rapidly determining whether a recharging well is arranged in a deep foundation pit containing a confined water layer.

[0035] The present invention has significant technical effects due to the adoption of the above technical solution:

[0036] The present invention provides an effective calculation basis, which can realize a quick judgment on whether a reinjection well needs to be arranged at any position around a foundation pit in a foundation pit project, that is, it provides a more accurate basis for arrangement, and can avoid the waste of resources caused by arranging reinjection wells at unnecessary positions. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1It is a schematic diagram of groundwater seepage during foundation pit dewatering in Example 1 of the present invention.

[0038] Figure 2 This is a water level drop simulation diagram in Example 3 of the present invention.

[0039] Figure 3 This is a sedimentation simulation diagram in Example 3 of the present invention. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0041] Example 1

[0042] A method for quickly determining whether a recharging well is arranged in a deep foundation pit containing a confined water layer, comprising the following steps:

[0043] Step S1, obtaining the water level drop at the location where the recharging well is to be arranged based on the pumping test and the actual horizontal distance from the location where the recharging well is to be arranged to the pumping well;

[0044] Step S2, obtaining the actual settlement of the location where the recharging well is to be arranged according to the water level drop at the location where the recharging well is to be arranged;

[0045] Step S3: based on the actual settlement of the location where the reinjection well is to be arranged obtained in step S2, determine whether it is necessary to arrange a reinjection well at the location where the reinjection well is to be arranged.

[0046] Wherein, step S1 specifically includes the following steps:

[0047] Step S11: Obtain the pumping influence radius R and the pumping well radius r through a pumping test w and the water level drop in the pumping area S w , where r w In the pumping test, the radius of the pumping well can be used. If it is a large-area precipitation calculation, the radius of the pumping area can be used. The calculation formula for the pumping influence radius R is:

[0048]

[0049] Where S1 is the water level drop of observation hole 1, S2 is the water level drop of observation hole 2, r1 is the distance from observation hole 1 to the pumping well, and r2 is the distance from observation hole 2 to the pumping well;

[0050] Step S12: Obtain the actual horizontal distance r from the location where the recharging well is to be laid to the pumping well, where

[0051] r=r1`+r2`+r3`+d;

[0052] Where r1' is the horizontal distance from the pumping well in the foundation pit to the inner edge of the ground-connected wall, r2' is the thickness of the ground-connected wall, r3' is the horizontal distance from the location of the recharging well to be laid to the outer edge of the ground-connected wall, and d is the seepage path distance of the water-stopping curtain.

[0053] The calculation formula for the seepage path distance d of the water-stop curtain is:

[0054] d = Hh;

[0055] In the formula, H is the depth of the water-stop curtain; h is the initial water level depth of the foundation pit;

[0056] Step S13, calculate the water level drop S' at the location where the recharging well is to be laid, the calculation formula is:

[0057]

[0058] Where S' is the water level drop at the location where the recharging well is to be laid, R is the pumping influence radius, and S w is the water level drop in the pumping area, r is the actual horizontal distance from the location of the recharging well to the pumping well, and r w It is the radius of the pumping well (the radius of the pumping well can be used for pumping tests; if it is a large-area precipitation calculation, the radius of the pumping area can be used).

[0059] Step S2 specifically includes obtaining the ground deformation caused by precipitation according to the water level drop S', that is, the actual settlement S at the location where the recharging well is to be arranged,

[0060]

[0061] Among them, when the calculation point is above the initial groundwater level,

[0062] Δσ zi =0

[0063] When the calculation point is located between the water level after precipitation and the initial groundwater level,

[0064] Δσ zi =γ w ·a0;

[0065] When the calculation point is below the water level after precipitation,

[0066] Δσ zi =γ w ·S′;

[0067] Where S is the ground deformation caused by precipitation, i.e., settlement; γ w is the density of water; Δσ zi is the additional effective stress at the midpoint of the i-th soil layer under the ground caused by precipitation; a0 is the vertical distance from the calculation point to the initial groundwater level; Δb iis the thickness of the i-th soil layer; E si is the compression modulus of the i-th soil layer.

[0068] In step S3, the actual settlement at the location where the recharging well is to be laid is compared with the foundation pit monitoring alarm value in the design specification, and whether to lay the recharging well is determined based on the comparison result. In actual construction, the corresponding design specifications will be given to the design unit and the construction unit before construction.

[0069] Example 2

[0070] A system for determining whether a recharge well is arranged in a deep foundation pit containing a confined water layer, comprising at least one processor and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method for rapidly determining whether a recharge well is arranged in a deep foundation pit containing a confined water layer in Example 1.

[0071] Example 3

[0072] This example provides a specific application of the method described in Example 1. Figure 1 As shown, the details are as follows:

[0073] The excavation depth of a foundation pit project is 19.5m, the thickness of the foundation pit ground-connected wall is 1.0m, the excavation depth of the pit-in-pit area is 20.5m, the area radius is 1.0m, the initial water level depth of the foundation pit is 2.5m, the pressurized water depth of the pit-in-pit area is lowered to 21.5m, the top surface of the aquifer is buried at a depth of 15.2m, the filter pipe depth of the pressure relief well is 23m, the depth of the water-stop curtain is 32.5m, and the foundation pit is dewatered by using an in-pit pumping well. The horizontal distance from the in-pit pumping well to the inner edge of the ground-connected wall is 7.0m. An out-of-pit recharge well is used on site, and the horizontal distance from the recharge well to be laid to the outer edge of the foundation pit ground-connected wall is 3.0m.

[0074] For this project, a MIDAS numerical simulation was conducted on the settlement difference between the arrangement of recharge wells around the foundation pit. The precipitation at the pit-in-pit position in the foundation pit is the deepest, so the settlement difference of the surrounding environment caused by the pumping well at this location was simulated.

[0075] The engineering geological parameters are as follows:

[0076] Soil layer Layer thickness / m Poisson's ratio Bulk density / KN / m3 Compression modulus / MPa Cohesion / kPa Internal friction angle / ° Miscellaneous fill 3.7 0.38 17.3 5.1 8.0 10.5 Silty clay 9 0.33 19.0 5.1 31.0 15.4 Clay layer 1 3.5 0.30 21.3 5.2 31.0 15.5 Pink sand 7.5 0.27 21.1 10.9 5.1 30.6 Clay layer 2 4.0 0.31 21.3 5.2 30.5 15.8 Strongly weathered rock 23.7 0.22 25.0 30 50.0 37.0

[0077] A pumping test was carried out on the foundation pit at the beginning of the project. When the G2 single well was selected for pumping, the water level drop in the observation well was as shown in the following table.

[0078] Statistics of water level drop-well distance in each observation well of single well pumping test

[0079] hashtag Distance to pumping well (m) Water level drop (m) G2 Pumping Well / 29.70 Y1 42.48 0.44 X1 51.82 0.39

[0080] According to the requirements of the specifications, such as the Technical Specifications for Monitoring of Construction Foundation Pit Engineering_GB50497-2009 regarding the monitoring alarm values ​​for foundation pits and supporting structures, it can be seen that the displacement around the foundation pit should be less than 35mm. Then, it is calculated whether a recharging well needs to be arranged on the outside of the specific foundation pit edge.

[0081] Table 8.0.4 Monitoring alarm values ​​for foundation pit and supporting structure

[0082]

[0083] 1. Theoretical Calculation

[0084] ① According to the calculation formula of the pumping influence radius R in Example 1, it can be obtained that the influence radius of this group of single well tests is about 244m.

[0085] ② Settlement calculation

[0086] Calculate the water level drop at a position of 3.0m around the foundation pit. The actual horizontal distance from the location where the recharging well is to be laid to the pumping well is r=7.0+1.0+3.0+(32.5-2.5)=41m (near the actual area where the recharging well is laid, the recharging well is at 3.0m).

[0087] According to the calculation formula of the water level drawdown S' in Example 1, S'=6.16m is obtained.

[0088] Calculate the settlement around the foundation pit. Based on the water level drop of S`=6.16m, the depth of the water level line at this location is 2.5m+6.16m=8.66m.

[0089] The settlement of the surface point is obtained by the cumulative settlement of the soil layer below it, but the lower the soil is, the smaller the deformation is. Since the confined water layer is pumped down by the foundation pit, the settlement of the soil layer below the confined water is negligible, so it is calculated to the depth of the impermeable layer under the confined water, which is 23.7m.

[0090] In summary, the soil layers above the initial water level are: part of the miscellaneous fill layer; the soil layers above the water level and below the initial water level are: part of the miscellaneous fill layer and part of the silty clay layer; the soil layers below the water level are part of the silty clay layer, clay layer 1 and silty sand layer. The calculated settlement consists of the above three parts. According to the calculation formula of the actual settlement S, S = (0 + 39.66 + 107.65) * 10-3m = 147.31mm.

[0091] The calculated structure shows that the settlement at the location where the recharge well is to be laid far exceeds the maximum value in the specification, and a recharge well needs to be laid.

[0092] 2. Numerical simulation

[0093] like Figure 2and Figure 3 As shown, the simulation values ​​are given respectively, and the calculated water level drop is 11.1m and the final settlement is 152.4mm.

[0094] Theoretical calculations Numerical simulation Comparative Analysis Water level drop / m 8.66 8.7 0.5％ Calculated value of settlement around foundation pit / mm 147.31 152.4 3.3％

[0095] The theoretical calculation is consistent with the numerical simulation, which can prove the feasibility of the calculation scheme of this application and can be applied in actual construction.

[0096] It is easy to understand that those skilled in the art can combine, split, reorganize, etc. the embodiments of the present application to obtain other embodiments based on one or several embodiments provided in the present application, and these embodiments do not exceed the protection scope of the present application.

[0097] In conclusion, the above is only a preferred embodiment of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the patent of the present invention.

Claims

1. A method for quickly determining whether a recharging well is arranged in a deep foundation pit containing a confined water layer, characterized in that: It includes the following steps: Step S1, obtaining the water level drop at the location where the recharging well is to be arranged based on the pumping test and the actual horizontal distance from the location where the recharging well is to be arranged to the pumping well; Step S2, obtaining the actual settlement of the location where the recharging well is to be arranged according to the water level drop at the location where the recharging well is to be arranged; Step S3: based on the actual settlement of the location where the reinjection well is to be arranged obtained in step S2, determine whether it is necessary to arrange a reinjection well at the location where the reinjection well is to be arranged.

2. The method for quickly determining whether a deep foundation pit recharging well containing a confined water layer is arranged according to claim 1, characterized in that: Step S1 specifically includes the following steps: Step S11: Obtain the pumping influence radius R and the pumping well radius r through a pumping test w and the water level drop in the pumping area S w ; Step S12: Obtain the actual horizontal distance r from the location where the recharging well is to be laid to the pumping well, where In the formula, r1` is the horizontal distance from the pumping well in the foundation pit to the inner edge of the ground-connected wall. is the thickness of the foundation pit ground wall, is the horizontal distance from the location of the recharging well to the outer edge of the foundation pit ground connection wall, and d is the seepage path distance of the water-stopping curtain; Step S13, calculate the water level drop S at the location where the recharging well is to be laid, and the calculation formula is: Where S' is the water level drop at the location where the recharging well is to be laid, R is the pumping influence radius, and S w is the water level drop in the pumping area, r is the actual horizontal distance from the location of the recharging well to the pumping well, and r w is the radius of the pumping well.

3. The method for quickly determining whether a recharging well in a deep foundation pit containing a confined water layer is arranged according to claim 1, characterized in that: Step S2 specifically includes obtaining the ground deformation caused by precipitation according to the water level drop S', that is, the actual settlement S at the location where the recharging well is to be arranged, Among them, when the calculation point is above the initial groundwater level, Board zi =0 When the calculation point is located between the water level after precipitation and the initial groundwater level, Board zi =c w ·a0; When the calculation point is below the water level after precipitation, Board zi =c w ·S′; Where S is the ground deformation caused by precipitation, i.e., settlement; γ w is the density of water; Δσ zi is the additional effective stress at the midpoint of the i-th soil layer under the ground caused by precipitation; a0 is the vertical distance from the calculation point to the initial groundwater level; Δb i is the thickness of the i-th soil layer; E si is the compression modulus of the i-th soil layer.

4. The method for quickly determining whether a deep foundation pit recharging well containing a confined water layer is arranged according to claim 1, characterized in that: In step S3, the actual settlement at the location where the recharging well is to be arranged is compared with the foundation pit monitoring alarm value in the design specification, and whether to arrange the recharging well is determined according to the comparison result.

5. The method for quickly determining whether a recharging well in a deep foundation pit containing a confined water layer is arranged according to claim 2, characterized in that: The calculation formula of pumping influence radius R is: Where S1 is the water level drop in observation hole 1, S2 is the water level drop in observation hole 2, r1 is the distance from observation hole 1 to the pumping well, and r2 is the distance from observation hole 2 to the pumping well.

6. The method for quickly determining whether a recharging well in a deep foundation pit containing a confined water layer is arranged according to claim 2, characterized in that: The calculation formula for the seepage path distance d of the water-stop curtain is: d = Hh; Where H is the depth of the water-stop curtain; h is the initial water level depth of the foundation pit.

7. A judgment system for whether a deep foundation pit recharging well containing a confined water layer is arranged, characterized in that: The method comprises at least one processor and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method according to any one of claims 1 to 5.

Images