CN110309520A - A Calculation Method and Application of Effective Depth of Impact of Incomplete Wells in Submerged Formation - Google Patents

Abstract

The present invention provides a method for calculating the effective impact depth of an incomplete well in a submerged formation and its application. The method includes: establishing a calculation formula for the single well flow rate of a complete well; establishing a calculation formula for the flow rate of an incomplete well; combining the single well flow rate of the complete well with the Incomplete well flow equivalent. Different from the prior art which ignores the effective impact depth in the foundation pit, the present invention obtains the effective impact depth in the foundation pit by establishing the equivalent calculation formula of the complete well single well flow calculation formula and the incomplete well flow calculation formula, and the effective impact depth can be clearly Increase the fitting accuracy of the precipitation curve outside the foundation pit of the incomplete well in the phreatic formation.

Description

A Calculation Method and Application of Effective Depth of Impact of Incomplete Wells in Submerged Formation

technical field

The invention relates to the measurement of foundation pit precipitation. More specifically, it relates to a calculation method and its application of the effective impact depth of an incomplete well in a phreatic formation.

Background technique

At present, the calculation methods for the surface settlement caused by the precipitation of foundation pits in submerged strata include JGJ 120-2012 "Code for Building Foundation Pit Support", JSJ 311-2013 "Technical Code for Construction Safety of Deep Foundation Pit Engineering" and SJG 05-2011 "Shenzhen These methods are all based on the layered sum method to estimate the settlement caused by precipitation. The calculation formula of the standard method is simple, but there is no clear calculation formula for the water level drawdown at any position from the precipitation well.

Most of the prior art is used to calculate the surface settlement of the precipitation outside the foundation pit. For the precipitation inside the foundation pit, because the influence of the effective impact depth of incomplete precipitation on the surface settlement outside the pit is ignored, the results obtained by using the calculation method in the prior art There is a large error with the actual.

In view of this, it is necessary to provide a calculation method and its application of the effective impact depth of incomplete wells in phreatic formations.

Contents of the invention

An object of the present invention is to provide a method for calculating the effective impact depth of an incomplete well in a phreatic formation.

Another object of the present invention is to provide an application of a calculation method for the effective impact depth of an incomplete well in a phreatic formation.

To achieve the above object, the present invention adopts the following technical solutions:

A method for calculating the effective impact depth of an incomplete well in a phreatic formation, comprising:

S1. Establish the formula for calculating the flow rate of a single well in a complete well:

S2. Establish the flow calculation formula for incomplete wells:

S3. The single well flow rate of the complete well is equivalent to the flow rate of the incomplete well, Q _incomplete =Q _complete ,

s _{w is incomplete} = s _{w is complete} , using Matlab software to calculate the effective impact depth H ₀ of incomplete wells in phreatic formations.

Preferably, when the method calculates the effective depth of incomplete wells in the foundation pit, the value of _H0 is the product of the value of _H0 calculated by using Matlab software and the amplification factor.

Preferably, the amplification factor is obtained through experiments based on precipitation in a single well and a double well, and the amplification factors are 1.18 and 1.32.

Preferably, when a single well is dewatered, the amplification factor is 1.18;

When the two wells are dewatered, the amplification factor is 1.32.

The present invention also provides the application of a calculation method for the effective impact depth of incomplete wells in phreatic formations, using the effective depth of incomplete wells in phreatic formations to divide the seepage bypass area and non-seepage bypass area in the foundation pit of incomplete phreatic formation wells. The steps of the division include:

S1. Obtain the fitted precipitation curve through experimental data processing:

In the formula, H represents to utilize Matlab software to calculate and obtain the product of the value of H ₀ and the magnification factor _;

S2. Carrying out second-order derivation to the fitted precipitation curve to obtain:

S3, seek the corresponding x value when h"=0, and obtain the distance between the inflection point and the retaining wall

In the precipitation curve, the area before the inflection point is the infiltration area, and the area after the inflection point is the non-infiltration area.

Preferably, the amplification factor is obtained through experiments based on precipitation in a single well and a double well, and the amplification factors are 1.18 and 1.32.

Preferably, when a single well is dewatered, the amplification factor is 1.18;

When the two wells are dewatered, the amplification factor is 1.32.

The beneficial effects of the present invention are as follows:

The present invention provides a calculation method for the effective impact depth of an incomplete well in a submerged formation, which is different from the prior art which ignores the effective impact depth in a foundation pit. The effective influence depth in the foundation pit can be obtained by using the effective calculation method, which can significantly increase the fitting accuracy of the precipitation curve outside the foundation pit of the well with incomplete phreatic formation.

In a preferred solution of the present invention, the new effective depth of influence is obtained by multiplying the effective depth of influence by the magnification factor, and the new effective depth of influence can significantly increase the fitting accuracy of the precipitation curve in the incomplete well foundation pit of the phreatic formation.

In addition, the present invention also provides the application of the above method to distinguish the seepage-circling area and non-seepage-circling area in the foundation pit by means of second-order derivation of the precipitation curve, thereby further increasing the applicability and accuracy of the precipitation curve.

Description of drawings

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Fig. 1 shows the flow chart of the calculation method of the effective depth of the incomplete well in the submerged formation of the present invention.

Fig. 2 shows the application flow chart of the calculation method of the effective influence depth of the incomplete well in the phreatic formation.

Figure 3 shows a plan view of the test model of the present invention.

Figure 4 shows one of the cross-sectional layouts of the test model of the present invention.

Fig. 5 shows the second sectional layout diagram of the test model of the present invention.

Fig. 6 shows that when the depth of burial is 0.07m, the precipitation curve of gravel cohesive soil layer of the present invention.

Fig. 7 shows that when the buried depth is 0.22m, the precipitation curve of the gravel cohesive soil layer of the present invention.

Fig. 8 shows that when the buried depth is 0.37m, the precipitation curve of the gravel cohesive soil layer of the present invention.

Fig. 9 shows that when the buried depth is 0.52m, the precipitation curve of the gravel cohesive soil layer of the present invention.

Detailed ways

In order to illustrate the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments and accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not limit the protection scope of the present invention.

In the embodiment of the present invention, H is the water content thickness of the soil layer before the precipitation, and _hw is the water content thickness of the soil layer at the nearest distance from the retaining wall outside the foundation pit after the precipitation is stable ( _hw can be subtracted by the water content thickness H of the soil layer before the precipitation. s _w ), H _a is the effective depth of the incomplete well in the foundation pit; s is the distance between the dewatering well and the retaining wall; α is the correction coefficient; x represents the different distances between the foundation pit and the retaining wall; r _w is the radius of the precipitation well; k is the permeability coefficient of the soil layer; l is the length of the filter _of the precipitation _well ;

Example 1

The present invention provides a calculation method for the effective impact depth of an incomplete well in a phreatic formation, as shown in Figure 1, comprising:

S1. Establish the formula for calculating the flow rate of a single well in a complete well:

S2. Establish the flow calculation formula for incomplete wells:

S3. The single well flow rate of the complete well is equivalent to the flow rate of the incomplete well, Q _incomplete =Q _complete ,

s _{w is incomplete} = s _{w is complete} , using Matlab software to calculate the effective impact depth H ₀ of incomplete wells in phreatic formations.

Of course, as known in the art, the symbols of the parameters in the formula can be taken from authoritative documents in the art.

Optionally, the effective depth of influence can be applied to the inside and outside of the foundation pit, and similarly, the effective depth of influence can be applied to single wells and double wells.

The corresponding result comparison can be obtained through the following tests, as shown in Figure 1-3:

Figure 1 and Figure 2 show the plane layout and cross-section of the incomplete well dewatering model test in the foundation pit. In Figure 1, the enclosure of the foundation pit and the dewatering well are arranged in the middle of the main test box to ensure that the water supply tank is outside the radius of influence Provide steady hydration.

The gravel-clay similar strata and fully weathered granite similar stratum were selected for experiments respectively. In order to ignore the influence of foundation pit excavation on the water level in the stratum, the tests simulated the precipitation process before foundation pit excavation. Taking the precipitation test of similar strata of gravel clayey soil as an example, the test process is as follows:

The pre-proportioned gravel cohesive soil samples were slowly spread into the box manually with a shovel. Every time 10cm of ground material is laid during filling, the ground is tamped immediately, and the number of times of tamping per square meter is consistent with the test tamping of materials with similar tamping force, so as to ensure the stability of the physical parameters of the soil layer. Whenever the test instrument, foundation pit enclosure structure and downwater pipe are buried deep, the drainage pipe at the bottom of the box is connected to the high water tank, and water is injected into the test box through the high water tank. The water injection speed can pass through the bottom drainage pipe Adjust the valve to ensure that the flow rate is stable and not too fast, so that the soil layer is saturated from bottom to top. After the soil layer is saturated, a certain settlement deformation will occur. It is necessary to continue to fill the soil sample to the required height. After 1 or 2 times of saturation and After the filling process, the monitoring instruments and soil samples can continue to be filled until the required height of the test is 1.1m. When the soil layer in the test box is consolidated, the surrounding water tanks and the main box maintain a water level of 1.1m, and the stratum is consolidated under the action of its own weight. When the displacement meter reading at the surface settlement observation point of the model box is less than 0.001mm/d, it indicates that the soil layer is consolidated. The structure has basically been completed, and the model test has reached the initial state before construction, and the conditions for the precipitation test are met. The test is mainly for pumping water at a fixed depth. In order to ensure that the water level in the well is always the required drawdown during the dewatering process, the water head of the pumping pipe must be fixed in the 5#, 1# and 1# and 3# dewatering wells before each dewatering test. Specify the precipitation depth (0.1m, 0.2m, 0.3m, 0.4m, 0.5m), through the test to obtain the precipitation of different depths of the gravel clay soil and fully weathered granite similar formations 5#, 1# and 1# and 3# precipitation wells Changes in pore water pressure before and after precipitation stabilization. Table 1-3 is the comparison of the data results of this test:

Table 1 Theoretical calculation results of effective impact depth

Table 2 Comparison of theoretical and experimental results for similar strata of gravel clayey soil

Table 3 Comparison of theoretical and experimental results for similar strata of fully weathered granite

Obviously, the calculation method of the present invention is more suitable for the calculation of the effective impact depth of incomplete wells outside foundation pits.

Therefore, preferably, when calculating the effective impact depth of incomplete wells in the foundation pit, it is necessary to multiply the amplification factor, which is obtained through experiments based on single well and double well precipitation, and the amplification factors are 1.18 and 1.32.

Optionally, when a single well is dewatering, the amplification factor is 1.18; when two wells are dewatering, the amplification factor is 1.32. Most of the actual subway stations are long and narrow, and the dewatering wells are mostly within 5m from the long-side ground connection wall, that is, the 0.1m range of the model test, and most of the foundation pits along the width direction are single-well or double-well dewatering, so the enlarged Coefficients meet actual needs.

Example 2

This embodiment is a verification test for the effective depth of influence. Through the design of the precipitation test in the foundation pit, the precipitation curve outside the foundation pit caused by the precipitation in the foundation pit of the submerged stratum is obtained; the effective depth of influence is brought into the precipitation curve and the precipitation curve is fitted by Matlab software. The fitting formula of the precipitation curve outside the foundation pit caused by the precipitation in the foundation pit of the phreatic formation is obtained, and the fitting formula is:

The results are shown in Figures 6-9. The test proves that the fitted precipitation curve obtained by using the effective influence depth has high accuracy and can adapt to the existing engineering needs.

Example 3

In practice, due to the existence of the retaining wall, there are seepage circumvention areas and non-circulation seepage areas outside the foundation pit, but the distinction between the seepage area and non-circulation seepage area in the prior art is mainly based on the specific data of the test model, and the error larger. Therefore, the infiltrated area and the non-infiltrated area can be accurately distinguished, so that the precise range of the infiltrated area can be obtained.

Therefore, the present invention also provides the application of a calculation method for the effective impact depth of incomplete wells in submerged formations. As shown in Figures 6 to 9, it can be seen that the precipitation curves are all in the form of "concave first and then convex". The concave area is the infiltration area, and the convex area is the non-infiltration area. The position of the inflection point where the curve changes from concave to convex is the boundary between the infiltration area and the non-infiltration area. It can be seen that the position of the inflection point can be obtained It can be divided into the surrounding seepage area and the non-circling seepage area. Utilize the effective impact depth of the incomplete well in the phreatic formation to divide the seepage circumvention zone and the non-seepage circumvention zone in the incomplete well foundation pit of the phreatic formation, as shown in Figure 2, the steps of the division include:

S1. Obtain the fitted precipitation curve through experimental data processing:

In the formula, H represents to utilize Matlab software to calculate and obtain the product of the value of H ₀ and the magnification factor _;

S2. Carrying out second-order derivation to the fitted precipitation curve to obtain:

S3, seek the corresponding x value when h"=0, and obtain the distance between the inflection point and the retaining wall

In the precipitation curve, the area before the inflection point is the infiltration area, and the area after the inflection point is the non-infiltration area.

Of course, the same as in Example 1, the amplification factor is obtained through experiments based on precipitation in a single well and a double well, and the amplification factors are 1.18 and 1.32.

Optionally, when a single well is dewatering, the amplification factor is 1.18; when two wells are dewatering, the amplification factor is 1.32.

For the above-mentioned method of dividing the seepage circumvention zone and the non-seepage circumvention zone, in this embodiment, a test for verification is provided. This embodiment selects the precipitation curve of the gravel cohesive soil layer as an example, as shown in Figure 6-9, the calculated The positions of the inflection points of the precipitation curve are all within the range of the experimental inflection point, which shows that the theoretical method can more accurately divide the infiltration area and the non-infiltration area outside the pit, which has guiding significance for foundation pit construction and monitoring.

Apparently, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those of ordinary skill in the art can also make It is impossible to exhaustively list all the implementation modes here, and any obvious changes or changes derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims (7)

1. A calculation method for the effective impact depth of an incomplete well in a phreatic formation, characterized in that it comprises: S1. Establish the formula for calculating the flow rate of a single well in a complete well: S2. Establish the flow calculation formula for incomplete wells: S3. The single well flow rate of the complete well is equivalent to the flow rate of the incomplete well, Q _incomplete = Q _complete , s _{w incomplete} = s _{w complete} , and the effective impact depth H ₀ of the incomplete well in the phreatic formation is calculated by using Matlab software. 2. according to the described method of claim ₁ , it is characterized in that, when described method calculates incomplete well effective depth of influence in foundation pit, described H The value is to utilize Matlab software to calculate the product of _H value and amplification factor . 3. The method according to claim 2, characterized in that, the amplification factor is obtained through experiments according to the precipitation of a single well and a double well, and the amplification factors are 1.18 and 1.32. 4. method according to claim 3, is characterized in that, When a single well is dewatered, the amplification factor is 1.18; When the two wells are dewatered, the amplification factor is 1.32. 5. An application method of a calculation method for the effective impact depth of an incomplete well in a phreatic formation, characterized in that, using the effective depth of influence of an incomplete well in a phreatic formation to divide the seepage-circling area and non-circling seepage in the foundation pit of an incomplete well in the phreatic formation district, the steps of dividing include: S1. Obtain the fitted precipitation curve through experimental data processing: In the formula, H represents to utilize Matlab software to calculate and obtain the product of the value of H ₀ and the magnification factor _; S2. Carrying out second-order derivation to the fitted precipitation curve to obtain: S3, seek the corresponding x value when h"=0, and obtain the distance between the inflection point and the retaining wall In the precipitation curve, the area before the inflection point is the infiltration area, and the area after the inflection point is the non-infiltration area. 6. The method according to claim 5, characterized in that, the amplification factor is obtained through experiments according to the precipitation of a single well and a double well, and the amplification factors are 1.18 and 1.32. 7. method according to claim 6, is characterized in that, When a single well is dewatered, the amplification factor is 1.18; When the two wells are dewatered, the amplification factor is 1.32.