Method for determining height and specific weight of mud in mechanical construction of open caisson

Abstract

The application provides a method for determining the height and gravity of mud in mechanical construction of a sinking well, comprising the following steps: determining the distance from the pressure water head height to the pressure roof, the distance from the sinking well bottom to the pressure roof, and the average gravity of the soil between the sinking well bottom and the pressure roof; determining the product of the mud gravity and the mud height; determining the gravity, internal friction angle, and cohesive force of each soil layer outside the sinking well; determining the active earth pressure coefficient of each soil layer of the sinking well side wall; determining the earth pressure outside the sinking well side wall; determining the passive earth pressure coefficient of the sinking well side wall by the mud; determining the unit length gravity of the sinking well, the width of the sinking well blade foot plane, the inclination angle, and the thickness of the sinking well; determining the vertical distance from the earth pressure action point of the sinking well side wall to the inner point of the blade foot; determining the force of the mud on the sinking well side wall; determining the vertical distance from the pressure action point of the sinking well side wall by the mud to the inner point of the blade foot; determining the moment of the inner point of the blade foot by the mud; and determining the mud height and the mud gravity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sinking well construction, in particular to a method for determining the height and specific gravity of mud in sinking well mechanical construction. BACKGROUND

[0002] In recent years, with the rapid development of underground space construction, the application scenarios of sinking well construction technology are also increasing, and the requirements for sinking well construction technology are also getting higher and higher. The traditional sinking well construction technology cannot meet the needs of today. The sinking well mechanical excavation construction technology just makes up for the defects of the traditional sinking well construction technology. In Zhang Zhenguang et al.'s "Underwater mechanical excavation construction technology of super-deep assembled vertical shaft in water-rich stratum: Taking a sinking well type parking facility construction project in Nanjing as an example", the sinking well mechanical excavation construction technology is introduced. The sinking well mechanical excavation technology uses a full-automatic mechanical vertical shaft excavator for excavation. During the entire excavation process, the operating personnel do not need to enter the wellbore. The excavated soil is transported into the slurry separation system through the slurry outlet pipe and is mixed into a certain proportion of mud, which is then injected into the wellbore through the slurry inlet pipe. The mud in the wellbore can prevent piping and other phenomena from occurring at the bottom of the sinking well. In summary, the mud plays a role in balancing the groundwater pressure in the sinking well mechanical construction, which can effectively prevent the piping phenomenon from occurring at the bottom of the sinking well and effectively reduce the instability risk of the excavation surface at the bottom of the sinking well. Therefore, the required injection height and specific gravity of the mud play an extremely important role in the safety of the sinking well mechanical construction. However, so far, there is no effective method to determine the required mud height and specific gravity. Therefore, the present application provides a method for determining the height and specific gravity of mud in sinking well mechanical construction. SUMMARY

[0003] The main purpose of the present application is to provide a method for determining the height and specific gravity of mud in sinking well mechanical construction, which can calculate the required mud height and specific gravity in the sinking well mechanical construction process, has the advantages of simple process and reliable results, and effectively avoids problems caused by the fact that the mud height and specific gravity do not meet the requirements.

[0004] In order to achieve the above purpose, the present application provides a method for determining the height and specific gravity of mud in sinking well mechanical construction, comprising the following steps:

[0005] 1) determining the distance H from the confined water head height to the confined roof, the distance h2 from the sinking well bottom to the confined roof, and the average specific gravity γ of the soil between the sinking well bottom and the confined roof s ;

[0006] 2) determining the product of the specific gravity of the mud and the height of the mud γ n h1;

[0007] When γ s h2≥K s γ wH

[0008] γ n h1=0,

[0009] In this case, the soil between the caisson bottom and the bearing roof has been able to balance the groundwater pressure, so the mud height h1 and the specific gravity γ n Any value meets the sudden gushing requirements, and the specific value only needs to meet the anti-overturning (i.e., step 11) requirements.

[0010] When γ s h2 s γ w H,

[0011] γ n h1=K s γ w H-γ s h2,

[0012] γ n : mud specific gravity; h1: mud height; K s : safety factor, take 1.05; γ w : water specific gravity, take 10 KN / m 3 .

[0013] 3) Determine the specific gravity γ i , internal friction angle φ 1i , and cohesive force c i of each soil layer outside the caisson;

[0014] 4) Determine the active earth pressure coefficient K ai of each soil layer of the caisson side wall;

[0015]

[0016] φ 1i : internal friction angle of soil layer i outside the caisson side wall.

[0017] The active earth pressure coefficients of each soil layer are different.

[0018] 5) Determine the earth pressure E a outside the caisson side wall;

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025] γ i : unit weight of soil layer i, if the soil layer is below the groundwater level, the buoyant unit weight γ' i , γ i , = γ i - γ w ; c i : cohesion of soil layer i; h i : thickness of soil layer i; σ i : active earth pressure intensity of soil layer i; m: total number of soil layers.

[0026] 6) Determine the passive earth pressure coefficient K of the mud on the side wall of the caisson p ;

[0027]

[0028] φ2: internal friction angle of the mud.

[0029] 7) Determine the unit weight G of the caisson per unit length, the width B1 of the caisson blade plane, the inclination angle θ, and the thickness d of the caisson.

[0030] 8) Determine the vertical distance a from the earth pressure action point of the mud on the side wall of the caisson to the inside point O of the blade a ;

[0031] 9) Determine the force F of the mud on the side wall of the caisson n ;

[0032]

[0033] where c: cohesion of the mud; K p : passive earth pressure coefficient of the mud on the side wall of the caisson; γ n : unit weight of the mud; h1: height of the mud.

[0034] 10) Determine the vertical distance a from the earth pressure action point of the mud on the side wall of the caisson to the inside point O of the blade n ;

[0035]

[0036] 11) Determine the moment M of the mud on the inside point O of the blade n ;

[0037]

[0038] where F n : force of the mud on the side wall of the caisson, a n : vertical distance from the earth pressure action point of the mud on the side wall of the caisson to the inside point O of the blade, c: cohesion of the mud, Kav : anti-overturning safety factor, take 1.3. Here If then take Continue to calculate.

[0039] 12) Determine the height h1 and the specific gravity γ of the mud n ;

[0040]

[0041]

[0042] Wherein when A>0, A=K s γ w H-γ s h2; when A<0, A=0;

[0043] Substitute the specific data to solve the final result, and the final result needs to meet h1>0, γ n >0 and the requirements of anti-inrush and anti-overturning. It should be noted that if the final depth of the caisson is greater than the buried depth of the confined water, when the excavation depth is greater than the buried depth of the confined water, the height h1 and the specific gravity γ n of the mud can take any value to meet the inrush requirements, and the specific value only needs to meet the anti-overturning (i.e. step 11) requirements.

[0044] The final result obtained by the above calculation is only the height and specific gravity of the mud at a certain depth in the mechanical caisson construction process. If the height and specific gravity of the mud in the entire process are needed, a plurality of excavation depths need to be selected at certain excavation depth intervals, and the height and specific gravity of the mud at each excavation depth are obtained by repeated calculation. Then, the height and specific gravity of the mud at each excavation depth obtained by calculation are plotted into a curve diagram. According to the plotted curve, the height and specific gravity of the mud required at each excavation depth of the caisson can be known. The smaller the depth interval, the higher the accuracy of the curve drawing. The curve represents the minimum height and specific gravity. When the value is taken, the point on the upper part of the curve can be taken.

[0045] Compared with the prior art, the beneficial effects of the present application are:

[0046] 1. The present application has clear arrangement, simple calculation and easy operation.

[0047] 2. The present application can quickly determine the height and specific gravity of the mud required in the mechanical caisson construction process, and the calculation result is reliable.

[0048] 3. The present application can effectively prevent the problems of inrush and instability of the caisson bottom caused by the mud not meeting the requirements in the mechanical caisson construction process. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 The schematic diagram of the caisson position relationship of the application;

[0050] Figure 2 The schematic diagram of the caisson structure parameter of the application;

[0051] Figure 3 The mud height curve diagram of the application;

[0052] Figure 4 The mud density curve diagram of the application. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.

[0054] In the description of the application, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom end" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0055] In the description of the application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "provided with", "sleeved / connected", "connected" and the like should be understood broadly, for example, "connected" can be wall-mounted connection, can be detachable connection, or integral connection, can be mechanical connection, can be electrical connection, can be direct connection, can be indirect connection through an intermediate medium, can be the communication between two elements inside, and for a person of ordinary skill in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0056] Reference Figure 1 and Figure 2 The embodiment provides a method for determining the mud height and density in caisson mechanical construction, comprising the following steps:

[0057] 1) determining the distance H from the pressure water head height to the pressure roof, the distance h2 from the caisson bottom to the pressure roof, and the average density γ of the soil between the caisson bottom and the pressure roof s ;

[0058] First, the elevation of the pressure roof is measured by exploration survey, then the elevation of the water level of the confined water is measured by the groundwater level monitor, and finally the difference between the two is the H.

[0059] First, the ground elevation is measured by the level gauge, then the open caisson excavation depth is determined, the open caisson bottom elevation is obtained by subtracting the excavation depth from the ground elevation, and finally the h2 is obtained by subtracting the pressure roof elevation from the open caisson bottom elevation.

[0060] First, the soil samples of each soil layer of the construction site are collected, then the specific gravity of each soil layer is obtained through indoor test, and finally the average specific gravity of the soil between the open caisson bottom and the pressure roof is obtained by weighted average of the specific gravity of the soil between the open caisson bottom and the pressure roof. s .

[0061] 2) Determine the product of the mud specific gravity and the mud height γ n h1;

[0062] When γ s h2≥K s γ w H,

[0063] γ n h1=0,

[0064] In this case, the soil between the open caisson bottom and the pressure roof can balance the groundwater pressure, so the mud height h1 and the specific gravity γ n Take any value to meet the heave requirements, and the specific value only needs to meet the anti-overturning requirements (i.e. step 11). According to the specific engineering requirements, one of the values can be determined, and then the other value can be obtained, such as setting the mud height to be 1-2m higher than the groundwater level, and then the specific gravity can be obtained.

[0065] When γ s h2<K s γ w H,

[0066] γ n h1=K s γ w H-γ s h2,

[0067] γ n : mud specific gravity; h1: mud height; K s : safety factor, take 1.05; γ w : water specific gravity, take 10KN / m 3 .

[0068] 3) Determine the specific gravity γ i , internal friction angle φ 1i , and cohesion c i of each soil layer outside the open caisson.

[0069] The weight γ of each soil layer can be obtained by taking soil samples from the construction site and conducting indoor soil tests i , the internal friction angle φ 1i , and the cohesion c i .

[0070] 4) Determine the active earth pressure coefficient K ai of each soil layer of the caisson side wall;

[0071]

[0072] φ 1i : the internal friction angle of the soil layer i outside the caisson side wall.

[0073] The active earth pressure coefficient of each soil layer is different.

[0074] 5) Determine the earth pressure E a outside the caisson side wall;

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081] γ i : the weight of soil layer i, if the soil layer is below the groundwater level, the buoyant weight γ' i , γ' i = γ i - γ w ; c i : the cohesion of soil layer i; h i : the thickness of soil layer i; σ i : the active earth pressure intensity of soil layer i, m: the total number of soil layers.

[0082] 6) Determine the passive earth pressure coefficient K p of the mud against the caisson side wall;

[0083]

[0084] φ2: the internal friction angle of the mud.

[0085] The internal friction angle φ2 of the mud is taken from the internal friction angle of the main component soil in the mud, which is also obtained by indoor triaxial test.

[0086] 7) Determine the self-weight of caisson per unit length G, the width of caisson blade plane B1, the angle of inclination θ, the thickness of caisson d.

[0087] When prefabricated concrete segments are used for caisson, the weight of each segment can be measured, and then multiplied by the number of segments to obtain the total weight, and then divided by the perimeter of the caisson, and finally the self-weight of caisson per unit length G can be obtained; when concrete is poured, the volume of caisson is multiplied by the density to obtain the mass of the segment, and then multiplied by the acceleration of gravity, and then divided by the perimeter of the caisson, and the self-weight of caisson per unit length G can also be obtained; the width of caisson blade plane B1, the angle of inclination θ, and the thickness of caisson d are measured by measuring ruler and protractor.

[0088] 8) Determine the vertical distance a from the point of action of soil pressure on the side wall of caisson to the inside point O of blade a .

[0089] 9) Determine the force F of mud on the side wall of caisson n ;

[0090]

[0091] Where c: cohesion of mud; K p : passive earth pressure coefficient of mud on the side wall of caisson; γ n : specific weight of mud; h1: height of mud.

[0092] 10) Determine the vertical distance a from the point of action of mud pressure on the side wall of caisson to the inside point O of blade n ;

[0093]

[0094] 11) Determine the moment M of mud on the inside point O of blade n ;

[0095]

[0096] Where F n : force of mud on the side wall of caisson, a n : vertical distance from the point of action of mud pressure on the side wall of caisson to the inside point O of blade, c: cohesion of mud, K av : safety factor against overturning, taken as 1.3. Here If , take and continue to calculate.

[0097] 12) Determine the value of height of mud h1 and specific weight of mud γ n ;

[0098]

[0099]

[0100] wherein when A>0, A=K s γ w H-γ s h2; when A<0, A=0;

[0101] Substitute the specific data to solve the final result, and the final result needs to meet h1>0, γ n >0 and the requirements of anti-bursting and anti-overturning. It needs to be noted that if the final depth of the caisson is greater than the buried depth of the confined water, when the excavation depth is greater than the buried depth of the confined water, the slurry height h1 and the specific gravity γ n take any value to meet the bursting requirement, and the specific value only needs to meet the anti-overturning requirement (i.e. step 11), one value can be determined according to the specific engineering requirements, and the other value can be determined, such as the slurry height being 1-2 m higher than the groundwater level, and the specific gravity can be determined.

[0102] For the above steps, it needs to be noted that the caisson excavation process is a dynamic process, and some parameters h2, γ s , G, a a , etc. will change, so each calculation is performed on the parameters of a certain excavation depth in the dynamic process, and thus only the slurry height and the specific gravity corresponding to a certain excavation depth can be obtained. As described above, in order to obtain the slurry height and the specific gravity required in the entire caisson excavation process, a plurality of excavation depths need to be selected at certain intervals, the slurry height and the specific gravity corresponding to each excavation depth need to be calculated repeatedly, and then the calculation results of each excavation depth need to be plotted into a curve diagram. The points on the curve diagram are the values of the slurry height and the specific gravity at each excavation depth, and the smaller the interval between the excavation depths, the higher the precision of the curve. Moreover, since the results obtained by the calculation are the minimum requirements, the points on the curve are the minimum requirement values, and thus the points on the upper part of the curve can be taken as the values.

[0103] The above-mentioned methods of obtaining calculation parameters are only provided as a method, and are not the only method, and other methods of obtaining calculation parameters can be used.

[0104] Embodiment

[0105] The excavation depth of a certain caisson is 50 m, the inner diameter of the caisson is 12.7 m, the outer diameter of the caisson is 13.1 m, the caisson construction adopts the caisson mechanical method, and it is known from the previous survey that the stratum at the caisson excavation site contains a confined water layer. In order to ensure that the caisson construction process does not occur bursting, the method of the present application is used to determine the slurry height and the specific gravity required in the caisson construction process.

[0106] According to the survey data, the conditions of each soil layer are as follows: the thickness of the sand filling is 8 m, the specific gravity γ is 18 KN / m3 , internal friction angle φ = 35.6°, cohesion c = 3 kPa, active earth pressure K a = 0.26; backfill silt thickness 5 m, unit weight γ = 17 KN / m 3 , internal friction angle φ = 2.5°, cohesion c = 11.3 kPa, active earth pressure K a = 0.92; plain fill thickness 12 m, unit weight γ = 18.5 KN / m 3 , cohesion c = 10 kPa, internal friction angle φ = 12.0°, active earth pressure K a = 0.65; silt thickness 4 m, unit weight γ = 16.5 KN / m 3 , internal friction angle φ = 2.6°, cohesion c = 9.3 kPa, active earth pressure K a = 0.91; coarse sand thickness 10 m, unit weight γ = 19 KN / m 3 , internal friction angle φ = 28.0°, cohesion c = 3 kPa, active earth pressure K a = 0.36; residual sandy clay thickness 9 m, unit weight γ = 18 KN / m 3 , internal friction angle φ = 22.1°, cohesion c = 27.4 kPa, active earth pressure K a = 0.45; fully weathered granite 20 m, unit weight γ = 19.5 KN / m 3 , internal friction angle φ = 26.0°, cohesion c = 30 kPa, active earth pressure K a = 0.39; coarse sand layer confined water level depth 3 m; groundwater level depth 3 m.

[0107] When the caisson is excavated to a depth of 10 m, the average unit weight γ of the soil layer between the caisson bottom and the confined top plate is calculated to be s = 17.84 KN / m 3 , the distance H between the confined water level and the confined top plate is 26 m, and the distance h2 between the caisson bottom and the confined top plate is 19 m; the γ s h2 = 338.96 KN / m 2 , K s γ w H = 273 KN / m 2 , γ s h2 > K s γ w H; the mud height h1 and unit weight γ n Take any value to meet the sudden gushing requirements, and the specific value only needs to meet the anti-overturning requirements.

[0108] When the caisson is excavated to a depth of 15 m, the average unit weight γ of the soil layer between the caisson bottom and the confined top plate is calculated to be s = 17.93 KN / m 3, the distance from the confined water level to the confined roof H = 26 m, the distance from the caisson bottom to the confined roof h2 = 14 m; through calculation, γ s h2 = 251.02 KN / m 2 , K s γ w H = 273 KN / m 2 , γ s h2 < K s γ w H, it is determined that the mud gravity multiplied by height equals 21.98 KN / m 2 ; it is determined that the earth pressure E a = 644.79 KN / m on the outside of the caisson sidewall; it is determined that the main component soil internal friction angle φ2 of the mud = 22.0°; it is determined that the passive earth pressure coefficient K p of the mud on the caisson sidewall = 2.2; it is determined that the cohesion c of the mud = 32 kpa; according to the measured caisson parameters, the unit length gravity G of the caisson = 143.61 KN / m, the caisson blade foot plane width B1 = 0.1 m, the inclination angle θ = 45°, and the caisson thickness d = 0.4 m; it is determined that the vertical distance a a from the earth pressure action point of the caisson sidewall to the inside point O of the blade foot = 4.05 m; it is determined that the moment M n of the mud on the inside point O of the blade foot = 3366.10 KN; it is determined that the calculation value of expression A = 21.98 KN / m 2 ; it is determined that the calculation value of expression D = 39.70 KN / m 2 ; it is determined that the calculation value of expression F = 35.73 KN / m; it is further determined that the mud height h1 = 9.67 m, and the mud gravity γ n = 2.27 KN / m 3 .

[0109] When the caisson is excavated to a depth of 17.5 m, the above steps are repeated, and it is determined that the mud height h1 = 10.39 m, and the mud gravity γ n = 6.93 KN / m 3 ; when the caisson is excavated to a depth of 20 m, the above steps are repeated, and it is determined that the mud height h1

[0110] = 11.39 m, and the mud gravity γ n = 10.05 KN / m 3 ; when the caisson is excavated to a depth of 22.5 m, the above steps are repeated, and it is determined that the mud height h1 = 12.32 m, and the mud gravity γ n = 13.05 KN / m 3 ; when the caisson is excavated to a depth of 25 m, the above steps are repeated, and it is determined that the mud height h1 = 13.26 m, and the mud gravity γ n = 15.61 KN / m 3When the caisson was excavated to a depth of 29m, the above steps were repeated, and the mud height h1 was found to be 15.12m, and the mud unit weight γ was... n =18.05KN / m 3 Further determine when γ s h2=K s γ w At time H, the excavation depth was 13.81m. Through the above steps, the mud height h1 = 9.32m, and the mud unit weight γ... n Meeting the basic requirements is sufficient; when the caisson excavation depth is greater than the depth of the confined water, the mud height h1 and the unit weight γ are required. n Any value can satisfy the surge requirement; the specific value only needs to meet the anti-overturning requirement.

[0111] The values ​​obtained from the above calculations are plotted as a curve as shown in the attached figure. Figure 3 , 4 As shown, the mud height and density corresponding to each excavation depth between 13.81m and 29m can be obtained by taking points on the curve. The mud height corresponding to each excavation depth outside this range can be taken as 1-2m higher than the groundwater level. The mud density can be obtained by substituting the specific mud height into the anti-overturning calculation formula (i.e., step 11).

[0112] The above description is merely a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention by those skilled in the art within the scope of the technology disclosed in the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A method for determining the height and density of a slurry for mechanical construction of a caisson, comprising the steps of: 1) determining the distance of the confined water head height to the confined roof , the distance of the caisson bottom to the confined roof , the average specific weight of the soil between the caisson bottom and the confined roof ; 2) Determine the product of the mud weight and the mud height ; When Time, ; When Time, ; Wherein : slurry density; : slurry height; : safety factor, take 1.05; : water density take 10 KN / m 3 ; 3) Determine the weight of each soil layer outside the caisson , internal friction angle , cohesion ; 4) Determining the active earth pressure coefficient of each soil layer of the caisson side wall ; ; wherein : internal friction angle of soil layer i outside the caisson side wall 5) Determining earth pressure outside the caisson side wall ; , ， ， ， ， ， : unit weight of soil layer i, if the soil layer is below the groundwater level, the buoyant unit weight is used , ; : cohesion of soil layer i; : thickness of soil layer i; : active earth pressure strength of soil layer i, m: total number of soil layers; 6) Determining the passive earth pressure coefficient of the slurry against the caisson side wall ; ; wherein : internal friction angle of the slurry; 7) determine the unit length of caisson self-weight G, caisson blade foot plane width B1, inclination angle , caisson thickness d; 8) Determine the vertical distance a from the point of action of the earth pressure on the side wall of the caisson to the point O inside the toe a ; 9) Determine the force F of the mud on the caisson side wall n ; ; where c: cohesion of the slurry; : passive earth pressure coefficient of the slurry on the caisson side wall; : slurry density; : slurry height; 10) Determine the vertical distance a of the mud pressure point to the inside of the toe point O n ; ; 11) Determine the moment of the mud force on the inside of the blade shoe at point O ; ; F = (a + c) * K n : mud force on the side wall of the open caisson, a n : vertical distance from the point of pressure of the mud on the side wall of the open caisson to the point O inside the blade foot, c: cohesive force of the mud, K av : safety factor against overturning, taken as 1.3; 12) Determine the height of the mud and the value of the mud density . ; ; wherein when A = 0; when A = 0; ; .

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