JPH1144184A - Method for determining water resistance performance of screw conveyor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quantitatively, determine the performance of a screw conveyor regarding water resistance. SOLUTION: A screw conveyor 22, attached to an earth pressure type shield and transferring muck in a cutter chamber at the front end of the shield toward the back of the shield while consolidating the same, has its water resistance performance determined by use of a determining formula. The apparent unit volume weight γt of the muck, the coefficient of friction μ between the muck and iron, the inclination angle θ of the rotation axis of a screw, the hydraulic pressure drop ΔPwp in a plug zone 54, and the length Lp of the plug zone 54 are substituted into the determining formula: γt (μcosθ+sinθ)-ΔPwp/Lp. The values in the determining formula are thereby determined, and if the values determined are positive, the water resistance performance of the screw conveyor 22 is determined to be sufficient, whereas if the values are negative, it is determined to be insufficient. Therefore, the water resistance performance of the screw conveyor 22 can be determined quantitatively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for judging the water stopping performance of a screw conveyer mounted on an earth pressure type or mud pressure type shield and transferring the excavated earth and sand in a cutter chamber at the front end of the shield in a compact state to the rear of the shield. Things.

[0002]

2. Description of the Related Art The shield method is a method of excavating at the front end of a shield, lining at the rear of the shield, moving the excavated earth and sand behind the shield, moving the shield forward, and constructing a tunnel. is there. Among such shield methods, an earth pressure type or mud pressure type shield method, which can be operated under atmospheric pressure and is advantageous in labor management and work efficiency, is attracting attention. In the earth pressure type or mud pressure type shield method, the earth and sand excavated by the cutter is retained in a state of being filled in the cutter chamber, and the face is suppressed by the cutter disk and the earth pressure of the earth and sand filled in the cutter chamber. In this method, the excavated earth and sand is consolidated, and the spirally consolidated earth and sand is made water-tight, thereby performing underground excavation while stabilizing the face.

In a shield machine used in such an earth pressure type or mud pressure type shield construction method, a cutter is disposed at a front end of the shield, a cutter chamber is provided between a back surface of the cutter and a front wall of the shield, and a shield chamber is provided. A screw conveyor is connected to the front wall in communication with the cutter chamber. The screw conveyor includes a cylindrical body, a screw blade rotatably disposed inside the cylindrical body, and a screw blade rotation drive unit, and the screw blade is provided in a spiral shape around the drive shaft and the outer periphery of the drive shaft. And a wing body. Excavated earth and sand is continuously accommodated in such a screw conveyor in a spiral state in a compacted state, so that the excavated earth and sand has water stopping properties.

[0004] Further, in order to oppose high soil water pressure in the cutter chamber, at the rear of the cylinder in which the screw blades are provided, a simple cylinder without screw blades is provided, and a discharge port is provided at the rear end. A screw conveyer with a plug zone function is also used in which a plug sheath is formed by connecting a plurality of screw sheath portions, and the screw sheath portion forms a plug zone for further filling and consolidating excavated earth and sand.

[0005]

However, since the soil water pressure in the cutter chamber varies from one excavation site to another, in order to ensure sufficient water stoppage and to stably discharge the soil, an appropriate screw conveyor for each excavation site is required. Must be selected.
However, conventionally, there is no method for quantitatively determining the water stopping performance of the screw conveyor based on theory, and the suitability of the screw conveyor has been determined mainly based on experience and experiments. For this reason, sometimes the required water stoppage cannot be ensured, or the screw conveyor becomes unnecessarily large due to an excessively high safety factor, resulting in increased costs. The present invention has been made to solve such a problem, and its object is to quantitatively determine the performance relating to the water stoppage of a screw conveyor, thereby ensuring sufficient water stoppage at a minimum necessary cost. It is an object of the present invention to provide a method for determining the water stopping performance of a screw conveyor, which enables stable soil removal.

[0006]

According to the present invention, an earth pressure type or mud pressure type shield is provided to achieve the above object.
A method for determining the water stopping performance of a screw conveyor that transfers excavated earth and sand in a cutter chamber at the front end of a shield to a rear side of the shield in a consolidation state, wherein a water pressure drop amount in the screw conveyor is ΔPwi, a unit weight of water is γw, The length of the passing portion of the earth and sand in the screw portion of the screw conveyor is Ls ′, the permeability of the screw portion is ks, the cross-sectional area of the passing portion of the earth and sand in the screw portion is As, and the screw conveyor is formed at the rear end. The first equation is defined assuming that the length of the plug zone is Lp, the hydraulic conductivity in the plug zone is kp, the cross-sectional area of the plug zone is Ap, and the amount of spring water at a discharge port provided at the rear end of the screw conveyor is Q. : Q =
ΔPwi / [γw ｛Ls ′ / (ks · As) + Lp /
(Kp · Ap)｝], and the amount of water pressure drop in the plug zone is ΔPwp,
The amount of water pressure drop ΔPwp is calculated by the formula: ΔPwp = γw · Lp · Q / (kp · Ap), the apparent unit volume of excavated earth and sand is γt, the friction coefficient between earth and sand is μ, and the screw conveyor is formed. Assuming that the inclination angle of the rotation axis of the screw is θ, a determination formula: γt (μcos θ + sin θ)
It is characterized in that the value of -ΔPwp / Lp is calculated, and the water stopping performance of the screw conveyor is determined based on whether the value of the calculated determination formula is positive or not. The present invention is also characterized in that the screw constituting the screw conveyor is formed by spirally winding a screw blade around a rotation axis. The present invention is also characterized in that the screws constituting the screw conveyor are ribbon screws.

In the method for determining the water stopping performance of a screw conveyor according to the present invention, the water pressure drop Δ
Pwi, unit volume weight γw of water, length Ls ′ of soil passing through the screw portion of the screw conveyor, permeability coefficient ks in the screw portion, cross sectional area As passing soil in the screw portion As, length Lp of plug zone, plug zone Is substituted into the right side of the first equation to calculate the amount of spring water Q. Further, the unit volume weight γw of water, the length Lp of the plug zone, the amount of spring water Q, the permeability coefficient kp in the plug zone,
The hydraulic pressure drop ΔPwp in the plug zone is calculated by substituting the cross-sectional area Ap of the plug zone into the right side of the second equation. Then, the apparent unit volume weight of the excavated earth and sand γt, the friction coefficient μ between the earth and sand, the inclination angle θ of the rotation axis of the screw constituting the screw conveyor, and the above-mentioned water pressure drop ΔPw
Substituting p and the length Lp of the plug zone into the above determination formula,
The value is determined. If the determined value is positive, it is determined that the water stopping performance of the screw conveyor is sufficient, while if the value is negative, it is determined that the water stopping performance is insufficient. Therefore, the water stopping performance of the screw conveyor can be quantitatively determined.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described based on embodiments with reference to the drawings. FIG. 1 is a partial cross-sectional side view of a screw conveyor for explaining an embodiment of a method for judging the water stopping performance of a screw conveyor according to the present invention, and FIG. 2 is a cross-sectional side view showing an example of an earth pressure type shield machine equipped with the screw conveyor. FIG. 3 is a sectional view of an opening groove and a slide plate portion constituting the screw conveyor shown in FIG. First, the shield machine 2 of FIG. 2 for performing the earth pressure type shield construction method will be described focusing on the periphery of the screw conveyor. The shield machine 2 includes a fish tail 4, a cutter wing 6, a kneading wing 8, a cutter chamber 10, a cutter driving motor 12, a shield jack 14, a middle folding jack 16, an erector 18, a segment 20, a screw conveyor 22, and the like. ing.

[0009] The screw conveyor 22 is disposed with its tip penetrating into the inside of the cutter chamber 10.
, And the excavated earth and sand is further transported backward by a belt conveyor (not shown). The screw conveyor 22 includes a casing 24, a rotating shaft 26, and a screw blade 28. The casing 24 is cylindrical and has a predetermined length. An inlet 30 for earth and sand is formed at one end in the longitudinal direction, and a discharge port 32 is provided at the other end. The inlet 30 is located in the cutter chamber 10,
A drive unit 34 is attached to an end of the casing 24 on the side of the discharge port 32. The rotating shaft 26 is disposed coaxially with the casing 24 inside the casing 24, and is driven to rotate by a driving device 34. The screw blade 28 is spirally wound around the rotation axis 26 and has an outer diameter of the casing 24.
Is formed to have a size facing the inner peripheral surface of the main body. The screw shaft 28 is removed from the rotating shaft portion 36 near the discharge port 32 over a predetermined axial length, and the rotating shaft portion 36 forms a bladeless space portion 38 in the casing 24.

The lower portion of the casing 24 forming the bladeless space 38 is provided with a casing 2 as shown in FIG.
4, an open groove 40 extending along the longitudinal direction is formed,
Opposite sides of the opening groove 40 are opposed to each other.
A guide groove 42 extending along the longitudinal direction of 0 is formed. A slide plate 44 having a length approximately twice the length of the opening groove 40 is slidably coupled to the guide groove 42.
A hole 46 is provided at the center in the longitudinal direction of the slide plate 44, and an on-off valve 48 is provided so as to communicate with the hole 46. The opening / closing valve 48 is composed of a case 50 and a valve body (not shown), and the opening of the valve body is adjusted by a hydraulic cylinder 52. It is configured.

Next, the operation will be described. When the rotary shaft 26 and the screw blade 28 are rotated by the driving device 34 during tunnel excavation, the earth and sand in the cutter chamber 10 is scraped up. When the opening area of the discharging port 32 is adjusted by the hydraulic cylinder 52, the earth and sand is accumulated and filled in the bladeless space 38, and when the discharging amount becomes smaller than the scraping amount, the discharging port is increased. A plug zone 54 is formed in the bladeless space 38 upstream of the blade 32, so that the earth and sand in the screw conveyor 22 can be stably transported while being suppressed, and the resistance to the earth pressure in the cutter chamber 10 is given. .

The magnitude of the resistance to the soil pressure in the cutter chamber 10 is determined by various parameters such as the length of the screw conveyor 22, the diameter of the screw conveyor 22, and the length of the plug zone 54. If the earth pressure in the plug zone 54 is a positive value, the above resistance due to the plug effect is larger than the fluid force due to the soil water pressure, and stable earth removal can be performed. On the other hand, plug zone 5
When the earth pressure in 4 is a negative value, the above-mentioned resistance force by the plug effect is smaller than the fluid force by the earth water pressure, and it is basically impossible to suppress the face water pressure only by earth and sand.

Therefore, the earth pressure in the plug zone 54 will be theoretically derived below with reference to FIG. First,
Symbols representing physical properties and dimensions are determined as follows. Ff: Friction force of excavated sediment Fg: Weight of excavated sediment Fp: Fluid force acting on sediment kp: Permeability coefficient in plug zone ks: Permeability coefficient in screw part μ: Friction coefficient between sand and iron Ka: Plug zone 54 Active earth pressure coefficient (Rankine) = tan ² (π / 4−φ / 2) generated from earth and sand in the ground P: Earth pressure in plug zone 54 Pwi: Face water pressure Pwo: Water pressure at earth discharging port 32 (atmospheric pressure 0K in case
gf / cm ² ) Pwp: Water pressure at plug zone start end (screw end) position ΔPwi = Pwi−Pwo ΔPwp = Pwp−Pwo (water pressure drop amount in plug zone 54) Q: Discharge port when face water pressure Pwi acts Spring water in 32 [gamma] t: apparent specific weight of sediment Ganmadaburyu: specific weight of water theta: the inclination angle of the screw Lp: plug zone length Ls: screw length d _1: screw shaft diameter d _2: screw casing diameter p: screw blade Pitch Ls': Length of passing portion of soil and sand in screw portion As: Cross-sectional area of passing portion of soil and sand in screw portion Ap: Plug zone area First, the frictional force Ff of the soil is

[0014]

(Equation 1)

The weight Fg of the earth and sand is

[0016]

(Equation 2)

The fluid force acting on the earth and sand in the plug zone 54 is

[0018]

(Equation 3)

## EQU1 ## In FIG. 1, the pressure balance state is expressed by the following equation. However, the examination position is a minute portion (Δx) in the plug zone 54.

[0020]

(Equation 4)

Therefore,

[0022]

(Equation 5)

Here,

[0024]

(Equation 6)

[0025]

(Equation 7)

In other words,

[0027]

(Equation 8)

And from this

[0029]

(Equation 9)

Is obtained. When the boundary condition x = 0, since the pressure P at the discharge port 32 is 0 kgf / cm ² , C =
-B / A, thus

[0031]

(Equation 10)

Therefore,

[0033]

[Equation 11]

Is obtained. Equation (11) is given by ΔPwp / L
p is a theoretical expression taking into account the term of water pressure. Also from Darcy's law

[0035]

(Equation 12)

The amount of spring water Q at the discharge port 32 is

[0037]

(Equation 13)

At this time, the water pressure drop amount ΔPwp in the plug zone 54 included in the equation (11) is obtained from the following equation.

[0039]

[Equation 14]

If the earth pressure P in the plug zone 54 represented by the equation (11) is a positive value as described above, stable earth removal can be performed. On the other hand, if the earth pressure P is a negative value, it is basically It will not be possible to reduce face water pressure with earth and sand alone. By the way, (1
In equation (1), the denominator and [] are always positive.
The determination formula of the molecule according to the present invention

[0041]

(Equation 15)

Whether the soil removal can be performed stably depends on whether the value is positive or negative, and therefore, the water stopping performance of the screw conveyor can be determined. That is, the judgment formula (15)
The value of the formula is calculated, and if the calculated value is positive, it can be determined that the screw conveyor 22 has the necessary water stopping performance, while if the value of the determination formula is negative, the water stopping of the screw conveyor 22 is determined. The performance can be determined to be insufficient.

Therefore, in order to determine the water stopping performance of the screw conveyor 22, first, the screw conveyor 2
2, the water pressure drop amount ΔPwi and the unit volume weight γ of water
w, the length Ls ′ of the passing portion of the earth and sand in the screw portion of the screw conveyor 22, the permeability coefficient ks in the screw portion, and the sectional area A of the passing portion of the earth and sand in the screw portion A
s, the length Lp of the plug zone 54, the permeability coefficient kp in the plug zone 54, and the sectional area Ap of the plug zone 54 are substituted into the right side of the equation (13) (the first equation according to the present invention) to calculate the amount of spring water Q. I do.

Then, the unit volume weight γw of water, the length Lp of the plug zone 54, the amount of spring water Q, the permeability kp in the plug zone 54, and the cross-sectional area Ap of the plug zone 54 are expressed by the following equation (14). The water pressure drop amount ΔPwp in the plug zone 54 is calculated by substituting into the right side of (Equation 2).

The apparent unit weight γt of the excavated earth and sand, the friction coefficient μ between earth and sand, the inclination angle θ of the screw rotation axis, the water pressure drop ΔPwp, the plug zone 54
Is substituted for the length Lp in the above-described determination formula, and its value is obtained.
If the obtained value is positive, it is determined that the water stopping performance of the screw conveyor 22 is sufficient, while if it is negative, it is determined that it is insufficient. Therefore, the water stopping performance of the screw conveyor 22 can be quantitatively determined by the water stopping performance determining method of the present embodiment. As a result, a screw conveyor with the required water-stop performance can be reliably selected,
Waste such as using a screw conveyor larger than necessary can be eliminated.

In the present embodiment, the screw of the screw conveyor 22 is formed by spirally winding the screw blade 28 around the rotary shaft 26, but a ribbon screw without the rotary shaft 26 is used. In this case, the present invention is also effective, and the water stopping performance of the screw conveyor 22 can be determined by basically the same procedure. In the present embodiment, the screw conveyor 22 provided in the earth pressure type shield machine has been described as an example. However, the same effect can be obtained by applying the present invention to the screw conveyor provided in the mud pressure type shield machine. .

[0047]

As described above, in the method for determining the water stopping performance of a screw conveyor according to the present invention, the amount of water pressure drop ΔPwi, the unit volume weight of water γw,
Part length Ls' of soil passing through the screw portion of the screw conveyor, hydraulic permeability ks at the screw portion, cross sectional area As passing soil at the screw portion As, length Lp of the plug zone, hydraulic conductivity k at the plug zone
The spring water amount Q is calculated by substituting p and the cross-sectional area Ap of the plug zone into the right side of the following first equation. The first equation: Q = ΔPwi / [γw ｛Ls ′ / (ks · A)
s) + Lp / (kp · Ap)}] Also, the unit volume weight of water γw and the length L of the plug zone
The hydraulic pressure drop ΔPwp in the plug zone is calculated by substituting p, the spring water amount Q, the permeability coefficient kp in the plug zone, and the cross-sectional area Ap of the plug zone into the right side of the following equation (2). The second formula: ΔPwp = γw · Lp · Q / (kp · Ap) Then, the apparent unit volume weight γt of the excavated earth and sand, the friction coefficient μ between the earth and sand, the inclination angle θ of the rotation axis of the screw constituting the screw conveyor, The above-mentioned water pressure drop amount ΔPwp and the length Lp of the plug zone are substituted into the following determination formula to determine the values. If the obtained value is positive, it is determined that the water stopping performance of the screw conveyor is sufficient. , A negative result is determined to be insufficient. Judgment formula: γt (μcos θ + sin θ) −ΔPwp /
Lp Therefore, the water stopping performance of the screw conveyor according to the present invention can quantitatively determine the water stopping performance of the screw conveyor. As a result, a screw conveyor having the required water stopping performance can be reliably selected, and waste such as using an unnecessarily large screw conveyor can be eliminated.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional side view of a screw conveyor for describing an embodiment of a method for determining water stopping performance of a screw conveyor according to the present invention.

FIG. 2 is a cross-sectional side view showing an example of an earth pressure type shield machine provided with a screw conveyor.

FIG. 3 is a sectional view of an opening groove and a slide plate portion constituting the screw conveyor shown in FIG. 2;

[Explanation of symbols]

 2 Shielding Machine 10 Cutter Chamber 14 Shield Jack 16 Center Folding Jack 22 Screw Conveyor 24 Casing 26 Rotating Shaft 28 Screw Blade 34 Drive 38 Bladeless Space 40 Opening Groove 42 Guide Groove 44 Slide Plate 48 Opening / closing Valve 54 Plug Zone

Claims (3)

[Claims] 1. A method for judging the water stopping performance of a screw conveyer equipped on an earth pressure type or mud pressure type shield for transferring excavated earth and sand in a cutter chamber at a front end of the shield to a rear side of the shield, the method comprising: ΔPw
i, the unit volume weight of water is γw, the length of the passing portion of soil and sand in the screw portion of the screw conveyor is Ls ′, the permeability coefficient of the screw portion is ks, and the cross-sectional area of the passing portion of the soil in the screw portion is As, The length of the plug zone formed at the rear end of the screw conveyor is Lp, and the permeability in the plug zone is k.
p, the sectional area of the plug zone is Ap, and the amount of spring water at a discharge port provided at the rear end of the screw conveyor is Q, and the first equation: Q = ΔPwi / [γw ｛Ls ′ / (ks · A)
s) + Lp / (kp · Ap)｝] to calculate the amount of spring water, and let the amount of water pressure drop in the plug zone be ΔPwp, and the second equation: ΔPwp = γw · Lp · Q / (kp · Ap) The amount ΔPwp is calculated, and the apparent unit weight of excavated earth and sand is γt, the friction coefficient between earth and sand is μ, the inclination angle of the rotation axis of the screw constituting the screw conveyor is θ, and the judgment formula is: γt (μcosθ + sinθ) −ΔPwp /
The value of Lp is calculated, and whether the calculated value of the judgment formula is positive or not is determined by:
Determining a water stopping performance of the screw conveyor. 2. The method for determining the water stopping performance of a screw conveyor according to claim 1, wherein the screw constituting the screw conveyor is formed by spirally winding a screw blade around a rotation axis. 3. The method according to claim 1, wherein the screw constituting the screw conveyor is a ribbon screw.