JPS5927838B2 - Face holding pressure control method for shield tunneling machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a face holding pressure control method for a shield tunneling machine.

Shield excavation is a type of shield excavation in which the ground is excavated in its natural state, and a pressure chamber for holding the face is filled with the excavated soil to prevent collapse, while a portion of the excavated soil is sequentially released from the pressure chamber to the atmospheric pressure chamber. There is a chance.

In this type of shield excavator, the present invention compacts the earth and sand at the end of the sludge drainage passage, dehydrates the earth, and reduces the pore ratio to reduce the hydraulic conductivity, thereby reducing the water content ratio of the sludge and the pressure chamber. The aim is to achieve good pressure adjustment.

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

Reference numeral 1 denotes a main body of the shield tunneling machine, which is divided by a partition wall 2 into a face holding pressure chamber 3 and an atmospheric pressure chamber 4.

A cutter 6 facing the face 5 is installed in the pressure chamber 3, and the earth and sand excavated by the rotation of the cutter 6 flows into the pressure chamber 3.
taken within.

7 is a screw conveyor that transfers and discharges excavated soil from the pressure chamber 3 to the atmospheric pressure chamber 4; this conveyor 7 penetrates the partition wall 2, and has an excavated soil inlet 8 that opens in the pressure chamber 3 and an excavated soil inlet 8 that opens in the atmospheric pressure chamber 4; A cylindrical casing 1 having a mud drainage port 9.
It is installed in 0.

The rotation shaft 11 of the screw conveyor 70 is connected to the output shaft of the drive motor 12 outside the mud removal port 9.

Reference numeral 13 denotes a cone valve fitted externally to the base of the rotating shaft 110 so as to be slidable in the axial direction. 15 in the closing direction.

The screw conveyor 7, cylindrical casing 10, and cone valve 13 constitute a screw discharger.

Therefore, when the drive motor 12 is operated to rotate the screw conveyor 7, the excavated soil taken into the pressure chamber 3 is sent into the cylindrical casing 10 from the input port 8,
The mud is transferred inside the casing 10 toward the mud removal port 9.

However, since the mud draining port 9 is closed under pressure by the cone valve 13, the excavated soil is compacted near the mud draining port 9 in the casing 10, and the sand plug 16 is placed in the position.
will be formed.

This sand plug 16 is made of excavated earth whose soil quality has been improved to the soil condition of the face ground or better, and the face pressure in the pressure chamber 3 is maintained by the sand plug 16.

When the screw conveyor 7 continues to transport the excavated soil, the conveyor's transport pressure becomes higher than the closing pressure of the cone valve 13, and the cone valve 13 closes the mud removal port 9.
The mud drain port 9 is opened in accordance with the differential pressure between the two as it retreats further,
The excavated soil is discharged into the atmosphere from this open part.

At this time, the sand plug 16 is still formed in the vicinity of the mud discharge port 9 inside the cylindrical casing 10, and the face pressure of the pressure chamber 3 is maintained even during the mud discharge.

Reference numeral 17 denotes a fixed sheath tube for reducing the friction of the rotating shaft 11 due to the formation of the sand plug 16.

The pressing pressure of the cone valve 14 is adjusted depending on soil conditions, and in this way the sand plug 16 is adjusted while balancing the earth and sand outflow resistance pressure Pc of the cone valve 14 and the transfer pressure (compaction pressure) Pmax of the screw conveyor 7. When the excavated earth and sand are released and discharged into the atmospheric pressure chamber 4, the balance relational expression between Pmax and Pc is as follows.

Pmax=Pc −f (μ2 tsK+ )μ−
Friction coefficient t between earth and sand and casing inner surface - length of sand plug formation zone = earth pressure coefficient D - casing inner diameter Due to compaction, the hydraulic permeability coefficient has the following relationship.

kl: k2-41: 72 t1 = gap ratio when permeability coefficient is 1 t2 - gap ratio when permeability coefficient is 2 Therefore, in order to properly adjust Pmax, the friction coefficient must be adjusted during compaction during sand plug formation. Since μ changes, it is necessary to change 't D and P c,
It can be seen that when the elements of D and t are constant, it is sufficient to change Pc.

When changing Pc, it is advantageous to adjust the stroke (displacement) amount of the cone valve 13 because it can be visually observed mechanically.

The stroke (displacement) amount of the cone valve 13 is related to the earth and sand outflow resistance pressure Pc of the cone valve 13.

That is, since the stroke (displacement) amount and the sediment outflow resistance pressure Pc change depending on the soil quality, in order to maintain the soil pressure within the initial setting value range of the pressure gauge 21, the stroke (displacement) amount of the cone valve 13, that is, the sediment outflow resistance pressure Pc, changes depending on the soil quality. It is preferable to control the resistance pressure Pc to bring the tonosho within the control range.

The soil outflow resistance pressure Pc depends on the outflow velocity of the soil volume (related to the excavation speed), the stroke (displacement) amount of the cone valve 13, and the soil conditions (for example, sand, clay, or silt, high water content, (e.g. small).

Therefore, the target value can be obtained by changing the earth and sand outflow resistance pressure Pc, that is, by adjusting the stroke (displacement) amount.

18 is a stroke detector.

The signal from the stroke detector 18 is input to the calculator 19, and when the value matches the control value calculated by the calculator 19, the control valve 20 of the cylinder device 14 is switched to the neutral state, and the control value is changed to the neutral state. When not, the control valve 20 is switched to operate the cylinder device 14 in a pushing or retracting manner.

The control value is a value within a certain range, and is set, for example, to an adjustment value between active earth pressure and passive earth pressure.

That is, the pressure in the pressure chamber 3 is detected by a pressure gauge (earth pressure gauge, pore water pressure gauge) 21 (the degree of filling with excavated earth and sand), and the signal is input to the computing unit 19, and the signal is set in the computing unit 19. Calculate with initial setting value.

The initial set value is determined by P2γh P: initial set value γ: density of the face portion h: slack height of the face portion, and the control value is calculated from this initial set value.

Next, when excavation is started and the amount of excavated soil is taken into the pressure chamber 3, the pressure inside the pressure chamber 3 increases, and this pressure is measured by the pressure gauge 21.
The signal is detected by the control valve 20, and when input as a signal to the calculator 19, it is compared with the control value, and if it is higher than the control value, a signal to open the cone valve 13 is input to the control valve 20, and the cone valve 13 is opened.

However, since the stroke (displacement) amount of the cone valve 13 changes depending on soil conditions, the stroke (displacement) amount is Decide whether to increase or decrease the amount (displacement).

Cone Valve 130The amount of stroke (displacement) can be increased or decreased depending on the soil quality, so the stroke (displacement) amount can be increased or decreased in the excavated state.
(displacement) amount adjustment is repeated to determine the amount of displacement.

In addition, in FIG. 2, 22 is a hydraulic pressure source.

The displacement power source for the cone valve 13 may be electric power in addition to hydraulic pressure (and the control valve 20 can be switched either manually or automatically.

As is clear from the above explanation, the present invention adjusts the compaction pressure of the sand plug by controlling the stroke (displacement) amount of the cone valve, so the amount of sludge discharged is adjusted by the displacement of the cone valve. .

Therefore, the pressure in the pressure chamber can always be set to match the soil conditions of the ground, depending on the amount of sludge discharged and the amount of excavated soil.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a shield tunneling machine, and FIG. 2 is an explanatory diagram of an embodiment of the present invention. 3... Pressure chamber, 4... Atmospheric pressure chamber, 7... Screw conveyor, 10... Cylindrical casing, 13... Cone valve, 14... Cylinder device, 16... Sand plug , 18... Stroke detector, 19... Arithmetic unit, 20... Control valve, 21... Pressure gauge.

Claims (1)

[Claims] 1. A screw discharger is provided between the face holding pressure chamber and the atmospheric pressure chamber, and a sand plug is formed at the mud discharge port of the screw discharger, and the plug discharges mud while maintaining the pressure in the pressure chamber. In the shield excavator, the amount of displacement of a valve that moves in and out of the mud removal port to adjust the compaction pressure of the mud removal plug is derived from a calculated value of a reference setting pressure and a pressure chamber pressure. A method for controlling the face holding pressure of a shield tunneling machine.