JPH035592A - Shielding method - Google Patents

Abstract

PURPOSE:To assure safety by controlling earth and sand bored with an adding agent for the countermeasure to natural ground pressure distribution as liquid earth and sand pressure, and discharging thereafter the liquid earth and sand by a closed pump having the shielding function for liquid. CONSTITUTION:An adding agent is mixed for liquefaction in earth and sand cut in the chamber 5 of a shielding boring machine 1 so as to function against the pressure of natural ground 3 with its pressure. The pressure gradient is obtained through detection of the pressure in the chamber 5 with a pressure sensor 9, and the adding rate of agent is controlled based on the difference with the pressure gradient of natural ground 3 estimated. Then the discharge amount of liquid sand and earth is controlled based on the difference thereof, and it is discharged with a closed earth discharge pump 13 having a liquid shielding function, in synchronization with boring. The safety is therefore assured.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a shield construction method in which excavated earth and sand are used to excavate while counteracting the pressure of other mountains.

[Conventional technology]

Conventional general shield construction methods include the mud pressure shield construction method and the mud pressure shield construction method, each of which has the following problems. ■ Mud water pressurized shield construction method (a) The face principle of the mud water pressurized shield construction method is to counteract other piles with mud water pressure (liquid pressure) filled with mud water (liquid) in the chamber of the shield excavator. As shown in FIG. 3, a difference occurs between the distribution Pa of the other mountain pressure and the distribution Pb of the mud pressure inside the chamber. False) The excavated earth and sand is discharged from the chamber as a liquid containing muddy water and earth and sand, so muddy water of 6 to 10 times the excavation volume is required. (C) The face pressure is increased by the water pump, and the flow rate is controlled by the discharge pump, so multiple valves are required. (d) Since excavated soil is transported as a liquid, it is necessary to separate the soil from water at the ridge of the transport pile. ■ Mud and earth pressure shield method (a) The mud and earth pressure shield method adds additives to the earth and sand cut by a cutter and mixes them in a chamber to plastically fluidize the earth and remove the mud generated by the excavation of the shield jack. It uses pressure to stabilize the face.
As shown in FIG. 4, the distribution Pc of mud pressure is small in the upper part and large in the lower part with respect to the distribution Pa of the rock pressure. Φ) Since the discharge of earth and sand from the chamber is carried out by a screw conveyor, this does not have the ability to shut off the pressure inside the chamber. (C) Pressure inside the chamber is controlled by increasing or decreasing the rotation of the screw conveyor, and pressure is maintained in the screw conveyor by the frictional resistance between the earth and sand and the screw face, and the earth and sand must have plasticity within a certain range of physical properties. Therefore, strict flow adjustment is required.

[Problem to be solved by the invention]

The problems of the present invention are as follows: (1) chamber pressure distribution relative to rock pressure distribution, (2) discharge of excavated soil, and (3) control of chamber pressure and discharge amount. The point is to solve the problem. (1) Pressure distribution in the chamber relative to the ground pressure distribution In the conventional mud water pressurization shield construction method, there was a risk of an eruption due to excessive pressure at the upper part of the face. In addition, in the mud pressurized shield method, the earth pressure is too low at the top and too high at the bottom.If the top pressure is set to be the same as the ground pressure to prevent face collapse, the total pressure inside the chamber will be too high, and a large shield excavation force will be required. Met. In the construction method of the present invention, water or an additive is added to the cut earth and sand to liquefy it, adjust the specific gravity of the earth and sand in the chamber, and achieve the same chamber pressure distribution as the rock pressure distribution. (2) Discharge of excavated earth and sand In the conventional mud water pressure shield construction method, excavated earth and sand are discharged as a liquid mixed with mud water using a centrifugal pump. However, because the centrifugal pump does not have a liquid shutoff function due to its structure, multiple valves were required in the pipeline. In addition, in the mud pressure shield method, a muddy material was added to the excavated soil and the plastic material was discharged by a screw conveyor, but the screw conveyor did not have a liquid-blocking function due to its structure, so it was not possible to prevent groundwater from gushing out. . In the construction method of the present invention, the excavated soil is liquefied soil, and this is used as a liquefaction pump or a screw pump. Since the chamber is discharged using a closed-type pump such as a piston pump, which has a liquid-blocking function due to its structure, the pressure inside the chamber can be maintained reliably. (3) Control of chamber pressure and discharge volume In the conventional mud water pressurization shield construction method, multiple valves are required to adjust the pressure with a water pump and the discharge flow rate with a discharge pump, and to stop the flow of fluid. , which required a complex control device. In addition, in the mud pressure shield method, the pressure and discharge amount are controlled by a screw conveyor, so the pressure holding capacity and discharge amount change significantly depending on the plasticity state of the soil, making it difficult to control it appropriately. In the construction method of the present invention, the liquefied earth and sand is discharged as described above using a closed pump that has a liquid blocking function.
Pressure and discharge volume can be precisely controlled.

[Means to solve the problem]

That is, the means adopted by the present invention are as follows. ■ Earth and sand cut by the cutter of the shield excavator,
The additives are mixed and liquefied in the chamber of the shield tunneling machine. In other words, in terms of soil consistency (hardness), which classifies soil properties into four stages: solid, semi-solid, plastic, and liquid based on differences in soil moisture content, the present invention treats excavated soil as liquid. . In addition, the mud in the conventional mud pressure shield construction method falls into the category of semi-solid or plastic state, and the mud in the mud water pressure shield construction method is a liquid that does not fit into any of the four classifications. (2) While the pressure of the liquid earth and sand in the chamber is used to counteract the rock pressure, the pressure in the chamber is detected by a plurality of pressure sensors and its pressure gradient is determined. The addition rate of the additive is adjusted according to the difference between this pressure gradient and the estimated pressure gradient of other mountains to make the pressure gradient of the ground and the pressure gradient in the chamber the same. ■ Adjust the discharge amount according to the difference between the chamber internal pressure and the estimated ground pressure, and synchronize with the excavation, and discharge the liquid earth and sand in the chamber using a closed pump with a liquid cutoff function.

[For production]

The pressure of the liquefied earth and sand in the chamber opposes the pressure of other mountains, and the pressure distribution is the same as the pressure distribution of other mountains. Since it is adjusted and discharged in synchronization with the excavation, precise face stability is always maintained even in large-section shields.

【Example】

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a system configuration diagram of the shield construction method of the present invention. The shield excavator 1 excavates with the shield jack 4 while rotating the cutter 2 and cutting the earth 3. The excavated earth and sand is mixed with an additive material fed from the ground as described below in the chamber 5 of the shield excavator 1 to form liquid earth and sand, and the liquid earth and sand is filled in the chamber 5 having a constant volume. The present invention prevents the face from collapsing by using the filled liquid earth and sand to counter the pressure from other mountains. The additive used here may be any material as long as it can liquefy the earth and sand, such as slurry, polymer, air bubbles, water, etc. The additive material is fed to the shield excavator 1 via a vibrator line as described below, and is injected into the chamber 5 from the injection lower by an additive injection pump 6 provided on the shield excavator 1 side, and then is injected into the chamber 5 through the cutter 2. It is mixed with earth and sand by the rotation of the , and further stirred by the agitator 8 . As the additive injection pump 6, a hermetic pump such as a rotary pump, a screw pump, a piston pump, etc., which has a liquid-blocking function due to its structure, is used. The pressure of the liquid earth and sand in the chamber 5 is detected by a plurality of pressure sensors (or earth pressure gauges) 9 arranged at regular intervals, and based on the detected pressure, the pressure of the liquid earth and sand in the chamber is determined by the control device 10 including the CPU. The slope is found. At the same time, the stroke meter 1 provided on the shield jack 4
1, the digging speed is detected. Then, based on these pressure gradients and excavation speeds, the control device 10 calculates the additive injection amount, and from this additive injection amount, the additive injection pump 6
The rotational speed of the chamber 5 is controlled, and the required amount of additive material is injected into the chamber 5. (a) The pressure gradient P of other mountains is as shown in Fig. 2.
In order to make a and the pressure gradient Pd in the chamber the same, the specific gravity of the earth and sand in the chamber 5 must be adjusted, and (b) it is necessary to inject the earth and sand to fluidize it as a liquid. Adjust the injection volume. The degree of adjustment of (a) and (b) differs depending on the soil quality, but it can be adjusted as follows. Regarding (a), since the ground pressure gradient can be determined from groundwater and ground conditions, the specific gravity of the earth and sand required for the chamber internal pressure can be estimated from this. Regarding (b), the water content ratio for fluidizing the cut earth and sand as a liquid can be determined by a soil test of the ground. The adjustment amount based on (a) is A, and the adjustment amount based on (b) is B.
If A>B, the specific gravity of the earth and sand in the chamber is adjusted by injecting water into the chamber. Conversely, if A<B, fluidization is promoted using special additives such as polymeric additives, and the apparent liquefaction water content ratio is lowered to create a relationship of A>B, and the specific gravity is adjusted by the injection amount. do. Specifically, regarding (a), the rock pressure (groundwater pressure + earth pressure) is determined through a geological survey, and the necessary specific gravity of the fluidized soil in the chamber is estimated. Regarding (g)), determine the liquid limit and physical properties required for the additive through soil tests, and from this determine the additive injection rate per unit volume of the ground. The actual injection of the additive is performed by calculating the amount of earth excavation in the control device 10 from the stroke of the shield jack 4 detected by the stroke meter 11, and calculating the injection amount per unit time from the above additive injection rate. Injection is performed by controlling the material injection pump 6. At the same time, the specific gravity of the liquid earth and sand in the chamber is detected by the earth pressure sensor 9, and the injection rate is calculated and corrected by the control device 10 depending on the magnitude of the specific gravity, so that the specific gravity of the liquid earth and sand in the chamber 5 is kept constant. Note that the flow rate, pressure, and specific gravity of the additive injected by the additive injection pump 6 are detected by a flow rate/pressure/density meter 12. Control of face pressure and excavation As the pressure inside chamber 5, which has a constant volume, increases due to the injection of additives into it and the old path of shield excavator 1, the pressure inside chamber 5 is increased by other pressure in order to stabilize the face. It is necessary to maintain the same pressure. Therefore, the face pressure is controlled by discharging the earth and sand in the chamber 5 using the soil discharge pump 13. As this soil discharge pump 13, similarly to the additive material injection pump 6, a closed type pump having a structurally liquid blocking function, such as a rotary pump, a screw pump, or a piston pump, is used. Basically, a chamber target pressure is set in advance in the control device 110, and the chamber internal pressure is monitored by the earth pressure sensor 9.
When the pressure is higher than the target pressure, the rotation of the soil discharge pump 13 is increased to increase the amount of discharged soil, and when the pressure is lower than the target pressure, the rotation of the soil discharge pump 13 is slowed down to decrease the amount of discharged soil. control to keep the pressure inside constant. The constant pressure after control can be maintained by stopping the additive injection vibro and the soil removal pump 13 and making the system itself a sealed structure. Note that the flow rate, pressure, and specific gravity of the earth and sand discharged by the earth discharge pump 13 are detected by a flow rate/pressure/density meter 14. The earth and sand from the excavation 111 trace row primary earth removal pump 13 is sent to the rear relay pump 16 via the pipeline 15, and then this relay pump 1
6, the oil is pumped through a pipeline 17 and transported outside the mine (above ground). When the pumping distance is long, a plurality of relay pumps 16 are used. In addition, instead of the pressure feeding using the relay pump 16 and the pipeline 17, it is also possible to carry out the transfer using a slider. Management of the excavated soil is necessary to determine whether or not stabilization of the standing face was carried out correctly. In this embodiment, the amount of additive material injected is detected by the flow rate/pressure/density meter 12, the amount of discharged earth and sand in the chamber is detected by the flow rate, pressure, and specific gravity meter 14, and the amount of shield excavation is detected by the stroke meter 11. The suitability of the amount of excavated soil is determined by total analysis. Sediment p treatment Since excavated soil is liquefied and discharged, it is necessary to separate the earth and sand from water. In this embodiment, as described above, the liquid earth and sand carried out from the relay pump 16 through the pipeline 17 is once put into the clean water mixer 18, and here, if necessary, the circulating water for earth and sand separation is supplied from the circulating water vibrator 19. The sample is removed by a vibrating sieve 20. Then, the liquid soil for inspection is transported to a hopper etc. by a belt conveyor 21, and the liquid soil other than the one for inspection is temporarily stored in a soil tank 22, and sent to a centrifugal separator @24 by a soil pump 23, where water and soil are separated. The water is conveyed to a hopper etc. by a belt conveyor 25, the water is temporarily stored in a circulating water tank 26, a part of which is used for soil separation by a circulating water pump 27 through a circulating water pipe 19 as described above, and surplus water is regulated. The water pump 28 sends the water to the adjustment water tank 29 . On the other hand, if necessary, a polymeric material or the like is added to the water in the adjustment water tank 29 from the additive plant 30 to adjust the physical properties, and the water is sent to the relay tank 33 via the pipeline 32 by the additive pump 31, and then The additive material is injected into the chamber 5 from the tank 33 by the additive material injection pump 6 as described above. Although an example has been shown in which the discharged liquid earth and sand is separated into water and earth and sand for treatment, it is also possible to add a solidifying agent or the like to the earth and sand carried out through the pipeline 17 for solidification treatment.

【Effect of the invention】

The shield construction method of the present invention has the following effects. ■ Since the face pressure distribution approximates the ground pressure distribution, an effective mountain retaining effect can be obtained with a large cross-section shield. ■ Since a hermetic pump is used to control the pressure at the face, 1
It also ensures pressure retention under high water pressure of 0 kg or more. ■ Because it is transported as liquid soil, the transportation pipe has less pumping resistance than the pump of the mud pressure shield, so it can be pumped over long distances, and the volume of circulating mud is 173% compared to the mud pressure shield. Since the size is 1/4, it can be small-scale and the earth and sand transportation cost can be reduced. ■ The system is simplified because there are fewer control targets such as face pressure control and sediment transport control. ■ Concerning the treatment of discharged sediment, running costs can be reduced because the amount of sediment processed is smaller compared to muddy water pressure shields. ■ Efficient construction work is possible even at great depths underground.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram of an example of the shield construction method of the present invention, and FIG. 2 is an explanatory diagram showing the relationship between the rock pressure distribution and the chamber internal pressure distribution therein. FIG. 3 is an explanatory diagram showing the relationship between the rock pressure distribution and the chamber pressure distribution in the conventional mud pressure shield construction method, and FIG. 4 is a similar explanatory diagram in the conventional mud pressure shield construction method. 1... Shield excavator, 2... Cutter, 3... Ground rock, 4... Shield jack, 5... Chamber, 6... Additive injection pump, 9... Pressure sensor, 11...
・Stroke meter, 13...Earth removal pump. Director of Civil Engineering Research Institute, Ministry of Construction Omotogumi Co., Ltd. Komatsu Ltd. Sanai Kogyo Co., Ltd. Tekken Construction Co., Ltd. Toyo Construction Co., Ltd. Toda Construction Co., Ltd. Tobishima Construction Co., Ltd. Nishimatsu Construction Co., Ltd. Japan Land Development Co., Ltd. Magumi Co., Ltd. Hitachi Construction Machinery Co., Ltd. Fujita Kogyo Co., Ltd. Fudo Construction Co., Ltd. Maeda Construction Co., Ltd.

Claims (1)

[Claims] 1. In the earth and sand cut by the cutter of the shield excavator,
Additives are mixed and liquefied in the chamber of the shield excavator, and the pressure of the liquefied earth and sand is used to counteract the ground pressure, while the pressure in the chamber is detected by multiple pressure sensors to determine the pressure gradient. , the addition rate of the additive is adjusted according to the difference between this pressure gradient and the estimated rock pressure gradient, and the amount of liquid earth and sand discharged from the chamber is adjusted according to the difference between the chamber internal pressure and the estimated rock pressure. This shield construction method is characterized by discharging liquid in synchronization with the excavation using a closed pump with a liquid blocking function.