JPH058318B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an earth and sand property measuring device for a shield excavator, and more particularly to an apparatus for measuring the properties of earth and sand excavated with a cutter wheel and taken into a chamber.

[Background of the invention]

As is well known, a shield excavator forms a chamber between the bulkhead of the shield body and the cutter wheel, and fills the chamber with earth and sand excavated by the cutter wheel. The shield is maintained at an earth pressure equivalent to (pressure + overburden earth pressure), and moves forward while discharging an amount of earth and sand with a screw conveyor that is commensurate with the shield's advancing speed. In this shield excavator, the cutter wheel rotates while the above-mentioned earth pressure is acting on it, so the cutter torque is designed to overcome the direct resistance of the earth and sand, the excavation resistance of the ground, and the adhesive resistance of the earth and sand. It has been decided.

On the other hand, the soil quality of the ground in the longitudinal direction of the tunnel generally varies widely, such as clayey soil, clay, sand, and gravel layer. Then, the N value that expresses the physical properties of the ground, the internal mast angle φ, the adhesive force c,
It is known that the cutting torque changes significantly depending on the water content ratio ω, etc. In addition, although it is possible to dig relatively well in soft and cohesive soil, in a sand layer with a low content of binder (fine-grained soil), the internal cutting angle φ is large, so the dirt sticks and the cutter wheel cannot rotate. It may occur.
At this time, the mud material (bentonite, clay, etc.) is injected from the mud material injection port, and the excavated soil and the mud material are thoroughly stirred with a cutter bit, cutter spoke, etc., so that the soil properties become plastic fluid. It is also known that it is possible to reduce the sagging torque.
Since the water-retaining gravel layer has high water permeability, the passage resistance to the screw conveyor's discharge port alone may not be enough to withstand high water pressure, and the soil discharge becomes muddy and does not get onto the screw conveyor. It also happens. In such cases, mud material (fine-grained soil) is injected from the mud material injection port to fill the gaps between sand particles and clog them, thereby reducing water permeability and making it possible to withstand high water pressure. It is known that, as a result, the soil discharge properties from the screw conveyor are improved. In addition, in Dotan, the water content is low and the adhesive force c is large, so the fluidity of the soil is poor and the cutting torque may be large. In this case, too, by injecting water, the adhesive force c can be lowered and good soil removal can be achieved. It is known to do. Good soil removal is generally limited to a slump value of about 5 to 15. Such agitation resistance of the earth and sand is small compared to the excavation torque.

By the way, in the shield excavator mentioned above, although individual countermeasures have been made possible based on a lot of experience, problems such as the inability to rotate the cutter wheel and mud spewing from the screw conveyor have not been encountered before. is happening. The main reason for this is that the face side is shielded by a bulkhead, making it impossible to see changes in the face ground.
For this reason, operators perform shield operations by estimating changes in the ground by visually observing changes in cutter torque and soil discharge from the screw conveyor. Whether or not the soil discharge properties are maintained at a slump value of about 5 to 15 can be determined by knowing the agitation resistance of the plastically fluidized soil, in other words, of the soil in the chamber.

However, in the method of determining soil properties from cutter torque, excavation resistance torque accounts for most of the cutter torque, and it is extremely difficult to know changes in stirring resistance torque, making it impossible to accurately grasp soil properties. In addition, the visual judgment method of soil removal from the screw conveyor has a significant time delay. In other words, there is usually a time lag of about 30 minutes before the soil excavated by the cutter wheel reaches the soil discharge port of the screw conveyor. Therefore, the soil discharge properties at the soil discharge port match the soil properties near the cutter wheel only when there is no change in the soil quality in the longitudinal direction of the tunnel. It becomes impossible to understand. Furthermore, the slump value of the discharged soil can be easily misunderstood based on its appearance alone, and the soil must be easily sampled and subjected to a slump test, so it can only be checked intermittently.

[Purpose of the invention]

An object of the present invention is to provide an earth and sand property measuring device for a shield excavator, which is capable of measuring the properties of earth and sand in a chamber by detecting the earth pressure received from the earth and sand when stirring the earth and sand in the chamber, and the static earth pressure. Our goal is to provide the following.

[Summary of the invention]

The earth and sand property measuring device of the present invention is provided with a stirring tool capable of stirring the earth and sand in the chamber on the back of the cutter wheel, and the earth pressure σ ₁ applied to the stirring tool from the earth and sand when the stirring tool rotates together with the cutter wheel.
Attach a first sensor to detect static earth pressure or earth pressure in a direction perpendicular to the rotating direction σ 3 to the partition wall of the stirring tool or shield body, and install the second sensor to detect earth pressure σ ₃ in the direction perpendicular to the direction of rotation, which is detected by the first and second sensors. This system is equipped with a measuring device that measures and displays the earth pressures σ ₁ and σ ₃ .

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a longitudinal sectional view of a shield excavator equipped with a method for determining soil properties according to the present invention, and FIG. 2 is a perspective view showing how the sensor in FIG. 1 is attached. In the figure, 1 is a shield main body, which is provided with a bulkhead 2 that separates the face and the inside of the machine. A cutter wheel 3 is installed on the front side of the partition wall 2 of the shield body 1, and has a large number of cutters 4 and a center bit 5. 6 is a chamber formed between the cutter wheel 3 and the partition wall 2 for taking in dirt; 7 is a screw conveyor for discharging dirt; the dirt in the chamber 6 is taken out from the lower part of the chamber 6 and conveyed to a belt conveyor 8; Discharge. 9
10 is the rotation shaft of the cutter wheel 3, 10 is the driving device of the cutter wheel 3, the pinion 11 and the mud material injection port provided in the center bit 5, and the passage 15 bored in the swivel joint 14 and the rotation shaft 9. The mud material sent through the pipe is injected into the excavated area. 16 is a stirring tool attached to the back of the cutter wheel 3 so as to stir the soil in the chamber 6; 17 and 18 are a first sensor and a second sensor fixed to the stirring tool 16; is installed at a position where it can detect the earth pressure σ ₁ received from the earth and sand when the stirring tool 16 rotates together with the cutter wheel 3, and the second sensor 18 is installed at a position where it can detect the static earth pressure σ ₃ . The detection signal of the first sensor 17 and the detection signal of the second sensor 18 are displayed as earth pressure in a triaxial stress state by a measuring device 20 provided in the machine via a signal repeater 19. The signal repeater 19 is installed near the swivel joint 14. Further, the signal cables 21 of the first and second sensors 17 and 18 are passed through the cutter wheel and the rotating shaft 9 and connected to the signal repeater 19.

The first sensor 17 and the second sensor 1
There is _a well _- known relationship between ^the earth pressures σ ₁ and σ ₃ detected from 8.
/2) ...(1) It is expressed as.

However, φ is the internal vertical angle of the earth and sand, and c is the adhesive force of the earth and sand. On the other hand, Figure 3 shows the actual result of collecting soil discharged from a screw conveyor and plotting the relationship between the slump value and the adhesive force c. An example graph diagram is shown.
Generally, what is considered to be good soil removal is soil with a slump value of about 0 to 15, which is well agitated and has plastic fluidity, and which has almost no internal slump angle φ≒0 and is sticky. Force c<0.2Kg/ ^cm2 .

Therefore, by substituting this value into equation (1), we get σ ₁ =σ ₃ +2c (2). Then, when formulas (1) and (2) are graphed, the fourth
The result will be as shown in the figure. In this diagram, the characteristics shown by the dotted line are when the soil is sand (c≈0), and the characteristics shown by the solid line are when the earth is removed well. In addition, for general earth and sand (φ≠0, c≠0), although not shown, the straight line is different from the characteristics of the solid line. σ ₃ is the earth pressure that normally prevents the collapse of the face, and is determined from the earth cover or slack height of the shield, and the actual situation in most shield works is σ ₃ >0.5Kg/cm ² . Since tunnels are often constructed substantially horizontally, σ ₃ is controlled to a substantially constant value.

Now, if we are digging with σ ₃ = 1Kg/cm ² constant,
If σ ₁ ≒ 1Kg/cm ² , plastic fluidization of the earth and sand has already been achieved at the 3rd part of the cutter wheel,
Soil removal will be good. Further, if the value of σ ₁ rises to, for example, 3 Kg/cm ² during excavation, it can be easily determined that the earth and sand near the first sensor 17 has changed to sand with an angle of φ=30° (c=0). Then, at this time, the operator can immediately inject the mud material from the injection port 13, and can improve the properties of the soil by sufficiently stirring it with the cutter wheel 3 portion.

As described above, in the present invention, the earth pressure σ ₁ and static earth pressure σ ₃ received from the earth and sand during stirring are detected and displayed in the chamber 6, which is not affected by the excavation force of the cutter wheel 3. Properties can be grasped accurately and sensitively. As a result, by injecting the mud material according to the properties of the soil, it is possible to maintain the properties of the soil discharged well, and to prevent situations such as the inability of the cutter wheel 3 to rotate and mud spraying from the screw conveyor 7. This makes it possible to prevent

In this embodiment, if the amount of sludge material to be injected is controlled by the comparison signal between the output signals (σ ₁ −σ ₃ ) of the first and second sensors and the set value (σ ₀ ), It is also possible to automate the injection of mud materials according to the properties of the soil.

Further, in this embodiment, an example is shown in which the second sensor 18 for detecting the static earth pressure σ ₃ is attached to the stirring tool 16, but the second sensor 18 may be attached to the partition wall 2.

In addition, the theoretical formula that completely expresses the stirring resistance in the present invention has not been completely established due to the large variations in experimental data of soil, and another way of thinking is to explain it using the ultimate bearing capacity (QD) of a shallow foundation. However, it is unclear which theory is better, so
The former was adopted and explained.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to measure and display the properties of the sediment inside the chamber. As a result, by injecting mud preparation materials according to the properties of the soil, the properties of the soil can be maintained in good condition, and situations such as the inability of the cutter wheel to rotate and mud spewing from the screw conveyor can be prevented. be able to.

[Brief explanation of drawings]

Fig. 1 and Fig. 2 show an embodiment of the present invention, Fig. 1 is a longitudinal cross-sectional view of a shield excavator that employs the soil property measuring device according to the present invention, and Fig. 2 shows the installation of the sensor in Fig. 1. FIG. 3 is a diagram showing an example of good earth removal, and FIG. 4 is a characteristic diagram showing triaxial stress in the present invention. DESCRIPTION OF SYMBOLS 1... Shield body, 2... Partition wall, 3... Cutting wheel, 6... Chamber, 7... Screw conveyor, 16... Stirring tool, 17... First sensor, 18... Second sensor, 20 ……Measuring instrument.

Claims (1)

[Claims] 1 A chamber is formed between the bulkhead of the shield body and the cutter wheel, the earth and sand excavated by the cutter wheel is taken into the chamber and filled, the chamber is maintained at an earth pressure equivalent to the face earth pressure, and the chamber is In the shield excavator, which moves forward while discharging the earth and sand inside with a screw conveyor,
A stirring tool capable of stirring the earth and sand in the chamber is provided on the back side of the cutter wheel, and the stirring tool is equipped with a mechanism for detecting the earth pressure σ ₁ in the moving direction received from the earth and sand when the stirring tool rotates together with the cutter wheel. A second sensor for detecting static earth pressure or earth pressure σ ₃ in a direction perpendicular to the rotating direction is attached to the stirring tool or the partition wall, and the earth pressure σ ₁ detected from the first and second sensors is installed. , σ ₃ A soil property measuring device for a shield excavator, characterized by being equipped with a measuring device that measures and displays σ 3.