JP2017106263A - Plastic fluidity grasping method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic fluidity grasping method capable of appropriately grasping plastic fluidity of excavated soil inside a chamber.SOLUTION: A plastic fluidity grasping method comprises the processes to: set an upper limit value and a lower limit value of anti-earth pressure acting on an object moving in a soil layer in a plastic fluid state; measure earth pressure with a first earth pressure gauge 6 installed on an agitation blade 31 and a second earth pressure gauge 7 installed on a chamber bulkhead 4; calculate the anti-earth pressure of excavated soil inside a chamber 5 on the basis of measurement results of the first earth pressure gauge 6 and the second earth pressure gauge 7; and estimate whether or not the excavated soil inside the chamber 5 is in the plastic fluid state by comparing the anti-earth pressure of the excavated soil with the upper limit value and the lower limit value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for grasping plastic fluidity.

The earth pressure type shield method is to excavate while stabilizing the face by applying the earth pressure of the excavated soil generated during excavation of the tunnel to the face. The excavated soil is made to have plastic fluidity by stirring with a stirring blade in the chamber.
In order to apply the earth pressure to the face uniformly and stably, it is necessary to accurately grasp the plastic fluidity of the excavated soil in the chamber and adjust it as necessary.
Therefore, Patent Document 1 discloses a method of estimating the flow direction and the size of excavated soil in the chamber based on the deformation amount of the measuring rod installed through the partition wall so as to be able to appear in and out of the chamber. .
Further, Patent Document 2 includes an exploration rod that protrudes into the chamber from an opening provided in a chamber partition wall of an excavator, and detects vibrations and penetration resistance that occur when the exploration rod penetrates the rod. A method for grasping the state of mud inside is disclosed.

JP 2008-169692 A JP-A-63-280191

The conventional method of grasping plastic fluidity is to measure the resistance value obtained from excavated soil staying in the chamber at a position away from the face (chamber bulkhead side). It is impossible to confirm that the earth pressure is applied uniformly and stably to the face. Moreover, there is a possibility that the measuring rod or the exploring rod protruding into the chamber may be damaged by contact with the rake or the like.
From such a viewpoint, an object of the present invention is to provide a method for grasping the plastic fluidity of excavated soil, which makes it possible to accurately grasp the plastic fluidity of the excavated soil in the chamber.

The method for grasping the plastic fluidity of the present invention for solving the above-mentioned problems includes a step of setting an upper limit value and a lower limit value of an anti-earth pressure acting on an object moving in a plastic fluidized soil layer, and a stirring blade. Based on the step of measuring the earth pressure with the first earth pressure gauge provided and the second earth pressure gauge provided on the chamber partition, the measurement result of the first earth pressure gauge and the measurement result of the second earth pressure gauge The step of calculating the anti-earth pressure of the excavated soil in the chamber and comparing the anti-earth pressure of the excavated soil with the upper limit value and the lower limit value to determine whether the excavated soil in the chamber is in a plastic flow state or not. And a step of estimating.
Note that it is desirable to estimate whether or not the excavated soil in the chamber is in a plastic flow state every time the cutter rotates once.
According to such a method for grasping the plastic fluidity, the properties of the excavated soil in the chamber are measured by a measuring device installed on the stirring blade that directly agitates the excavated soil. It is possible to grasp that earth pressure is applied to the face uniformly and stably.

  According to the method for grasping the plastic fluidity of excavated soil according to the present invention, the plastic fluidity in the chamber can be accurately grasped.

It is sectional drawing which shows the shield excavator which concerns on embodiment of this invention. It is a front view which shows the cutter of the shield excavator shown in FIG. It is a schematic diagram which shows an example of anti-earth pressure distribution. It is sectional drawing which shows an experimental apparatus typically. It is an example of an experimental result, Comprising: It is a graph which shows the relationship between the sliding speed of clay soil, and earth pressure. It is an example of an experimental result, Comprising: It is a graph which shows the relationship between the sliding speed of sandy soil, and earth pressure. It is an example of an experimental result, Comprising: It is a graph which shows the relationship between the sliding speed of gravel soil, and earth pressure.

In the embodiment of the present invention, a case where a tunnel is constructed by the earth pressure shield method will be described. In the earth pressure type shield method, the excavated soil generated by excavation of the natural ground is agitated in the chamber to give plastic fluidity, and the earth pressure of this excavated soil is applied to the face to stabilize the face. Do excavation. In order to ensure the stability and workability of the face, it is necessary to apply earth pressure to the face uniformly and stably.
To make the earth pressure against the face evenly and stably, ascertain the plastic fluidity of the excavated soil in the chamber accurately, and adjust the injection amount and injection location of additive materials such as mud and foam materials as needed. Need to be adjusted.
In the present embodiment, the property of the excavated soil in the chamber is accurately determined by a plastic fluidity grasping method including a preparation step, a threshold setting step, a soil pressure measurement step, an anti-earth pressure calculation step, and an estimation step. To grasp.

In addition, the shield excavator 1 of this embodiment is provided with the cutter 3 provided in the front surface of the cylindrical shield machine main body 2 and the shield machine main body 2 as shown in FIG. The front surface (face side surface) of the shield machine main body 2 is shielded by the chamber partition wall 4. A chamber 5 into which excavated soil is taken is formed between the cutter 3 and the chamber partition wall 4.
The cutter 3 includes a plurality of cutter bits (not shown) on the front surface (side surface), and cuts natural ground by rotating. On the back surface of the cutter 3, a plurality of stirring blades 31 for stirring the excavated soil in the chamber 5 are provided. The arrangement and number of the stirring blades 31 are not limited and may be set as appropriate.
As shown in FIG. 2, a earth pressure gauge (first earth pressure gauge) 6 is fixed to at least a part of the plurality of stirring blades 31. In the present embodiment, ten first earth pressure gauges 6 are arranged so as to be evenly distributed with respect to the cutter 3. In addition, arrangement | positioning and the number of the 1st earth pressure gauge 6 are not limited, What is necessary is just to set suitably. For example, the first earth pressure gauge 6 may be installed on each stirring blade 31. The first earth pressure gauge 6 rotates as the cutter 3 rotates. The first earth pressure gauge 6 of the present embodiment is attached to the front side and the rear side of the stirring blade 31 in the rotation direction.
A plurality of earth pressure gauges (second earth pressure gauges) 7 are provided on the surface of the chamber partition wall 4 on the chamber 5 side (face side) (see FIG. 1). The number and arrangement of the second earth pressure gauges 7 are not limited and may be set as appropriate.
The first earth pressure gauge 6 and the second earth pressure gauge 7 are connected to a drag measurement system (not shown) via a control panel 8. The drag measurement system stores the measured values of the first earth pressure gauge 6 and the second earth pressure gauge 7 and calculates the earth pressure of the excavated soil in the chamber 5 based on the measurement result.

  In the preparation process, the representative soil quality for each construction cycle (the ground corresponding to each segment ring) is selected based on the longitudinal profile of the soil layer created based on the boring columnar diagram. For the representative soil quality, select the soil quality that is expected to become dominant in the excavated soil generated by excavating natural ground. That is, the proportion of each soil in the segment width (distance per cycle: 1.6 m in this embodiment) pitch is calculated from the soil profile, and the soil having the most dominant proportion is selected as the representative soil. . In this embodiment, it classify | categorizes into three types of soil types, viscous soil, sandy soil, and gravel soil.

The threshold setting step is a step of setting an upper limit value and a lower limit value of the anti-earth pressure acting on the object moving in the soil layer in the plastic flow state.
In the present embodiment, the upper limit value and lower limit value of the earth pressure in the plastic flow state (hereinafter referred to as “the upper limit of the earth pressure in the plastic flow state” for each of the three types of soil properties of the viscous soil, the sandy soil, and the gravel soil are set. The value corresponding to the representative soil quality is selected from “the upper limit value of plastic flow” and “the lower limit value of plastic flow”.
The plastic flow upper limit value and the plastic flow lower limit value are thresholds for determining whether or not the plastic flow state is present. In other words, if the anti-earth pressure in the chamber exceeds the upper limit of plastic flow, the excavated soil is in a plastic state, and if the anti-earth pressure is lower than the lower limit of the plastic flow, the excavated soil is evaluated as in a fluid state. can do.

In the present embodiment, the plastic flow upper limit value and the plastic flow lower limit value are set by an experiment using excavated soil collected at the site or the like. In this experiment, excavated soil is put into an earth tank together with an additive, and stirred with a stirring rod that simulates a stirring blade, and earth pressure in a plastic state, a plastic flow state, and a fluid state is measured by an earth pressure gauge installed on the stirring rod. Measure. The plastic state, the plastic flow state, and the flow state are determined based on the result of the slump test on the excavated soil (bubble mixed soil).
The experimental method is not limited to the above method. Moreover, the setting method of a plastic flow upper limit and a plastic flow lower limit is not limited, For example, you may set based on the existing data.

The earth pressure measuring step is a step of measuring the earth pressure of the excavated soil in the chamber 5. In the earth pressure measurement process, the rotation angle of the cutter 3 (the position of the stirring blade 31) is measured based on information from an encoder or the like in accordance with the earth pressure measurement timing.
In the present embodiment, the earth pressure is measured by the first earth pressure gauge 6 provided on the stirring blade 31 and the second earth pressure gauge 7 provided on the chamber partition wall 4.
The first earth pressure gauge 6 measures the earth pressure acting on the stirring blade 31 when the stirring blade 31 rotates (moves).
The second earth pressure gauge 7 measures the earth pressure acting on the surface of the chamber partition wall 4.
The measurement results of the first earth pressure gauge 6 and the second earth pressure gauge 7 are input to the drag measurement system together with the position information of the stirring blade 31.

The anti-earth pressure calculation step is a step of calculating the anti-earth pressure of the excavated soil in the chamber 5 based on the measurement result of the first earth pressure gauge 6 and the measurement result of the second earth pressure gauge 7 input to the drag measurement system. .
The anti-earth pressure is calculated by subtracting the static earth pressure from the measured value of the first earth pressure gauge 6. Here, the static earth pressure is an earth pressure acting on the chamber partition wall 4 calculated based on a measured value by the second earth pressure gauge 7.
The anti-earth pressure is calculated at the position of each first earth pressure gauge 6. That is, the anti-earth pressure is calculated by subtracting the static earth pressure corresponding to the height position of the first earth pressure gauge 6 from the measured value of the first earth pressure gauge 6. The height position of the first earth pressure gauge 6 is calculated based on the rotation angle of the cutter 3.
In the present embodiment, the anti-earth pressure is calculated every time the cutter rotates once, but the frequency of calculating the anti-earth pressure is not limited.

The estimation step is a step of estimating the properties of the excavated soil in the chamber 5 using the anti-earth pressure calculated by the drag measuring system.
The properties of the excavated soil are determined by comparing the calculated anti-earth pressure with the plastic flow upper limit value and the plastic flow lower limit value. That is, when the anti-earth pressure exceeds the plastic flow upper limit value, it is estimated that the excavated soil is in a plastic state, and when the anti-earth pressure is within the range of the plastic flow upper limit value to the plastic flow lower limit value, the excavated soil is in the plastic flow state. It is estimated that the excavated soil is in a fluid state when it is below the lower limit of plastic flow.
The soil property is estimated (determined) for each position of each first earth pressure gauge 6 and the property distribution with respect to the tunnel cross section is calculated based on the estimation result.
The region between the adjacent first earth pressure gauges 6 calculates the anti-earth pressure by proportionally allocating from the relationship between the anti-earth pressure difference between the adjacent first earth pressure gauges 6 and the distance, and based on this anti-earth pressure. Estimate the properties. The calculation method of the anti-earth pressure distribution is not limited.

In the present embodiment, the calculated distribution of the properties of the excavated soil is displayed on the monitor of the drag measurement system (see FIG. 3). At this time, the plastic state, the plastic flow state, and the flow state are displayed in different colors.
In the present embodiment, the ratio of each property of plasticity, plastic flow and flow to the excavation cross-sectional area is calculated from the area ratio. As a result of calculating the area ratio, if the ratio of the plastic state, the ratio of the fluid state, or the sum of the ratio of the plastic state and the fluid state exceeds a predetermined value (for example, 50%), it is displayed on the monitor of the drag measurement system. A warning is displayed and a warning sound is sounded. The worker adjusts the amount of injection of the additive and the injection location according to the warning of the drag measurement system.

According to the plastic fluidity grasping method of the present embodiment, the earth and sand of the entire cross section can be uniformly and effectively improved.
That is, according to the method for grasping plastic fluidity, the property of the excavated soil in the chamber 5 can be grasped easily and accurately by visually recognizing on the screen. Therefore, processing necessary for plastic fluidization can be appropriately performed. For example, by confirming the distribution of properties, the injection amount of the additive can be increased for positions where the degree of plasticity is high, and the injection amount of the additive can be reduced for positions where the fluidity is high. In addition, it is possible to ensure uniform plastic fluidity and to make the earth pressure uniform on the face. In this embodiment, the operator manually adjusts the injection amount of the additive based on the distribution of the properties of the excavated soil, but the drag measurement system uses the properties of the excavated soil and the soil quality. You may adjust automatically via the control board 8 by transmitting a signal based on a relationship or the like.
The additive material injection holes are formed in both the cutter 3 and the chamber partition 4. In order to make the earth pressure on the face uniform, an additive is injected from an injection hole formed in the cutter 3. On the other hand, for the excavated soil in the chamber 5, the additive material is injected from the injection hole formed in the chamber partition wall 4, and the excavated soil is agitated into a plastic flow state, and then the excavated soil is passed through the screw conveyor. Is discharged.
In addition, the material cost can be reduced by injecting only the necessary amount of the additive into the necessary portion.

Next, an experimental method for setting the reference values (the plastic flow upper limit value and the plastic flow lower limit value) of the properties of the excavated soil will be described.
First, with respect to viscous soil, sandy soil, and gravel soil, the amount of additive is changed to generate a bubble mixed soil in a fluid state, a plastic fluid state, and a plastic state. The property is confirmed by a slump test.
Next, as shown in FIG. 4, the bubble mixed soil 10 is put into the soil tank 11, and the stirring bar 13 to which the earth pressure gauge 12 is fixed is placed in the layer (the soil layer) of the bubble mixed soil 10 in the soil tank 11. While making it slide, the earth pressure was measured with the earth pressure gauge 12. The earth pressure is measured while changing the sliding speed of the stirring bar 13, and is measured at least three times for each sliding speed.
A plastic flow upper limit value and a plastic flow lower limit value are set based on the measurement result of the earth pressure measured for each of the bubble mixed soils 10 having different properties.

As shown in FIGS. 5 to 7, as a result of the experiment, the earth pressure showed different values depending on the properties of the bubble mixed soil. That is, it was confirmed that the properties of the bubble-mixed soil can be determined by the magnitude of the earth pressure. Therefore, in the present embodiment, the plastic flow upper limit value is determined based on the measurement result of the earth pressure of the bubble mixed soil in the plastic state and the bubble mixed soil in the plastic flow state (for example, viscous soil: 20 kPa, sandy soil: 30 kPa, gravel soil: 50 kPa). Similarly, based on the measurement result of the earth pressure between the bubble mixed soil in the plastic flow state and the bubble mixed soil in the flow state, the plastic flow lower limit value is an intermediate value of each assumed value group (for example, clay soil: 5 kPa, sand (Soil: 7 kPa, gravel soil: 9 kPa).
In addition, as shown in FIGS. 5-7, even if it was a case where the speed of a stirring rod was changed, the big change did not arise in the earth pressure measurement value. Therefore, it was demonstrated that even if there is a difference in the moving speed of the stirring blade depending on the distance from the rotation axis of the cutter 3 (attachment position to the cutter 3), there is no difference in the anti-earth pressure. Accordingly, the anti-earth pressure of the excavated soil is calculated based on the measured value of the earth pressure gauge 6 attached to the stirring blade 31 protruding from the back surface of the cutter 3, and is used for grasping the distribution of the properties of the excavated soil. be able to.
The maximum sliding speed of the stirring bar 13 is set to the speed at the position of the earth pressure gauge disposed on the outermost side of the cutter when the cutter of the shield machine is rotated at the maximum rotational speed. The minimum sliding speed of the stirring bar 13 is set to the speed at the position of the earth pressure gauge disposed on the innermost side of the cutter when the cutter of the shield machine is rotated at the minimum number of rotations. Then, an experiment is performed by changing the speed of the stirring bar 13 within the range of the maximum speed and the minimum speed, and a threshold value is set. In addition, what is necessary is just to set the range of the sliding speed of the stirring rod 13 suitably according to the rotation speed of the shield machine to be used.

The embodiment according to the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and the above-described components can be appropriately changed without departing from the spirit of the present invention.
In the embodiment, the case where the property distribution of excavated soil is displayed on the monitor has been described. However, the property distribution need not necessarily be displayed on the monitor.

DESCRIPTION OF SYMBOLS 1 Shield machine 2 Shield machine body 3 Cutter 4 Chamber partition 5 Chamber 6 First earth pressure gauge (first earth pressure gauge)
7 Second earth pressure gauge (second earth pressure gauge)
8 Control panel

Claims (2)

A step of setting an upper limit value and a lower limit value of the anti-earth pressure acting on an object moving in the soil layer in the plastic flow state;
A step of measuring the earth pressure with a first earth pressure gauge provided on the stirring blade and a second earth pressure gauge provided on the chamber partition;
Calculating the anti-earth pressure of the excavated soil in the chamber based on the measurement result of the first earth pressure gauge and the measurement result of the second earth pressure gauge;
Comparing the anti-earth pressure of the excavated soil with the upper limit value and the lower limit value, and estimating whether the excavated soil in the chamber is in a plastic flow state or not. How to grasp sex.   The method for grasping plastic fluidity according to claim 1, wherein it is estimated whether or not the excavated soil in the chamber is in a plastic fluid state every time the cutter rotates once.

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