JPH074176A - Method for exploring natural ground collapse in shield work - Google Patents

Abstract

(57) [Summary] [Purpose] In the shield work, the boundary between the ground and the collapse can be easily and accurately determined even on soft ground, and if the strata are changing, the changes in the strata should be understood. To be able to correctly evaluate the amount of ground collapse. [Structure] An exploration rod 10 having a vibration sensor 11 and a load sensor 12 incorporated therein is penetrated from the outer peripheral surface of the shield body 1 into the ground, the penetration stroke is taken as the horizontal axis, and the vibration sensor output value and the penetration resistance are taken as the vertical axis. The inflection point where the vibration sensor output value and the penetration resistance change is found on the graph, and the soil quality of each section on the calibration data obtained in advance from the vibration sensor output value and the penetration resistance before and after the inflection point Then, the amount of rock mass collapse is estimated from a plurality of information obtained by adding soil properties to the inflection point and penetration resistance obtained earlier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for exploring ground collapse in shield work, and more specifically, a method for exploring the collapse situation of the ground around the shield in order to prevent accidents such as depression of the ground surface. Regarding

[0002]

2. Description of the Related Art As a conventional technique of this type, as shown in FIG. 8, a shield rod 1 having an earth pressure gauge 31 at its tip is used for a shield body 1 by a penetrating device 32 such as a hydraulic jack.
It is determined that the earth pressure gauge 31 is in contact with the ground due to the pressure change of the earth pressure gauge pressure receiving surface, and the penetration stroke of the exploration rod 30 at that time is the distance to the ground, that is, the earth movement. There is a method of setting the amount of collapse. In FIG. 8, 33 is an amplifier that amplifies the output signal of the earth pressure gauge 31,
34 is a hydraulic switching valve for operating the penetration device 32, 35 is a flow meter type stroke sensor, 36 is a display panel, 37 is an earth pressure display meter, 38 is a stroke display meter, 39 is an undisturbed ground around the shield. Part, 40 is a collapsed part that is loosened due to the influence of excavation, and S is the amount of rock mass collapsed.

[0003]

Since the above-mentioned prior art is intended to estimate the collapse position and the collapse amount of the natural rock by capturing only the phenomenon that the tip earth pressure of the exploration rod relatively rises. It had the following problems.

(1) In soft ground, the pressure change at the tip of the rod may not be noticeable. In that case, considering the soil quality, depth, area of earth pressure gauge pressure receiving surface, etc., the penetration stroke when a certain rock contact pressure is set is the distance to the rock. It is necessary to know the soil quality in advance, and for that purpose separate measures must be taken.

(2) When the formation changes in the intrusion direction, the earth pressure at the tip of the exploration rod changes due to the formation change, and for example, when there is a rapid formation change from a sand layer to a cohesive soil layer, Since the tip soil pressure is smaller in the cohesive soil layer than in the sand layer, it is possible to erroneously judge that the amount of collapse has increased. Also, when the strata changes in the direction of excavation, the soil pressure at the collapse position in the sand layer is higher than the soil pressure at the collapse position in the cohesive soil layer, so the soil layer collapses when it changes from the cohesive soil layer to the sand layer. Nevertheless, it is easy to make a mistake because it is possible to make a false decision that it has not collapsed, because it is impossible to grasp the changes in the stratum.

The object of the present invention is to easily determine the boundary between the rock mass and the collapse part in soft ground, to obtain the amount of rock mass collapse with high accuracy, and in the case where the stratum changes. The purpose of the present invention is to provide a method for exploring rock mass collapse in shield construction, which enables the amount of rock mass collapse to be evaluated correctly after grasping the changes in the stratum.

[0007]

In order to achieve the above-mentioned object, the invention according to claim 1 penetrates a probe rod having a vibration sensor and a load sensor into the ground from the outer peripheral surface of the shield, and when the rod penetrates. Input the output signal of the vibration sensor that detects the generated vibration, the output signal of the load sensor that detects the penetration resistance, and the output signal of the stroke sensor that detects the penetration stroke to the processing device, and set the stroke as the horizontal axis and output the vibration sensor. A graph with the vertical axis of the value and the penetration resistance is output, the inflection point where the vibration sensor output value and the penetration resistance change is found on this graph, and the vibration sensor output value and the penetration that are obtained in advance for each soil particle size are also found. From the relationship with the resistance, the soil quality for each section corresponding to the output value of the vibration sensor and the penetration resistance in the stroke section before and after the inflection point was discriminated, and the variation obtained earlier was determined. And the point, and estimates the collapse of the natural ground from the plurality of information plus soil of each section in the penetration resistance at that before and after the stroke section.

According to the second aspect of the present invention, when the inflection point cannot be found on the graph, the vibration sensor throughout the entire stroke section is obtained from the relationship between the vibration sensor output value and the penetration resistance obtained in advance for each soil particle size. The soil properties corresponding to the average values of the output value and the intrusion resistance are discriminated, and the information of the intrusion resistance and soil properties obtained in this exploration are used to determine the intrusion resistance and It is characterized by estimating the amount of ground collapse by comparing it with each soil information.

[0009]

[Operation] The vibration sensor converts the vibration generated by the crushing of the external soil particles and the friction between the soil particles and the vibration caused by the friction between the tip of the rod and the soil into the electric signal when the exploration rod penetrates into the ground. It is converted and output, and specifically, an acceleration sensor, an AE (acoustic emission) sensor, or the like is used.

The load sensor converts the static penetration resistance received by the tip of the exploration rod into an electric signal and outputs it, and the stroke sensor converts the penetration stroke of the exploration rod into an electric signal and outputs it.

As described in detail in JP-A-63-279141, when an acceleration sensor is used as the vibration sensor, the effective value of the vibration acceleration detected when the exploration rod penetrates into the ground is the soil. The effective value level tends to increase as the particle size increases. However, even in the same soil, the effective value level differs depending on the tightening condition, and the effective value level increases as the density or confining pressure increases. Further, along with this, the penetration resistance detected by the load sensor also increases.

As shown in FIG. 4, when the effective value level of the vibration acceleration is plotted on the vertical axis and the penetration resistance is plotted on the horizontal axis, respectively, and expressed in a logarithmic log graph, the effective value level of the vibration acceleration increases with the penetration resistance in any soil type. Increase almost linearly, and the increment of the effective value level (the slope of the straight line in the figure) depends on the soil type. It is known that the larger the soil particle size, the greater the slope and that the straight lines extend at almost the same point.

In the present invention, the relationship between the vibration acceleration and the penetration resistance for each grain size of soil as shown in FIG. 4 is obtained in advance as calibration data, and as described below, the target ground for performing the collapse survey is described. It is used for soil classification.

The case where an acceleration sensor is used as a vibration sensor will be described as an example. As a procedure for rock mass collapse exploration, first, an exploration rod is penetrated into the ground from the outer peripheral surface of the shield, and the acceleration sensor, load sensor and Each output signal of the stroke sensor is input to the processing device to output a graph in which the horizontal axis represents stroke and the vertical axis represents vibration acceleration (effective value) and penetration resistance. If inflection points of vibration acceleration and penetration resistance are found on this graph,
On the calibration data obtained in advance, the soil quality of each section corresponding to the vibration acceleration and the penetration resistance in the stroke section before and after the inflection point is determined. As a result, if the soil quality of both sections was the same, the inflection point could be recognized as the boundary between the rock mass and the collapse area, and if the soil quality of both sections was not the same, there was a change in the stratum in the intrusion direction. Therefore, it is possible to correctly evaluate the amount of ground collapse after grasping the changes in the strata.

When the inflection point cannot be found on the graph, the soil properties corresponding to the average values of the vibration acceleration and the penetration resistance over the entire stroke section are discriminated on the calibration data. If there is a change in the stratum in the excavation direction by comparing each information of the intrusion resistance and soil quality obtained by the exploration with the information of each of the penetration resistance and soil quality obtained at the previous point in the excavation direction backward point, The amount of ground collapse can be correctly evaluated after grasping the changes in the stratum.

[0016]

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

FIG. 1 is a diagram showing an embodiment of the present invention. Although the type of the shield is arbitrary, it is shown as an example when it is applied to an earth pressure type shield. In the figure, 1 is a shield body, 2
Is a partition wall that divides the shield body into the face and the inside of the machine, 3
Is a cutter head that is rotatably supported on the front part of the shield body and excavates the natural ground. 4 is a cutter driving device that transmits a rotational force to the cutter head 3 through a gear 5 and a center shaft 6. 7 is excavated earth and sand. An agitating chamber for taking in and agitating and holding a face, 8 is a screw bear for carrying earth and sand out of the agitating chamber, and 9 is a shield jack for propelling the shield body.

Reference numeral 10 is an exploration rod that penetrates into the ground from the outer peripheral surface of the shield body 1 for exploration of the ground collapse, 11 is a vibration sensor built in the exploration rod 10, 12 is a load sensor, and 13 is a load sensor. A penetrating device such as a hydraulic jack for penetrating the exploration rod 10, 14 is a reaction force attached to the shield body for taking a penetration reaction force of the exploration rod 10, and 15 is between the exploration rod 10 and the shield body. The earth and sand seal is installed, and the output signals of the vibration sensor 11 and the load sensor 12 are transmitted to the processing device 17 through the signal line 16.

FIG. 2 is a detailed diagram showing the system configuration of the rock mass collapse exploration device. An example in which an acceleration sensor is used as the vibration sensor will be described below, but another vibration sensor such as an AE sensor may be used instead.

As shown in FIG. 2, the exploring rod 10 has a pipe-shaped main body portion 10a and a tip cone portion 10b mounted so as to be capable of minute displacement with respect to the main body portion 10a.
The penetrating device 13 is connected to the main body portion 10a. The acceleration sensor 11 is attached to the inner surface of the tip cone portion 10b, and detects vibration generated in the tip cone portion 10b due to friction and crushing of soil particles when the rod penetrates. The output signal of the acceleration sensor 11 is amplified by the amplifier 18, and is further input to the processing device 17 as a signal corresponding to the effective value of the vibration acceleration by the effective value converter 19. The load sensor (load cell) 12 having a cylindrical shape has a front end fixed to the tip cone portion 10b and a rear end fixed to the rod body portion 10a in the inner rear portion, and is statically received by the tip cone portion 10b when the rod penetrates. The penetration resistance is detected, and its output signal is amplified by the amplifier 20 and input to the processing device 17. Reference numeral 21 denotes a stroke sensor that detects a penetrating stroke of the exploration rod 10. The output signal of the stroke sensor 21 is amplified by the amplifier 22 and input to the processing device 17. Stroke sensor 2
1 may be a potentiometer type stroke sensor mechanically interlocked with the exploration rod 10 or a flow meter type stroke sensor as shown in FIG. Processor 1
Numeral 7 is a recorder (X-Y) as a graph in which the above three types of input signals are sampled, and the collected actual measurement data are plotted by taking the stroke on the horizontal axis and the effective value of vibration acceleration and penetration resistance on the vertical axis. It is output from the recorder) 23.

Next, a method for exploring natural ground collapse using the above apparatus will be specifically described.

The procedure of rock mass exploration in normal time is as shown in FIG. First, after initializing the processing device 17, the probe rod 10 is penetrated into the ground, and the output signals of the vibration sensor 11, the load sensor 12, and the stroke sensor 21 are input to the processing device 17, and the stroke is changed horizontally. The graph is output with the vertical axis representing the effective value of vibration acceleration and the penetration resistance. Now, assuming that a graph as shown in FIG. 5 is output, the inflection point at which the level of vibration acceleration and the level of penetration resistance changes is found on this graph, and the strokes before and after the inflection point are the boundaries A, B. Divide into. Then, the soil quality is discriminated using the calibration data for each of these sections. As described in the section [Operation], the calibration data is a logarithmic graph showing the relationship between the vibration acceleration and the penetration resistance for each soil particle size, which is grasped in advance by the calibration experiment, and is shown in FIG. Thus, the intersection point A ′ of the vibration acceleration VA and the penetration resistance RA in the section A and the intersection point B ′ of the vibration acceleration VB and the penetration resistance RB in the section B are respectively taken on the calibration graph,
If these two points A'and B'are on a straight line with the same grain size, the soil properties of both sections A and B are judged to be the same. In this case, since the soil properties of both sections A and B are the same and the penetration resistance is in the relation of RA <RB, the inflection point obtained earlier is that the ground point 39 and the collapse portion shown in FIG. It can be judged that it is the boundary with 40, and the collapse amount S can be estimated from the penetration stroke to the inflection point.

Here, consider the case where the formation changes in the intrusion direction. Generally, in the undisturbed ground, according to the standard penetration test, the N value tends to increase as the soil particle size increases. For example, when the formation changes rapidly from a sand layer to a cohesive soil layer, the penetration resistance (rod tip earth pressure in the prior art) when the exploration rod penetrates the cohesive soil layer is smaller than that of the sand layer. If you do not have information other than, there is a possibility that you will be erroneously determined that the amount of collapse has increased. However, looking at the effective value level of the vibration acceleration together with the penetration resistance, the intersection of each measured value of the vibration acceleration and the penetration resistance in the stroke section before and after the inflection point (A ′ in FIG. 6,
It was found that B ') was not on a straight line with the same grain size in the calibration data, and that there was a change in the formation, and further that the level of penetration resistance decreased due to a change from a sand layer to a cohesive soil layer. Since it is possible to judge the presence or absence of the collapse after that, it is not necessary to make the wrong judgment as described above.

Next, a method for exploring the ground collapse when the stratum changes in the direction of excavation will be described.

When the inflection point cannot be found on the output graph of the recorder 23, the entire stroke section (A + B in FIG. 5)
Soil quality corresponding to each average value of vibration acceleration and penetration resistance through the above was discriminated on the calibration graph, and whether there was a change in the strata in comparison with the soil information obtained at the previous point at the location behind the excavation direction. Determine whether For example, we had previously obtained information that we had been excavating the clay layer and had not collapsed, but in this exploration we assume that the soil quality has changed to sandy soil. Here, (a) of FIG. 7 is a recorder output graph in the cohesive soil layer (Va is the average level of the vibration acceleration effective value at this time, Ra is the average level of the penetration resistance),
It is assumed that (b) is a recorder output graph in the sand layer (Vb is the average level of the vibration acceleration effective value at this time, Rb is the average level of the penetration resistance), and Va <Vb, Ra≈Rb.
Such a change in soil quality cannot be immediately recognized even when looking at the excavated soil carried out inside the shield machine, so the amount of collapse is determined only by the penetration resistance (rod tip earth pressure in conventional technology). When the penetration resistance of the same level is accidentally shown as in (a) and (b) of FIG. 7, there is a possibility that it is erroneously determined that it has not collapsed as before.

However, looking at the effective value level of vibration acceleration together with the penetration resistance, it can be seen from the calibration data that the soil quality has changed from cohesive soil to sandy soil. Generally, in undisturbed ground, sandy soil tends to show higher penetration resistance, so assuming that it showed the same level of penetration resistance as cohesive soil,
It is possible to grasp that it is not a sandy soil that is too compact and alert the excavation manager. In this way, by determining the soil quality from the vibration acceleration and the penetration resistance, it is possible to avoid making an erroneous determination that the soil has not collapsed even though the stratum has changed and collapsed in the excavation direction.

In the above explanation, the formation change between the cohesive soil layer and the sand layer has been described, but this is a representative example of the formation change, and it goes without saying that it can also be applied to other formation changes. Nor.

[0028]

According to the first aspect of the present invention, the output signals of the vibration sensor, the load sensor and the stroke sensor when the exploration rod is penetrated into the ground are input to the processing device to determine the stroke. By outputting a graph with the horizontal axis as the horizontal axis and the vibration sensor output value and the vertical axis as the vertical axis, an inflection that shows the boundary between the ground and the collapse area is obtained not only from the penetration resistance but also from the change in the vibration sensor output value. Since the point can be found, even if the ground is soft and the change in the penetration resistance does not significantly appear, it is possible to easily and accurately estimate the amount of ground collapse without overlooking the inflection point. In addition, from the relationship between the vibration sensor output value for each particle size of soil obtained in advance and the penetration resistance, the soil quality for each section corresponding to the vibration sensor output value and the penetration resistance in the stroke section before and after the inflection point is determined. By discriminating, if the stratum changes in the intrusion direction, it is possible to correctly assess the amount of ground collapse after grasping the change in the stratum, and it is possible to change the sand layer to the cohesive soil layer and reduce the intrusion resistance. No more erroneous judgment that the amount of collapse has increased.

Further, according to the second aspect of the invention, when the inflection point cannot be found on the graph, the total is calculated from the relation between the vibration sensor output value for each soil particle size and the penetration resistance obtained in advance. The soil quality corresponding to each average value of the vibration sensor output value and penetration resistance through the stroke section is determined,
By comparing each information of the intrusion resistance and soil obtained by this survey with each information of the intrusion resistance and soil obtained at the last point in the excavation direction, the stratum changes in the excavation direction. In this case, it is possible to correctly evaluate the amount of ground collapse after grasping the changes in the stratum, and to make a false judgment that it has not collapsed, despite the fact that the soil has changed from a cohesive soil layer to a loose sand layer and has collapsed. Disappears.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a shield showing an embodiment of the present invention.

FIG. 2 is a system configuration diagram of the rock mass collapse exploration device in FIG.

FIG. 3 is a flow chart showing the procedure of the method for exploring natural ground collapse according to the present invention.

FIG. 4 is a graph (calibration data) showing the relationship between the vibration acceleration effective value level and the penetration resistance obtained for each particle size of soil.

FIG. 5 is a graph showing an example of actually measured data when a rod penetrates, with a horizontal axis representing a stroke and a vertical axis representing vibration acceleration and penetration resistance.

FIG. 6 is an explanatory diagram of soil type determination on calibration data.

FIG. 7 is an explanatory diagram of a method for exploring the ground collapse when the stratum changes in the direction of excavation, (a) is a graph showing the measured data in the cohesive soil layer, and (b) is the measured data in the sand layer. It is a graph shown.

FIG. 8 is an explanatory view of a method for exploring natural ground collapse according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Shield main body, 10 ... Exploration rod, 11 ... Vibration sensor (acceleration sensor), 12 ... Load sensor, 13 ... Penetration device, 17 ... Processing device, 21 ... Stroke sensor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Manabu Nakano 650 Jinrachi-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura factory (72) Masao Sato 2 Sanbancho, Chiyoda-ku, Tokyo Tobishima Construction Co., Ltd. (72) Inventor Matsuo Tanaka 2 Sanbancho, Chiyoda-ku, Tokyo, Tobishima Construction Co., Ltd. (72) Inventor Eisuke Numaguchi Sanbancho, Chiyoda-ku, Tokyo Tokyo, Tobishima Construction Co., Ltd.

Claims (2)

[Claims] 1. A load sensor for detecting a penetration resistance and an output signal of a vibration sensor for detecting vibration generated at the time of rod penetration by penetrating an exploration rod having a vibration sensor and a load sensor into the ground from the outer peripheral surface of the shield. Input the output signal of the stroke sensor and the output signal of the stroke sensor that detects the intrusion stroke to the processing device, and output a graph with the stroke as the horizontal axis and the vibration sensor output value and the intrusion resistance as the vertical axis. The inflection point where the sensor output value and the penetration resistance change was found, and the vibration sensor output value in the stroke section before and after the inflection point was further calculated based on the relationship between the vibration sensor output value and the penetration resistance that were previously obtained for each soil particle size. And soil resistance for each section corresponding to the intrusion resistance and the inflection point obtained earlier and the soil resistance for each section in the intrusion resistance before and after the inflection point A method for exploring natural ground collapse in shield construction, which is characterized by estimating the amount of natural ground collapse from a plurality of information including. 2. The ground collapse investigation method according to claim 1, wherein when an inflection point cannot be found on the graph, the relationship between the vibration sensor output value and the penetration resistance obtained in advance for each soil particle size is used. The soil properties corresponding to the average values of the vibration sensor output value and the intrusion resistance throughout the entire stroke section are determined, and the various information of the intrusion resistance and soil properties obtained in this exploration are used for the previous exploration at the backward point in the excavation direction. A method for exploring natural ground collapse in shield construction, characterized by estimating the amount of natural ground collapse by comparing it with each of the information on penetration resistance and soil quality obtained at that time.