JP2020197082A - Measurement system, measurement method, and interval determination method - Google Patents

Abstract

To accurately monitor the entire behavior of the ground including the surroundings of an excavation region throughout periods for pit excavation/earth-retaining work.SOLUTION: The measurement system comprises: a slope angle information acquisition unit that acquires information representing a slope angle of core materials that is measured using a first slope angle detection unit composed of a plurality of slope angle detection parts attached to a core material at a predetermined first interval and in a longitudinal direction, and acquires information representing a slope angle of core materials that is measured using a second slope angle detection unit composed of a plurality of slope angle detection parts attached to a core material at a predetermined second interval and in a horizontal direction that is perpendicular to the longitudinal direction, for an earth-retaining wall configured using core materials that are long with respect to an excavation direction that is the vertical direction; and an output unit that outputs information representing first relative displacement based on the information representing the slope angle acquired by the first slope angle detection unit, and information representing second relative displacement based on the information representing the slope angle acquired by the second slope angle detection unit.SELECTED DRAWING: Figure 10

Description

The present invention relates to a measurement system, a measurement method, and an interval determination method.

In the conventional measurement management of root cutting and retaining work, simple measurement of the displacement of the head of the retaining wall with a piano wire and measurement of the depth distribution of horizontal displacement with an inclinometer are performed. However, with the conventional method, only point / linear and local measurement data can be obtained, and it is difficult to grasp the overall behavior of the retaining wall at a glance.

From the above background, a three-dimensional measurement system for the retaining wall has been proposed as a measurement method capable of performing an area evaluation for the measurement management of the retaining wall (Patent Document 1). This system is characterized by arranging a plurality of sensors (displacement meter or inclinometer) on the surface of the retaining wall and visualizing the displacement data in three dimensions. By arranging the sensor in combination with an expensive high-sensitivity sensor and an inexpensive low-sensitivity sensor, it is possible to perform measurement at a low cost.

Japanese Unexamined Patent Publication No. 2011-94442 JP-A-2019-52467

FIG. 9 is a side view schematically showing the displacement pattern of the retaining wall. FIG. 9 (a) shows a modified example after the primary root cutting, and FIG. 9 (b) shows a modified example after the secondary root cutting. Further, FIG. 9 (c) shows a modified example of rotation, and FIG. 9 (d) shows a modified example of translation. When the system described in Patent Document 1 is operated independently, the displacement data obtained is the relative displacement of the retaining wall due to the nature that no fixed point is provided, and even if the deformation / rotation of the retaining wall is captured. It is not possible to capture behavior such as translation. In addition, since the sensor must be placed on the surface of the retaining wall, that is, after excavation, the measurement is for a sensor that has already been displaced, and it is desirable to reexamine the measurement method.

Therefore, the inventor of the present application attaches a MEMS type acceleration sensor (hereinafter referred to as a sensor) to the core material of the retaining wall to measure the relative displacement in the horizontal (out-of-plane) direction of the wall surface in the measurement management of the root cutting / retaining work. It has been proposed (see Patent Document 2).
Here, it is desirable that the sensor installation interval can be determined so as to satisfy the accuracy required for the retaining measurement.

The present invention has been made in view of the above circumstances, and is a measurement system and measurement capable of accurately monitoring the overall behavior of the ground including the periphery of the excavation area during the entire period of root cutting / retaining work. It is an object of the present invention to provide a method and an interval determination method.

In order to solve the above problems, one aspect of the present invention is a retaining wall configured by using a core material having a longitudinal direction in the excavation direction, which is a vertical direction, at a predetermined first interval in the longitudinal direction. Information representing the tilt angle of the core material measured by using the first tilt angle detection unit composed of a plurality of tilt angle detection units attached to the first tilt angle detection unit is acquired from the first tilt angle detection unit, and the longitudinal direction The core material measured using a second tilt angle detection unit composed of a plurality of tilt angle detection units attached to the core material at predetermined second intervals in the horizontal direction, which is a direction orthogonal to the core material. The tilt angle information acquisition unit that acquires the information representing the tilt angle of the second tilt angle detection unit, and the information representing the first relative displacement based on the information representing the tilt angle acquired from the first tilt angle detection unit. The measurement system includes an output unit that outputs information representing a second relative displacement based on information representing the tilt angle acquired from the second tilt angle detection unit.

Further, one aspect of the present invention is a plurality of retaining walls formed by using a core material having a longitudinal direction in the excavation direction, which is a vertical direction, attached to the core material at a predetermined first interval in the longitudinal direction. Information representing the tilt angle of the core material measured by using the first tilt angle detection unit composed of the tilt angle detection unit of the above is acquired from the first tilt angle detection unit and is orthogonal to the longitudinal direction. Represents the tilt angle of the core material measured by using a second tilt angle detection unit composed of a plurality of tilt angle detection units attached to the core material at a predetermined second interval in the horizontal direction, which is the direction. Information representing the first relative displacement based on the information representing the tilt angle acquired from the first tilt angle detection unit by the output unit using the tilt angle information acquisition unit that acquires information from the second tilt angle detection unit. The measurement method is characterized by outputting the information representing the second relative displacement based on the information representing the tilt angle acquired from the second tilt angle detection unit.

Further, one aspect of the present invention is the minimum unit of displacement in which the predetermined first interval and the predetermined second interval in the measurement system described above are detected by the inclination angle detection unit, and the inclination angle detection unit. Is an interval determination method characterized in that is determined according to the smallest unit that can be detected.

According to the present invention, it is possible to accurately monitor the overall behavior of the ground including the periphery of the excavation area during the entire period of root cutting / retaining work.

It is a schematic diagram for demonstrating the configuration example of the measurement system which concerns on 1st reference example. It is a perspective view which shows typically the example of the displacement of the retaining wall 2 shown in FIG. It is a schematic diagram for demonstrating the configuration example of the measurement system which concerns on 2nd reference example. It is a top view which shows typically the example of the displacement of the retaining wall 2 shown in FIG. It is a schematic diagram for demonstrating the configuration example of the measurement system which concerns on 3rd reference example. It is a schematic diagram which shows the structural example of the tape type inclinometer 40 shown in FIG. It is a schematic diagram which shows the example of attachment to the core material 21 of the tape type inclinometer 40 shown in FIG. It is a schematic diagram which shows the calculation example of the displacement of a retaining wall. It is a schematic diagram which shows the example of the displacement of a retaining wall. It is a schematic diagram for demonstrating the structural example of the measurement system 100 which concerns on 1st Embodiment of this invention. It is a schematic diagram for demonstrating the structural example of the 3-axis MEMS acceleration sensor (tilt angle detection part 4) which concerns on 1st Embodiment of this invention. It is a figure which shows the relationship between the accuracy of the acceleration sensor shown in FIG. 11 and the installation interval in a depth direction (excavation direction). It is a figure which shows typically the example of the relative displacement of the retaining wall 2 in the excavation plane. It is a figure which shows the relationship between the accuracy of the acceleration sensor shown in FIG. 11 and the installation interval in a horizontal direction.

Hereinafter, reference examples and embodiments of the present invention will be described with reference to the drawings.

<1st reference example>
FIG. 1 is a schematic diagram for explaining a configuration example of the measurement system 1 according to the first reference example. The measurement system 1 shown in FIG. 1 includes an absolute position information acquisition unit 11, an inclination angle information acquisition unit 12, and an output unit 13. The absolute position information acquisition unit 11 is an absolute measurement point 3 of a predetermined measurement point 3 of the head 2a of the retaining wall 2 (hereinafter, also referred to as the retaining wall head 2a) configured by using the core material 21 having a longitudinal direction in the excavation direction. Get the information that represents the position. In the example shown in FIG. 1, the absolute position information acquisition unit 11 acquires information representing the absolute position of a predetermined measurement point 3 of the retaining wall head 2a measured by the absolute position measurement unit 30 in a non-contact manner. The tilt angle information acquisition unit 12 tilts information indicating the tilt angle of the core material 21 measured by using a plurality of tilt angle detection units 4 attached to the core material 21 at predetermined intervals in the longitudinal direction of the core material 21. Acquired for each angle detection unit 4. The plurality of inclination angle detection units 4 are attached to the core material 21 in advance, for example, before the construction of the retaining wall 2. The inclination angle detecting unit 4 may be attached to all of the plurality of core members 21 constituting the retaining wall 2, or may be attached to a part of the core members 21 (for example, at predetermined intervals of the core members 21). The output unit 13 is a core material based on information representing the absolute displacement of the measurement point 3 based on the information representing the absolute position acquired by the absolute position information acquisition unit 11 and information representing the tilt angle acquired by the tilt angle information acquisition unit 12. Information representing the relative displacement of 21 is also output. The measurement system 1 can be composed of, for example, a combination of a computer such as a notebook personal computer and a peripheral device such as a communication device. The output unit 13 may be a display device of the above computer or a display device of another computer such as a mobile terminal.

The absolute position measuring unit 30 can be configured by using, for example, a total station. A total station is a surveying instrument that combines a light wave rangefinder that measures distance and a theodolite that measures angles. In this case, for example, the reflection prisms are fixedly installed at each measurement point 3 of the retaining wall head 2a, and the reflection prisms are sequentially measured from the total station installed at the fixed point (or referring to the fixed point). The absolute position information acquisition unit 11 acquires information (angle and distance) representing the absolute position of the measurement point 3 of the retaining wall head 2a from the total station. The output unit 13 (or the absolute position information acquisition unit 11) compares, for example, the coordinate values based on the acquired information (angle and distance) with the coordinate values based on the past measurement results, so that the output unit 13 (or the absolute position information acquisition unit 11) of each measurement point 3 Calculate the absolute displacement.

Alternatively, the absolute position measurement unit 30 may be a device (or system) for measuring the position using a global navigation satellite system (GNSS (Global Navigation Satellite System)). In this case, the absolute position measurement unit 30 collects, for example, a GNSS receiver fixedly (or semi-fixed) installed at each measurement point 3 of the retaining wall head 2a, and position information measured by the GNSS receiver. Then, it can be composed of a terminal for transmitting to the absolute position information acquisition unit 11. In this case as well, the output unit 13 (or the absolute position information acquisition unit 11) compares, for example, the coordinate values based on the acquired information with the coordinate values based on the past measurement results, so that the absolute position of each measurement point 3 is absolute. Calculate the amount of displacement.

Further, each inclination angle detection unit 4 can be configured by using, for example, a 3-axis MEMS (Micro Electro Electro Mechanical Systems) acceleration sensor. Each inclination angle detection unit 4 detects the gravitational acceleration of three orthogonal axes and outputs information indicating the detection result. The tilt angle information acquisition unit 12 acquires information indicating the detection result output by each tilt angle detection unit 4 as information representing the tilt angle of the core material 21. The output unit 13 (or the inclination angle information acquisition unit 12) calculates the horizontal displacement amount by converting the detection result of the gravitational acceleration of the three axes into the inclination angle and further multiplying the inclination angle by the distance from the predetermined reference point. To do.

FIG. 8 is a side view schematically showing the relationship between the tilt angle and the relative displacement (displacement with respect to the reference line) for the four tilt angle detection units 4. FIG. 8 shows four positions of the tilt angle detecting unit 4 as measurement point P ₁ to P ₄ respectively. Reference line is a vertical line passing through the measurement point P _1. θ _n is the tilt angle formed by the survey line connecting the station P _n and the station P _{n + 1} with respect to the reference line, δ _n is the displacement of the station P _{n + 1 with} respect to the reference line, and l is the distance between the stations (each tilt angle detector). (Distance between 4) (where n = 1-3). The displacement δ _n of P _{n + 1} when there are n survey lines is represented by δ _n = l × (θ ₁ + θ ₂ + ... θ _n-1 + θ _n ).

The tilt angle detection unit 4 is not limited to the three-axis acceleration sensor, but is a pendulum type or a float type that detects the tilt angle by detecting the deviation between the weight or liquid surface suspended in the direction of gravity and the tilted object. It may be configured by using an inclination sensor such as.

Further, in this reference example and the embodiment, the "mountain retaining wall" means to protect the side surface of the root cutting, prevent the collapse of earth and sand and spring water, and ensure the safety of other structures in the vicinity during excavation. It is a partition for. The mountain retaining wall is also called an earth retaining wall. Examples of the retaining wall include a main pile horizontal sheet pile wall, a steel sheet pile wall, a steel pipe sheet pile wall, a soil cement solidified continuous wall, and an underground continuous wall. The main pile horizontal sheet pile wall is a wall constructed by driving parent piles (H-shaped steel) into the ground at predetermined intervals and fitting horizontal sheet piles between the main piles (interval part 22 in FIG. 1). In this case, the parent pile is the core material. The steel sheet pile wall is a wall constructed continuously in the ground by engaging the joint portions of a plurality of steel sheet piles with each other. In this case, the steel sheet pile is the core material. The steel pipe sheet pile wall is a wall constructed continuously in the ground by engaging the joint portions of a plurality of steel pipe sheet piles with each other. In this case, the steel pipe sheet pile is the core material. Further, the intermediate portion 22 in FIG. 1 does not exist. A soil cement solidified continuous wall or an underground continuous wall is a wall or the like constructed continuously in the ground from a core material (H-shaped steel or a reinforcing bar cage) and concrete (cement milk). In addition, "root cutting" is the excavation of earth and sand and rock below the ground surface to create foundations and underground structures. The "core material" is a member that shares the yield strength as a part of the retaining wall, and is, for example, an H-shaped steel, a steel sheet pile, a steel pipe sheet pile, a secondary concrete product, or the like.

Further, the "information representing the absolute position of a predetermined measurement point on the head of the retaining wall" includes numerical data representing the absolute position of the measurement point and numerical data as a reference when calculating the absolute position. For example, when the absolute position is represented by latitude, longitude and height in a predetermined geodetic system, the numerical data representing the absolute position of the measurement point is the numerical data representing latitude, longitude and height. Further, the numerical data that serves as a reference when calculating the absolute position is numerical data that can be converted into numerical data representing latitude, longitude, and height by a predetermined conversion process, and is used when calculating the absolute position. It is numerical data that specifies the position of the measurement point. The numerical data that serves as a reference when calculating the absolute position is, for example, numerical data that represents the distance and angle from the fixed point to the measurement point (or with reference to the fixed point).

Further, the "information indicating the inclination angle of the core material" is each inclination attached to the core material 21 with reference to a predetermined position (a predetermined point, a predetermined line, or a predetermined surface) on the core material 21. It includes information representing the tilt angle detected by the angle detection unit 4 and information that serves as a reference when calculating the tilt angle corresponding to each tilt angle detection unit 4. The information representing the detected tilt angle is digital or analog data representing the angle of one axis or two axes representing the tilt angle. The reference information when calculating the inclination angle is, for example, digital or analog data representing the gravitational acceleration of three axes.

Further, the "absolute displacement" is a temporal (temporal) change in the position of the measurement point in the predetermined geodetic system, or a temporal change in the position of the measurement point with respect to the predetermined fixed point. Further, the "relative displacement" of the core material is a change in the position of each measurement point on the core material due to deformation of the core material with reference to a predetermined point (a predetermined reference line or a reference surface) on the core material. Deviation).

As shown in FIG. 2, for example, the output unit 13 outputs information representing the absolute displacement AD of the measurement point 3 and information representing the relative displacement RD of each inclination angle detection unit 4 of the core material 21 together. FIG. 2 is a perspective view schematically showing an example of displacement of the retaining wall 2 shown in FIG. In FIG. 2, the same reference numerals are used for the same configurations as those shown in FIG. In FIG. 2, the absolute displacement AD of the measurement point 3 is indicated by a chain line arrow, and the relative displacement RD corresponding to each inclination angle detection unit 4 is indicated by a solid line arrow. Further, the retaining wall 2 and the core material 21 at the time of construction (before excavation) are indicated by chain lines, the retaining wall 2 at the time of displacement is indicated by a broken line, and the core material 21 at the time of displacement is indicated by a solid line.

As described above, the measurement system 1 of this reference example includes an absolute position information acquisition unit 11, an inclination angle information acquisition unit 12, and an output unit 13. Then, the absolute position information acquisition unit 11 acquires information representing the absolute position of a predetermined measurement point 3 of the retaining wall head 2a configured by using the core material 21 having a longitudinal direction in the excavation direction. Further, the inclination angle information acquisition unit 12 detects the inclination angle of information indicating the inclination angle of the core material 21 measured by using a plurality of inclination angle detection units 4 attached to the core material 21 at predetermined intervals in the longitudinal direction. Obtained for each part 4. Further, the output unit 13 represents the information representing the absolute displacement based on the information representing the absolute position acquired by the absolute position information acquisition unit 11 and the relative displacement based on the information representing the tilt angle acquired by the tilt angle information acquisition unit 12. The information is also output. Therefore, it is possible to easily monitor the overall behavior of the ground including the periphery of the excavation area during the entire period of root cutting and retaining work.

<Second reference example>
Next, the measurement system 1a according to the second reference example will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic diagram for explaining a configuration example of the measurement system 1a according to the second reference example. FIG. 4 is a plan view schematically showing an example of displacement of the retaining wall 2 shown in FIG. In addition, in FIG. 3 and FIG. 4, the same reference numerals are used for the same configurations as those shown in FIGS. 1 and 2.

The measurement system 1a shown in FIG. 3 includes a data processing device 8 and a notebook personal computer 9. The data processing device 8 shown in FIG. 3 corresponds to the absolute position information acquisition unit 11 and the inclination angle information acquisition unit 12 of the first reference example shown in FIG. Further, the notebook personal computer 9 shown in FIG. 3 corresponds to the output unit 13 of the first reference example shown in FIG.

The measurement system 1a shown in FIG. 3 measures the absolute displacement in the horizontal and vertical directions for the retaining wall head 2a, and the inclination angle detecting unit 4 arranged in the retaining wall 2 measures the horizontal (out-of-plane) direction of the wall surface. It is a measurement system that three-dimensionally visualizes the overall behavior of the ground including the area around the excavation area in root cutting and retaining work in combination with the measurement of relative displacement.

A non-contact measuring instrument is used to measure the absolute displacement of the head of the retaining wall 2a. For example, the reflection prism 3a is installed on the head portion 2a of the retaining wall, the reflection prism 3a is sequentially measured from the total station 31 installed at the fixed point (or referring to the fixed point), and the absolute displacement amount of each point is calculated. If the accuracy can be ensured, a method may be used in which a GNSS observation point is provided on the head 2a of the retaining wall and the absolute displacement is measured by using the satellite 32 of the global navigation satellite system.

The relative displacement of the retaining wall 2 is measured by using the inclination angle detecting unit 4 installed in advance (or at the same time as the construction) before the retaining wall. As the inclination angle detection unit 4, a MEMS acceleration sensor, which is inexpensive for an inclinometer, can be installed on the retaining core material 21 (H-shaped steel). The measurement of the relative displacement is intended to capture the surface behavior of the retaining wall 2, and is realized by building the core material 21 in which the plurality of inclination angle detecting portions 4 are arranged at intervals of 2 to 5.

By combining the absolute displacement data and the relative displacement data of the retaining wall 2 measured by the above method, the overall behavior of the retaining wall 2 generated during excavation can be grasped three-dimensionally. FIG. 4 shows a planar schematic diagram of the obtained measurement results. In FIG. 4, the mountain retaining wall 2 before mining is shown as a retaining wall 2-1 and the retaining wall 2 after mining is shown as a retaining wall 2-2. In the example shown in FIG. 4, in the retaining wall 2-2, an absolute displacement AD which is a translation with respect to the retaining wall 2-1 and a relative displacement RD which is a deformation with respect to the retaining wall 2-1 occur.

The measurement system 1a shown in FIG. 3 takes the measurement data into the data processing device 8 by wireless communication, plots the data on the display screen 91 corresponding to the surface of the retaining wall 2, and displays the displaced image of the retaining wall 2. Visualize.

Further, when the structure 5 is close to the vicinity of the excavation area, the reflection prism 301a is installed in the structure 5, the reflection prism 301a is sequentially measured from the total station 31, and the absolute displacement amount of each point is calculated. By measuring the displacement of the nearby structure 5 using a non-contact measuring instrument, it is possible to quantitatively evaluate the influence of the displacement of the retaining wall 2 on the periphery.

According to this reference example, it is possible to easily monitor the overall behavior of the ground including the periphery of the excavation area during the entire period of root cutting / retaining work. This makes it easier to capture the phenomenon that causes the displacement. In other words, this system is used to ensure safety during construction and to make decisions on selecting countermeasures when a problem occurs.

<Third reference example>
Next, the measurement system 1b according to the third reference example will be described with reference to FIGS. 5 to 7. FIG. 5 is a schematic diagram for explaining a configuration example of the measurement system 1b according to the third reference example. FIG. 6 is a plan view schematically showing a configuration example of the tape type inclinometer 40 shown in FIG. FIG. 7 is a schematic view showing an example of attaching the tape type inclinometer 40 shown in FIG. 6 to the core material 21. In FIGS. 5 to 7, the same reference numerals are used for the same configurations as those shown in FIGS. 1 and 2.

The measurement system 1b shown in FIG. 5 has the same configuration as the measurement system 1 shown in FIG. 1 or the measurement system 1a shown in FIG. In this case, the measurement system 1b shown in FIG. 5 is installed in the field office 201. In the third reference example, the configuration for measuring the information used by the measurement system 1b, and the configuration for measuring the inclination angle of the core material 21, is different from the first reference example and the second reference example. Note that FIG. 5 omits the illustration of the configuration related to the measurement of absolute displacement.

The measurement system 1b shown in FIG. 5 measures the inclination angle of the core material 21 using the tape type inclinometer 40 shown in FIG. Further, the measurement system 1b acquires the data measured by the tape type inclinometer 40 via the transmission unit 101 and the reception unit 102. As shown in FIG. 6, the transmission unit 101 includes a power supply 401, a data logger 402, and a transmitter 403. The power supply 401 supplies a predetermined electric power to the tape type inclinometer 40. The data logger 402 records the data measured by the tape-type inclinometer 40 and transmits / receives a predetermined control signal to / from the tape-type inclinometer 40. The transmitter 403 transmits the data recorded in the data logger 402 to the receiving unit 102. Further, the receiving unit 102 receives the data transmitted by the transmitter 403 and transmits it to the measurement system 1b.

The tape-type inclinometer 40 shown in FIG. 6 is composed of a tape-shaped flexible substrate 41, a plurality of sensors 42, wirings 51 to 55 for electrically connecting the sensors 42, electrode fittings 43 to 47, 63 to 67, and the like. There is. The sensor 42 is equipped with a MEMS 3-axis acceleration sensor and a CPU (central processing unit). For signal transmission, for example, a communication standard (1-WIRE (registered trademark), SDI (serial digital interface), etc.) for measuring by connecting a plurality of sensors 42 to one cable in a worm-like manner is used. The sensor 42 has a configuration corresponding to the tilt angle detection unit 4 in the first reference example and the second reference example. That is, in the tape type inclinometer 40, the sensor 42 having a configuration corresponding to the inclination angle detection unit 4 is continuously connected on the tape-shaped substrate.

In the tape type inclinometer 40, a plurality of units 4a having one sensor 42 are continuously connected, and the sensors 42 are arranged at intervals of several tens of cm, for example. Further, an identification ID (identification code) is assigned to the sensor 42. In the measurement of the horizontal displacement amount, the sensor 42 detects the change in the gravitational acceleration of the three orthogonal axes, converts this into an inclination angle, and further multiplies the inclination angle by the distance to convert it into the horizontal displacement amount.

The electrode fittings 63 to 67 that electrically connect the units 4a have a structure that can be cut in the width direction, and electrodes that can be wired from the cut portion are formed between the cut units 4a. Power is supplied from the electrode fittings 43 and 44 at the end of the tape (end of the flexible substrate 41), and measurement data is collected by connecting the electrode fittings 45 to 47 at the end of the tape and the data logger 402.

Inclination data is collected according to the following procedure. (1) A measurement request is issued by designating an ID from the data logger 402 side. (2) Only the sensor 42 corresponding to the ID responds and transmits the measurement data. (3) The data logger 402 interprets and stores the data.

Next, an example of attaching the tape type inclinometer 40 to the core material 21 will be described with reference to FIG. 7. As shown in FIG. 7, the tape-type inclinometer 40 can be installed on the retaining core member 21. For example, when the core material 21 is an H-shaped steel, the tape-type inclinometer 40 cut according to the length of the core material 21 is a web 21a (FIG. 7A) or a flange 21b (FIG. 7B) using an adhesive or the like. It can be pasted on 7 (b)).

As shown in FIG. 5, the data measured by the tape type inclinometer 40 installed on the retaining wall 2 is collected by the data logger 402 shown in FIG. 6, and the collected data is received by the field office 201 by wireless communication. It is transmitted to the section 102, and the site office 201 can constantly monitor the detailed displacement of the retaining wall.

According to the third reference example, by using a relatively inexpensive sensor, it is possible to reduce the physical cost as compared with the measurement using the conventional inclinometer. In addition, it is possible to acquire high-density and continuous data on the displacement of the retaining wall, and a detailed displacement distribution can be obtained.

<First Embodiment>
Next, the measurement system 100 according to the first embodiment of the present invention will be described with reference to FIGS. 10, 11, 12, 13, 14, and 8.
FIG. 10 is a schematic diagram for explaining a configuration example of the measurement system 100 according to the first embodiment of the present invention. In addition, FIG. 11 is a schematic diagram for explaining a configuration example of the 3-axis MEMS acceleration sensor (tilt angle detection unit 4) according to the first embodiment of the present invention. Further, FIG. 12 is a diagram showing the relationship between the accuracy of the acceleration sensor shown in FIG. 11 and the installation interval in the depth direction (excavation direction). Further, FIG. 13 is a diagram schematically showing an example of the relative displacement of the retaining wall 2 on the excavation plane. Further, FIG. 14 is a diagram showing the relationship between the accuracy of the acceleration sensor shown in FIG. 11 and the installation interval in the horizontal direction.
In FIG. 10, the same reference numerals are used for the same configurations as those shown in FIG. That is, the measurement system 100 is configured in a form corresponding to the measurement system 1 shown in FIG.
Here, the differences between FIGS. 1 and 10 are as follows.
That is, in FIG. 10 showing the measurement system 100, the inclination angle detection unit is composed of a plurality of inclination angle detection units 4 attached to the core material 21 at a predetermined first interval lv in the longitudinal direction (excavation direction). The tilt angle detection unit 4v (first tilt angle detection unit).
That is, in FIG. 1 showing the measurement system 1, five (plurality) inclination angle detection units 4 are attached to the core material 21 at predetermined intervals (constant intervals) in the longitudinal direction (excavation direction).
On the other hand, in FIG. 10 showing the measurement system 100, the core material 21 is provided with five (plurality) inclination angle detection units 4 constituting the inclination angle detection unit 4v in the longitudinal direction (excavation direction). It is attached at the first interval lv.

Further, in FIG. 10 showing the measurement system 100, the inclination angle detection unit detects a plurality of inclination angles attached to the core material 21 at a predetermined second interval lh in the horizontal direction, which is a direction orthogonal to the longitudinal direction. The tilt angle detection unit 4h (second tilt angle detection unit) composed of the unit 4.
That is, in FIG. 1, which shows the measurement system 1, two (two) inclination angle detecting portions 4 in the horizontal direction, which is a direction perpendicular to the longitudinal direction, are provided at predetermined intervals (constant intervals) on the core material 21. ) Is attached.
On the other hand, in FIG. 10 showing the measurement system 100, the core material 21 has two (plurality) tilt angles constituting the tilt angle detection unit 4h in the horizontal direction, which is a direction perpendicular to the longitudinal direction. The detection unit 4 is attached at a predetermined second interval lh.

As described above, in the measurement system 100 of the present embodiment, in the measurement management of the retaining wall 2, the MEMS type acceleration sensor (tilt angle detection unit 4) is attached to the core material 21 of the retaining wall 2 and the wall surface is horizontal (outside the plane). When measuring the relative displacement in the direction, the tilt angle detection units 4v and 4h have installation intervals (predetermined first interval lv, predetermined second interval hl) determined by a rational installation method of the sensor based on the sensor accuracy. )have.

Further, as shown in FIG. 10, the output unit 13 includes a first interval determination unit 13v for determining a predetermined first interval lv and a second interval determination unit 13h for determining a predetermined second interval lh. It is composed of.

[Determination of installation interval lv in the depth direction]
Therefore, first, a method of determining the installation interval lv (predetermined first interval) in the depth direction will be described.
As shown in FIG. 11, the 3-axis MEMS acceleration sensor (tilt angle detection unit 4) can detect the tilt angle of the measuring point by detecting the direction of action of gravity. As shown in FIG. 11, in the three-dimensional Cartesian coordinate system O-xyz, when the tilt angle detection unit 4 rotates one axis around the y-axis, the acceleration detected by the tilt angle detection unit 4 is αx, αz. The inclination angle θy around the y-axis is calculated by the following equation (1).
θy = sin ^-1 (αx / 1G) ... (1)
In addition, "1G" represents the gravity applied to the earth = about 9.806 m / sec ^ 2.

Here, by multiplying the inclination angle θy by the distance l from the base point, the horizontal displacement amount δx of the measuring point can be obtained as expressed by the following equation (2).
δx = l · sinθy… (2)

Therefore, the correlation between the acceleration αx detected by the tilt angle detection unit 4, the distance l from the base point, and the horizontal displacement amount δx of the station is determined by the following equation (3) using equations (1) and (2). ).
l = δx ・ (1G / αx)… (3)
Here, if the minimum unit αx_min that the inclination angle detection unit 4 can detect is substituted for αx in the above equation (3) and the minimum displacement unit δx_min required for retaining measurement management is substituted for δx, the sensor in the depth direction of the retaining wall ( Tilt angle detection unit 4) The installation interval lv is expressed by the following equation (4).

lv = δx_min ・ (1G / αx_min) ... (4)
In the conventional retaining measurement, displacement measurement in millimeters (mm) has been carried out using a multi-stage inclinometer or an insertion inclinometer.
Therefore, when δx_min = 0.01 mm, the measurement accuracy is excessive, and when δx_min = 1 mm, the measurement accuracy for guaranteeing the resolution in millimeters is insufficient.

Taking these factors into consideration, it is rational to set the minimum displacement unit δx_min required for the sensor (tilt angle detection unit 4) to 0.05 to 0.5 mm in practice as expressed by the following equation (5). is there.
0.05 ≤ δx_min ≤ 0.5 ... (5)
Here, assuming that δx_min = 0.1 that satisfies the above equation (5), a trial calculation of the installation interval lv in the depth direction using the equation (4) is as shown in FIG.

That is, as shown in FIG. 12, the relationship between the minimum unit αx (accuracy of the acceleration sensor) that can be detected by the sensor and the installation interval lv in the depth direction (excavation direction) can be understood.
That is, the first interval determination unit 13v in the output unit 13 can detect the minimum displacement unit δx_min (minimum unit of displacement detected by the inclination angle detection unit) required for the sensor (tilt angle detection unit 4) and the sensor. The installation interval lv as shown in FIG. 12 is determined according to the minimum unit αx.
As a result, the output unit 13 uses the determined installation interval lv, and as shown in FIG. 8, the measurement point P1 (base point: the lowest inclination angle detection unit 4 in the excavation direction) when there are n survey lines. Horizontal displacement amount δ1, ..., of the measuring point P2 (the position of the second inclination angle detection unit 4 from the bottom in the excavation direction) corresponding to the reference line which is a straight line in the vertical direction (excavation direction) passing through the position). The horizontal displacement amount δn of the station Pn + 1 (the position of the (n + 1) th tilt angle detection unit 4 from the bottom in the excavation direction), that is, n horizontal displacement amounts δ1 to horizontal displacement amount δn (first relative displacement). Information) can be obtained accurately.

[Determination of installation interval lh in the horizontal direction]
Subsequently, a method of determining the installation interval lh (predetermined second interval) in the horizontal direction will be described.
Since it is difficult to easily measure the stress state in the management of the abdomen, which is a timbering support, visual observation is the main method. However, the abdomen is often hidden by the inspection passage of the retaining wall or the girder, and there is a problem that visual observation itself is difficult.
Here, "raising the belly" is a member used for retaining the pile so that the soil does not collapse when excavating the ground, that is, when excavating the ground, a sheet pile or the like is used to prevent the surrounding soil from collapsing. It is a member that holds the mountain retaining wall 2 so that it does not collapse. In the present embodiment, the "raised abdomen" is attached to the core material 21 at a distance of a predetermined distance from the retaining wall head 2a in the depth direction, for example, as described in Japanese Patent Application Laid-Open No. 2018-188874. ing.

That is, the tilt angle detection unit 4h (second tilt angle detection unit) as the sensor (tilt angle detection unit 4) is located at the position of the abdomen attached to the core material 21 (in the core material 21 shown in FIG. 1). Any one of the tilt angle detection units 4h including the first tilt angle detection unit 4 from the mountain retaining wall head 2a to the fifth tilt angle detection unit 4h. It is assumed that it is installed corresponding to the position of the tilt angle detection unit 4h).
Therefore, in the present embodiment, the installation interval lh of the tilt angle detection unit 4 constituting the sensor (tilt angle detection unit 4h) in the horizontal direction is proposed for the measurement management of the abdomen. The proposed installation interval lh is determined by the second interval determination unit 13h as the installation interval lh of the inclination angle detection unit 4 constituting the sensor (inclination angle detection unit 4h) in the horizontal direction.

First, the deflection angle θx of the abdomen is expressed by the following equation (6).
θx = δx'/ Le ... (6)
Here, Le is the effective span length of the abdomen, and δx'is the deflection of the abdomen.

Since the allowable deflection of the abdomen differs depending on the installation status of the mountain retaining frame, the specific deflection limit is not described in the mountain retaining design guideline. In the design, the abdomen is stress-verified as a beam material that receives an evenly distributed load, and safety is confirmed. The maximum deflection of the fixed beam at both ends (the girder between the raised part attached to the retaining wall at one end and the raised part attached to the retaining wall at the other end) is 1/300 according to the steel structure design standard. It is shown as follows.

Therefore, it is rational to set the allowable deflection angle θx for abdominal upset to θx ≦ 1/300.
Since the abdominal length is designed in units of 0.1 m (100 mm), substituting Le = 100 (mm) into equation (6), the conditions for the minimum unit of abdominal deflection δx_min'(mm) are as follows. It becomes like the equation (7).
δx_min'≤1 / 3 ... (7)

Here, by substituting l, θx, and δx shown in FIG. 13, which schematically shows an example of the relative displacement of the retaining wall 2 on the excavation plane, into the following equations (11) to (12), the equation ( 13) can be obtained.
θx = sin ^-1 (αx / 1G) ... (11)
δx = l · sinθx… (12)
l = δx ・ (1G / αx)… (13)

Here, if the minimum unit αx_min that can be detected by the tilt angle detection unit 4 is substituted for αx in the above equation (13) and the minimum displacement unit δx_min'required for the retaining measurement management is substituted for δx, the sensor in the horizontal direction of the retaining wall is obtained. (Inclination angle detection unit 4) The installation interval lh has the same shape as the equation (4) and is represented by the following equation (8).
lh = δx_min'・ (1G / αx_min) ... (8)
Here, assuming that δx_min'= 0.3 that satisfies the equation (7), the installation interval lh in the horizontal direction can be calculated as shown in FIG. 14 using the equation (8).

That is, as shown in FIG. 14, the relationship between the minimum unit αx (accuracy of the acceleration sensor) that can be detected by the sensor and the installation interval lh in the horizontal direction can be understood.
That is, the second interval determination unit 13h in the output unit 13 detects the minimum displacement unit δx_min'(minimum unit of displacement detected by the inclination angle detection unit) required for the sensor (tilt angle detection unit 4) and the sensor. The installation interval lh as shown in FIG. 14 is determined according to the minimum possible unit αx.
As a result, the output unit 13 uses the determined installation interval lh, and as shown in FIG. 8, the station P1 (base point: the position closest to the four corners of the excavation plane before deformation) when there are n survey lines. The position of the second tilt angle detection unit 4 corresponding to the reference line, which is a straight line in the horizontal direction passing through the position of the inclination angle detection unit 4 attached to the station P2 (the position of the second inclination angle detection unit 4 separated from the measurement point P1 by the installation interval lh). Horizontal displacement amount δ1, ..., Horizontal displacement amount δn at the station Pn + 1 (position of the (n + 1) th tilt angle detection unit 4 separated from the station P1 by the installation interval lh × n), that is, n horizontal displacement amounts. δ1 to horizontal displacement amount δn (information representing the second relative displacement) can be accurately obtained.

As described above, in the measurement system 100, the installation interval of the acceleration sensor (tilt angle detection unit 4) used for the retaining measurement in the depth direction is designed based on the equation (4). As a result, δx_min in the formula (4) can be practically in the range of the formula (5) (0.05 to 0.5 mm).
In addition, the measurement system 100 can be used for measuring and managing the deflection of the abdomen.
Further, in the measurement system 100, the installation interval of the acceleration sensor (tilt angle detection unit 4) used for the retaining measurement in the horizontal direction is designed based on the equation (8). As a result, δx_min'of the formula (8) can be practically within the range of the formula (7) (1/3 mm or less).

In this way, when the acceleration sensor (tilt angle detection unit 4) is used for the retaining measurement, the accuracy required for the retaining measurement is achieved by using the proposed design formulas (5) and (7) in the measurement system 100. It is possible to determine the performance and installation interval (predetermined first interval, predetermined second interval) of the sensor that satisfies (the minimum unit of displacement δx_min required for the sensor (tilt angle detection unit 4)).
That is, in the measurement system 100, in the measurement management of the retaining wall 2, a MEMS type acceleration sensor (tilt angle detecting unit 4) is attached to the core material of the retaining wall 2 to measure the relative displacement in the horizontal (out-of-plane) direction of the wall surface. At that time, the tilt angle detection units 4v and 4h have an installation interval (predetermined first interval lv, predetermined second interval hl) determined by a rational installation method of the sensor based on the sensor accuracy.

Therefore, according to the embodiment of the present invention, the overall behavior of the ground including the periphery of the excavation area during the entire period of the root cutting / retaining work is the inclination angle arranged with a predetermined first interval lv. The detection unit 4v (first tilt angle detection unit) and the tilt angle detection unit 4h (second tilt angle detection unit) arranged with a predetermined second interval lh enable highly accurate monitoring.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and the design and the like within a range not deviating from the gist of the present invention are also included. For example, as shown in FIG. 10, the measurement system 100 acquires absolute position information that represents the absolute position of a predetermined measurement point 3 of the retaining wall head 2a measured by the absolute position measurement unit 30 in a non-contact manner. It may have a part 11. Thereby, the measurement system 100 can output the information representing the absolute displacement based on the information representing the absolute position, the information representing the first relative displacement, and the information representing the second relative displacement together.

1,1a, 1b, 100 ... Measurement system, 2 ... Mountain retaining wall, 2a ... Mountain retaining wall head, 3 ... Measurement point, 4 ... Tilt angle detector, 4v, 4h ... Tilt angle detection unit, 11 ... Absolute position information acquisition Unit, 12 ... Tilt angle information acquisition unit, 13 ... Output unit, 21 ... Core material, 40 ... Tape type inclinometer, 42 ... Sensor

Claims (6)

In a retaining wall constructed by using a core material having a longitudinal direction in the excavation direction which is a vertical direction, the retaining wall is composed of a plurality of inclination angle detection units attached to the core material at a predetermined first interval in the longitudinal direction. Information representing the tilt angle of the core material measured by using the first tilt angle detection unit is acquired from the first tilt angle detection unit.
The measurement was performed using a second tilt angle detection unit composed of a plurality of tilt angle detection units attached to the core material at predetermined second intervals in the horizontal direction, which is a direction orthogonal to the longitudinal direction. An inclination angle information acquisition unit that acquires information indicating an inclination angle of the core material from the second inclination angle detection unit, and
Information representing the first relative displacement based on the information representing the tilt angle acquired from the first tilt angle detection unit and the second relative displacement based on the information representing the tilt angle acquired from the second tilt angle detection unit. A measurement system characterized by having an output unit that outputs information to be represented. The output unit determines the predetermined first interval and the predetermined second interval according to the minimum unit of displacement detected by the inclination angle detection unit and the minimum unit that can be detected by the inclination angle detection unit. The measurement system according to claim 1, wherein the measurement system is characterized in that. The measurement system according to claim 1 or 2, wherein the second inclination angle detection unit is attached corresponding to an arrangement position of an abdomen attached to the core material. An absolute position information acquisition unit that acquires information representing an absolute position of a predetermined measurement point of the head of the retaining wall in the longitudinal direction is provided.
The output unit
It is characterized by outputting information representing the first relative displacement, information representing the second relative displacement, and information representing absolute displacement based on the information representing the absolute position acquired by the absolute position information acquisition unit. The measurement system according to any one of claims 1 to 3. In a retaining wall constructed by using a core material having a longitudinal direction in the excavation direction which is a vertical direction, the retaining wall is composed of a plurality of inclination angle detection units attached to the core material at a predetermined first interval in the longitudinal direction. Information representing the tilt angle of the core material measured by using the first tilt angle detection unit is acquired from the first tilt angle detection unit.
The measurement was performed using a second tilt angle detection unit composed of a plurality of tilt angle detection units attached to the core material at predetermined second intervals in the horizontal direction, which is a direction orthogonal to the longitudinal direction. Using the tilt angle information acquisition unit that acquires information representing the tilt angle of the core material from the second tilt angle detection unit,
The output unit is based on the information representing the first relative displacement based on the information representing the tilt angle acquired from the first tilt angle detection unit and the information representing the tilt angle acquired from the second tilt angle detection unit. 2 A measurement method characterized by outputting information representing relative displacement. The predetermined first interval and the predetermined second interval in the measurement system according to claim 1 are set to the minimum unit of displacement detected by the inclination angle detection unit and the minimum unit that can be detected by the inclination angle detection unit. An interval determination method characterized in that the determination is made accordingly.

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