CN102102537B - Tunnel surrounding rock radial stress strain distributed monitoring technology - Google Patents

Abstract

The invention belongs to the technical field of geotechnical engineering monitoring, and relates to a distributed optical fiber sensing technology-based tunnel surrounding rock radial stress strain distributed monitoring technology. A distributed optical fiber sensor is conveyed to a hole bottom of a radial monitoring hole through a supporting rod member; the supporting rod member (1) and a grouting exhaust pipe (13) are plugged in the hole at a hole orifice through a hole orifice fixing system; a grouting hole (4) is connected to a grouting machine through a grouting pipe; a gap between the optical fiber sensor and a surrounding rock is filled by injecting grout which is matched with modulus of deformation of the surrounding rock into the hole, so that the optical fiber sensor and the surrounding rock cooperatively deform; the optical fiber sensor comprises a distributed optical fiber strain optical fiber sensor and a temperature optical fiber sensor; the distributed optical fiber sensor of each monitoring hole is connected in series to an optical fiber strain analyzer Brillouin optical time domain reflectormeter (BOTDR) by fusion welding; measurement and positioning functions of Brillouin frequency shift on each point of an optical fiber are finished by measuring power of received Brillouin backscattered light; and strain distribution and temperature distribution in the radial direction in the surrounding rock can be obtained to evaluate and forecast the stability of the surrounding rock according to the linear relation between the Brillouin frequency shift and the strain as well as the temperature.

Description

Distributed Monitoring Technology of Radial Stress and Strain in Tunnel Surrounding Rock

technical field

The invention belongs to the technical field of geotechnical engineering monitoring, and relates to a distributed monitoring technology for radial deformation of tunnel surrounding rock based on distributed optical fiber sensing technology.

Background technique

Our country is currently in a period of large-scale construction, and a large number of tunnel projects have appeared in various fields such as transportation, national defense, and water conservancy. During the construction and use of the tunnel, the stress and strain of the surrounding rock will change, and it is an extremely important task to ensure the stability and safety of the surrounding rock. Radial stress and strain monitoring of tunnel surrounding rock is the main means and basis for determining the influence range of tunnel surrounding rock loosening circle, judging the stability of surrounding rock, grasping the development and change law of stress and strain of surrounding rock, and evaluating the support effect.

During the excavation of the tunnel, because the rock and soil on one side are excavated to unload the surrounding rock, the surrounding rock changes from a state of stress balance to an unbalanced state. A state of equilibrium to maintain the stability of the surrounding rock. During the stress redistribution process of the surrounding rock, a surrounding rock loosening circle will be generated, and the rock and soil mass inside the circle will undergo radial stress-strain changes, while the outside of the circle will basically not be affected. Monitoring the radial deformation of the surrounding rock is one of the most reliable methods to determine the influence range of the surrounding rock loose circle and ensure the stability and safety of the surrounding rock. The more common monitoring contents of tunnel surrounding rock stability safety monitoring include surrounding rock deformation and displacement monitoring, support structure and surrounding rock contact stress monitoring, etc. ) and optical measuring instruments (levels, total stations, etc.). These monitoring methods can only monitor some information on the surrounding rock interface but cannot understand the stress and strain inside the entire surrounding rock; conventional sensors are mostly point sensors, which are required when the monitoring area is large and the spatial density of monitoring points is high. The deployment of a large number of sensors will inevitably lead to a sharp increase in the complexity and cost of the monitoring work, and the lack of connection between the monitoring data cannot reflect the overall deformation law of the surrounding rock. In addition, due to the interference of corrosion and lightning, the service life and stability of conventional electrical sensing elements are difficult to meet the requirements of long-term monitoring. Therefore, a new distributed optical fiber monitoring method is of great significance to the monitoring of tunnel surrounding rock in modern engineering.

Distributed sensing technology based on Brillouin Optical Time Domain Reflectormeter (abbreviation: BOTDR) is a cutting-edge technology developed in the field of optoelectronic information in recent years. In addition to the corrosion resistance of general optical fiber sensing technology , anti-interference and other characteristics, the most important thing is that it has the characteristics of distributed measurement, which can obtain the strain and temperature information of any point along the optical fiber. This technology is used to monitor the radial deformation of the surrounding rock of the tunnel, evaluate the loose circle of the surrounding rock, and evaluate and predict the stability of the surrounding rock.

Contents of the invention

Aiming at the existing problems in surrounding rock monitoring, combined with the characteristics of tunnel surrounding rock stress redistribution, a monitoring technology for tunnel surrounding rock deformation based on distributed optical fiber sensing technology is proposed.

The purpose of the present invention is achieved like this:

A distributed monitoring technology for the radial stress and strain of the surrounding rock of the tunnel. The monitoring hole is drilled radially along the tunnel; the distributed optical fiber sensor is sent to the bottom of the radial monitoring hole through the support rod of the fixed support system; The orifice fixing system fixes the support rods, the grouting exhaust pipe and seals the orifice; the gap between the optical fiber sensor and the surrounding rock is filled by grouting, so that the optical fiber sensor and the surrounding rock are deformed in coordination; the optical fiber sensor includes distributed optical fiber strain sensors and The temperature-compensated optical fiber sensor, the distributed optical fiber strain sensor applies quantitative pre-tension through the spring balance, and the temperature-compensated optical fiber sensor does not apply pre-tension; the distributed optical fiber strain sensor is a GFRP reinforced tight-sleeve single-mode optical fiber sensor, which is used for strain monitoring The temperature compensation optical fiber sensor is an armored loose-tube single-mode optical fiber sensor, which is used for temperature compensation of the strain amount; the distributed optical fiber sensor of each monitoring hole is connected to the optical fiber strain analyzer BOTDR in series by welding; the transmission of the strain amount and temperature The sensing is based on Brillouin backscattering. By measuring the received Brillouin backscattering light power, the measurement and positioning functions of the Brillouin frequency shift of each point on the fiber are completed; according to the Brillouin frequency shift and strain The linear relationship between the temperature and the radial strain distribution inside the surrounding rock can be obtained, and the radial strain distribution of the tunnel surrounding rock can be obtained by removing the influence of temperature; by multiplying and summing the measured strain distribution, the The radial deformation of the surrounding rock can be used to evaluate and predict the stability of the surrounding rock.

Specifically, the monitoring holes are drilled along the radial direction of the tunnel, and the layout position is determined according to the actual monitoring needs; the diameter of the monitoring holes is 70 mm to 90 mm, and the length of the monitoring holes can be selected to be more than 1.5 times the calculated value or empirical value of the surrounding rock loose circle, so that the monitoring The hole passes through the bottom of the loose circle of the surrounding rock to reach the stable area of the surrounding rock.

The fixed support system is composed of optical fiber sensor support rods, grouting exhaust pipes, and orifice fixing systems; the support rods are made of high-strength stainless steel pipes, each section of rods is 1m long, and the rods are connected by external joints. It is suitable for monitoring holes of different lengths; arc grooves are left at the ends of the rods to fix the optical fiber sensors; the exhaust pipes are made of PVC pipes, each section is 2m to 3m, and are connected by PVC pipe joints. During installation, one end of the grouting exhaust pipe is equipped with an umbrella-shaped protective cover, which is connected to the bottom of the monitoring hole one by one, and the other end of the grouting exhaust pipe is drawn from the outlet of the grouting exhaust pipe on the cover plate of the orifice fixing system; The fixing system includes two parts, the sleeve and the cover plate; the diameter of the sleeve is slightly larger than the monitoring aperture, and there is a circular skirt at the tail, and there are bolt fixing holes on the skirt; the diameter of the cover plate is the same as that of the sleeve skirt, and there is a Bolt fixing holes corresponding to the skirt, rubber gaskets are placed between the cover plate and the sleeve skirt; the support rod is fixed at the center of the cover plate, and two optical fiber sensor lead-out holes and one grouting hole are opened in the middle area of the cover plate hole, 1 grouted exhaust pipe outlet.

By injecting grout into the borehole, it is used to fill the gap between the optical fiber sensor and the surrounding rock, so that the optical fiber sensor and the surrounding rock are deformed in harmony. The ratio of the grout needs to be determined according to the modulus of the tunnel surrounding rock.

The sensing of optical fiber strain and temperature is based on Brillouin backscattering technology. There is a good linear relationship between the frequency shift of the Brillouin backscattered light and the strain and temperature changes of the fiber. When the stress and strain of the surrounding rock change, the optical fiber sensor implanted in the surrounding rock deforms synchronously with the rock and soil to generate tension and compression. By measuring the frequency shift of the Brillouin backscattered light, and according to the linear relationship between the frequency shift and the strain and temperature, the location of the optical fiber sensor, the strain distribution and temperature distribution of the surrounding rock can be obtained, through product, integral, etc. Calculate the stress and deformation (displacement) of the surrounding rock in the radial direction of the tunnel. The precise spatial location of the event point on the optical fiber can be carried out by optical time domain reflectometry.

The linear relationship between the above frequency shift and strain temperature is:

${\mathrm{<span\; class="notranslate">\; \&nu;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&nu;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; \&PartialD;</span>{\mathrm{<span\; class="notranslate">\; \&nu;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; \&PartialD;</span>{\mathrm{<span\; class="notranslate">\; \&nu;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

The relationship between frequency shift and temperature of temperature compensation optical fiber is:

${\mathrm{<span\; class="notranslate">\; \&nu;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&nu;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; \&PartialD;</span>{\mathrm{<span\; class="notranslate">\; \&nu;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

The relationship between frequency shift and strain after deducting the influence of temperature is:

${\mathrm{<span\; class="notranslate">\; \&nu;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&nu;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; \&PartialD;</span>{\mathrm{<span\; class="notranslate">\; \&nu;</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

where ν _B (ε, T) is the frequency shift of Brillouin backscattered light under the action of strain and temperature, ν _B (0) is the initial frequency shift, ε, T are the strain and temperature acting on the optical fiber sensor .

The integral method for radial displacement calculation is:

${\mathrm{<span\; class="notranslate">\; S</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; dz</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

In the formula, S ₍₀₎ is the radial displacement value of the surrounding rock at the bottom of the measuring hole. Generally, the bottom of the hole is far away from the loose circle of the surrounding rock, and its displacement is zero, that is, S ₍₀₎ = 0; S _(h) is h The radial displacement value at ; ε _(z) is the strain distribution.

In order to meet the real-time and long-term requirements of radial stress and strain monitoring of tunnel surrounding rock, a monitoring system needs to be constructed. The system is composed of distributed optical fiber sensors, supporting fixtures, BOTDR data acquisition instrument, and data processing software; the strain distribution and temperature distribution of optical fiber sensors are measured by the data acquisition equipment BOTDR; the data processing software analyzes and analyzes the measured strain distribution data. calculate.

The greatest feature of the present invention is to invent a method for monitoring internal deformation of surrounding rocks by using distributed optical fiber sensing technology, and to construct a corresponding monitoring system. The first advantage of this distributed monitoring system is that sensors are implanted inside the surrounding rock to monitor the strain distribution inside the surrounding rock including the entire loose ring along the radial direction of the tunnel; the second advantage is that it can realize distributed monitoring and grasp the surrounding rock The deformation law in the overall radial direction; the third advantage is that the characteristics of optical fibers can be used to realize remote and long-distance monitoring; the fourth advantage is that due to the use of optical fibers and optical signals, it can be used in harsh environments such as lightning and humidity; fifth The first advantage is that it can realize automatic measurement and analysis, obtain the change law of deformation, displacement and stress of large-area rock and soil relatively quickly, give the loose circle range of surrounding rock in time, evaluate the integrity safety of surrounding rock and give early warning.

Description of drawings

Fig. 1 is a schematic diagram of a cover plate and a support bar of a fixed support system.

Fig. 2 is a schematic diagram of the sleeve of the orifice fixing system.

Fig. 3 is a schematic diagram of the assembly of the support rod and the optical fiber sensor.

Figure 4 is a schematic diagram of the grouting exhaust pipe.

Figure 5 is a schematic diagram of the connection of the grouting exhaust pipe.

In the figure, 1. Support rod, 2. Fixing bolt hole, 3. Rubber washer, 4. Grouting hole, 5. Optical fiber sensor outlet hole, 6. Support rod hole, 7. Grouting exhaust pipe outlet, 8 , the cover plate of the orifice fixing system, 9, the sleeve of the orifice fixing system, 10, the arc groove, 11, the distributed optical fiber strain sensor, 12, the temperature compensation sensor, 13, the grouting exhaust pipe, 14, Vent, 15, umbrella-shaped protective cover, 16, PVC pipe joint.

Detailed ways

Embodiments of the present invention are described in conjunction with accompanying drawings:

A distributed monitoring technology for radial stress and strain of surrounding rock in tunnels. Monitoring holes are drilled radially along the tunnel; distributed optical fiber sensors are sent to the bottom of the radial monitoring holes through the support rod 1 of the fixed support system; Fix the supporting rods, grouting exhaust pipe 13 and seal the orifice through the hole fixing system; fill the gap between the fiber optic sensor and the surrounding rock by grouting, so that the fiber sensor and the surrounding rock can be deformed in coordination; the fiber optic sensor includes distributed fiber optic strain Sensors and temperature-compensated optical fiber sensors, distributed optical fiber strain sensors apply quantitative pre-tension through spring scales, and temperature-compensated optical fiber sensors do not apply pre-tension; the distributed optical fiber strain sensors are GFRP reinforced tight-sleeved single-mode optical The temperature compensation optical fiber sensor is an armored loose-tube single-mode optical fiber sensor, which is used for temperature compensation of the strain amount; the distributed optical fiber sensor of each monitoring hole is connected to the optical fiber strain analyzer BOTDR in series by welding; the strain amount and temperature All sensors are based on Brillouin backscattering. By measuring the received Brillouin backscattering light power, the measurement and positioning functions of the Brillouin frequency shift of each point on the optical fiber are completed; according to the Brillouin frequency shift The linear relationship between strain and temperature can be used to obtain the radial strain distribution and temperature distribution inside the surrounding rock, and the radial strain distribution of the tunnel surrounding rock can be obtained by removing the influence of temperature; by multiplying and summing the measured strain distribution The radial deformation of the surrounding rock is obtained by calculation, and then the stability of the surrounding rock is evaluated and predicted.

The fixed support system is composed of an optical fiber sensor support bar 1, a grouting exhaust pipe 13, and an orifice fixing system; the support bar is made of high-strength stainless steel pipe, each section of the bar is 1m long, and external joints are used between the bars Connected to apply to monitoring holes of different lengths; arc grooves are left at the end of the rod to fix the fiber optic sensor; the exhaust pipe is made of PVC pipes, each section is 2m to 3m, and is connected through PVC pipe joints. During installation, one end of the grouting exhaust pipe is equipped with an umbrella-shaped protective cover, which is connected to the bottom of the monitoring hole one by one, and the other end of the grouting exhaust pipe is drawn from the grouting exhaust pipe outlet 7 of the cover plate of the orifice fixing system; the hole The mouth fixing system consists of two parts, the sleeve 9 and the cover plate 8; the diameter of the sleeve is slightly larger than the monitoring aperture, and there is a circular skirt at the tail, and a bolt fixing hole is left on the skirt; the diameter of the cover plate is the same as the sleeve skirt, and the most A bolt fixing hole corresponding to the skirt is left on the outside, and a rubber gasket is placed between the cover and the skirt of the sleeve; the support rod is fixed at the center of the cover, and two fiber optic sensor lead-out holes are set in the middle area of the cover 5. One grouting hole 4, one grouting exhaust pipe outlet 7.

The specific operation steps of the device involved in the technology of the present invention:

1) Drill a monitoring hole on the surrounding rock with a diameter of 70mm to 90mm. The measuring hole passes through the bottom of the surrounding rock loose circle to reach the stable area of the surrounding rock. The length of the measuring hole is 1.5 times the calculated or empirical value of the surrounding rock loose circle;

2) Drive into the sleeve (9), the diameter of the sleeve is slightly larger than the measuring hole, and the length of the sleeve is generally 50cm;

3) The length of the measuring hole, intercepting the distributed optical fiber strain sensor (11), the length is generally determined by (2L+5) m, wherein L is the length of the measuring hole; the temperature compensation sensor (12) is an armored loose-tube single-mode optical fiber sensor, The length is (L+5)m, and it can be arranged side by side with the distributed optical fiber strain sensor;

4) The midpoint of the distributed optical fiber strain sensor and the end of the temperature compensation sensor (corresponding to the bottom of the measuring hole) are fixed in the arc groove (10) at the top of the support rod (1), and the fiber optic sensor is connected through the support rod Send it into the monitoring hole, and the top of the support rod should reach the bottom of the measuring hole;

5) The supporting rod is fixed on the cover plate (8) of the hole fixing system, the cover plate and the skirt of the sleeve (9) are fixed by bolts, and a rubber gasket (3) is placed between the cover plate and the sleeve skirt to prevent Grout leakage occurs during grouting, the two ends of the optical fiber sensor are introduced and drawn out from the optical fiber sensor outlet hole (5) respectively, one end of the grouting exhaust pipe is connected to the grouting exhaust pipe outlet (7) on the cover plate, and the other end extends into the bottom of the measuring hole ;

6) Use a spring balance at the outlet of the optical fiber sensor to apply a quantitative pre-tension force to the strain optical fiber sensor, and inject the filling slurry through the grouting hole (4) under the premise of maintaining the pre-tension force, and remove the pre-tension force after the slurry solidifies;

7) BOTDR measures the strain distribution and temperature distribution of the optical fiber sensor, and the data processing and analysis software calculates the measured optical fiber strain and temperature data to obtain the deformation of the tunnel surrounding rock.

The above-mentioned distributed optical fiber measurement system, the distributed optical fiber sensor is composed of GFRP reinforced tight-sleeved single-mode optical fiber sensor and armored loose-sleeved single-mode optical fiber sensor, and the GFRP reinforced tight-sleeved single-mode optical fiber sensor is used for radial strain measurement of tunnel surrounding rock ; The armored loose-tube single-mode optical fiber sensor is used for radial temperature measurement of tunnel surrounding rock, and provides temperature compensation for strain measurement.

In the above-mentioned distributed optical fiber measurement system, a distributed optical fiber sensor is implanted inside the surrounding rock of the tunnel through the monitoring hole to measure the radial strain distribution inside the surrounding rock, and the temperature sensor provides temperature compensation.

In the above-mentioned distributed optical fiber measurement system, the optical fiber at the bottom of the hole is located outside the loosening circle of the surrounding rock, and the bottom of the hole is used as the base point, and the deformation distribution of the surrounding rock of the tunnel relative to the bottom of the hole is calculated from the strain distribution of the optical fiber.

In the above-mentioned distributed optical fiber measurement system, the optical fiber is not only a sensing element, but also a transmission medium for sensing information.

In the above-mentioned distributed optical fiber measurement system, the backscattered light collection device is a BOTDR. It can obtain the frequency shift of Brillouin scattered light at any point on the optical fiber, and at the same time obtain the strain distribution and temperature distribution in the borehole.

In the above-mentioned distributed optical fiber measuring system, data processing software calculates the measured data.

Claims (3)

1. A tunnel surrounding rock radial stress-strain distributed monitoring method is characterized in that: along the radial direction of the tunnel, the monitoring hole is drilled; the distributed optical fiber sensor is sent to the hole of the radial monitoring hole by the support bar of the fixed support system Bottom; the orifice fixes the support rods, grouting exhaust pipe and seals the orifice through the orifice fixing system; fills the gap between the optical fiber sensor and the surrounding rock by grouting, so that the optical fiber sensor and the surrounding rock are coordinated and deformed; the distributed optical fiber The sensor includes a distributed optical fiber strain sensor and a temperature-compensated optical fiber sensor. The distributed optical fiber strain sensor applies a quantitative pre-tension force through a spring balance; the temperature-compensated optical fiber sensor does not apply a pre-tension force; the distributed optical fiber strain sensor is a GFRP reinforced tight-buffered single-mode optical fiber sensor for the monitoring of strain; the temperature compensation optical fiber sensor is an armored loose-tube single-mode optical fiber sensor for temperature compensation of strain in long-term monitoring; the distributed optical fiber sensors of each monitoring hole are connected in series by welding Optical fiber strain analyzer BOTDR; the sensing of strain and temperature is based on Brillouin backscattering. By measuring the received Brillouin backscattering light power, the Brillouin frequency shift measurement of each point on the fiber is completed. and positioning function; according to the linear relationship between Brillouin frequency shift and strain and temperature, the radial strain distribution and temperature distribution inside the surrounding rock can be obtained, and the radial strain distribution of the tunnel surrounding rock can be obtained by removing the influence of temperature; through The measured strain distribution is multiplied and summed to obtain the radial deformation of the surrounding rock, and then the stability of the surrounding rock is evaluated and predicted; the diameter of the monitoring hole is 70mm to 90mm, and the length of the monitoring hole is selected as the loosening circle of the surrounding rock The calculated value or empirical value is more than 1.5 times, so that the monitoring hole passes through the bottom of the loose circle of surrounding rock to reach the stable area of surrounding rock. 2. by the tunnel surrounding rock radial stress-strain distribution monitoring method described in claim 1, it is characterized in that said monitoring hole passes through the surrounding rock loose influence circle, and the bottom of the hole reaches the stable region of the surrounding rock, with the bottom of the hole as the base point, to The distribution of the radial deformation of the surrounding rock can be obtained by performing an integral operation on the above strain distribution. 3. The radial stress-strain distributed monitoring method of tunnel surrounding rock according to claim 1 is characterized in that: the fixed support system is supported by an optical fiber sensor rod (1), a grouting exhaust pipe (13), a sleeve Tube (9) and cover plate (8); the supporting rods (1) are made of high-strength stainless steel tubes, each rod is 1m long, and the rods are connected by external joints to be suitable for monitoring holes of different lengths; the supporting rods (1) An arc groove (10) is left at one end to fix the fiber optic sensor. The fixing method uses adhesive tape to bind the distributed fiber optic sensor on the support rod, and the distributed fiber optic strain sensor and the temperature compensation sensor are connected to the support rod. relationship; the grouting exhaust pipe (13) adopts PVC pipe material, and each section is 2m to 3m, and is connected to the required length by the PVC pipe joint (16); Cover (15), connected joint by joint until the bottom of the monitoring hole, the other end of the grouting exhaust pipe (13) is drawn from the grouting exhaust pipe outlet (7) of the cover plate (8) of the orifice fixing system; the umbrella-shaped protective cover (15) is used to prevent the grouting exhaust pipe (13) from extending into the drilling process, and the rock and soil debris will block the nozzle; the orifice fixing system consists of two parts: the sleeve (9) and the cover plate (8); the sleeve The diameter of the cylinder is slightly larger than the diameter of the monitoring aperture, and there is a circular skirt at the tail, and there are fixing bolt holes (2) on the skirt; the diameter of the cover plate is the same as that of the sleeve skirt, and there are bolt fixing holes corresponding to the skirt on the outermost side , a rubber gasket (3) is placed between the cover plate and the sleeve skirt; the support bar is fixed at the center of the cover plate, and the optical fiber sensor lead-out hole (5), grouting hole (4), and grouting hole (4) are set in the middle area of the cover plate. Exhaust pipe outlet (7).

Images