CN-115628699-B - Latch-type roof caving distributed optical fiber monitoring sensor and roof damage degree calculation method

CN115628699BCN 115628699 BCN115628699 BCN 115628699BCN-115628699-B

Abstract

The invention relates to a distributed optical fiber monitoring sensor for roof fall of a latch-type roof and a roof damage degree calculating method, and belongs to the technical field of geotechnical engineering safety monitoring. The invention provides a clamp-tooth type roof falling distributed optical fiber monitoring sensor, which is fixedly arranged on a roof rock matrix in a monitoring area through a fixed buckle along the longitudinal direction of a roadway, acquires distributed optical fiber light intensity signals, performs position calibration on the distributed optical fiber monitoring area through a mode of bending to change light intensity, converts the calibrated light intensity signals of the distributed optical fiber monitoring area into strain information of each position on an optical fiber through an analysis demodulator, performs fitting analysis according to the evolution trend of strain change curves on the distributed optical fiber and typical optical fiber monitoring response modes when different types of roof are damaged, judges the deformation damage types of the roof, draws a roof deformation damage schematic diagram according to the judged damage types, and calculates the damage degree of the roof according to calculation formulas under different damage modes.

Inventors

DAI FENG
REN MIN
WU SHUNCHUAN
CHENG HAIYONG
SUN WEI
WANG CHAO

Assignees

昆明理工大学

Dates

Publication Date: 20260512
Application Date: 20221103

Claims (2)

1. The top plate damage degree calculation method based on the latch-type top plate falling distributed optical fiber monitoring sensor is characterized by comprising an optical fiber core (1), a tight wrapping layer (2) and a loose wrapping layer (4), wherein the tight wrapping layer (2) is sleeved on the optical fiber core (1), annular latches (3) are uniformly arranged on the outer side surface of the optical fiber core (1), and the loose wrapping layer (4) is sleeved on the annular latches (3); the method for calculating the damage degree of the top plate comprises the following specific steps: S1, fixing a latch-type roof falling distributed optical fiber monitoring sensor on a roof rock matrix in a monitoring area along the longitudinal direction of a roadway through a fixed buckle, wherein the fixed buckle comprises an annular clamping groove matched with an annular latch and an expansion screw, and the annular latch is clamped with the annular clamping groove of the fixed buckle; S2, acquiring a distributed optical fiber light intensity signal, and calibrating the position of a distributed optical fiber monitoring area in a mode of bending and changing light intensity; S3, converting the light intensity signals of the calibrated distributed optical fiber monitoring area into strain information of each position on the optical fiber through an analysis demodulator; s4, judging the deformation and damage type of the top plate according to the evolution trend of the strain change curve on the distributed optical fiber, wherein the judging method of the deformation and damage type of the top plate comprises the following steps: The distributed optical fibers between the adjacent fixed buckles P1 and P2 are uniformly stretched and deformed, and the outer distributed optical fibers of the fixed buckles P1 and P2 are not deformed, so that the top plate is damaged in a stretching damage mode, namely a stretching crack appears in the middle of the rock stratum of the top plate, and the crack opening degree is larger and larger; The distributed optical fibers are subjected to abrupt stretching deformation at a certain position between the adjacent fixed buckles P1 and P2, the deformation of other sections of distributed optical fibers between the fixed buckles P1 and P2 is small deformation, the outside distributed optical fibers of the fixed buckles P1 and P2 are not deformed, and then the top plate is damaged in a shearing damage mode, namely a shearing crack appears in the middle of a top plate rock stratum, and rock mass on two sides of the crack is more and more staggered; The distributed optical fiber between the adjacent fixed buckles P1 and P2 sequentially deforms in three sections of alpha, beta and gamma, the deformation of the alpha section is small, the deformation of the beta section suddenly rises, the deformation of the gamma section is micro-deformation, the deformation of the gamma section is smaller than the deformation of the alpha section, the outside distributed optical fiber of the fixed buckles P1 and P2 is not deformed, the top plate damage type is stretch-shear mixed damage type, namely a crack appears in the middle of a top plate rock stratum, the opening degree of the crack is larger and larger, rock bodies on two sides are staggered, the alpha deformation is the deformation of the front section distributed optical fiber of a sliding rock body, the beta deformation is the deformation of the distributed optical fiber at the corners of the rock body, and the gamma deformation is the deformation of the rear end distributed optical fiber of the sliding rock body; The distributed optical fibers between the adjacent fixed buckles P1 and P2 are deformed in different modes of alpha, beta, gamma, delta and epsilon, the deformation of the alpha, gamma and epsilon is constant, the deformation of the gamma is smaller than that of the alpha, the deformation of the gamma is smaller than that of the epsilon, the deformation of the beta and delta is suddenly jumped, the outer distributed optical fibers of the fixed buckles P1 and P2 are not deformed, and then the roof is damaged in the form of boulder falling, namely a certain rock in a roof stratum slides downwards; The distributed optical fibers between the adjacent fixed buckles P1 and P2 show arc-shaped continuous variable stretching deformation, and the outside distributed optical fibers of the fixed buckles P1 and P2 are not deformed, so that the top plate damage type is bending damage type, namely the whole top plate rock layer is subjected to sinking bending deformation; and S5, drawing a deformation damage schematic diagram of the top plate according to the judged damage type, and calculating the damage degree of the top plate according to calculation formulas under different damage modes.
2. The method for calculating the damage degree of the top plate based on the latch-type top plate falling distributed optical fiber monitoring sensor according to claim 1, is characterized in that the method for calculating the damage degree of the top plate comprises the following steps: For the stretching fracture failure mode of the rock stratum of the tunnel roof, the stretching crack cracking width of the rock stratum between the fixing buckles P1 and P2 And rock mass dislocation displacement Calculated according to the following formula: ; Wherein, the For the length of the fiber between the snaps P1 and P2 before deformation, The length of the deformed optical fiber between the buckle P1 and the buckle P2; For the drift damage mode of the rock stratum of the tunnel roof, the stretching crack cracking width of the rock stratum between the fixing buckles P1 and P2 And rock mass dislocation displacement Calculated according to the following formula: Or (b) ; Wherein, the For the length of the fiber between the snaps P1 and P2 before deformation, For the deformed length of the optical fiber between the snaps P1 and P2, For maximum values of local deformation of the optical fiber caused by rock mass staggering angle, Is a deformation coefficient and is obtained according to experimental tests; For a roadway roof strata stretching and dislocation mixed damage mode, fixing the stretching crack cracking width of strata between the buckles P1 and P2 And rock mass dislocation displacement Calculated according to the following formula: Or (b) ; Wherein, the For the length of the fiber between the snaps P1 and P2 before deformation, For the deformed length of the optical fiber between the snaps P1 and P2, For maximum values of local deformation of the optical fiber caused by rock mass staggering angle, Is a deformation coefficient and is obtained according to experimental tests; For the falling damage mode of the roadway roof strata boulder, the tension crack cracking width of the strata between the fixing buckles P1 and P2 And rock mass dislocation displacement Calculated according to the following formula: Or (b) ; Wherein, the For the length of the fiber between the snaps P1 and P2 before deformation, For the deformed length of the optical fiber between the snaps P1 and P2, For maximum values of local deformation of the optical fiber caused by rock mass staggering angle, Is a deformation coefficient and is obtained according to experimental tests; For the bending settlement damage mode of the rock stratum of the tunnel roof, the transverse range of the sinking deformation of the rock stratum And maximum subsidence displacement of the formation Calculated according to the following formula: ; Wherein, the For the length of the fiber between the snaps P1 and P2 before deformation, Is the deformed length of the optical fiber between the buckle P1 and the buckle P2.

Description

Latch-type roof caving distributed optical fiber monitoring sensor and roof damage degree calculation method Technical Field The invention relates to a distributed optical fiber monitoring sensor for roof fall of a latch-type roof and a roof damage degree calculating method, and belongs to the technical field of geotechnical engineering safety monitoring. Background With the development of infrastructure construction, more and more underground engineering constructions such as underground tunnels, underground mines, underground chambers and the like are completed or are being constructed. The available space is excavated in the underground rock mass, wherein the most common type of disaster event is the roof fall or collapse problem. Roof collapse is commonly caused by overlarge exposed areas of rock formations or excessive fragmentation of rock masses, and is mostly a large-scale overall caving. For underground spaces with poor supporting conditions, accidents of unsteady falling of independent rock blocks are frequent, and the underground spaces belong to local caving. Whether the whole falling in a large range or the partial falling in a small range is extremely easy to damage the safety of workers and mechanical equipment. Therefore, an effective monitoring sensor and a roof damage degree calculating method are developed aiming at roof falling disasters, and the method has great significance for early warning and protection of roof falling accidents. For underground excavation spaces such as mine roadways, mine stopes, tunnels, chambers and the like, the exposed area is often a large range extending from several kilometers to several tens of kilometers. The stability of the top plate is not everywhere equal, and the occurrence of popping is highly likely in some unpredictable areas. At present, common monitoring means for roof fall generally comprise a roof separation layer instrument, an anchor rod stress meter, microseismic monitoring, ultrasonic monitoring, conductivity monitoring and the like. The separation layer instrument and the anchor rod stress meter are point type monitoring means, and only displacement and stress change states of a certain point of the top plate can be monitored. When the arrangement of the monitoring sensor is unreasonable, the omission of the falling area is often caused, and the overall stability of the top plate cannot be effectively monitored. The monitoring means such as ultrasonic wave, conductivity, microseismic are all indirect physical quantity monitoring, and the actual response state of the top plate cannot be intuitively reflected due to the complex rock formation, so that the monitoring effect is very unstable and the result is unreliable. The distributed optical fiber sensing technology is suitable for large-scale monitoring, and the commonly applied distributed optical fiber sensing technology mainly comprises an optical time domain reflection and frequency domain reflection technology (R/B-OTDR/OFDR) based on optical fiber Raman scattering or Brillouin scattering, a polarized optical time domain reflection technology (P-OTDR) based on optical fiber Rayleigh scattering, a long-distance optical interference technology, a quasi-distributed optical fiber Bragg grating multiplexing technology and the like. At present, the distributed optical fiber sensor is not widely applied to roof fall monitoring, large-scale monitoring cannot be realized in a mode of being buried in roof drilling holes in most cases, and a concrete guniting fixing mode is often adopted in a situation that few optical fibers are laid longitudinally along a roadway, so that on one hand, the layout cost is not economical enough, and on the other hand, the common double-layer cladding distributed optical fiber is easy to separate from an optical fiber outer cladding from an optical fiber core, and the monitoring result is distorted. The deformation/caving forms of the top plate are various, and the top plate with a block structure can be subjected to stretching damage, shearing dislocation damage or stretching-dislocation mixed damage, and the top plate with a layered structure can be subjected to bending settlement deformation damage. Although the distributed optical fiber monitoring means is partially applied to roof deformation/caving monitoring, the error of the monitoring result is large, and the roof damage degree cannot be directly analyzed and calculated based on the response result of the distributed optical fiber monitoring roof deformation. Disclosure of Invention Aiming at the problems that the error of a monitoring result is large and the damage degree of the top plate cannot be directly analyzed and calculated in the distributed optical fiber monitoring, the invention provides a latch-type top plate falling distributed optical fiber monitoring sensor and a top plate damage degree calculating method. The utility model provides a latch type roof falls distributed optical fiber monitor