Sensorised split set bolt and kit for monitoring stresses in rock masses

Abstract

The present utility model relates to a sensorised split set bolt comprising at least one hexagonal mesh for securing one or more sensors, which can be used to monitor stresses in rock masses during road, railway and mining tunnel construction, among others, preventing cost overruns, delays and unwanted accidents. The invention further relates to a kit for equipping the split set bolt with a sensor.

Description

[0001]SENSORIZED SPLIT SET BOLT AND KIT FOR MONITORING STRESS IN ROCK MASSES This utility model describes a sensorized split set bolt with at least one hexagonal mesh for securing one or more sensors. It is useful for monitoring stress in rock masses during the construction of road, railway, and mining tunnels, among others, preventing cost overruns, delays, and unwanted accidents. The model also describes a kit for sensorizing the split set bolt. Background Currently, tunnels are designed using a small amount of correlated data to create a geological model, but with a high degree of uncertainty. Therefore, calculations are always performed with a high Factor of Safety (FS), which entails significant expense.Furthermore, continuous monitoring is necessary during tunnel construction to verify geotechnical data in real time and modify calculations based on changes in the ground, which entails ongoing re-engineering efforts. When a tunnel is excavated, whether by blasting, mechanical means, or with a TBM (Tunnel Boring Machine), also known as a "mole" or "topo" (see Figure 1), the tunnel tends to close, and the behavior of the rock mass depends on the geotechnical characteristics of the materials. Therefore, continuous monitoring of the excavation is essential for feedback analysis, allowing for the correction of initial geotechnical data to optimize excavation methods, materials, support systems, and other factors.Within this monitoring process, there are various options available on the market, including convergence systems using tapes and topographic surveys, subsidence measurements, pressure cells, and more. Each of these provides a range of data that confirms the construction is within expected parameters and that the work is progressing safely. During the project design phase, structural engineers require a series of parameters to estimate the future behavior of the tunnel. These parameters must be defined during one or more site investigations. Based on this information, a model is created using software and programs that define the support structures and construction procedures.Typically, inside a tunnel or mine gallery, it is important to measure: - Deformations of the tunnel or gallery lining, taking two types of measurements: the absolute vertical movement of the tunnel section and the displacements between two fixed points located on its exposed surface, i.e., convergences. - Measurement of loads on the lining: The acting load can be obtained using three methods: indirectly, by measuring deformations with mechanical devices or vibrating wires; directly, with load cells; or by using pressure cells installed inside the lining. - Deformations in the final lining: In the case of a generic tunnel, to monitor all these aspects, the following equipment would be necessary, except in cases of particular complexity: Extensometers, Pressure cells, Load cells, Convergence tapes.The following products are currently used in the market: Bassett Convergence System (BCS): These systems use pairs of accelerometer sensors to measure variations in the movements of arms of known length to determine the resultant of the total movement. Taking into account its dimensions and characteristics, the Bassett arc is adapted to the tunnel section, allowing for a corresponding traffic flow pattern. In its most basic form, a BCS system comprises a short arm and a sensor, and a long arm and a sensor; these parts are repeated for the number of sensor pairs required to monitor a given tunnel (or structure). A BCS is created by articulated arms forming a loop (open or closed) around the interior of the tunnel.The sensors placed on the short and long arms form a triangle with each other and a reference point; any resulting displacement affects the ratio of this triangle, and the soil software calculates the resulting change to display the data both as a graphical representation and as X and Y graphs for each point. This system allows for near real-time monitoring of tunnel deformations. Its drawback is that it only recognizes forces when they manifest on the tunnel surface and not as measurements taken at depth. Pressure Cells: Earth pressure cells (or total pressure cells) are used to monitor total pressure in dams and embankments or placed at the interface between the structure and the excavation wall. Earth pressure cells are constructed from two stainless steel plates welded together around their periphery. This annular space between the plates is filled with de-aired oil.The pressure pad is connected to the transducer via a stainless steel tube, forming a closed hydraulic system. An electrical signal provides the applied pressure, which can be read remotely on a variety of portable readout units or data loggers. This technology allows for pressure measurements, but only in a surface layer; it would not be applicable to a rock mass. Extensometers: Borehole extensometers are rugged and easy-to-install extensometers consisting of a reference head at the surface and one or more anchor points embedded in a borehole and connected to the reference head by rigid rods. Multiple anchors record changes in distance from each other and from the reference head. Thus, a greater number of anchors and wider spacing produces more accurate data on ground deformation. This system uses rods to be inserted into the ground.These can be pre-assembled fiberglass rods that are coiled at the factory and shipped ready for installation. The complete assembly is inserted into the borehole, grout is injected, and the anchors are secured to the rock or soil, while still allowing free movement of each rod within the sleeve. The relative movements between the anchors and the reference head are measured manually with clamp-on or linear transducers mounted on the reference head for remote monitoring. Vibrating wire in-line extensometers are primarily used in underground applications such as tunnels, dams, open-pit mines, and underground caverns. These extensometers are fully enclosed assemblies consisting of multiple extension sections assembled in series.Unlike conventional borehole extensometers, the vibrating wire inline extensometer is installed flush with the ground surface and, due to its multi-point, series-connected design, provides a greater measurement range than a standard borehole extensometer. While its use with rods allows for in-depth readings of forces on a construction site, it has the limitation that, due to its fiberglass casing, it may not withstand the pressure of a rock mass, making it more suitable for non-rocky soils. The convergence tape: This is a precision instrument that measures displacements and deformations. In construction, for accurate displacement measurements, it is advisable to fix the tape using fixing screws. Depending on the type of measurement, a series of displacement measurements at different positions are necessary.It requires fastening screws with protective caps, 250 mm long for concrete and 50 mm for galvanized steel. Convergence measurement is the fastest, most economical, and most widely used instrumentation for monitoring tunnel excavation. It consists of a typical convergence measurement section using a strain gauge tape. The measurement is taken between points anchored to the rock or shotcrete along the tunnel perimeter. Depending on the system, these points have a threaded end or a hook where the measuring device is attached. The measuring point must be protected with a cap to isolate it from ambient dust, which is usually very abundant in tunnels under construction. The strain gauge tape is a metal measuring tape, along with a system that allows it to be set under a certain constant tension and a dial indicator that reads to the nearest tenth of a millimeter.The tape should be taut so that it is as close as possible to a straight line between the measurement points. The measuring section should be positioned and measurements taken as soon as possible after excavation, otherwise a large part of the resulting deformations will be lost. However, a significant percentage of the movement occurs ahead of the face (approximately 30%) and another percentage occurs before measurements begin (approximately 20%), so convergence measurements only capture about 50% of the total movement, or even less. Measurements should be taken daily until the movements have stabilized, and even twice daily if the variation is very abrupt. It is also advisable to perform subsequent verification measurements monthly.Convergence measurement is a relative measurement; that is, only the variation in distances between measurement points is known, not their actual movement. Therefore, it cannot record pressures at the site as a sensor-equipped bolt can. Inclinometers: An inclinometer is a measuring instrument used to measure the inclination of a plane relative to the Earth's surface. In geotechnical engineering, an inclinometer is an instrument used to measure horizontal displacements on slopes and unstable terrain. They can be used to monitor lateral deformation of soil and rock in various geotechnical applications such as deep excavations, retaining walls, open excavations, and embankment stability.These are generally hand-operated instruments, but digital models and others for stable ground mounting, called "in-place" inclinometers, also exist. These are used to take near real-time automated measurements of lateral displacements in soils, rocks, and structures, including the direction of slope and embankment movement, monitoring of lateral movements in embankments and dams, deflection of concrete or asphalt on the upstream face of rockfill dams, deviations of bridge piers and abutments, pile foundations, diaphragm wall control, and stability in tunnels and shafts. This equipment is limited to use at ground level or on tunnel walls. Rock bolt load cell: In Mitri, H. Evaluation of rock support performance through instrumentation and monitoring of bolt axial load.In Proceedings of the 11th Underground Coal Operators' Conference, Wollongong, Australia, 21–23 March 2011; pp. 136–140; Mitri, H.; Laroche, L. New technology for ground monitoring in underground mines using instrumente rockbolts. In Proceedings of the Mine Planning and Equipment Selection Symposium, Wroclaw, Poland, 1–3 September 2004; pp.469– 478; and Mitri, H.; Marwan, J. A new rockbolt axial load measuring device. In Proceedings of the 20th International Conference on Ground Control in Mining, Morgantown, WV, USA, 7–9 August 2001; pp.367–373, a load cell for rock bolts was designed by placing a metal strain gauge inside the bolt head through a small hole drilled in its center, and such techniques were implemented in practical application.Later, Mitri (2011) introduced an improved rock bolt load cell based on the coupler load cell concept, which has improved performance in terms of measuring the ultimate strength of the rock bolt, shipping, and installation. Load monitoring is based on fiber Bragg grating (FBG) sensors. Most rock bolts on the market are made of steel, but a small portion are made of composite materials such as glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP). Embedding fiber optic sensors within composite materials is very effective for transferring stress and protecting the fragile optical fiber from mechanical damage (Frank, A.; Nellen, PM; Broennimann, R.; Sennhauser, UJ Fiber optic bragg grating sensors embedded in gfrp rockbolts. In Proceedings of the 1999 Symposium on Smart Structures and Materials, Newport Beach, CA, USA, 1–4 March 1999; pp.497–504). GFRP rock bolts manufactured / equipped with FBG sensors by embedding FBG sensors in the GFRP rock bolts during the pultrusion process. FBG sensors correspond to a microstructure, typically a few millimeters long, that can be photoinscribed into the core of a standard single-mode telecommunications fiber. This is generated by transversely illuminating the fiber with an ultraviolet laser beam, using a phase mask to create an interference pattern in the fiber core, inducing a permanent change in the physical characteristics of the silicon matrix. Tensile tests indicated that the embedded FBG sensors could withstand a high stress of 1.5%. However, for steel rock bolts, deformation can reach up to 20%. Direct mounting of FBG sensors along the bolt axis can easily damage the sensor under load. In Schroeck, M.Ecke, W.; Graupner, A. Strain monitoring in steel rock bolts using fbg sensor arrays. Proc. SPIE 2000, 4074. A special arrangement of FBG sensors was designed to measure a large relative strain. In their design, they found a neutral line in the cylinder housing, along which the effects of elongation and contraction cancel each other out. An FBG sensor attached to the rock bolt at a slight angle from the neutral angle will give a predictable relationship with the elongation of the rock bolt. Three FBG sensors were installed at 17°, 29°, and 40° with respect to the circumferential direction of the bolt to produce strain transfer ratios of −15%, 0%, and +15% with respect to the bolt strain, respectively. The Bragg wavelength change and applied voltage versus load for the compressed sensor (17◦), the neutral sensor (29◦) and the elongated sensor (40◦).In this tilting method, it is feasible to measure the large elongation of steel rock bolts without breaking the FBG sensors. In Moerman, W.; Taerwe, L.; De Waele, W.; Degrieck, J.; Himpe, J. Measuring ground anchor forces of a quay wall with Bragg sensors. J. Struct. Eng. 2005, 131, 322–328, FBG sensors were applied to the load cell, which was placed between the bearing plate and the anchor plate to measure the force on the ground anchor. Each load cell was equipped with three FBG sensors and the load cell was calibrated to have a linear response and an accuracy of 3.5 kN. The FBG-equipped load cells were installed on a quay wall to monitor the anchor force over the long term. In Ho, SCM; Li, W.; Wang, B.; Song, G. A Load Measuring Anchor Plate for Rock Bolt Using Fiber Optic Sensor. Smart Mater. In 2017, the FBG sensor was instrumented on the load-bearing plate to measure the axial load of the rock bolt.This method ensured that the FBG sensor was not overloaded. Other applications of FBG sensors in load monitoring include monitoring the axial tension of rock bolts during subway tunnel construction using the test model and investigating the load transfer mechanism from the anchor to the ground and the distribution of tensile force along the tendon. This type of technology cannot determine the magnitude or direction of the stresses received. Load monitoring based on distributed Brillouin scattering: Unlike quasi-distributed FBG sensors, the fiber optic Brillouin scattering sensing technique is truly distributed, which can be advantageously used to measure the stress distribution along the rock bolt. In Iten, M.; Puzrin, AM Monitoring of stress distribution along a ground anchor using Brillouin scattering. Proc.In SPIE 2010, 7647, the Brillouin optical time-domain analysis (BOTDA) distributed fiber optic detection technique was examined to evaluate stress distribution along ground anchors. Three different methods of integrating fiber optic sensors into steel tendons were investigated: external longitudinal trench integration, internal integration, and helical integration. Among these methods, the internal and trench integration methods were best suited for monitoring distributed stress and were therefore applied to the wall of an excavation pit for field testing. The stress distribution under different pull-out forces was clearly observed using the Brillouin distributed technique. (Moffat, RA; Beltran, JF; Herrera, R. Applications of BOTDA fiber optics to the monitoring of underground structures. Geomech. Eng.)In 2015, 9, 397–414, the BOTDR technique for monitoring the load condition of rock bolts was experimentally tested. Regarding patent documents, KR20140049407A (Taekyung Eng) refers to a rock bolt with a gauge, comprising: a bolt body inserted into a borehole in a tunnel bedrock layer and fixed by a grouting process, having a hollow hole formed longitudinally therein; and a fiber optic sensor portion inserted into the hollow hole of the bolt body to measure the axial force applied thereto and the underground displacement of the bedrock layer when the bolt body is installed in the tunnel bedrock layer.Its use can reduce construction times and prevent degradation of the tunnel structure's safety due to the drilling process by avoiding drilling through the bedrock to install the measuring unit for coupling the fiber optic sensor. CN106523032A (China Railway 19. thBureau Group 1st Eng Co Ltd) refers to a device used to provide early warning of sudden changes in the surrounding weak rock during machine tunnel excavation. It is primarily designed to address the current problem of long monitoring and early warning times for deformation of the weak rock surrounding the tunnel and its support structures. Two fixing bolts are mounted on the vault, and two gusset plates are each fitted with a fixing bolt. Lower laser reflector detection plates are mounted on the fixing bolts on the gusset plates, and an upper laser reflector detection plate is mounted on the front fixing bolt on the vault. A laser receiving and transmitting sensor is mounted on the vault, and the sensor's three laser emitting heads are aligned with the centers of the laser reflector detection plates.In the vault and the corresponding hips, a data line from the laser receiver and the sending sensor is connected to a lighting power line in the tunnel, and an early warning speaker from the sensor is connected to the junction of the data line and the lighting power line. CN114382495A (Zhongji Tianji and Mech Equipment Manufacturing Co Ltd) refers to a system and method for detecting the working condition of the main bearing load of a protective tunnel boring machine. A plurality of load sensors are installed on a connecting flange face of a protective body and a main drive of a protective tunnel boring machine; a line from the load sensor is connected to the data unit and the data transmission and real-time unit. According to the method and system for detecting the working condition of the main bearing load of the protective tunnel boring machine,The loaded state of the main bearing can be detected simply and efficiently. CN110986812A (Univ. China Mining) refers to a method and device for monitoring stress and strain in the rock lines surrounding the underground roadway of coal mines in real time, where a monitoring anchor bar is used to support the rock surrounding the roadway, comprising: an anchor bar body and an anchor bar tray that displays different colors under different deformation conditions; and a color capture sensor and a signal transmission device are installed; and when the roadway surrounding the rock deforms, the stress state and strain elongation rate of the anchor bar tray change.The color reflected by the anchor rod tray under lamp irradiation changes; a color capture sensor monitors the color of the anchor rod tray in real time; a processor processes the color signal and then sends it to a display terminal; and safety measures are taken based on the deformation status of the anchor rod tray. The surrounding road's rock deformation condition can be monitored in real time, preventing the influence of human factors. WO03069122A2 (US Gov Health & Human Serv; Sunder Man Carl B; Johnson Jeffrey Craig; Signer Steve P) refers to a rock bolt with a hollow body and a space along the hollow body.and where a strain gauge is fixed to an interior surface of the rock bolt and is accessible from outside. The rock bolt may include a data logger within the hollow body and coupled to receive signals from one or more strain gauges and record these signals in memory. The data logger may comprise a data port adapted to be accessible from outside a borehole into which the rock bolt is inserted. The data logger may also include at least one visual and one audible alarm. A graphical user interface software program may be used to download data from the data logger and configure certain operating parameters of the data logger. CN102221332A (Xian University of Science and Technology) refers to a layered soil sinking apparatus having a fiber grid with a sensor capable of detecting sedimentation of unconsolidated strata, and a data processing system.and installation method. The fiber optic grid is an array of sensors onto which a broadband light source with a demodulator and coupler is applied. A light signal passing through the sensor is fed into the fiber optic grid demodulator via the coupler, which converts the light signal into an electrical signal used to calculate a center wavelength value for each sensor in the grid. The data is transferred to a wavelength data acquisition module, a data analysis module, a time display wavelength module, a real-time monitoring curve module, an information alert module, a forecast alarm system module, and similar modules, respectively; and another data analysis path is connected to a memory and a data processing module, respectively. The device has a simple structure and is unaffected by harsh environments.It is resistant to corrosion and electromagnetic interference, safe and reliable, convenient to use, and widely applicable to stratum sedimentation; detection and transmission are integrated. Geological terrain observation device and method, specifically the fiber grid multipoint detection device and long-term observation-scale monitoring system and method. CN114964579A (CCTEG China Coal Research Institute) refers to a mining stress monitoring system comprising a computer, a switch,a plurality of voltage-sensing demodulation substations and a plurality of voltage-sensing branches by means of a grid array. The computer displays and records voltage distribution data for the entire underground monitoring area; the switch establishes the TCP / IP connection between the computer and each voltage-sensing demodulation substation; each voltage-sensing branch of the grid array comprises a plurality of voltage sensors on a fiber grid,The voltage sensors form a distributed sensing network, giving rise to a hybrid multiplexing technology. The second end of each voltage sensing demodulation substation is connected to at least one voltage sensing branch of the grid array in the fiber grid sensing network and controls the corresponding voltage sensing branch of the grid array to detect voltage and demodulate the returned voltage sensing data. The system can perform intensive, real-time online monitoring of underground voltage, avoid a monitoring blind spot, and reduce monitoring costs. However, the need remains for sensorized split-set bolts that allow a designer to obtain the parameters estimated in the project and reliably verify, during construction, whether the initially projected data matches the estimates.and a kit for sensorizing Split Set bolts. Site reconnaissance is always limited at the preliminary and final design stages, and it's often not just about cost savings. Frequently, factors such as access or permits for areas where construction will take place remain unexplored, leading to a lack of knowledge about the environment in that area. Furthermore, the construction of any infrastructure involves, in some way, interaction with the surrounding environment. This sensorized Split Set bolt minimizes this interaction, impacting adjacent infrastructure as little as possible, and can verify that the construction progress is within the designed parameters. It monitors both the infrastructure under construction and adjacent structures, if they are deemed potentially affected. Rock bolt reinforcement systems minimize deformations induced by the dead weight of the loosened rock.as well as those induced by the redistribution of stresses in the rock surrounding the excavation. In general, their operating principle is to stabilize rock blocks and / or surface deformations of the excavation by restricting the relative displacements of adjacent rock blocks. In massive or slightly fractured rock and in fractured rock, the main role of rock bolts is to control the stability of potentially unstable rock blocks and wedges. This is also called the "wedge effect." In fractured and intensely fractured and / or weak rock, the bolts impart new properties to the rock surrounding the excavation. Installed radially, each bolt creates a bulb of resistance, which, by interacting with the bulbs of adjacent bolts, forms a load-bearing rock arch that works in compression, known as the "arch effect."The same principle that provides stability to the excavation. There are other principles under which rock bolts operate for specific treatments, such as stitching fault zones, shear zones, and other weak zones, installed across these areas. The split set bolt consists of a tube slotted along its length; one end is tapered, and the other has a welded ring to hold the plate. When this bolt is press-fitted into a smaller-diameter borehole, radial pressure is generated along its entire length against the borehole walls, partially closing the slot during this process. The friction at the contact between the borehole surface and the outer surface of the slotted tube constitutes the anchorage, which resists movement or separation of the rock surrounding the bolt, thus indirectly achieving load-bearing tension. The diameter of the slotted tubes varies from 35 to 46 mm.with lengths of 5 to 12 feet. They can achieve anchorage values ​​of 1 to 1.5 tons per foot of bolt length, depending mainly on the drill hole diameter, the length of the anchor zone, and the rock type. The following considerations are important for their use: Split set bolts are mostly used for temporary reinforcement, usually forming combined reinforcement systems in soils of fair to poor quality. Their use is not recommended in intensely fractured and weak rock. Installation is simple, requiring only a jackleg drill or a jumbo. They provide immediate reinforcement action after installation and allow for easy mesh installation. The drill hole diameter is crucial for their effectiveness; the recommended diameter for 39 mm split set bolts is 35 to 38 mm.With larger diameters, there is a risk of inadequate anchoring, and with smaller diameters, they are very difficult to insert. They are susceptible to corrosion in the presence of water unless galvanized. Proper installation can be difficult with longer split set bolts. Consequently, this type of bolt only serves to secure the rock mass. This utility model relates to a sensorized split set bolt, making it sensitive to different movements and stresses present in the rock masses, instead of solely serving a securing function. These different movements and stresses can be identified and transmitted in real time, assisting in taking the necessary measures to support the stability of the rock mass and the safety of the tunnel or civil engineering work. In this way,The following improvements or advantages over the initial use of this type of bolt would be achieved: - Real-time monitoring of the direction and intensity of stresses in the slopes where they are installed. - The possibility of zoning tunnels based on rock type, degree of fracturing or weathering, and the type of stresses to which the rock is subjected. This zoning will allow for the reinforcement or reduction of the type of support, both temporary and permanent, provided to the tunnel or civil engineering work, thus enabling optimal cost control. - Reduction of the risk of human and / or material losses thanks to the early warning system provided by the sensors located on the bolts in the event of potential rock mass collapses. This sensorized Split Set bolt allows for continuous stress monitoring in rock masses.These devices are used both for the routine support of tunnels and galleries in civil engineering and mining, and also for monitoring rock masses and making decisions based on predictive analytics derived from the captured data. Thus, the present sensorized Split Set bolt for monitoring stress in rock masses comprises a tube slotted along its length, with one end tapered and the other having a welded ring to hold a plate. Inside, preferably at the end or center, is located at least one sensor mounting means, selected from at least one proximity sensor and at least one accelerometer. The mounting means corresponds to a resistant and flexible hexagonal mesh, where the ratio of the length of the side of the hexagon to its height is 5:6. The present kit for sensorizing the Split Set bolt comprises at least one sensor mounting means, at least one proximity sensor, and one accelerometer.and a sensor installation tool on the mesh and on a Split set bolt, where the fastening medium corresponds to a resistant and flexible hexagonal mesh, where the ratio of hexagon side length to height is 5:6. The sensors for sensing the Split set bolt can be selected from proximity and accelerometer sensors. The sensors are fixed to a hexagonal mesh, see Fig. 2, and inserted into the bolt using a custom-designed sensor installation tool, see Figs. 3 and 13. The hexagonal mesh for the sensors can be located in the center or at the end of the slotted tube of the Split set bolt, Figs. 14A and 14B. Compression measurements on the bolts were performed using a custom-designed support (mold) that helps position the bolt in a hydraulic press for laboratory testing. See Fig. 4. The support is made of a material that transmits the force exerted by the press on the bolt.without altering the possible results, for example, concrete. Figures 5 and 6 show data (measurements) from the acceleration and proximity sensors under a constant load, which are consistent with the data provided by the compression machine and its deformation measurement. Each sensor was wired and connected to a development board (Arduino UNO or the interconnection board) to record the measurement data from each sensor. Controller integration was performed, evaluating the connection and effective communication between the main components (sensors, boards, etc.). A mounting system for the selected sensors was designed and manufactured based on a flexible 50 mm x 60 mm hexagonal mesh using digital modeling with Fusion 360 software and 3D printing with TPU filament. The printed mesh meets expectations in terms of strength and flexibility.This makes it a viable option for use in various applications. See Figs. 7A-7C. A sensor installation and clamping system was designed and manufactured, allowing for greater accuracy, speed, and quality of installation. See Figs. 8A-8D. The proximity sensor is located inside (see Fig. 9) the Split Set bolt, as is the accelerometer, which facilitates readings related to bolt compression and helps understand the relationship between the magnitude of the pressure exerted on the bolt and the detected acceleration. The data and measurements obtained in the tests (Figs. 11A-12F) show that the sensors measure variations in geometry with increasing pressure / compression exerted on the bolt (see Fig. 10), and even the resulting acceleration, which is very important for tunnel environments.both mining and civil works. It was determined that proximity sensors and accelerometers are capable of measuring small variations since the movement continues to be recorded smoothly, but identifiably, in both compression and decompression. Mechanical Tests Split Tubes Compression Press Automatic control press 300 Ton, sensitivity 0.1KN and speed 4.5 N / sec. See Fig. 20A and 20B Sample 1: Short bolt compressed at the center and acceleration sensor (accelerometer), m / s, 2 , direction of the load Z axis Sample 2: Short bolt compressed at the end and acceleration sensor (accelerometer), m / s 2 , direction of the load Z axis Sample 3: Long bolt compressed to the center and acceleration sensor (accelerometer), m / s 2 , direction of the load Z axis Sample 3: Long bolt compressed to the rim and acceleration sensor (accelerometer), m / s 2 , direction of the load Z axis Sample 4: Long bolt compressed to the center and acceleration sensor (accelerometer), m / s 2 , direction of the load Z axis Thus, the present Split Set bolt comprises a tube grooved along its length, with one end tapered and the other having a welded ring to hold a plate. Inside the plate, a clamping means for selected sensors (proximity sensor and accelerometer) is located in the center. This clamping means consists of a resistant and flexible hexagonal mesh, where the ratio of the length of the hexagon side to its height is 5:6. Brief Description of the Figures: Figure 1 shows a TBM system (previous artwork). Figure 2 shows the resistant and flexible hexagonal mesh for clamping the sensors. Figure 3 shows the custom-designed sensor installation tool for incorporating the hexagonal mesh clamping mesh inside the grooved tube of the Split Set bolt. Figure 4 shows the custom-designed mold for performing compression measurements on the Split Set bolts.Figures 5 and 6 show data (measurements) from the free acceleration and proximity sensors under a constant load. Figures 7A-7D show the mounting medium (flexible hexagonal mesh) for the selected proximity and accelerometer sensors. Figures 8A-8C show the sensor mounting medium and the sensor mounting medium inside the slotted tube of the Split Set bolt. Figure 9 shows the proximity sensor located inside the Split Set bolt. Figure 10 shows sensors that measure the geometry variations due to an increase in the pressure / compression exerted on the bolt. Figures 11A-11F show accelerometer measurements when supported by the flexible hexagonal mesh and located at the center and end, respectively, of the slotted tube of the Split Set bolt, for the X-axis (Figs. 11A and 11B), Y-axis (Figs. 11C and 11D), and Z-axis (Figs. 11E and 11F).Figures 12A-12C show proximity sensor measurements when supported by the flexible hexagonal mesh, located in the center (Figs. 12A and 12B) and at the end (Fig. 12C), respectively, of the slotted tube of the Split set bolt. Figure 13 shows the installation of the flexible hexagonal mesh in the center, inside, of the slotted tube of the Split set bolt. Figures 14A and 14B show the slotted tube of the Split set bolt with a flexible hexagonal mesh located inside, in the center (Fig. 14A) and at one end (Fig. 14B).

Claims

CLAIMS 1. A sensorized split bolt set for monitoring stress in rock masses comprising a tube slotted along its length, one end of which is tapered and the other having a welded ring to hold a plate, and inside, at least one sensor clamping means is located, selected from at least one proximity sensor and at least one accelerometer, wherein the clamping means corresponds to a resistant and flexible hexagonal mesh, wherein the ratio of the length of the side of the hexagon to its height is 5:

6.

2. The split bolt set of claim 1 wherein the sensor clamping means located inside the slotted tube is located in the center or at one end of the slotted tube. 3.Kit for sensorizing Split set bolt comprising at least one clamping means for sensors, at least one proximity sensor and one accelerometer, and a tool for installing sensors on the mesh and on a Split set bolt, where the clamping means corresponds to a hexagonal, strong and flexible mesh, where the ratio: length of side of the hexagon to height is 5:6.

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