锚喷支护施工工艺措施（Bolt shotcrete support construction technology measures）

锚喷支护施工工艺措施（Bolt shotcrete support construction technology measures） 锚喷支护施工工艺措施(Bolt shotcrete support construction technology measures) Bolt shotcrete support construction technology measures In order to ensure the quality of anchor bolt, strengthen field quality control and standardize bolt shotcrete support, the following measures are formulated. First, bolt construction technology measures 1 、 construction process Construction process of mortar bolt Construction process flow chart of mortar bolt (first grouting and post inserting bar) Block diagram of construction process of mortar bolt (first post grouting) 2, construction process measures (1) field test; Before the construction of the anchor rod, the following anchor work is carried out: A and through laboratory test, 2~3 sets of mortar mixture ratio meeting the design requirements were screened, and the experiment outline was approved for production test. B, compactness of grouting test: selection and field bolt diameter and length of anchor hole, aperture and tilt of the same bolt and a plastic tube (or pipe), using the same and grouting materials and mixing ratio of cement grout or cement mortar, grouting technology and grouting construction site according to the same, maintenance 7 after check the compactness of the pipe section. Different types and lengths of bolts need to be tested. The test plan submitted to the supervisor for approval, and the test was conducted according to the approved plan, the supervisor in the process of test site. Test section grouting density is not less than 90%, otherwise, it is necessary to further improve the test process, and then test, until 90% or more of the grouting density. (2) make hole A, bit selection to meet the requirements, drilling points have obvious signs, the opening position in any direction deviation should be less than 100mm. B, the direction of the bore of the anchor hole meets the requirements of the construction drawing. The construction drawings are not specified, the system of bolt hole axis direction should be perpendicular to the excavation surface smooth; hole axis direction of the local reinforcement bolt and sliding surface and sliding surface of the opposite tendency and the tendency of the 45? Angle, azimuth deviation should be no greater than 5?. The depth of the anchor hole must meet the design requirements, and the deviation of the hole depth shall be no more than 50mm. The bore diameter of C and mortar bolts shall be greater than the diameter of anchor bolts. When adopting the program of grouting first and placing anchor bolt, the diameter of drilling should be more than 15mm of the diameter of bolt. When the procedure of bolting and grouting is adopted, the drilling diameter shall be greater than the diameter of the bolt by more than 25mm. D, after drilling with high pressure air, water cleaning, the hole in the loose rock powder and water clean; if you do not need to insert the anchor hole shall be affixed immediately, or blockage of appropriate protection, in the bolt installation prior to drilling check to determine whether the need to wash. E, drilling end, each drill bore aperture, Kong Xiang, Kong Shen and hole bottom cleanliness check record carefully. Installation and grouting of anchor rod When the first grouting is inserted, the anchor rod is built: A, in the borehole is filled with slurry immediately after insertion, bolt insertion direction and hole to consistent, insertion process to the appropriate rotation (artificial or torsion wrench niusong); B, bolt insertion speed to slow, "spring", to rotate and then plug to send, try to avoid knocking placed. When the bolt is inserted, the grouted bolt is built: According to on-site bolt hole hole, when the hole length is less than 6m, not more than 10 degrees upward tilt, without setting into the return pipe; when the length is greater than 6m, the hole incline more than 10 degrees, must be set into the return pipe; the 9m bolt must be set into slurry return pipe. A, the anchor immediately after installation grouting; B, enclosed grouting bolt, the hole should be unobstructed, the orifice should be firmly blocked. Grouting from the grouting pipe until the orifice bleeding. C, during grouting, if grout is found near the rock bolt, it shall be blocked and filled so as not to continue to flow. D, the slurry should be used as soon as possible mixing, after mixing more than 1h of the slurry should be abandoned. E, regardless of any cause of grouting interruption, should be pulled out of the anchor rod, and the use of pressure water in 30min grouting irrigation holes. If the drill hole is partially filled during the re installation, it shall be drilled to the required depth. F, after grouting, shall not be struck, hit or applied any other load before the final grouting. Two 、 self advancing bolt construction technology 1 、 construction process Construction flow chart of self advancing anchor rod 2, construction process measures (1) field test; To ensure its durability, all rods shall be wrapped in cement paste or cement mortar. Therefore, before the construction, for different conditions of the rock bolt should be tested by such as grouting pressure, grout injection technique was used to determine the parameters, and to ensure that the rod can be cement grout or cement mortar coating. (2) anchor rod installation; Check the anchor hole, drill hole, whether there is foreign material blockage; if there is, should clean up. Connecting drill bit and anchor rod, rock drill and drill tail, drilling rig, connecting sleeve and drill tail, anchor rod and drilling machine connecting sleeve, etc.. The position of the bolt anchor hole alignment design, drilling machine should give wind or water, then drilling, drilling in the broken rock, water hole blockage, so in drilling, the drilling speed should slow down, multi turn, less impact, pay attention to the water outflow from the borehole in the situation, if there is water hole the blocking phenomenon, should retreat anchor around 500mm, and repeatedly sweep holes, the hole is smooth, then slowly forward, until the design depth. Drilling into the design depth, use water or air to wash holes, check whether the drill hole is unblocked, and then pull the anchor rod from the drilling rig connecting sleeve, the bolt is exposed according to the design requirements. Use the steel pipe to plug the plug through the exposed end of the bolt into the orifice, 100mm or so as the sealing hole for grouting, such as grouting pressure is larger or the surrounding rock is broken, also can use anchor agent to seal the hole. (3) grouting of bolt; Check whether the grouting pump and its fittings are complete and normal. The water cement ratio or particle size and humidity of cement mortar or cement mortar meet the design requirements. Check whether the anchor hole is unblocked or not, adjust the flow gauge to make mortar water to ash ratio to the design value, and the mortar from the pump outlet must be even, no intermittent uneven phenomenon. The rapid quick connector for connecting bolt and grouting pipe and pump, start the pump grouting, the process should be continuous perfusion, no stopping, must be completed first, observe the slurry from the grout stopping plug flow or pressure to the edge of the design value expression, can stop the pump. If in the process of grouting, pipe plugging phenomenon, should promptly clean up the bolt and grouting hose and pump, if the pump pressure gauge pressure, should reverse the motor 1-2 second pressure relief, can remove the connector, the motor reversing time must be short. When the completion of a grouting bolt, joint grouting should be quickly unloaded hose and bolt, cleaning and installation to another anchor bars, and grouting, if the pump stop time is longer, the root should be let go before the front bolt grouting uneven mortar, to avoid clogging. During the whole grouting process, the operators should cooperate closely and act quickly to ensure the continuity of the grouting process. No percussion, impact, or any other loading shall be allowed prior to the final solidification of the grout. (4) other The size, size and material of the steel pipe used as hollow anchor bolt shall comply with the design requirements. The front end of the hollow anchor rod should be machined into a sharp angle of no more than 45. The exposed end of the rod can be processed into 100 to 150mm pipe threads. Hollow bolt with smaller diameter and shorter length of the impact type pneumatic tool into the hollow bolt surrounding rock; large diameter, longer length of the general need to drill holes can be used as a hard casing follow-up method for drilling. When grouting through the hollow anchor bolt to the surrounding rock, the grouting will be carried out after the surrounding rock is covered with sprayed concrete. A hollow bolt used for grouting; opening on the wall of a tube within the length of 1/3 to 1/4 of the front of the rod. The hole diameter is from 6 to 8mm, the hole distance is 100 to 150mm along the axis of the pipe, and the ring is 90mm and the plum blossom type is arranged. An exhaust hole with an aperture of about 12mm is designed on the pallet. The hole between the anchor and the hole wall should be blocked. Grouting slurry should be added with early strength agent, water reducing agent and expansion agent of cement paste. Grouting pressure shall be determined by test and shall not exceed 1MPa. When grouting, when the exhaust pipe is discharged, the exhaust pipe is blocked and continues to be poured to the preset pressure, and the perfusion is stopped and the steel pipe is sealed. The design length of the self advancing anchor bar above 1333m slope above the entrance slope is 4m. Because of the space restriction of the bent frame, the 4m bolt can not be constructed, and 2 2m bolts are used to connect the casing with the casing. When the bent frame has enough space, the 4m self advancing anchor rod is adopted. Three. Construction technology of dry shotcrete 1 、 construction process The construction of dry spraying process, shotcrete bolt construction and excavation, follow up the parallel cross operation, in addition to the special geological section of the first anchor program after spraying, the other parts are on a first anchor after injection procedure construction, grouting construction process for: Construction process flow diagram of shotcrete 2, shotcrete construction process measures The operation of each process must first seriously follow the design documents and construction specifications. Combined with past construction experience, the main points of each process are as follows: Field test Combined with the previous construction experience, through laboratory tests, the production parameters and mix ratio of shotcrete can be optimized to meet the construction requirements and meet the design requirements. The methods and procedures are as follows: A, screening 2~3 sets of mixture ratio through laboratory test, and writing test outline for approval, for production test; B, select the site (or Supervision designated), according to the different types and locations of surrounding rock, selected 6~9 representative parts for production test; C, according to the design and testing program, used in conjunction with the screened than were spraying, spraying range tentative 10m (or a unit volume), in a jet rock surface with sufficient wood or bottomless steel mould according to the specifications (detection, anti permeability, compressive strength, tensile bond strength and rock face etc. at the same time, according to the test specification) respectively sampling standard test block curing under the same conditions; D compares the physical properties of the specimens that meet the design requirements (including the extent of the impact of the blast); E, finishing analysis, test record, comprehensive rebound amount, strength guarantee rate and construction work efficiency, and so on, choose proper mix proportion and construction technological parameter, submit to design supervision unit for approval. Preparation work The injection quality control sign shall be well laid, sufficient ventilation and lighting shall be provided in the operation area, and all mechanical equipment and pipelines shall be checked before spraying to ensure normal construction. The surface of water treatment measures are prepared, ready to deal with materials, contact with good warehouse surface sampling preparation. Mixing and transportation With the mixing ratio test strictly according to the accurate compounding of stirring, stirring time enough to mix, transportation and storage should be waterproof, anti pollution, into the machine before the strict screening, the transportation, storage time should comply with the relevant technical indicators. Steel fiber concrete batching and mixing to be uniform. The transportation is carried by concrete mixing truck. Mixing cement used in accordance with national standards of ordinary portland cement, its label is not less than P.O32.5. Aggregate: mixing with fine aggregate should be used in coarse, hard and durable sand, fineness modulus should be greater than 2.5, the moisture content control in 5 ~ 7%; coarse aggregate by hard durable pebbles or gravel, the particle size is less than 15mm; do not use containing active silica aggregate. Water: mixing water shall comply with the bidding documents. Admixture: quality accelerator should comply with the relevant provisions of the DL/T5100 and the requirements of the construction drawings and the quality certificate of manufacturer, initial setting time is not more than 5min, the final setting time not more than 10min, shall be subject to the approval of the supervisor selection of additives. The mixing shall be subject to the following provisions: The forced mixer mixing capacity of less than 400L, the stirring time shall not be less than 1min; the self falling mixer mixing, stirring time shall not be less than 2min; the mixture is additive, stirring time should be extended; the steel fiber reinforced concrete steel fiber material feeder for adding steel fibers to the mixture, stirring time not less than 3min. Cleaning rock face Remove slag pumice, excavation face wall and debris; handle smooth excavation face; installation work platform; flushing with high pressure on the surface of Feng Shui gun, mud rock water and easy deliquescence, using compressed air cleaning rock surface; buried concrete thickness control injection mark; the surface by spraying water pipe buried site drainage, The effect is not good water aquifer can be set of blind drainage, of water can be cut water drainage. After the acceptance of the warehouse surface, the micro seepage rock surface shall be dried by wind before the spray is started. In addition to the slope soil slope and slope of loose stone, dross clean, but also deal with the slope leveling compaction, and then from the bottom up segmentation followed by injection. Spraying concrete on loose soil is strictly forbidden. Steel mesh Slope protection: spray C20 concrete, steel mesh, anchor rod, drain hole. The steel mesh is made of smooth steel bars (I grade steel bars) with yield strength of 240MPa. The first jet 3cm ~ 5cm thick concrete, and then try to close to the rock hanging steel mesh, the sag of large parts can be added, expansion screw tensioning steel wire mesh, hang Pu steel mesh and anchor, and additional reinforcement (or bolts) are firmly connected, finally 2 times to 4 times of spraying design thickness. The injection points The concrete operation segments and segments are carried out in sequence, and the spraying order is from top to bottom so as to prevent the rebound material from covering the non spraying surface. Layered spray, the latter layer of concrete in the previous layer after the end of the condensate, and if the final 1h after the re injection, should first use high-pressure Feng Shui sprayed layer. The spraying operation follows the excavation face, and the concrete is condensed to the next cycle. The firing time shall not be less than 3h. Strict implementation of jet spraying operation machine: operation procedures should be continuous feeding to the injection machine; injection machine working pressure remained stable; completed or aborted injection operation, should be injection machine and conveying material clean product tube, to prevent pipe blockage. In order to reduce the amount of springback and improve the quality of spraying, the nozzle should be in good working condition. The air pressure is adjusted, the nozzle is kept perpendicular to the spray surface, the spray distance is controlled in the range of 0.6m to 1.2m, and the correct spiral trajectory is adopted to spray the construction technology. Just after the injection part should be examined (by spraying thick buried the set point, probe and high precision instrument section detection) does not meet the thickness requirements, timely spray treatment. The net should be sprayed to no obvious net. Four, wet spraying concrete construction technology In the tunnel, the wet spraying process is carried out by Meister (MEYCO) spraying machine, and the small slope wet spraying machine is used for artificial shotcrete. 1, shotcrete construction process Construction process flow chart 2, shotcrete construction process measures (1) preparation before injection; Mixing ratio The mix proportion of shotcrete shall be determined by laboratory test and field large sample test, and shall meet the requirements of construction drawing. Under the premise of guaranteeing the performance index of shotcrete layer, the amount of cement and water shall be reduced as much as possible. The amount of mixed elerating should be determined by field tests, sprayed concrete initial setting and final setting time should meet the construction drawings and site injection process requirements, mix ratio test results shall be submitted to the engineer, on-site grouting concrete mix should be accordance with the approved construction than the supervision engineer. For steel fiber shotcrete, steel should be selected to test the fiber content, and shall comply with the requirements of the construction drawings, the ratio in addition to meet the requirements of CECS38:92 and the above requirements should also meet the minimum requirements of toughness of steel fiber reinforced concrete. Minimum toughness value of steel fiber reinforced concrete Mixing and transportation of concrete All qualified cement, steel fiber, micro fiber, sand and water reducing agent are uniformly placed in the material warehouse (silo) of mixing station, and the steel fiber should be stored in a fixed warehouse. After the quality department according to the Opening Notice of concrete, the test room according to the opening notice requirements to provide concrete mixing ratio to the mixing station. Mixing station in accordance with the opening notice, concrete mix ratio requirements, timely inspection of raw materials, the amount of materials to meet the needs of the supply. Adjust the weighing device and running equipment of the mixing station. The allowable deviation of weighing shall conform to the following provisions: 1. Cement and accelerator are all 2%; 2, sand and stone are + 3%. When the concrete is mixed, cement, steel fiber, sand, water and water reducing agent are added into the concrete mixing tank to be stirred. Mixing time is not less than 180s, steel fiber in the concrete distribution is uniform, not a mass. The laboratory tests the slump of the concrete at the concrete outlet and the work face of the concrete and reasonably adjusts the concrete slump to meet the requirements. Ensure the slump control between 8 ~ 12cm concrete in the process of transportation, should try to shorten the delivery time, to avoid the separation and concrete slump loss is too large. Mixture in transportation, storage process, to prevent rain, water dripping and large stones and other debris mixed into the mixture before entering the jet machine must be screened. Preparation of the job site A surface treatment Sprayed concrete, should be the bedrock surface clean, clean the loose stones, injection half an hour before flushing the rock and make an operation of rock surface in semi dry state, for water and easy deliquescence, mud rock, application of high pressure air cleaning rock surface will be the bedrock surface clean. Cleaning sequence should go up and down, and there is water seepage on the bedrock surface, it should be first connected to the drain pipe to lead, to prevent spraying concrete seepage and wash away. B embedded shotcrete thickness control sign, the length of the rod is determined according to the thickness requirement of concrete. C work area is well ventilated and adequate for lighting. Before the operation of D injection, the injection, supply, air, water and electricity should be checked and run thoroughly. Technical preparation Make clear the scope of concrete injection (indicating elevation and pile number) on the spot, carry out cross sectional survey in time, check whether or not the surface of concrete injection bin is under excavation, organize excavation acceptance and rock surface cleaning and acceptance before entering the next process. Injection equipment preparation Injection equipment should be good performance, feeding is continuous and uniform, the feeding pipe should be able to withstand at least 0.8MPa working pressure, and wear resistance, the manipulator should be flexible and convenient operation, can be up and down along the nozzle moving parallel to the rock surface, can do circular motion in a diameter. Spraying car should be arranged according to the site spray situation, reasonable placement position, put down support feet, connect good cable, wind pipe, speed accelerator according to need to calculate and move to the scene. (2) stratified spraying; First, when the spraying operation starts, the hopper and the feed pipe are lubricated with a paste (50 to 100kg of water). First, the operation starts with spraying the car to send the wind and water supply, check and adjust the wind pressure, the air pressure control at 9kg/cm2, the water pressure is 4kg/cm2. Then turn on the mainframe and feed it at last. When the concrete enters the spraying hopper, the injection speed of the spraying vehicle is adjusted at the start of the main machine, and the injection speed should be controlled at 10 ~ 15m3/h. According to the requirement of concrete mix ratio, the speed setting additive quantity is controlled by the speed of injection and the parameter of adding amount of accelerator. The amount of setting agent of accelerator is adjusted to control the adding amount of accelerator. When the material is delivered to the nozzle, the air valve is opened and the accelerating agent pump is started, and the accelerator is penetrated into the concrete by the high wind pressure at the nozzle so as to achieve the effect of quick coagulation. The distance between spray gun and rock surface and injection angle The distance from the rock face to the spray gun usually takes 0.6 to 1.2m, so that the best effect can be reached: the minimum resilience and the best compactness. The spray gun and the spray surface should keep 700 ~ 900 of the jet steel fiber reinforced concrete and the uniform distribution, due to the impact of non-standard operation caused by the gun is reduced to a minimum, the vertical working surface of the sprayed concrete, continuously and smoothly according to the circular or elliptical rotating jet. Spraying concrete and shotcrete sequence In order to make the concrete spray evenly and reduce the influence of nonstandard operation, besides the strict control of distance and angle, the way and order of spraying must be paid attention to. There are mainly two kinds of injection methods: one is based on concrete curved beam injection material from left to right (or vice versa) parallel superposition; the other is a concrete in a spiral way about 300mm injection, with a ring beam material half circle from left to right (or vice versa) for lateral movement. Through the practice, after a rebound injection quality and relatively easy to control, high efficiency, so generally used after an injection mode, in accordance with the first wall bottom arch, concave convex, first after the order from the bottom to the concrete spraying operation. 6, in the cavern of sprayed concrete, should be stratified to spray, spray a thick 5cm within the application, 5cm more than a jet spraying layer, thickness of roof control in 3 ~ 6cm, Local overbreak point is 5 ~ 10cm; stratified injection, after injection should be carried out in a layer of a layer of concrete before the final set, but not the interval is too long, if the final setting of 1h after injection, cleaning the surface of the concrete application of Feng Shui, in order to combine between the layers, resilient material shall be used repeatedly. When the spraying operation is close to the excavation face, the time interval of the concrete final setting to the next cycle shall not be less than 4h. The mixing of concrete, the parking time should not exceed 2 hours. Sprayed concrete shall be buried with spraying thickness mark, and shall be sprayed to the design level after approval by the engineer. The addition and dosage of the accelerator should be strictly controlled, and the duty leader and technical personnel should follow the inspection. The operation is completed or aborted, jet jet, jet car must be de Maistre (MEYCO) (or small wet spraying machine) and feeding tube cleaning clean. The rebound ratio of arch should not be greater than 25% in shotcrete, and the rebound ratio of side wall (Bian Po) should not be greater than 15%. To check, sprayed concrete compressive strength have on-site spraying and sampling, 3 in each group, material or mix change, should be another group. (3) construction of shotcrete with reinforced wire mesh (or machine woven mesh); Use of steel mesh A, the mesh size of reinforcing steel mesh, the specifications of steel bars used and the quality of the steel shall meet the requirements of the construction drawings, and the thickness of the protective layer shall not be less than 5cm. B and steel mesh shall be laid along the excavation surface, and the distance between the steel mesh and the wall shall be 3 to 5cm. The binding must be firm, and the steel mesh and the anchor bolt are connected together in the position of the anchor bolt. No anchor bolt shall be divided into 1 to 1.5m intervals, using impact drilling, drilling, reinforcing bar, bent hook and fixed reinforcing bar net. The thickness of shotcrete support of C and steel net shall meet the design requirements and the instructions of the supervising engineer. D when using the setting machine manufactured by the factory, the test of shotcrete shall be carried out to select the aggregate size and gradation (the laying requirements shall be the same as the steel mesh). Construction of shotcrete (or woven mesh) shotcrete Construction specification of reinforced concrete mesh (or wire mesh) shotcrete construction. Shall be governed by the relevant provisions of articles 6.7.1 to 6.7.2 of GBJ86-85. Five 、 steel fiber shotcrete construction 1 、 wet spraying steel fiber concrete construction process Construction process flow chart Unqualified qualified 2, wet sprayed steel fiber concrete construction measures (1) preparation before injection; Spray on the spray surface inspection of concrete, clear surface excavation blasting vibration of rock pumice or loose; flushing, water and easy to mud rock, should adopt high pressure wind sweeping rock surface; buried concrete thickness control injection mark; operation area should have good ventilation and adequate lighting; on construction machinery and equipment, wind, water pipes and wires to conduct a comprehensive inspection and test run; Water Leakage or seepage phenomenon serious area, the water hose will divert, construction drainage, water diversion work should be done before. Spray car according to the spray protection area set the correct position, put down support feet, power cable, wind pipe connection is good, speed accelerator according to need to calculate after, and carried to the scene. (2) mixing and transportation of mixture; Mixing in mixing plant mixing, spraying concrete in different parts of the mix, should be strictly in accordance with the approval of the engineer with the mixing ratio; mix the mixture by concrete mixing truck transport to the site, to spray car feed additives. (3) stratified spraying; Spraying operation should adopt the first wall, the back arch, the bottom-up, the first concave and the convex sequence construction. The nozzle and the spray surface should be vertical as far as possible, and the deflection angle should be controlled within 20 degrees. The distance between the nozzle and the spray surface should be about 1 meters. According to the actual situation, the spraying distance and direction should be adjusted at any time in order to ensure uniform and dense spraying layer, thus reducing the rebound amount of the aggregate. In the tunnel shotcrete, should be stratified to spray, spray a thick 5cm within the application, 5cm more than a jet spraying layer, thickness of roof control in 3~6cm, the local overbreak point may be 5~10cm; stratified injection, after injection should be carried out in a layer of a layer of concrete after the final set. But not if the interval is too long, the final setting of 1~2h after injection, Application of Feng Shui cleaning concrete surface, in order to facilitate the combination between layers. Mixing concrete parking time should not exceed 2 hours. Before spraying concrete, steel bars shall be embedded or the anchor rods shall be used as spraying thickness marks, and shall be sprayed to the design level after approval by the supervising engineer. The addition and dosage of the accelerator should be strictly controlled, and the duty leader and technical personnel should follow the inspection. When each layer is sprayed, it can not be concentrated once, to a layer thickness, a layer of thickness of 3~6cm, and then wait for its final coagulation, and then second layers of spray. When the spraying operation is finished or the jet is interrupted for some reasons, the deposited material in the spray truck and the delivery pipe must be removed. Six 、 concrete maintenance and quality inspection When the spray is finished for 2 hours, the water shall be sprayed and maintained, and the curing time shall be no less than 7d. When the temperature is lower than +5 degrees, water conservation shall not be allowed, and if necessary, insulation and anti freeze measures shall be adopted. Special maintenance personnel should be arranged at the site where large quantities of steel fiber reinforced concrete are sprayed. Take the core test in time and summarize the test report on time, and carry out quality evaluation and quality acceptance in time. The drill core shall be taken as the tensile test of the core sample with the diameter of 100mm as specified by the supervisor, and the data of the test result shall be reported to the supervisor. All drilled core shall be backfilled with dry cement mortar. Shotcrete construction is completed, should be according to the quality of pipe inspection procedure and supervision department regulations were issued by the inspection and assessment unit engineering standards. Seven, safety protection 1, shotcrete operators should bring special protective equipment, such as: masks, eyepiece, gloves, etc., construction personnel to enter the scene must be required to wear helmets and other protection. 2, high-altitude work must wear safety rope, seat belt. 3. Other safety protection shall be carried out in accordance with the requirements of the Ministry of safety supervision