NB/T 51043-2015Technical Specification for Repairing Collapse Shaft of Production Mine (English PDF)

Foreword

This document was issued on 27 October 2015 by the National Energy Administration of the PRC and takes effect on 1 March 2016.

It is a NB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

It is classified under ICS 73.020, Chinese classification P 00/09.

By Announcement No. 6 of 2015, dated 27 October 2015, the National Energy Administration approved and issued 96 energy industry standards (NB), including this specification, which is listed as item 62 with an approval date of 2015-10-27 and an implementation date of 2016-03-01.

This specification was formulated in accordance with the Notice of the National Energy Administration on Issuing the First Batch of Energy Sector Industry Standard Formulation and Revision Plans for 2012 (Guoneng Keji [2012] No. 83) and the Notice on Issuing the Administrative Measures for Industry Standardization in the Energy Sector (Trial) and Their Implementing Rules (Guonengju Keji [2009] No. 52). The drafting group carried out extensive investigation and research, summarized practical experience, referred to relevant domestic and foreign codes and standards, and widely solicited opinions.

This specification consists of 8 chapters and 2 appendices. Its main contents include general provisions, terms, basic regulations, investigation and assessment of vertical shaft collapse, repair and remediation of vertical shafts, removal and installation of vertical shaft equipment, auxiliary facilities, and acceptance and trial operation.

This specification is administered by the National Energy Administration; the China Coal Construction Association is responsible for its routine management, and Hunan Chuxiang Construction Engineering Co., Ltd. is responsible for the interpretation of specific technical content. Opinions or suggestions arising during implementation should be sent to Hunan Chuxiang Construction Engineering Co., Ltd. (No. 102 Xinmei Road, Tianxin District, Changsha, Hunan Province; postcode 410114).

Chief development organizations: Hunan Chuxiang Construction Engineering Co., Ltd.; Xishan Coal and Electricity Construction Engineering Group Co., Ltd.; Henan Energy and Chemical Construction Group Co., Ltd.

Participating development organizations: Pingmei Shenma Construction Engineering Group Co., Ltd.; Xiangtan University.

1 Scope

NB/T 51043-2015 governs the remediation and reconstruction of collapsed vertical shafts in operating coal mines. A shaft collapse in a working mine is a crisis: the shaft is the mine's lifeline for hoisting, ventilation and access, and the collapsed section is unstable, often water-bearing and surrounded by disturbed ground. The standard sets the general provisions and defined terms, then classifies shaft collapse damage into grades I to III by the height of the collapsed section and sets out the principles and the twelve stages of a remediation. It covers the investigation that must precede any work - the preliminary and the detailed survey of the collapse, the condition of the lining above and below, the hydrogeology and the state of the surrounding ground. The treatment follows: the stabilisation and consolidation of the collapsed zone, the grouting of loose material and of water-bearing strata, the removal of debris, and the repair of the shaft wall with its support and lining. The standard then deals with the restoration of the shaft equipment - the guides, buntons, pipes and cables - and the hoisting system, and with the safety measures that apply throughout, including monitoring of deformation and water inflow. The inspection and acceptance of the repaired shaft and the records to be kept close the standard. It applies to coal mines in China.

1.0.1 This specification is formulated to standardize the repair and remediation of collapsed vertical shafts, so that the work is safe and reliable, technically mature and economically reasonable.

1.0.2 This specification is applicable to repair and remediation projects for collapsed vertical shafts of production mines.

1.0.3 The repair and remediation of a collapsed vertical shaft is an emergency rescue and disaster relief operation, and the scheme shall be formulated on the principles of safety, speed and economy.

1.0.4 The repair and remediation of a vertical shaft shall be closely coordinated with the production activities of the whole mine, under unified command and dispatching.

1.0.5 In addition to this specification, vertical shaft repair work shall also comply with the provisions of the relevant current national standards, codes and regulations.

2 Terms

2.0.1 Shaft collapse: the phenomenon of fragmentation and caving of the shaft wall and the surrounding rock of a vertical shaft.

2.0.2 Collapse height: the distance from the upper edge to the lower edge of the part of the shaft wall that has collapsed or fragmented.

2.0.3 Cavity of collapse: the void formed after the surrounding rock has caved in.

2.0.4 Temporary supporting: support installed before permanent support in order to temporarily maintain the stability of the surrounding rock and ensure the safety of operations.

2.0.5 Permanent supporting: support installed to maintain the stability of the rock surrounding the shaft or roadway throughout its service life.

2.0.6 Construction platform: a working platform built during construction for safe and convenient operation.

2.0.7 Temporary hoists system: a hoisting and transport system set up temporarily during production and construction to move materials, facilities and personnel up and down.

3 Basic Regulations

3.1.1 According to the cause of collapse, vertical shaft collapses are classified into collapses affected by mining and collapses not affected by mining.

3.1.2 According to the collapse height and the damage to the ventilation, drainage and power supply systems and to the shaft equipment, the damage grade of a vertical shaft collapse may be determined in accordance with Table 3.1.2 (damage grades of vertical shaft collapse in production mines).

Table 3.1.2, grade I: cumulative collapse height not more than 5 m, and height of any single section not more than 3 m.

Table 3.1.2, grade II: cumulative height greater than 5 m and not more than 20 m, or height of a single section greater than 3 m and not more than 10 m.

Table 3.1.2, grade III: cumulative height greater than 20 m, or height of a single collapsed section greater than 10 m.

Note to Table 3.1.2: for a grade I or grade II collapse, where the ventilation, drainage or power supply system is damaged or the shaft equipment is damaged, the collapse damage grade shall be raised by one grade.

3.2.1 Before repair and remediation, a special demonstration of the necessity and feasibility of repairing the collapsed shaft shall be carried out, and a decision shall be made either to repair or to rebuild.

3.2.2 After a vertical shaft collapse, a special assessment of the underground safe production conditions shall be carried out, giving a conclusive opinion on whether to maintain, stop or partially stop mine production activities.

3.2.3 The repair and remediation scheme shall be selected according to factors such as the purpose of the shaft, the cause of collapse, the degree of damage and the geological conditions of the damaged section.

3.2.4 The repair of the vertical shaft wall may be carried out in three sections: reinforcement above the collapsed section, repair of the collapsed section, and reinforcement below the collapsed section.

3.2.5 Before repair and remediation of a collapsed vertical shaft begins, the hoisting, ventilation, drainage, compressed air, water supply, power supply, signalling, communication and lighting systems of the mine shall be restored or established.

3.2.6 Before repair and remediation construction, gas and other harmful gases underground and at the working face shall be checked and special safety technical measures shall be prepared; in coal and gas outburst mines, all operations disturbing outburst coal seams shall be stopped.

3.3.1 Repair and remediation should follow the procedure below. Item 1, establishment of a headquarters: set up a headquarters composed of the safety, technical, production and other departments.

Item 2, preliminary investigation: collect and analyse the original archive data of the mine shaft, carry out site investigation, establish a deformation monitoring network for underground and surface buildings and structures, make a preliminary analysis of the cause of collapse, make a preliminary assessment of the current state and safety of the collapse, and propose an emergency response plan.

Item 3, detailed investigation: on the basis of the preliminary investigation results, prepare a detailed investigation plan, further ascertain the current state of the collapse, determine the damage grade, assess the current safety of the shaft, and propose revisions to the emergency response plan.

Items 4 and 5: scheme design, preparing the repair and remediation scheme for the collapsed vertical shaft on the basis of the detailed investigation results; expert review, organizing experts to review the scheme design.

Items 6 and 7: repair and remediation design, prepared according to the expert review opinions and submitted to the competent superior authority for approval; construction organization design, prepared according to the repair and remediation design.

Item 8, construction and supervision: organize construction according to the repair and remediation design and the construction organization design, and supervise the construction process.

Items 9 and 10: equipment installation, restoring the shaft equipment and systems of the vertical shaft; project quality acceptance, organized after the shaft, its equipment and systems have been restored and passed self-inspection.

Items 11 and 12: trial operation, a joint trial operation of the shaft functions for not less than 1 month after the project quality acceptance is passed; completion acceptance, organized after the trial operation is passed.

3.3.2 Where conditions for detailed investigation of the collapsed shaft are not available, emergency rescue may proceed directly on the basis of the emergency response plan drawn up from the preliminary investigation. Once the collapse is effectively controlled, work shall proceed in accordance with items 3 to 12 of clause 3.3.1 of this specification.

3.3.3 After completion of the shaft repair, deformation observation shall be carried out on the shaft and the surface buildings and structures.

4 Exploration and Assessment of Vertical Shaft Collapse

4.1.1 Investigation and assessment of a vertical shaft collapse shall be divided into two stages, preliminary investigation and detailed investigation. The preliminary investigation shall establish the basic site situation, make a preliminary assessment and prepare the detailed investigation plan and the emergency response plan; the detailed investigation shall be based on the preliminary investigation and provide the basis for the repair and remediation design.

4.1.2 Before the preliminary investigation, the following data shall be obtained: 1 the geological data of the mine; 2 the water inflow of the mine; 3 the survey data relating to the collapsed vertical shaft; 4 the mining and excavation data of this mine and of adjacent mines.

Items 5 to 8: the surface and underground correlation plan; the original design documents of the vertical shaft; the completion acceptance data of the vertical shaft; other relevant data of the mine.

4.1.3 For a vertical shaft with grade II or grade III damage, the scope of investigation and assessment shall include, in addition to the collapsed shaft, the adjacent surface and underground buildings and structures that may be affected.

4.1.4 The site situation shall be recorded in detail during investigation and assessment; the preliminary investigation may be recorded in accordance with Appendix A and the detailed investigation in accordance with Appendix B of this specification.

4.2.1 A special investigation plan shall be prepared before the investigation of a vertical shaft collapse.

4.2.2 Personnel entering the collapsed shaft to carry out investigation work shall proceed in order from top to bottom.

4.2.3 The method of investigating a vertical shaft collapse shall be selected according to site conditions.

4.2.4 The main contents of the investigation of a vertical shaft collapse are: 1 the collapse, deformation, cracking, inclination and fragmentation of the shaft; 2 the damage to the hoisting system; 3 the damage to the shaft equipment.

Items 4 to 6: the damage to the underground ventilation, drainage, water supply, power supply, lighting, communication and signalling systems; the damage to surface buildings and structures; the damage to neighbouring shafts and roadways.

Items 7 to 9: the accumulation of collapsed material in the shaft and an estimate of its volume; the harmful gas conditions of the mine, with the collapsed shaft as the focus; the water inflow conditions of the mine, with the collapsed shaft as the focus.

Items 10 and 11: review of the measured geological section drawing of the shaft; collection of the relevant geological data of the mine.

4.2.5 The key points of the investigation of the collapsed section are: 1 the position of the collapse; 2 the height of the collapsed section and the volume and shape of the collapse cavity; 3 the failure of the surrounding rock in the collapsed section.

Items 4 to 6: the original support structure of the shaft and its damage; the damage to the shaft equipment; the engineering geological and hydrogeological conditions of the collapsed section.

4.2.6 The key points of the investigation of adjacent shafts, roadways and surface buildings and structures are: 1 the damage to adjacent shafts and roadways; 2 surface subsidence and the damage to buildings and structures.

4.3.1 A special assessment shall be carried out on the collapsed vertical shaft.

4.3.2 The assessment of a vertical shaft collapse shall cover: 1 basic situation, an overview of the collapsed vertical shaft; 2 investigation methods, the methods and instruments used in the investigation.

Item 3, collapse situation: a description of the vertical shaft collapse, including schematic diagrams and photographic and video records.

Item 4, cause analysis: on the basis of the investigation results and an analysis of the current state of the collapse, infer the main causes and the triggering mechanism of the vertical shaft collapse.

Item 5, assessment of current state: analyse the stability of the shaft, determine the damage grade of the vertical shaft collapse and make a judgement on the development trend of the collapse.

Item 6, safety assessment: comprehensively analyse the collected information and data together with the investigation results, carry out hazard identification and risk evaluation of the collapsed vertical shaft, and give a conclusive opinion on the safety of the repair and remediation work and on the safety of underground production.

Items 7 and 8: assessment of repair value, see clause 3.2.1 of this specification; recommendations, identifying possible construction difficulties and safety hazards of the repair and remediation, giving an opinion on the repair and remediation of the collapsed shaft, and giving an opinion on whether underground production activities should be stopped.

5 Management and Remediation of Vertical Shaft Collapse

5.1.1 The repair and remediation of the shaft shall follow the repair and remediation principles established in Section 3.2 of this specification.

5.1.2 A special design shall be prepared for the repair and remediation of the shaft, and a review of it shall be organized.

5.1.3 During the repair and remediation of the shaft, deformation observation shall be carried out on the shaft and on the surface buildings and structures within the zone affected by the vertical shaft collapse.

5.1.4 Before repair and remediation construction of the shaft, the time at which shaft wall repair begins shall be determined according to the rate of change of the deformation observation data.

5.1.5 The design of shaft repair and remediation shall adopt the dynamic design method: according to feedback from construction and monitoring, the design scheme and the selected design parameters shall be verified, and where conditions differ from those of the original design, the original design shall be supplemented or modified.

5.1.6 For a vertical shaft collapse caused by groundwater or quicksand, the water inflow and quicksand shall be treated before repair and remediation.

5.2.1 The establishment or modification of a temporary hoisting system shall be subject to comparison of schemes and demonstration.

5.2.2 Where the original hoisting system is usable, it shall be used; where the original hoisting system can be made usable by modification, the temporary hoisting system shall be established on the basis of the original system; where the original hoisting system cannot be modified or the shaft has no hoisting system, a new temporary hoisting system shall be established.

5.2.3 When a temporary hoisting system is established, a shaft sealing deck, a fixed deck and safety railings shall be installed at the shaft mouth, and a sheave platform and a dumping platform shall be installed on the headframe.

5.2.4 Not fewer than 3 stabilizing devices shall be provided for each deck of the hanging scaffold.

5.3.1 The support used to repair the wall of a collapsed vertical shaft is divided into temporary support and permanent support. The support scheme shall be selected in accordance with the following: 1 temporary support should use rock bolts with mesh and shotcrete, steel shaft rings or similar supports, or a combined support formed from them.

Item 2: permanent support should use a reinforced concrete shaft wall; where the zone affected by the collapse is large and the surrounding rock is fragmented, a composite shaft wall should be used.

Item 2, sub-item 1): where the shaft wall is cast using the top of the collapsed material or the top of the fill as the construction platform, the reinforced concrete shaft wall should be built in sections, working within each section from bottom to top; the section height shall be determined according to the surrounding rock but shall not exceed 5 m, and shall be reduced when passing through coal or through fragmented and loose rock.

Item 2, sub-items 2) and 3): the strength grade of the reinforced concrete used for the shaft wall shall be higher than the design strength of the original wall concrete; concrete shall be placed symmetrically and evenly, not more than 300 mm high per lift, with waterproofing measures taken before placing and an early-strength agent added.

Item 3: in the repair of the collapsed section of a hoisting shaft, shotcrete, mesh-reinforced shotcrete, rock bolts, metal mesh, steel shaft rings and similar shall not be used as the permanent inner shaft wall.

5.3.2 When the vertical shaft is in a stage of violent collapse and the zone affected by the collapse is expanding rapidly, the shaft shall be backfilled immediately.

5.3.3 The construction platform for repair and remediation should be selected as follows: 1 for a shaft with grade I collapse damage, if the original shaft equipment is usable after overhaul, a construction platform may be formed by modifying the original hoisting conveyance; otherwise a hanging scaffold should be used as the construction platform.

Item 2: for a shaft with grade II or grade III collapse damage, where the collapsed material has accumulated up to the collapsed section, a construction platform may be built on top of the accumulated material, or a hanging scaffold may be used as the construction platform.

Item 3: for a shaft with grade II or grade III collapse damage, where the collapsed material has not accumulated up to the collapsed section, the shaft may be backfilled up to the collapsed section to form a construction platform.

5.3.4 Repair and remediation of the shaft wall shall proceed in the order: above the collapsed section, then the collapsed section, then below the collapsed section.

5.3.5 Repair of the shaft wall above the collapsed section shall comply with the following: 1 failed old shaft wall shall be removed, and the broken edge of the wall shall be trimmed into steps.

Item 2: for a shaft with grade I damage, the old shaft wall over not less than 5 m above the collapsed section shall be reinforced; for a shaft with grade II or grade III damage, the old shaft wall over not less than 10 m above the collapsed section shall be reinforced.

Item 3: the reinforcement design of the old shaft wall shall take into account the effect of the change in shaft diameter on the function of the shaft.

5.3.6 Repair and remediation of the shaft wall in the collapsed section shall comply with the following: 1 temporary support of the surrounding rock shall be installed before the shaft wall in the collapsed section is repaired; 2 temporary support of the collapse cavity and removal of loose rock shall proceed from near to far.

Items 3 and 4: after loose rock has been removed from the collapsed section, the exposed surrounding rock shall first be sealed with shotcrete 30 mm to 50 mm thick; where conditions in the collapse cavity do not allow temporary support to be installed, no work shall be carried out inside the cavity.

5.3.7 Repair and remediation of the old shaft wall below the collapsed section shall proceed as follows: 1 remove the cracked and deformed old shaft wall; 2 reinforce the old shaft wall over 5 m to 10 m below the broken edge.

5.3.8 The method of filling the collapse cavity may be selected in accordance with Table 5.3.8 (methods of filling the collapse cavity).

Table 5.3.8, No. 1, cavity fully provided with temporary support: fill the collapse cavity at the same time as the shaft wall is built.

Table 5.3.8, No. 2, cavity partly provided with temporary support: fill the collapse cavity at the same time as the shaft wall is built; where the filling is not complete, carry out secondary filling by grouting behind the wall after the wall has been restored.

Table 5.3.8, No. 3, conditions for temporary support not available in the cavity: backfill the shaft and the collapse cavity.

Table 5.3.8, No. 4, cavity partly filled by collapsed material: the part filled by collapsed material shall first be consolidated by grouting; the unfilled part shall be filled at the same time as the shaft wall is built.

5.3.9 The shaft wall of the repaired section and the filling behind the wall shall comply with the following: 1 where the collapse cavity has not been filled before wall repair, filling of the cavity may proceed from bottom to top together with the casting of the shaft wall.

Item 2: where the collapse cavity was filled before wall repair by method No. 3 of Table 5.3.8, excavation and temporary support shall proceed from top to bottom, and after the design section height has been reached, permanent support shall be installed from bottom to top.

Items 3 and 4: the strength of the repair support structure in the collapsed section shall be not less than that of the original support structure; construction joints where the new and old shaft walls meet shall be treated by grouting.

Items 5 and 6: for a vertical shaft collapse caused by mining influence or by a fall in the groundwater level, compressible devices shall be installed in the repaired section to form a compressible section; for a shaft with grade II or grade III damage, a wall base shall be provided at the lower junction of the new and old shaft walls.

Item 7: during shaft wall repair, construction records such as construction logs and acceptance records of concealed works shall be kept; measured longitudinal and cross sections of the shaft, a geological column of the shaft and sketches of the collapsed section shall be drawn; the water inflow of the shaft shall be measured regularly and a ledger kept.

5.3.10 The design and construction of rock bolts (cables) shall comply with the following: 1 rock bolts (cables) may form a combined support with metal mesh, shotcrete or steel shaft rings; 2 the design of bolt (cable) support should use the engineering analogy method, or combine it with monitoring measurement and theoretical calculation.

Item 3: the type of rock bolt (cable) may be selected according to the collapse situation, the geological conditions and the function of the vertical shaft.

Item 4: before rock bolts (cables) are installed in strata with fragmented rock, well-developed fractures or abundant groundwater, the water should be drained and the surrounding rock should then be sealed with shotcrete.

5.4.1 General provisions: 1 before shaft grouting, the drilling technique, grout mix proportions, grouting method and grouting technique should be established by trial construction at a representative location, in order to obtain the grouting parameters.

Items 2 and 3: surface grouting, working-face grouting or grouting behind the wall shall be selected for the repair and remediation of a collapsed vertical shaft according to the collapse situation; before shaft wall repair, the mined-out areas within the zone of mining influence shall first be filled by grouting.

5.4.2 Grouting behind the wall shall comply with the following: 1 after the shaft wall has been restored, grouting behind the wall shall be carried out on the old shaft wall within 10 m above and below the collapsed section, on the restored new wall of the collapsed section and at the junctions of the new and old shaft walls.

Items 2 and 3: grouting behind the wall in the collapsed section shall be carried out only when the wall concrete has reached not less than 70% of its design strength; grout holes should be arranged in a staggered quincunx pattern.

Item 4: grouting should proceed in sections from top to bottom, and within each section from bottom to top, followed by a repeat grouting pass from top to bottom.

Item 5: the grouting station should be located close to the grouting point. A working-face grouting station may be set up on the hanging scaffold or in a roadway connected to the shaft.

5.4.3 Surface grouting should be used for filling mined-out areas or where conditions for underground grouting are not available.

5.4.4 Grouting of mined-out areas affecting the stability of the shaft shall comply with the following: 1 the spatial distribution of the mined-out areas shall be ascertained before construction; 2 grout holes shall penetrate into the mined-out area.

Items 3 and 4: grout holes shall be combined with construction investigation, and the grouting scheme shall be adjusted according to the geological conditions revealed by drilling; grout holes should be laid out sparse first and dense later, and drilled near first and far later.

Items 5 and 6: the density of grout holes along the strike of the coal seam should be less than their density along the dip of the coal seam; after the mined-out area has been fully grouted, grout shall be injected into the caved zone and the fractured zone of the mined-out area.

5.4.5 Reinforcement grouting from the working face shall comply with the following: 1 reinforcement grouting from the working face shall be used in the following cases: 1) where the collapse height is large and the shaft has been backfilled above the collapsed section to form a construction platform for shaft repair; 2) reinforcement and water sealing of soft layers and fragmented rock within the zone affected by the collapse; 3) reinforcement of the material accumulated in the collapse cavity.

Item 2: in reinforcement grouting of collapsed accumulations, the grout spread radius and the initial setting time of the grout shall be controlled, and the reinforced zone shall not extend beyond the cavity.

Item 3: grouting materials may be selected as follows: 1) filling materials should be mainly inert materials, taking into account locally available, low-cost, non-polluting materials with a high stone-forming rate; the strength of the set grout should be 3 MPa to 5 MPa.

Item 3, sub-items 2) and 3): materials for water-sealing grouting should be cement-clay grout, cement-fly ash grout, cement-sodium silicate grout and chemical grout; reinforcement of the surrounding rock should use cement grout and cement-sodium silicate grout.

5.4.6 The effectiveness of shaft grouting shall be verified.

5.5.1 Clearing of collapsed material should proceed from top to bottom.

5.5.2 During clearing of collapsed material, measures shall be in place to prevent objects falling from height; removed equipment, loose wall rock, broken rock and similar shall not be thrown directly down the shaft.

5.5.3 Before clearing of collapsed material begins, the following preparations shall be made: 1 prepare safety technical measures; 2 ascertain the basic composition and accumulation of the collapsed material and estimate the workload.

Items 3 and 4: coordinate the division of work among the trades as required by the construction organization design for the repair and remediation of the collapsed shaft; designate a surface stockpile area for collapsed material and determine the surface transport scheme.

5.5.4 Clearing of the part of the collapsed section filled with collapsed material shall be carried out in sections, alternating with shaft wall support, with support installed promptly.

5.5.5 Clearing should be carried out by classifying the collapsed material by type, shape and size: rock and concrete blocks that cannot be carried manually or are larger than the opening of the loading conveyance should be broken into smaller pieces underground before being hoisted out; irregularly shaped shaft equipment shall be cut into sections and bundled before being hoisted out.

5.5.6 When collapsed material is cleared manually, voids below the working face shall be probed; any void found shall be dealt with before work may continue.

5.5.7 During hoisting, the hoisted material shall not scrape or strike the shaft equipment, the shaft wall, the hanging scaffold, the fixed deck or the bell mouth.

6 Removal and Installation of Vertical Shaft Equipment

6.1.1 Before repair and remediation, the deformation and damage of the original shaft equipment and surface facilities shall be inspected, and the safety and repair value of the original equipment shall be demonstrated.

6.1.2 Shaft equipment may be restored according to the original design; where improvements are needed, a design change shall be made.

6.1.3 Shaft equipment shall be classified and marked in place with conspicuous signs according to the conclusions of inspection and demonstration.

6.2.1 Removal work shall proceed from top to bottom.

6.2.2 Damaged shaft equipment between the collapsed section and the top of the accumulated collapsed material shall be removed first; removal of shaft equipment below the top of the accumulated material shall proceed together with the clearing of collapsed material.

6.2.3 Removed equipment shall be hoisted to the shaft mouth or to the shaft bottom station and shall not be dropped to the bottom of the shaft.

6.2.4 Shaft equipment to be removed shall first be secured to prevent it falling during removal.

6.2.5 Damaged shaft equipment should be hoisted to the surface for repair.

6.3.1 Damaged shaft equipment shall be replaced and shall not be used in a downgraded condition; repaired shaft equipment shall be used only after passing inspection.

6.3.2 Except for cage-resting beams, top beams of wooden wedge guides, top beams and bottom beams of steel guide frames, and brackets of drainage and water supply pipes, which shall be restored in beam pockets, the damaged brackets of other wedge guide beams, steel frame support beams and similar may be restored with resin rock bolts.

6.3.3 Vertical rigid shaft equipment, pipelines and similar in the repaired section of the shaft wall shall use structural forms that accommodate settlement of the shaft wall.

7 Auxiliary Facilities

7.0.1 Where the original ventilation system has been damaged, a temporary ventilation system shall be established, complying with the following: 1 the air quantity, air velocity and harmful gas content at the working face shall meet the requirements of the Coal Mine Safety Regulations.

Item 2: ventilation may be provided by forcing air with auxiliary fans, or full-pressure ventilation may be achieved by changing the airflow direction, controlling the air velocity and similar means.

Item 3: auxiliary ventilation shall use the "three dedicated" power supply or be provided with standby auxiliary fans of equal capacity with automatic switchover; the auxiliary fans and their starting devices shall be located at the intake airway more than 20 m from the shaft mouth.

7.0.2 Drainage system: where water accumulates at the working face, a sump shall be provided at the working face.

7.0.3 Compressed air supply: undamaged compressed air mains above the collapse zone of the shaft may be used, or new compressed air pipes may be laid, to supply air to the working face.

7.0.4 Signalling and communication system: audible and visual signals and communication links shall be provided between the working face, the hanging scaffold, the shaft mouth and the winder house.

7.0.5 Power supply system: where the original power supply system has been damaged, a temporary power supply system shall be established.

7.0.6 Lighting for shaft repair and remediation work shall be ensured; lighting facilities shall be installed on the construction platform and above and below the hanging scaffold.

8 Acceptance of Project and Commissioning

8.1.1 After completion of the repair and remediation project for a collapsed vertical shaft, the construction unit shall organize the relevant personnel to carry out self-inspection; after passing self-inspection, it shall submit an application for project acceptance to the production unit, which shall organize the project acceptance.

8.1.2 The acceptance of a vertical shaft collapse repair and remediation project shall include the following documents: 1 the investigation and assessment report of the collapse repair and remediation; 2 the repair and remediation design documents; 3 minutes of drawing review and records of design disclosure; 4 the construction organization design.

Items 5 to 7: design change documents; as-built drawings of the collapse repair and remediation; copies of the qualification certificates of the design, construction, supervision and testing or inspection units.

Items 8 to 10: the collapse accident cause analysis report and handling records; construction logs, construction records, construction self-inspection and intermediate acceptance records; acceptance records of concealed works and acceptance reports of sub-item works.

Items 11 to 13: the ledger of shaft water leakage and the measured records of changes in water quantity; monitoring reports of surface and underground buildings and structures; pull-out test records of rock bolts (cables).

Items 14 to 17: test reports of concrete specimens; material test reports and certificates of conformity; the verification report on the effectiveness of shaft grouting; other relevant documents.

8.2.1 After the project quality acceptance has been passed, trial operation of the repaired vertical shaft shall be carried out.

8.2.2 A trial operation implementation plan shall be prepared before trial operation.

8.2.3 During trial operation, monitoring of the shaft equipment, the key parts of the headframe and the operating condition of the hoisting system shall be intensified.

8.2.4 During trial operation, records shall be kept, problems found shall be rectified promptly, and the trial operation period shall be extended according to the actual situation.

8.2.5 The trial operation period shall be not less than 1 month, and a trial operation report shall be provided at the end of the trial operation.

8.2.6 After the trial operation has been passed, completion acceptance shall be organized and a completion report submitted.