Circular No. 16/2020/TT-BTNMT stipulates technical procedures for excavation work and geological and mineral sampling at excavation sites.

CIRCULAR

TECHNICAL REGULATIONS ON THE WORK OF OPENING AND DIGGING ENGINEERING PROJECTS AND TAKING GEOLOGICAL SAMPLES, MINERALS AT OPENING AND DIGGING ENGINEERING PROJECTS Clauseg at the excavation worksite

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Pursuant to the Law on Minerals dated November 17, 2010;

Pursuant to Decree No. 36/2017/NĐ-CP dated April 4, 2017 of the Government on the functions, tasks, powers, and organizational structure of the Ministry of Natural Resources and Environment;

At the proposal of the Director General of the Vietnam Geological and Mineral Resources Administration, the Director of the Science and Technology Department, and the Director of the Legal Department;

The Minister of Natural Resources and Environment issues this Circular on technical regulations for the work of opening and digging engineering projects and taking geological samples, minerals at opening and digging engineering projects.

PART I

GENERAL PROVISIONS

Article 1. Scope of Regulation

This Circular stipulates technical procedures for the work of opening and digging engineering projects and taking samples at such projects in basic geological surveys on minerals and mineral exploration. This Circular does not regulate geophysical and hydrogeological works related to the implementation of opening and digging engineering projects. Such works shall be carried out in accordance with laws on minerals and other relevant laws.

Article 2. Applicability

This Circular applies to state management agencies on geology and minerals, organizations, and individuals involved in basic geological surveys on minerals and mineral exploration.

Article 3. Explanation of Terms

In this Circular, the following terms are understood as follows:

1. Engineering projects include: clearing exposed surfaces, pits, trenches, wells, and tunnels in basic geological surveys on minerals and mineral exploration.

2. Clearing exposed surfaces is a simple geological project that requires cleaning up at locations where geological and mineral objects have been discovered during geological mapping and mineral resource assessment.

3. Pits are simple geological projects designed to discover minerals, study geological and mineral characteristics, and take geological and mineral samples.

4. Trenches are simple geological projects with rectangular cross-sections designed to discover and clarify geological structures, thickness, relationships between ore bodies and surrounding rocks, and collect various types of geological and mineral samples.

5. Wells are main geological projects including shallow and deep wells, designed to discover and control ore bodies that may lie horizontally or be placer deposits; clarify geological and mineral characteristics, and collect various types of geological and mineral samples.

6. Shafts are main underground geological projects including horizontal and inclined shafts, designed to discover and control ore bodies, clarify geological features, ore body boundaries, and collect various types of geological and mineral samples.

7. Exhaust ventilation is a method using fans at entrances or mouths of projects to extract air from within the projects and allow clean air to circulate inside.

8. Supply ventilation is a method using fans at entrances or mouths of projects to push fresh air into the projects and allow air inside to escape.

9. Combined ventilation is a method combining both exhaust and supply ventilation methods.

10. Geological and mineral samples include various types of samples such as block samples, point samples, trench samples, stripping layer samples, and block samples, taken to serve the purposes of: analyzing mineral composition, rock structure, fossils, isotopes, mechanical properties, specific gravity, geophysical parameters, original rock geochemistry; detecting mineralization through rolling stones; checking for potential mineralization in exposed surfaces; assessing mineral quality and recovery rate.

11. Block samples are samples taken in their original form from rocks or ores at opening and digging engineering projects.

12. Point samples are samples taken in the form of several uniform-sized blocks from the sampling object according to a designed grid, then combined.

13. Point samples are taken in the form of point trenches or point grids.

14. Trench samples are samples taken along trenches at opening and digging engineering projects on geological and mineral objects.

15. The size of trench samples depends on geological and mineral objects and the distribution characteristics of ore components, determined in the basic geological survey project plan on minerals and the mineral exploration project plan (hereinafter referred to as the geological project plan).

16. Stripping layer samples are samples taken by stripping a layer of mineral across the entire distribution area of the exposed ore body at the opening and digging engineering project.

17. Block samples are samples taken in the form of complete layers or strata containing ore or in layers of rock requiring research. The size and weight depend on specific research purposes, determined in the geological project plan.

Chapter II

TECHNICAL REGULATIONS ON THE WORK OF OPENING AND DIGGING ENGINEERING PROJECTS AND TAKING GEOLOGICAL SAMPLES, MINERALS AT OPENING AND DIGGING ENGINEERING PROJECTS

Section 1

TECHNICAL REGULATIONS ON THE WORK OF OPENING AND DIGGING ENGINEERING PROJECTS

Article 4. General Requirements for Excavation Works

1. For geological projects using adits that must be implemented according to the approved project by the competent authority, the adits must meet the following requirements:

a) Prepare a design description for the adit based on the synthesis of field survey results, fully reflecting the contents: topography-geomorphology, geology, geophysics, hydrogeology-geotechnical geology; specifically describing the characteristics and scale of adverse impacts affecting the works;

b) Have a design drawing for the adit designed based on the synthesis and analysis of information specified in point a of this clause, combined with the analysis of mineral exploration signs, ore body characteristics, exploration network, ensuring the highest efficiency of the adit regarding the distance from the adit entrance to the ore body, safety level, and environmental protection. The planned cross-sections must show the types of rock strata cut through, the expected distance to encounter geological objects, and minerals;

c) Have measures to ensure construction safety and environmental protection in accordance with the provisions of the law;

d) Have a construction plan and schedule.

2. During the excavation of trenches, shafts, and adits where explosives are used, blasting operations must comply with the provisions of the law.

3. Support materials for excavation works: trenches and shafts deeper than 2.0 meters and adits must be supported to ensure safety. Support materials include wood, concrete, reinforced concrete, and metal. The support materials must meet the current technical standards, regulations, and technical provisions.

4. Machinery and equipment for drainage work:

a) Pumps must comply with the current technical standards, regulations, and technical provisions. Depending on the flow rate of water entering the excavation works, suitable pumps with appropriate capacity should be used;

b) The electric motor of the pump must be waterproof;

c) Water discharge pipes from the pump out of the excavation works must comply with the current technical standards, regulations, and technical provisions. If the wastewater has a high acid concentration, the pipes must be made of acid-resistant material or treated to prevent acid corrosion.

5. Ventilation equipment: all trench, shaft, and adit excavation works must have ventilation equipment to provide sufficient clean air, limit dust, toxic gas, and explosive gas concentrations, ensuring safety. Ventilation equipment includes:

a) Fans must have a capacity equal to or greater than the calculated capacity;

b) Air ducts must comply with the current technical standards, regulations, and technical provisions. The diameter of the ducts ranges from 108mm to 700mm, ensuring tightness and no air leakage, with a maximum air loss rate not exceeding 5.0% per 100 meters of pipe;

c) Install ventilation fans according to the following rules:

In case of using the push method, the distance between the fan and the exhaust airflow must be at least 10 meters;

In case a single fan cannot supply the required air volume for the works as calculated, multiple fans connected in series or parallel must be used, and there must be a design ensuring technical requirements and safety. When connected in series, the suction port of the subsequent fan must be placed at a position where the pressure from the first fan still remains about 20%.

6. Photography:

a) All excavation works must be photographed with a sign indicating the work number; photographs must be taken before construction starts and after the completion of the work filling;

b) When photographing geological objects and minerals, a scale must be placed next to the object being photographed. Use a camera to take photographs. The photographs must be clear and reflect the geological objects and minerals being photographed.

Article 5. Preparatory work before construction

1. Before excavation of the project, the site must be prepared. The project site includes the excavation area, material storage areas, worker camps, and waste disposal sites. Depending on the requirements for excavation equipment and the type of project, the site area should be reasonably arranged to ensure the following requirements are met:

a) For trench projects: the trench edges and slopes must be cleared to ensure a minimum distance of 1.0m from the trench edge and slope outward. Around the trench, there must be drainage channels.

b) For well projects: the site must be cleared with a minimum area of 30m² for deep wells and 24.0m² for shallow wells. The height of the well surface must be at least 0.5m higher than the highest water level expected during construction.

c) For shaft projects: the site and earth transportation routes must be prepared to ensure safety and convenience for people and equipment during work.

2. Construction service roads: access roads up and down the project site must be constructed to ensure safety during movement and work.

3. Shelters and camps:

a) Well openings must have shelters to ensure safety for people and equipment during construction.

b) Worker shelters and camps must be at least 5.0m away from the project.

Article 6. Construction of Cleaned Exposure Projects and Pit Projects

1. Cleaned exposure: the size and area of cleaned exposure must be clearly defined to identify objects that need to be described and sampled.

2. Pit dimensions: the pit opening cross-section must be 1.0m, the depth not exceeding 2.0m, and the bottom cross-section between 0.8m and 1.0m.², depth not exceeding 2.0m and bottom cross-section area from 0.8m²to 1.0m².

3. Construction techniques:

a) Cleaned exposure: the area to be cleared depends on the geological and mineral objects. Clearing exposure involves clearing vegetation, excavating geological and mineral objects for study and sampling. The volume of cleared exposure is determined based on actual construction.

b) Pits: construction must follow the specified dimensions in Clause 2 of this Article. For pits in areas prone to collapse, support and bracing must be provided throughout the construction period to ensure safety, collect technical data, and take samples.

Article 7. Construction of Trenches

1. Trench dimensions: the trench width must be 1.0m, length not exceeding 5.0m, and depth not exceeding 8.0m. If the trench has support and bracing, the width after bracing must not be less than 0.7m.

2. Distance between trenches: when excavating trenches along a line, each trench must be at least 1.0m apart. In areas where existing trench and well projects are present, new trenches must maintain a minimum distance of 3.0m from existing trenches and wells if excavated parallel to them.

3. The construction area of trenches must install warning signs, and the construction team must closely coordinate and provide timely information to ensure safety during construction.

4. Excavated soil and rock from trenches must be disposed of at least 1.0m away from the trench edge for trenches deeper than 2.0m, and at least 2.0m away for trenches deeper than 2.0m. Waste disposal areas should be located in lower terrain areas relative to the trench, ensuring the height of the disposed soil and rock does not exceed 0.5m above the trench opening. For trenches deeper than 2.0m, suitable equipment must be used to transport soil and rock from the trench bottom to the ground surface.

The spoil dump is arranged on the lower terrain side of the trench, ensuring that the height of the dumped spoil does not exceed 0.5m above the trench mouth. For trenches with a depth of 2.0m or more, appropriate equipment must be used to transport the spoil from the trench bottom to the surface.

For trenches deeper than 2.0m, support and bracing must be maintained throughout the construction, surveying, collecting original data, and taking geological and mineral samples to ensure safety for workers and equipment. Support materials must comply with the provisions of Clause 3, Article 4 of this Circular. Specific support work is as follows:

The distance between supports is from 0.5m to 1.0m. The maximum bracing distance is 0.8m (note to leave space for ladder access). The topmost support must protrude at least 0.2m above ground level.

6. Stop excavation to collect original data and take samples: for trenches deeper than 2.0m, stop excavation every 2.0m for geological technicians to measure, collect original data, and take samples.

7. When constructing trench works where water appears, drainage work must be carried out. Pumps and equipment must comply with the provisions of Clause 4, Article 4 of this Circular. Drainage shall be carried out based on the flow rate of water entering the construction site as follows:

6. Stop excavation to collect original data and take samples: for trenches deeper than 2.0m, stop excavation every 2.0m to allow geological technicians to measure, collect original data, and take samples.

7. When constructing trenches with exposed water, water drainage work must be carried out. Water pumping machinery and equipment must comply with the provisions of Clause 4, Article 4 of this Circular. Drainage will be carried out based on the flow rate of water entering the trench as follows:

a) For trenches with a water inflow rate of less than 0.3m³/h, use containers for drainage. If the flow rate is from 0.3m³/h to 2.0m³/h, use buckets or manual pumps. For flow rates greater than 2.0m³/h, use mechanical pumps for drainage.

b) Pumps must be placed on stable stands or suspended by cables with a minimum load capacity three times the weight of the pump to ensure safety.

c) Water pipes must be arranged at the corner of the trench to facilitate construction.

Article 8. Construction of wells

1. Well dimensions:

a) Dimensions of shallow wells:

For a well mouth cross-section of (1.4x1.4)m, the bottom cross-section can be (1.2x1.2)m; for a well mouth cross-section of (1.2x1.4)m, the bottom cross-section can be (1.0x1.2)m. The depth of the well must not exceed 10m. The well excavation must not be twisted or skewed.

b) Dimensions of deep wells:

For deep wells from 10m to 30m: excavation size (1.4x2.0)m, support size (1.2x1.8)m.

For deep wells from 30m to 60m: excavation size (1.8x2.4)m, support cross-section (1.6x1.8)m.

2. Coordination during construction: wells under construction must have warning signs to alert passersby. In a well project, when two or more people work simultaneously, coordination must be ensured to guarantee safety.

3. Soil and rock excavated from the well must be dumped at least 3.0m away from the well edge, with the height of soil and rock dumping not exceeding 0.5m above the well mouth. Suitable equipment must be used to transport soil and rock waste from the well bottom to the ground surface.

4. Stop excavation to collect technical data and take samples: during well construction, every 2.0m stop excavation once for geological technicians to measure, collect data, and take samples.

5. When digging a well, support and bracing must be provided to ensure safety for personnel and equipment throughout the construction period and during the collection of original data and sampling. Support materials comply with the provisions of Clause 3, Article 4 of this Circular. Specific support and bracing operations are as follows:

a) During well construction, the unbraced section within the well must not exceed 2.0m. For wells with loose sand from 0.2m to 0.4m;

b) Wells encountering water with a flow rate into the well ≥ 0.3m³/h, strata with a rock grade lower than Grade IV require immediate support and continuous support;

c) For stable, dry, non-sliding rock with a grade of V or higher, single supports should be used;

d) Depending on the stability of the rock, the distance between main supports ranges from 0.5m to 1.0m. Main supports must abut the well wall by at least 0.2m. From 2.0m to 2.5m, there is one main support, with the bracing distance ranging from 0.5m to 1.5m. Supports are tightly braced by pillars and connected to beams using nails and ensuring they are perpendicular to the pillars.

6. When constructing a well with exposed water, drainage operations must be carried out. Machinery and equipment for pumping water must comply with the provisions of Clause 4, Article 4 of this Circular. Drainage operations must follow the provisions of points a, b, and point c, Clause 7, Article 7 of this Circular.

7. To ensure worker safety, ventilation operations must be conducted in all well projects. Ventilation equipment and installation methods must comply with the provisions of Clause 5, Article 4 of this Circular.

a) For well projects without toxic gases, explosive gases, or flammable dust, ventilation can be achieved through forced or suction methods.

b) For well projects with toxic gases, explosive gases, or flammable dust, a combined ventilation method must be used.

c) The air duct is placed on one side of the well wall, with the air duct outlet facing downwards towards the well bottom, not exceeding 6.0m from the bottom.

8. Lighting: for shallow wells up to 10m, natural light is used. For deep wells over 10m, artificial lighting must be used as specified in Article 10 of this Circular.

9. Backfilling the well: carried out according to the provisions of Clause 9, Article 7 of this Circular.

Article 9. Construction of shaft works

1. Shaft dimensions: based on the length of the shaft (horizontal and inclined shafts), the dimensions of the shaft are as follows:

For shaft lengths up to 50m, the dimensions (width, height of the shaft) before support are (1,6x1,9)m, and the minimum dimensions after support are (1,4x1,8)m.

For shaft lengths up to 100m, the dimensions (width, height of the shaft) before support are (1,8x1,9)m, and the minimum dimensions after support are (1,6x1,8)m.

For shaft lengths up to 300m, the dimensions (width, height of the shaft) before support are (2,0x2,0)m, and the minimum dimensions after support are (1,8x1,9)m.

2. Earth and rock excavated from the shaft must be dumped within the designated waste rock area, at least 5,0m away from the shaft entrance. At the waste disposal site, ensure that the height of the dumped earth and rock does not exceed 1,5m. The dumping area must have warning signs.

3. Stop excavation to collect technical documentation and take samples: during shaft construction, stop excavation every 5,0m to allow geological technicians to measure, collect documentation, and take samples.

4. Shafts must be supported to ensure safety for people and equipment throughout the construction period and the collection of original data and sampling. Support materials comply with the provisions of Clause 3, Article 4 of this Circular.

a) The length of the unsupported shaft while advancing the shaft face shall not exceed 2,0m;

b) For shafts excavated in solid rock masses with rock grades VI or higher, with a vault cross-section, support may not be necessary;

c) The shaft door section must be continuously supported over a minimum distance of 5,0m and securely braced. The shaft door must have a sturdy roof cover to prevent rock slides from above;

d) Sections of weak shafts, areas where different rock layers meet, places encountering fault zones, and branch points (three-way, four-way intersections) must be continuously supported. For shafts excavated in more stable rock types, the distance between supports ranges from 0,5m to 1,0m;

đ) Based on the direction and magnitude of the rock pressure acting on the support, choose the shape and structure of the support. The support peg must fit tightly, wedge firmly, and be securely braced. The depth of the support peg must not exceed 1/3 of the diameter of the wooden support;

e) For horizontal shafts: the cross-section of the support should be perpendicular to the centerline of the shaft. The base of the support column should be placed in positioning holes deeper than the bottom of the shaft by 10cm to 30cm towards the side with water channels; positioning holes should be deeper than the bottom of the drainage channel by 5cm to 10cm;

g) For inclined shafts: when the angle of inclination of the shaft is less than 12°, carry out support work according to the provisions of point e of this clause. When the angle of inclination is from 12° to 45°, additional columns must be installed. When the angle of inclination exceeds 45°, support work must be carried out according to the provisions of Clause 5, Article 8 of this Circular.

5. When constructing shafts with exposed water, water drainage operations must be performed. Machinery and equipment for drainage must comply with the provisions of Clause 4, Article 4 of this Circular.

a) In horizontal shaft projects, use channels for drainage, with drainage channels in horizontal shafts having a slope directed towards the shaft entrance. For underground shaft projects, dig water collection pits and then use pumps to remove water. Determine the size of the drainage channels based on geological and hydrological conditions during construction to ensure safety;

b) In inclined shaft projects, drainage operations must be carried out according to the provisions of point a of this clause. If the water flow rate is too large, dig water collection pits and use pumps to remove water;

c) Pumps in inclined shafts must be placed on sturdy brackets. For inclined shafts, the pump must be placed at least 0,5m above the floor of the shaft and must have a safety cable. The discharge pipe of the pump must be made of flexible rubber tubing for easy movement.

6. Ventilation systems must be installed in shaft projects to ensure safety. Ventilation equipment and installation methods must comply with the provisions of Clause 5, Article 4 of this Circular.

a) For shafts without toxic gases, explosive gases, or flammable dust, use forced ventilation;

b) For shafts with toxic gases, explosive gases, or flammable dust, install large-capacity fans or use combined ventilation methods;

c) When using exhaust ventilation, place the exhaust fan at least 10m away from the face of the shaft. The fan should be mounted on a sliding frame for easy movement when blasting occurs;

d) The air duct at the face of the shaft must use flexible tubing for easy movement. The end of the flexible air duct must have metal rings (at least two rings) or a rigid section of 2,0m in length to ensure the air duct outlet cross-section. The connection between the air duct and the local fan must be made of metal with a length of at least 1,0m;

đ) The air duct must be placed on one side of the top of the shaft project. The end of the air duct must face the face of the shaft, no more than 8,0m away from the face;

7. Lighting: natural light for shaft depths up to 10m. For shafts deeper than 10m, lighting must comply with the provisions of Article 10 of this Circular.

8. Upon completion of construction, seal the shaft entrance to the surface by building a wall with bricks, stones, or concrete. The wall must be built on a foundation of bedrock, with a thickness ranging from 30cm to 50cm, and must have warning signs to ensure safety.

Article 10. Lighting in wells and shafts with depths of 10 meters or more

1. Lighting in wells:

a) Light source: use battery lamps or electric lights. Personal lighting devices must ensure sufficient light for workers to work. The electricity used for lighting must have a voltage not exceeding 127V, and the wiring must be of insulated type to prevent leakage. A certain number of battery lamps must be reserved in case of power failure;

b) Distance between light sources: there must be at least one lamp every 5.0m to 10m;

c) Wiring must be installed along the well walls and securely fastened, with fixing points no more than 6.0m apart. In cases where construction passes through easily collapsing soil layers, protective equipment for the wiring must be provided. All light bulbs must be protected by metal grills.

2. Lighting in shafts:

a) Light source: use the lighting source as specified in point a, Clause 1 of this Article;

b) Distance between light sources: there must be at least one lamp every 15m to 20m. At locations where carts avoid each other, at curved sections, and at shaft mirrors, there must be lighting to ensure safety;

c) Electrical wiring can be buried under the floor or mounted on the shaft walls. If buried, it must pass through protective pipes and be buried at least 0.3m deep. If mounted vertically on the walls, it must be fixed with nails or passed through metal rings, with fixing points no more than 3.0m apart;

d) Before conducting blasting operations, all lamps within a range of 15 to 20m from the shaft mirror must be removed.

3. Around the shaft entrance and well mouth where waste rock is discharged during night work, there must be lighting, with the number of lamps arranged reasonably according to the cross-section of the project and the area to be illuminated.

4. Lighting in wells and shafts containing flammable dust and explosive gases may only use explosion-proof lamps. Only those responsible may use mine lamps to test toxic gases.

Article 11. Completion of Construction Projects

1. A project to clear out exposures, pits, trenches, wells, and shafts is considered completed when all geological and mineral information has been collected, samples taken, and photographs of the project taken in accordance with this Circular and Clauses 2 and 3 of this Article.

2. Conduct coordinate measurements of excavation projects before completing the construction project to include them in relevant maps. Coordinate measurements shall be carried out in accordance with the provisions of the law.

3. Establish completion records for excavation projects in accordance with Circular No. 26/2019/TT-BTNMT dated December 31, 2019, issued by the Minister of Natural Resources and Environment regarding the review and approval of geological investigation reports on minerals.

Section 2

GEOLOGICAL AND MINERAL SAMPLING AT EXCAVATION PROJECTS

Article 12. General Requirements for Sampling at Excavation Projects

1. Sampling at excavation projects must comply with the approved geological project description, plan, and tasks. When encountering ore bodies, detailed and systematic sampling must be conducted to assess the quality of the ore and associated valuable components. The sampling locations must be recorded on original documentation. The types and quantities of samples taken must be appropriate for the research objectives and specified in detail in the geological project.

2. Sampling methods must be suitable for the distribution characteristics and properties of the material being sampled. These methods must be specifically designed in the geological project and adjusted appropriately based on actual construction conditions in accordance with the law.

3. Tools and techniques for taking, packaging, transporting, and preserving samples must ensure that they do not fall, mix, or change the nature of the sample material, affecting the representativeness of the sample. Field samples, processed samples, and samples sent for analysis must have a label indicating the sample number using durable materials that will not tear, deteriorate, or lose the sample number.

4. The location of long-term storage samples must be accurately determined depending on the stage of investigation. For trench samples, block samples (technical, technological samples), and lump samples (paleontological, isotopic age samples), detailed drawings showing the distribution characteristics, geological structure, and sampling location must be included in the sampling record and project drawings.

5. Samples must be taken separately when they can be distinguished by eye at the site due to differences in composition, structure, architecture, color, and other characteristics.

6. In cases where mineral materials are too small to have independent value and their distribution patterns are already known, different types of ores can be combined into one sample.

7. For mineral deposits where the boundaries are unclear and can only be determined through sample analysis, the samples must include the altered rock adjacent to the deposit and the unaltered surrounding rock.

Article 13. Rock Samples

1. Rock samples used for observing and describing petrographic or mineralization characteristics with rectangular or cubic shapes have dimensions of length, width, and thickness (9x6x3) cm.

2. Rock samples used for petrographic analysis, mineral texture, isotopic analysis have dimensions of length, width, and thickness ranging from (5x3x2) cm to (9x6x3) cm. Petrographic structural samples must determine the dip direction before sampling. Samples must be fresh and solid.

3. Rock samples for mechanical and physical property analysis, with small bulk density, have dimensions of length, width, and thickness ranging from (10x10x10) cm to (30x30x30) cm. Samples must be wrapped in wax or candle.

4. Rock samples for physical parameter analysis:

Geophysical parameter samples are taken and kept in their original intact state. After collection, samples must be wrapped in cloth, wax, candle, or appropriate tools to minimize changes in their initial state.

a) Density measurement samples: maximum dimensions of length, width, and thickness (10x10x10) cm.

b) Magnetic parameter samples: maximum dimensions of length, width, and thickness (20x10x5) cm; to determine the residual magnetic vector Jn and paleomagnetic samples, cubes or rectangular blocks with edge lengths of 5.0 cm to 20 cm should be taken, determining the northward orientation of the sample and the orientation of two square block edges.

c) Electrical parameter samples: at least one relatively flat surface, minimum dimensions of (10x10x10) cm.

d) Radioactive parameter samples: minimum dimensions of (7x7x7) cm.

đ) Radioactivity chemical samples (to determine emanation coefficients, radioactive equilibrium) are taken in their original intact form, with dimensions of (10x10x10) cm.

5. Paleontological research rock samples are taken with sizes ensuring the maximum determination of fossil characteristics.

Article 14. Channel Samples

1. Channel samples are arranged perpendicular to the ore body. For ore bodies with a dip angle of 90°-45°, horizontal channel samples are taken; for ore bodies with a dip angle less than 45°, vertical channel samples are taken.

2. Based on the characteristics of the ore body's variation, channel samples are continuously taken throughout the entire thickness of the ore body and some samples are taken from pillar rocks and wall rocks at intervals equal to the thickness of the interbedded rock layers within the ore body.

3. Based on the degree of uniformity of the ore, channel samples are taken in rectangular or triangular shapes with corresponding widths from 5.0 cm to 10 cm, depths from 3.0 cm to 5.0 cm. The specific length of the channel sample is as follows:

a) In cases where the ore body is thin, with non-uniform structure and composition, the length of one channel sample ranges from 0.4 m to 1.0 m.

b) In cases where the ore body is thick, with relatively uniform structure and composition, the length of one channel sample ranges from 1.0 m to 3.0 m.

4. The sequence for taking channel samples is as follows:

a) Clean and flatten the location where the sample will be taken;

b) Describe the geology, determine the position and size of the channel sample to be taken;

c) Lay down a tarp to catch the sample;

d) Use tools and equipment to take the sample;

đ) Measure and check the dimensions of the channel and weigh the sample mass;

e) Record the sample number on the sample bag and write the sample number on the bag.

Article 15. Spot Samples, Channel Spot Samples, Grid Spot Samples

1. Spot samples are used in the collection of primary rock geochemical samples, in the search and discovery of mineralization according to rolling stones or to check the possibility of mineralization in large outcrops with unclear mineralization. Spot samples must be uniform. The weight of one spot sample ranges from 5.0 kg to 10 kg.

2. Channel spot samples are used in investigations and evaluations of minerals that can be easily distinguished by the naked eye, with component contents varying regularly along a certain direction (layered, banded, zoned, striped) such as construction materials, cement limestone, phosphorite, and other minerals.

Channel spot samples are a set of rock samples taken along one or several lines perpendicular or nearly perpendicular to the ore body trend. The total length of the sample complies with the provisions of points a and b, Clause 3, Article 14 of this Circular. The distance between each rock sample ranges from 5.0 cm to 20 cm.

3. Grid spot samples are used for minerals with distribution characteristics in clusters, leopard skin patterns, without clear regularity, or with unclear regularity.

Samples are taken in small pieces distributed in a rectangular, square, triangular, or diamond grid pattern. Each sample piece has dimensions of approximately 1.0 cm to 3.0 cm, taken at grid intersections. The distance between grid intersections depends on the degree of uniformity and the size of the ore zones, outcrops, and may vary between 10 cm and 20 cm.

4. The sequence for taking spot, channel spot, and grid spot samples is as follows:

a) Clean and flatten the location where the sample will be taken;

b) Describe the geology, determine the position and size of the spot sample to be taken according to the channel or grid;

c) Lay down a tarp to catch the sample;

d) Use tools and equipment to take the sample;

đ) Measure and check the dimensions of the spots, channels, grids taken and weigh the sample mass;

e) Record the sample number on the sample bag and write the sample number on the bag.

Article 16. Stripping Sample

1. Stripping samples are used in the investigation of mineral types with uneven distribution of components in two directions: thickness and dip direction or thickness and strike direction.

2. Stripping samples are taken in the shape of a rectangle, one side being the thickness of the ore body, and the other side following the variation direction of the ore body in the mining excavation work.

3. The area for sample collection must be flat, and the depth of sampling must be uniform to ensure the representativeness of the sample.

4. The procedure for taking stripping samples is as follows:

a) Clean and flatten the location where the sample will be taken;

b) Describe the geology, determine the location of the layer from which the sample is taken, measure the size and layout of the sample;

c) Lay down a tarp to catch the sample;

d) Use tools and equipment to take the sample;

d) Weigh the mass of the sample;

e) Record the sample number on the sample bag and write the sample number on the bag.

Article 17. Block Sample

1. Block samples are taken at clean outcrops, pits, trenches, or wells. Block samples are used in basic geological investigations of minerals and mineral exploration. Block samples are used for non-metallic minerals when the crystal size and degree of integrity of these minerals determine their value, such as mica, crystalline quartz, and stone slabs, to determine the quality of the mineral and recovery rate. They are also used for technological sampling, heavy sand sampling, large bulk density sampling, and checking other sampling methods during exploration of reserves classes 121 and 122.

2. The quantity and size of block samples must be designed in the geological project based on the characteristics of the ore body, the degree of component variation, and the type of mineral.

3. Taking block samples to determine the recovery rate of stone slabs and decorative stones:

a) Clean and flatten the location where the sample will be taken;

b) Describe the geology, determine the location of the sample, measure the size and layout of the sample;

c) Use tools and equipment to take whole block samples according to the determined size;

d) Write the sample number on the sample.

4. Block samples used as technological samples:

a) Clean and flatten the location where the sample will be taken;

b) Describe the geology, determine the location of the sample, measure the size and layout of the sample;

c) Line up plastic sheets to catch the sample and shield around it to prevent sample loss;

d) Use tools, equipment, or explosives to take samples according to the determined size;

d) Weigh the mass of the sample;

e) Record the sample number and write it on the sample.

5. Taking block samples as heavy sand samples:

a) Determine the layer or stratum containing the product;

b) Describe the geology, determine the location of the layer or stratum from which the sample is taken;

c) Lay down a tarp to catch the sample;

d) Use tools and equipment to take the sample;

d) Weigh the mass of the sample;

e) Record the sample number and write it on the sample.

6. Block samples as grade samples:

a) Determine the layer containing the product;

b) Describe the geology, determine the location of the layer from which the sample is taken, measure the size and layout of the sample;

c) Lay down a tarp to catch the sample;

d) Use tools and equipment to take the sample;

d) Weigh the mass of the sample;

e) Separate the ore and non-ore parts manually, by washing or by appropriate methods;

g) Weigh the ore obtained;

h) Fill out the sample number form and place it in the bag containing the separated ore sample, write the sample number on the bag.

7. Taking block samples to check sampling methods in mineral exploration shall be carried out as specified in the technological sampling provisions of Clause 4 of this Article.

8. Large bulk density block samples are taken in the shape of a rectangular box or cube with the following procedures:

a) Clean and flatten the location where the sample will be taken;

b) Describe the geology, determine the location of the sample, measure the size and layout of the sample, determine the volume of the sample;

c) Use tools and equipment to take whole block samples according to the determined size;

d) Wrap in cloth, cover with wax or paraffin;

d) Weigh the mass of the sample;

e) Record the sample number and write it on the sample.

Chapter III

IMPLEMENTING PROVISIONS

Article 18. Effective Date

This Circular takes effect from February 8, 2021. In cases where the legal normative documents referred to for application under this Circular are amended, supplemented, or replaced, they shall be implemented in accordance with the provisions of the amended, supplemented, or replacing documents.

Article 19. Implementation

The Vietnam General Department of Geology and Mineral Resources is responsible for inspecting and guiding the implementation of this Circular. Ministries, ministerial-level agencies, provincial People's Committees, provincial Departments of Natural Resources and Environment, centrally-administered city Departments of Natural Resources and Environment, and organizations and individuals related to this matter are responsible for implementing this Circular./.