CECS: 2290 Soil anchor design and construction specifications CECS22:90
Some standard content:
Soil Anchor Design and Construction Specifications
CECS22:90
Editor: Construction Research Institute of Ministry of Metallurgy Approval: China Association for Engineering Construction Standardization Date of Approval: November 6, 1990
1991 Beijing
Soil anchors are increasingly used in deep foundation pit support, slope reinforcement, landslide control, pool anti-floating, retaining wall anchoring and structural anti-overturning projects in my country. In order to make the design and construction of soil anchors meet the requirements of advanced technology, economic rationality and quality assurance, China Association for Engineering Construction Standardization commissioned Construction Research Institute of Ministry of Metallurgy to compile this specification. This specification is based on the summary of my country's practical experience in soil anchors over the years, after many comments and revisions, and finally the Construction Research Institute of Ministry of Metallurgy organized a domestic expert meeting for review and finalization.
The "Soil Anchor Design and Construction Specifications" is now approved, numbered CECS22:90. It is recommended for use by various engineering construction design and construction units. If you find any need for modification or supplement during use, please send your comments and relevant information to the Construction Research Institute of the Ministry of Metallurgy, No. 33 Xitucheng Road, Beijing (Postal Code: 100088). China Association for Engineering Construction Standardization
November 6, 1990
Main Symbols
Chapter 1 General Provisions
Chapter 2 Design of Soil Anchors
Section 1 General Provisions
Section 2 Structural Types of Soil Anchors
Section 3 Arrangement and Structural Parameters of Soil Anchors Chapter 3 Raw Materials of Soil Anchors
Chapter 4 Construction of Soil Anchors
Section 1
General Provisions
Section 2 Drilling
Section 3 Assembly and Placement of Rods (Prestressed Rebars)Section 4 Grouting
Section 5 Tensioning and Locking
Chapter 5 Testing and Monitoring of Soil Anchors
Section 1 General Provisions
Section 2 Basic Tests
Section 3 Acceptance Tests
Section 4 Creep Tests
Section 5 Long-term Monitoring of Anchor Prestress Chapter 6 Anti-corrosion of soil anchor rods
Section 1 General provisions
Section 2 Anti-corrosion methods
Chapter 7 Project acceptance
Appendix I Explanation of terms related to the specification
Appendix 2 Recommended values of bond strength between soil layer and anchor body Appendix 3 Verification method for stability of deep rupture surface of anchor sheet pile Appendix 4 Standard values of strength of steel wire, steel hinge and steel bar Appendix 5 Specifications of prestressed steel hinge anchor
Appendix 6 Table of commonly used construction equipment for soil anchor rods Appendix 7 Summary of soil anchor rod construction record tables Appendix 8 Summary of anchor rod test record tables and drawings Additional notes
Chapter 1 General
Article 1.0.1 A soil anchor rod is a tension rod buried deep in the soil layer. One end of it is connected to the engineering structure and the other end is anchored in the soil layer. Prestress is usually applied to it to withstand the tension generated by soil pressure, water pressure or wind load, etc., to maintain the stability of the structure. Article 1.0.2 This specification applies to the design and construction of temporary or permanent anchors in various soil layers. Article 1.0.3 The design and construction of soil anchors shall comply with the requirements of the relevant national standards in force in addition to complying with this specification.
Chapter II Design of Soil Anchors
Section I General Provisions
Article 2.1.1 When planning to use soil anchors, the safety, economy and construction feasibility of soil anchoring projects shall be fully studied.
Article 2.1.2 The following basic work must be done before designing: 1. Carefully investigate the terrain, site, surrounding existing buildings, facilities, road traffic and weather and other matters related to the anchoring project.
2. Through engineering geological drilling and relevant soil tests, the types of soil layers within the scope of the anchoring project and the soil's shear strength, particle grading, permeability, water erosion and other physical and mechanical properties and chemical properties are mastered. Article 2.1.3 Anchors with a service life of less than 2 years can be designed as temporary anchors; anchors with a service life of more than 2 years should be designed as permanent anchors. Article 2.1.4 Basic tests must be carried out first when designing permanent anchors. Article 2.1.5 The anchoring section of permanent anchors should not be set in the following untreated soil layers: 1. Organic soil.
2. Soil layers with liquid limit Wi>50%.
3. Soil layers with relative density D<0.3.
Section 2 Structural Types of Soil Anchors
Article 2.2.1 Soil anchors generally consist of three parts: anchor head, free section and anchoring section. The anchoring section uses cement slurry or cement mortar to bond the rod body (prestressed tendons) to the soil to form the anchor body of the anchor. Article 2.2.2 According to the soil type, engineering characteristics and use requirements, the anchor body structure of the soil anchor can be designed as cylindrical, end enlarged head or continuous spherical type, see Figure 2.2.2-1, Figure 2.2.2-2 and Figure 2.2.2-3. Article 2.2.3 For anchors anchored in sandy soil and hard clay layers and requiring higher bearing capacity, it is advisable to use end enlarged head anchors; for anchors anchored in silt and silty soil layers and requiring higher bearing capacity, it is advisable to use continuous spherical anchors.
Section 3 Arrangement and structural parameter design of soil anchor rods Article 2.3.1 The arrangement of soil anchor rods shall comply with the following provisions: 1. The spacing between the upper and lower rows of anchor rods should not be less than 2.5m; the horizontal spacing between anchor rods should not be less than 2.0m; 2. The thickness of the soil layer overlying the anchor rod anchor body should not be less than 4.0m, and the length of the anchor rod anchoring section should not be less than 4.0m. 3. The inclination angle of the inclined anchor rod should not be less than 13° and should not be greater than 45°, preferably 15°~35. Article 2.3.2 The anchor rod installation coefficient K value should be determined according to Table 2.3.2. Chapter 3 Raw materials for soil anchor rods
Article 3.0.1 The material of the prestressed rod body should be steel hinge wire, high-strength steel wire or high-strength threaded steel bar. When the prestressing value is small or the anchor length is less than 20m, the prestressing tendons can also use Grade II or Grade II steel bars. Article 3.0.2 The anchor and the force-bearing parts connecting the anchor rod body should be able to withstand 95% of the ultimate tensile force of the rod body.
Article 3.0.3 The plastic sleeve material should meet the following requirements: 1. It has sufficient strength to ensure that it will not be damaged during processing and installation. 2. It has water resistance and chemical stability. 3. It has no adverse reaction with cement mortar and preservatives. Article 3.0.4 The isolation frame should be composed of steel, plastic or other materials that are harmless to the rod body. Wooden isolation frames shall not be used.
Article 3.0.5 The anti-corrosion material shall meet the following requirements: 1. It should maintain its durability within the service life of the anchor rod. 2. It shall not crack, become brittle or become fluid within the specified working temperature or during the tensioning process. 3. It shall not have adverse reactions with adjacent materials and shall maintain its chemical stability and waterproofness. 4. It shall not impose any restrictions on the deformation of the free section of the anchor rod. Article 3.0.6 Cement paste materials shall meet the following requirements: 1. Ordinary Portland cement is suitable for cement, and sulfate-resistant cement can be used when necessary. 2. High-alumina cement shall not be used.
3. Fine aggregate shall be fine sand with a particle size of less than 2 mm. The mud content of sand shall not exceed 3% by weight, and the content of harmful substances such as mica, organic matter, sulfide and sulfate in sand shall not exceed 1% by weight.
4. The mixed water shall not contain harmful substances that affect the normal coagulation and hardening of cement, and sewage shall not be used. Permanent anchors shall not use acidic water with a pH value of less than 4.0 and water with a sulfate content of more than 1% of the water weight calculated as SO4.
5. When necessary, the cement slurry may increase the amount of admixtures such as water seepage control or delayed coagulation, but they must meet the product standards. The total chloride content in the cement slurry shall not exceed 0.1% of the cement weight. Except for secondary splitting grouting and free section filling grouting, expansion agents are generally not suitable. Chapter 4 Soil Anchor Construction
Section 1 General Provisions
Article 4.1.1 Before carrying out anchor construction, the design conditions, soil conditions and environmental conditions should be fully checked, and the construction organization design should be prepared under the premise of ensuring construction safety. Article 4.1.2 Before construction, the raw material model, variety, specification and quality of each component of the anchor should be carefully checked, and the main technical performance of the raw materials should be checked to see if they meet the design requirements. Article 4.1.3 Before the construction of engineering anchors, two anchors should be taken for experimental operations of drilling, grouting, tensioning and locking to assess the adaptability of the construction technology and construction equipment. Section 2 Drilling
Article 4.2.1 The drilling of soil anchors should comply with the following provisions 1. Before drilling, determine the hole position and make marks according to the design requirements and soil conditions. 2. The horizontal hole spacing error of the anchor should not be greater than 50mm, and the vertical hole spacing error should not be greater than 100mm.
3. The deflection size of the bottom of the borehole should not be greater than 3% of the anchor length. The drilling direction can be controlled by a borehole inclinometer.
4. The anchor hole depth should not be less than the design length, nor should it be greater than 1% of the design length. 5. Before placing the anchor, the wet borehole should be flushed with water until clear water flows out of the hole. 6. The drilling records should be organized according to Appendix 7.1 of Appendix 7 of this specification. Section 4.2.2. Drilling equipment: The selection of drilling equipment must meet the requirements of soil anchor drilling. For hard clay soil and soil layers that are not easy to collapse, geological drilling rigs, spiral drilling rigs or soil anchor special drilling rigs should be used; for saturated clay soil and soil layers that are easy to collapse, soil anchor special drilling rigs with wall protection casing should be used. The models and main performances of commonly used drilling equipment are shown in Appendix VI of this specification.
Article 4.2.3 The drilling of continuous spherical anchors formed by secondary high-pressure grouting shall also comply with the following provisions: 1. The drilling hole should be protected by casing, and the hole should be drilled to the designed length at one time. 2. After the drilling is completed, the drill rod should be pulled out immediately, the prestressed tendons should be enlarged, and then the casing should be pulled out. Article 4.2.4 The drilling of enlarged head anchors shall also comply with the following provisions: 1. The end enlarged head can be enlarged by mechanical or blasting method, and the amount of explosive for blasting enlargement should be determined by test according to the soil conditions.
2. The size of the enlarged head should be measured before installing the anchor. Section 3 Assembly and placement of the rod body (prestressed tendons) Article 4.3.1 When using II and III grade steel bars as the anchor rod body, the assembly of the rod body shall comply with the following provisions: 1. The steel bars shall be straight, degreased and derusted before assembly. 2. The joints of II and III grade steel bars shall be welded lap joints, with a welding length of 30d but not less than 500mm. The connection of parallel steel bars shall also be welded. 3. A centering bracket shall be set every 1.0 to 2.0m in the direction of the axis of the rod body, and the exhaust pipe shall be firmly tied to the anchor rod body.
4. The free section of the rod body shall be wrapped with plastic cloth or plastic pipe, and the connection with the anchor body shall be tied with lead wire. 5. The rod body shall be treated with anti-corrosion according to the anti-corrosion requirements. Article 4.3.2 When using steel hinge wire or high-strength steel wire as the anchor rod body, the assembly of the rod body shall comply with the following regulations:
1. The steel hinge wire or high-strength steel wire shall be degreased and rusted, and cut strictly according to the design size, with the length error of each strand not exceeding 50mm.
2. The steel hinge wire or high-strength steel wire shall be arranged straightly according to a certain rule, and an isolation frame shall be set every 1.0 to 1.5m along the axis of the rod body. The protective layer of the rod body shall not be less than 2.0cm, and the prestressed tendons (including exhaust pipes) shall be tied firmly. Galvanized materials shall not be used for tying materials. The free section of the three rod bodies shall be wrapped with plastic pipes, and the plastic pipe mouth at the intersection with the anchor section shall be sealed and tied with lead wire.
4. Anti-corrosion treatment shall be carried out according to anti-corrosion requirements. Article 4.3.3 The assembly of the continuous spherical anchor rod body formed by secondary high-pressure grouting shall also comply with the following provisions:
1. When arranging steel strands or high-strength steel wires, the grouting sleeve and the grouting stop sealing device shall be placed at the same time. 2. The grouting stop sealing device shall be set at the boundary between the free section and the anchor section and have good sealing performance.
3. It is advisable to use a sealing bag as a grouting stop sealing device. The two ends of the sealing bag shall be firmly tied to the anchor rod body. At least one grouting valve shall be left on the grouting sleeve wrapped by the sealing bag. Article 4.3.4 When assembling the enlarged head anchor rod body, the rod body at the enlarged head shall be partially strengthened. Article 4.3.5 The placement of the anchor rod body shall comply with the following provisions: 1. Before the rod body is placed in the borehole, the quality of the rod body shall be checked to ensure that the rod body assembly meets the design requirements. 2. When placing the rod body, the rod body should be prevented from twisting, pressing and bending. The grouting pipe should be placed in the borehole together with the anchor rod. The head of the grouting pipe should be 50-100mm from the bottom of the hole, and the angle of the rod body should be consistent with the drilling angle. 3. The depth of the rod body inserted into the large hole should not be less than 95% of the length of the anchor rod. After the rod body is placed, it should not be knocked at will or heavy objects should not be hung.
Section 4 Grouting
Article 4.4.1 Anchor grouting should comply with the following provisions: 1. The grouting material should be determined according to the design requirements. Generally, cement mortar with a cement-sand ratio of 1:1-1:2 and a water-cement ratio of 0.38-0.45 or pure cement slurry with a water-cement ratio of 0.40-0.45 should be selected. If necessary, a certain amount of admixtures or admixtures can be added.
2. The grouting slurry should be stirred evenly and used as soon as it is stirred. The slurry should be used up before the initial setting, and stones and debris should be strictly prevented from mixing with the slurry.
3. When the grouting operation starts or stops for a long time before re-operation, it is advisable to lubricate the grouting pump and grouting pipeline with water or thin cement slurry.
4. The insertion depth of the grouting pipe is shown in the second paragraph of Article 4.3.5. 5. Grouting can be stopped when the grout overflows from the hole or the exhaust pipe stops exhausting. 6. When the grout cannot fill the anchor body after hardening, grouting should be carried out. 7. Grouting records should be organized according to Appendix 7.2 of Appendix 7 of this specification. Article 4.4.2 The design strength of the grouting body should not be less than 20MPa. Article 4.4.3 The grouting of the continuous spherical anchor formed by the secondary high-pressure grouting should also comply with the following provisions. 1. The grouting material should be pure cement slurry with a water-cement ratio of 0.45 to 0.50. 2. The first normal pressure grouting operation should start from the bottom of the hole until the grout overflows from the hole. 3. The grouting of the stop grouting sealing device should be carried out after the grout overflows from the hole, and the grouting pressure should not be less than 2.5MPa.
4. After the completion of the primary normal pressure grouting, the grouting pipe, grouting gun and grouting sleeve shall be cleaned. 5. The secondary high pressure grouting of the anchor body shall be carried out when the strength of the cement stone body formed by the primary grouting reaches 5.0MPa. The grouting pressure and grouting time can be determined according to the volume of the anchor body, and shall be carried out in sections from bottom to top.
Section 5 Tensioning and Locking
Article 4.5.1 The pressure bearing surface of the pedestal shall be flat and perpendicular to the axis direction of the anchor rod. Article 4.5.2 The tensioning of the anchor rod shall comply with the following provisions: 1. Before tensioning the anchor rod, the tensioning equipment shall be calibrated. 2. Tensioning can only be carried out when the concrete strength of the anchor body and the pedestal is greater than 15.0MPa. 3. Anchor tensioning should be carried out according to a certain procedure. The tensioning sequence of anchors should take into account the mutual influence of adjacent anchors. 4. Before the anchor is formally tensioned, the design axial tension value N of 0.1~0.2 should be taken, and the anchor should be pre-tensioned 1~2 times to make the contact of each part close and the rod body straight. The control stress αcona of permanent anchor tensioning should not exceed 0.60folk, and the control stress Qcon of temporary anchor tensioning should not exceed 0.65fok
Article 4.5.3 The anchor is tensioned to 1.1~1.2N, and the soil is kept for 10min when it is sandy soil and 15min when it is clay soil, and then unloaded to the locking load for locking operation. The anchor tensioning load classification and observation time should comply with the provisions of Table 4.5.3. The anchor tensioning and locking construction records should be organized according to Appendix 7.3 of Appendix 7 of this specification. Article 4.5.4 Anchor locking work should use anchors that meet technical requirements. The specifications of anchors used to lock prestressed steel strands are shown in Appendix V of this specification. Article 4.5.5 After the anchor is locked, if there is a significant loss of prestress, compensatory tensioning should be carried out. Chapter V Soil Anchor Test and Monitoring
Section I General Provisions
Article 5.1.1 When the anchor strength is greater than 15.0MPa, the anchor test can be carried out. Article 5.1.2 The rated pressure of the loading device for anchor test must be greater than the test pressure. Article 5.1.3 The reaction device for anchor test should maintain sufficient strength and rigidity under the maximum test load.
Article 5.1.4 The detection device (dynamometer, displacement meter, stopwatch) for anchor test should meet the accuracy required by the product design.
Section II Basic Test
Article 5.2.1 Basic tests must be carried out for any new type of anchor or existing anchor used in soil layers that have not been used before.The length error of each strand shall not exceed 50mm.
2. The steel hinge wire or high-strength steel wire shall be arranged straightly according to a certain rule, and an isolation frame shall be set every 1.0-1.5m along the axis of the rod body. The protective layer of the rod body shall not be less than 2.0cm. The prestressed tendons (including exhaust pipes) shall be tied firmly, and the tying materials shall not be galvanized materials. The free section of the three rod bodies shall be wrapped with plastic pipes, and the plastic pipe mouth at the intersection with the anchor section shall be sealed and tied with lead wire.
4. Anti-corrosion treatment shall be carried out according to anti-corrosion requirements. Article 4.3.3 The assembly of the continuous spherical anchor rod body formed by secondary high-pressure grouting shall also comply with the following provisions:
1. When arranging steel hinge wires or high-strength steel wires, the grouting sleeve and the grouting stop sealing device shall be placed at the same time. 2. The grouting stop sealing device shall be set at the boundary between the free section and the anchor section, and have good sealing performance.
3. It is advisable to use a sealing bag as a grout-stopping sealing device. Both ends of the sealing bag should be firmly tied to the anchor rod body. At least one grouting valve should be left on the grouting sleeve wrapped by the sealing bag. Article 4.3.4 When assembling the enlarged head type anchor rod body, the rod body at the enlarged head should be partially strengthened. Article 4.3.5 The placement of the anchor rod body should comply with the following regulations: 1. Before the rod body is placed in the borehole, the quality of the rod body should be checked to ensure that the rod body assembly meets the design requirements. 2. When placing the rod body, the rod body should be prevented from twisting, pressing and bending. The grouting pipe should be placed in the borehole together with the anchor rod. The head of the grouting pipe should be 50-100mm from the bottom of the hole, and the angle of the rod body should be consistent with the drilling angle. 3. The depth of the rod body inserted into the large hole should not be less than 95% of the length of the anchor rod. After the rod body is placed, it should not be knocked at will or heavy objects should not be hung.
Section 4 Grouting
Article 4.4.1 Grouting of anchor rods shall comply with the following provisions: 1. Grouting materials shall be determined according to design requirements. Generally, cement mortar with a cement-sand ratio of 1:1 to 1:2 and a water-cement ratio of 0.38 to 0.45 or pure cement slurry with a water-cement ratio of 0.40 to 0.45 shall be selected. If necessary, a certain amount of admixtures or admixtures may be added.
2. Grouting slurry shall be stirred evenly and used immediately after stirring. The slurry shall be used up before initial setting, and stones and debris shall be strictly prevented from mixing with the slurry.
3. When the grouting operation starts and stops for a long time before re-operation, it is advisable to lubricate the grouting pump and grouting pipeline with water or dilute cement slurry.
4. The insertion depth of the grouting pipe is shown in the second paragraph of Article 4.3.5. 5. Grouting can be stopped when the slurry overflows from the orifice or the exhaust pipe stops exhausting. 6. When the slurry cannot fill the anchor body after hardening, grouting should be carried out. 7. Grouting records should be organized according to Appendix 7.2 of Appendix 7 of this specification. Article 4.4.2 The design strength of the grouting body should not be less than 20MPa. Article 4.4.3 The grouting of the continuous spherical anchor formed by the secondary high-pressure grouting should also comply with the following provisions. 1. The grouting material should be pure cement slurry with a water-cement ratio of 0.45 to 0.50. 2. The primary normal pressure grouting operation should start from the bottom of the hole until the slurry overflows from the hole. 3. The grouting of the grouting sealing device should be carried out after the slurry overflows from the hole. The grouting pressure should not be less than 2.5MPa.
4. After the primary normal pressure grouting is completed, the grouting pipe, grouting gun and grouting sleeve should be cleaned. 5. The secondary high-pressure grouting of the anchor body should be carried out when the strength of the cement stone body formed by the primary grouting reaches 5.0MPa. The grouting pressure and grouting time can be determined according to the volume of the anchor body, and it should be carried out in sections from bottom to top.
Section 5 Tensioning and Locking
Article 4.5.1 The bearing surface of the pedestal shall be flat and perpendicular to the axis of the anchor rod. Article 4.5.2 The tensioning of the anchor rod shall comply with the following provisions: 1. Before tensioning the anchor rod, the tensioning equipment shall be calibrated. 2. Tensioning can only be carried out when the strength of the anchor body and the pedestal concrete is greater than 15.0MPa. 3. Anchor rod tensioning shall be carried out according to a certain procedure, and the tensioning sequence of anchor rods shall take into account the mutual influence of adjacent anchor rods. 4. Before the anchor rod is formally tensioned, the design axial tension value N of 0.1~0.2 shall be taken, and the anchor rod shall be pre-tensioned 1~2 times to make its various parts in close contact and the rod body completely straight. The tension control stress αcona of permanent anchor rods shall not exceed 0.60folk, and the tension control stress Qcon of temporary anchor rods shall not exceed 0.65folk
Article 4.5.3 The anchor rods shall be tensioned to 1.1~1.2N, and maintained for 10min when the soil is sandy soil, and maintained for 15min when it is clay soil, and then unloaded to the locking load for locking operation. The anchor rod tensioning load classification and observation time shall comply with the provisions of Table 4.5.3. The anchor rod tensioning and locking construction records shall be organized according to Appendix 7.3 of Appendix 7 of this specification. Article 4.5.4 Anchor rod locking work shall use anchors that meet technical requirements. The specifications of anchors used to lock prestressed steel strands are shown in Appendix 5 of this specification. Article 4.5.5 After the anchor rods are locked, if obvious prestress loss is found, compensatory tensioning shall be carried out. Chapter 5 Testing and Monitoring of Soil Anchors
Section 1 General Provisions
Article 5.1.1 When the anchor strength is greater than 15.0MPa, the anchor test can be carried out. Article 5.1.2 The rated pressure of the loading device for anchor test must be greater than the test pressure. Article 5.1.3 The reaction device for anchor test should maintain sufficient strength and rigidity under the maximum test load.
Article 5.1.4 The detection device (dynamometer, displacement meter, stopwatch) for anchor test should meet the accuracy required by the product design.
Section 2 Basic Tests
Article 5.2.1 Basic tests must be carried out for any new type of anchor or existing anchor used in soil layers that have not been used before.The length error of each strand shall not exceed 50mm.
2. The steel hinge wire or high-strength steel wire shall be arranged straightly according to a certain rule, and an isolation frame shall be set every 1.0-1.5m along the axis of the rod body. The protective layer of the rod body shall not be less than 2.0cm. The prestressed tendons (including exhaust pipes) shall be tied firmly, and the tying materials shall not be galvanized materials. The free section of the three rod bodies shall be wrapped with plastic pipes, and the plastic pipe mouth at the intersection with the anchor section shall be sealed and tied with lead wire.
4. Anti-corrosion treatment shall be carried out according to anti-corrosion requirements. Article 4.3.3 The assembly of the continuous spherical anchor rod body formed by secondary high-pressure grouting shall also comply with the following provisions:
1. When arranging steel hinge wires or high-strength steel wires, the grouting sleeve and the grouting stop sealing device shall be placed at the same time. 2. The grouting stop sealing device shall be set at the boundary between the free section and the anchor section, and have good sealing performance.
3. It is advisable to use a sealing bag as a grout-stopping sealing device. Both ends of the sealing bag should be firmly tied to the anchor rod body. At least one grouting valve should be left on the grouting sleeve wrapped by the sealing bag. Article 4.3.4 When assembling the enlarged head type anchor rod body, the rod body at the enlarged head should be partially strengthened. Article 4.3.5 The placement of the anchor rod body should comply with the following regulations: 1. Before the rod body is placed in the borehole, the quality of the rod body should be checked to ensure that the rod body assembly meets the design requirements. 2. When placing the rod body, the rod body should be prevented from twisting, pressing and bending. The grouting pipe should be placed in the borehole together with the anchor rod. The head of the grouting pipe should be 50-100mm from the bottom of the hole, and the angle of the rod body should be consistent with the drilling angle. 3. The depth of the rod body inserted into the large hole should not be less than 95% of the length of the anchor rod. After the rod body is placed, it should not be knocked at will or heavy objects should not be hung.
Section 4 Grouting
Article 4.4.1 Grouting of anchor rods shall comply with the following provisions: 1. Grouting materials shall be determined according to design requirements. Generally, cement mortar with a cement-sand ratio of 1:1 to 1:2 and a water-cement ratio of 0.38 to 0.45 or pure cement slurry with a water-cement ratio of 0.40 to 0.45 shall be selected. If necessary, a certain amount of admixtures or admixtures may be added.
2. Grouting slurry shall be stirred evenly and used immediately after stirring. The slurry shall be used up before initial setting, and stones and debris shall be strictly prevented from mixing with the slurry.
3. When the grouting operation starts and stops for a long time before re-operation, it is advisable to lubricate the grouting pump and grouting pipeline with water or dilute cement slurry.
4. The insertion depth of the grouting pipe is shown in the second paragraph of Article 4.3.5. 5. Grouting can be stopped when the slurry overflows from the orifice or the exhaust pipe stops exhausting. 6. When the slurry cannot fill the anchor body after hardening, grouting should be carried out. 7. Grouting records should be organized according to Appendix 7.2 of Appendix 7 of this specification. Article 4.4.2 The design strength of the grouting body should not be less than 20MPa. Article 4.4.3 The grouting of the continuous spherical anchor formed by the secondary high-pressure grouting should also comply with the following provisions. 1. The grouting material should be pure cement slurry with a water-cement ratio of 0.45 to 0.50. 2. The primary normal pressure grouting operation should start from the bottom of the hole until the slurry overflows from the hole. 3. The grouting of the grouting sealing device should be carried out after the slurry overflows from the hole. The grouting pressure should not be less than 2.5MPa.
4. After the primary normal pressure grouting is completed, the grouting pipe, grouting gun and grouting sleeve should be cleaned. 5. The secondary high-pressure grouting of the anchor body should be carried out when the strength of the cement stone body formed by the primary grouting reaches 5.0MPa. The grouting pressure and grouting time can be determined according to the volume of the anchor body, and it should be carried out in sections from bottom to top.
Section 5 Tensioning and Locking
Article 4.5.1 The bearing surface of the pedestal shall be flat and perpendicular to the axis of the anchor rod. Article 4.5.2 The tensioning of the anchor rod shall comply with the following provisions: 1. Before tensioning the anchor rod, the tensioning equipment shall be calibrated. 2. Tensioning can only be carried out when the strength of the anchor body and the pedestal concrete is greater than 15.0MPa. 3. Anchor rod tensioning shall be carried out according to a certain procedure, and the tensioning sequence of anchor rods shall take into account the mutual influence of adjacent anchor rods. 4. Before the anchor rod is formally tensioned, the design axial tension value N of 0.1~0.2 shall be taken, and the anchor rod shall be pre-tensioned 1~2 times to make its various parts in close contact and the rod body completely straight. The tension control stress αcona of permanent anchor rods shall not exceed 0.60folk, and the tension control stress Qcon of temporary anchor rods shall not exceed 0.65folk
Article 4.5.3 The anchor rods shall be tensioned to 1.1~1.2N, and maintained for 10min when the soil is sandy soil, and maintained for 15min when it is clay soil, and then unloaded to the locking load for locking operation. The anchor rod tensioning load classification and observation time shall comply with the provisions of Table 4.5.3. The anchor rod tensioning and locking construction records shall be organized according to Appendix 7.3 of Appendix 7 of this specification. Article 4.5.4 Anchor rod locking work shall use anchors that meet technical requirements. The specifications of anchors used to lock prestressed steel strands are shown in Appendix 5 of this specification. Article 4.5.5 After the anchor rods are locked, if obvious prestress loss is found, compensatory tensioning shall be carried out. Chapter 5 Testing and Monitoring of Soil Anchors
Section 1 General Provisions
Article 5.1.1 When the anchor strength is greater than 15.0MPa, the anchor test can be carried out. Article 5.1.2 The rated pressure of the loading device for anchor test must be greater than the test pressure. Article 5.1.3 The reaction device for anchor test should maintain sufficient strength and rigidity under the maximum test load.
Article 5.1.4 The detection device (dynamometer, displacement meter, stopwatch) for anchor test should meet the accuracy required by the product design.
Section 2 Basic Tests
Article 5.2.1 Basic tests must be carried out for any new type of anchor or existing anchor used in soil layers that have not been used before.The tensioning of 2 anchor rods shall comply with the following provisions: 1. Before tensioning the anchor rods, the tensioning equipment shall be calibrated. 2. Tensioning can only be carried out when the strength of the anchor body and the pedestal concrete is greater than 15.0MPa. 3. Anchor rod tensioning shall be carried out according to a certain procedure, and the tensioning sequence of anchor rods shall take into account the mutual influence of adjacent anchor rods. 4. Before the anchor rods are formally tensioned, 0.1~0.2 design axial tension value N shall be taken, and the anchor rods shall be pre-tensioned 1~2 times to make the contact of each part close and the rod body completely straight. The tension control stress αcona of permanent anchor rods shall not exceed 0.60folk, and the tension control stress Qcon of temporary anchor rods shall not exceed 0.65folk
Article 4.5.3 The anchor rods shall be tensioned to 1.1~1.2N, and maintained for 10min when the soil is sandy soil, and maintained for 15min when it is clay soil, and then unloaded to the locking load for locking operation. The anchor rod tensioning load classification and observation time shall comply with the provisions of Table 4.5.3. The anchor rod tensioning and locking construction records shall be organized according to Appendix 7.3 of Appendix 7 of this specification. Article 4.5.4 Anchor rod locking work shall use anchors that meet technical requirements. The specifications of anchors used to lock prestressed steel strands are shown in Appendix 5 of this specification. Article 4.5.5 After the anchor rods are locked, if obvious prestress loss is found, compensatory tensioning shall be carried out. Chapter 5 Testing and Monitoring of Soil Anchors
Section 1 General Provisions
Article 5.1.1 When the anchor strength is greater than 15.0MPa, the anchor test can be carried out. Article 5.1.2 The rated pressure of the loading device for anchor test must be greater than the test pressure. Article 5.1.3 The reaction device for anchor test should maintain sufficient strength and rigidity under the maximum test load.
Article 5.1.4 The detection device (dynamometer, displacement meter, stopwatch) for anchor test should meet the accuracy required by the product design.
Section 2 Basic Tests
Article 5.2.1 Basic tests must be carried out for any new type of anchor or existing anchor used in soil layers that have not been used before.The tensioning of 2 anchor rods shall comply with the following provisions: 1. Before tensioning the anchor rods, the tensioning equipment shall be calibrated. 2. Tensioning can only be carried out when the strength of the anchor body and the pedestal concrete is greater than 15.0MPa. 3. Anchor rod tensioning shall be carried out according to a certain procedure, and the tensioning sequence of anchor rods shall take into account the mutual influence of adjacent anchor rods. 4. Before the anchor rods are formally tensioned, 0.1~0.2 design axial tension value N shall be taken, and the anchor rods shall be pre-tensioned 1~2 times to make the contact of each part close and the rod body completely straight. The tension control stress αcona of permanent anchor rods shall not exceed 0.60folk, and the tension control stress Qcon of temporary anchor rods shall not exceed 0.65folk
Article 4.5.3 The anchor rods shall be tensioned to 1.1~1.2N, and maintained for 10min when the soil is sandy soil, and maintained for 15min when it is clay soil, and then unloaded to the locking load for locking operation. The anchor rod tensioning load classification and observation time shall comply with the provisions of Table 4.5.3. The anchor rod tensioning and locking construction records shall be organized according to Appendix 7.3 of Appendix 7 of this specification. Article 4.5.4 Anchor rod locking work shall use anchors that meet technical requirements. The specifications of anchors used to lock prestressed steel strands are shown in Appendix 5 of this specification. Article 4.5.5 After the anchor rods are locked, if obvious prestress loss is found, compensatory tensioning shall be carried out. Chapter 5 Testing and Monitoring of Soil Anchors
Section 1 General Provisions
Article 5.1.1 When the anchor strength is greater than 15.0MPa, the anchor test can be carried out. Article 5.1.2 The rated pressure of the loading device for anchor test must be greater than the test pressure. Article 5.1.3 The reaction device for anchor test should maintain sufficient strength and rigidity under the maximum test load.
Article 5.1.4 The detection device (dynamometer, displacement meter, stopwatch) for anchor test should meet the accuracy required by the product design. Www.bzxZ.net
Section 2 Basic Tests
Article 5.2.1 Basic tests must be carried out for any new type of anchor or existing anchor used in soil layers that have not been used before.
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