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Anchor Cage Foundation Construction Process for Wind Mill Project

Anchor Cage Foundation Project

In recent years, wind power has been increasing in both the number and scale in China, however, most wind generator mainly used in wind farms adopt anchor cage foundation, main function of anchor plate is to connect the bolt and concrete structure, the upper structure of main parts, so the anchor plate is responsible for the wind machine structure are all load to the anchor cage foundation, ensure its structure with high stability. However, the foundation anchor plate is not deeply buried, the wall of the foundation anchor plate has few pores, the amount of internal reinforcement is small, there is no fixed pin, and the foundation reinforcement is not welded together, resulting in poor durability, load resistance and integrity of the foundation ring. The prestressed anchor bolt foundation is mainly distributed in the whole foundation by anchor bolt. The steel bar and anchor bolt adopt alternate frame, which has a high integrity. In addition, a high-strength tensioning tool is used to apply pretension on the anchor bolt, which enhances its durability and load-resisting ability.

Wind Foundation Anchor Cage
Wind Foundation Anchor Cage

The wind mill foundation used in a wind farm is a plate independent form, with a diameter length of 18 m and a buried depth of 3 m. The wind mill anchor cage foundation mainly applies the pre-stressed anchor and bolt technology and is installed in the construction site. The installation of high strength anchor bolts and anchor plate is strictly required. After secondary grouting, the flatness error of anchor plate should be controlled within 2 mm.

The pre-stressed anchor bolt foundation construction technology is used in many project, and the process is mainly as follows: pre-construction work, selection of embedded parts, setting and adjusting lower anchor plate, matching fixed anchor bolt and upper anchor plate, setting common anchor bolt, reasonably combining and inspecting anchor bolt, and then starting the construction of reinforcement and concrete.

Anchor Bolt Assembly Test and Standard

Test items Type test Factory inspection Standard method
Chemical composition 20MnTiB 、42CrMoA、40CrNiMoA、30CrMnSiA GB/T3077 — 1999
35VB GB/T1231-2006 Appendix A
45、35 GB/T699 — 1999
Tolerance class Bolts, screws, studs GB/T3103.1 — 2002
Nut GB/T3103.1 — 2002
washer GB/T3103.3 — 2000
Mechanical properties Bolts, screws, studs GB/T 3098.1 — 2010
Nut GB/T 3098.2 — 2000
Dacromet coating thickness   GB/T 18684 — 2002
Salt spray test   GB/T18684 — 2002
Ammonia drop test   GB/T18684 — 2002
Adhesion test   GB/T18684 — 2002
Surface defects Bolts, screws, studs GB / T5779.1 – 2000 GB / T5779.3 – 2000
Nut GB / T5779.2 – 2000

Pre-construction of Anchor Cage Foundation

  • Determine the number of anchor bolts, check the appearance of upper and lower anchor plates, anchor bolts and thread, and clean up non-conforming materials.
  • The anchor bolt assembly shall be delivered to the site by loading truck and protected by cork pad to prevent deformation of the upper and lower anchor plate and damage to the original state of screw thread.
  • The embedded parts shall be retained, and the embedded parts of the anchor plate shall be set according to the standard of the foundation design drawing of the prestressed anchor bolt, and the quantity, size and position of the embedded parts shall be adjusted.

Set Down Anchor Plate and Adjust Its Flatness

  1. The lower anchor plate is mainly raised by the crane, and then moved to the position of 300mm above the embedded parts to stop the movement. First, the bolts of the lower anchor plate are inserted into the corresponding screw hole, and the bolts from inside to outside are exactly corresponding to the embedded parts. At this time, the crane lowers the lower anchor plate to the top of the embedded parts.
  2. The center of the lower anchor plate is matched with the foundation center. The bolts of the lower anchor plate and embedded parts are tightly welded together, and the height is controlled at ≥ 6mm.
  3. The plane of the lower anchor plate tends to be flat. By rotating the supporting anchor bolts, the lower anchor plate meets the height requirements of the drawing design, and its levelness is controlled at ≤ 3mm. Figure 1 shows setting the lower anchor plate and adjusting its flatness.
Auto Pouring Concrete to Anchor Cage Foundation

The Positioning Anchor Bolt and Upper Anchor Plate Are Paired Together

The upper anchor plate is hoisted by the crane, and the upper positioning anchor bolts are evenly matched from top to bottom on all bolt holes of the upper anchor plate, and then the anchor bolts are firmly fixed with temporary nuts. The anchor bolts are fixed with black nuts, and the outside of the anchor bolts is wrapped with PVC sleeves Tube, plus a heat-shrinkable tube sleeve. Nylon adjusting nut is used to fix the head of the anchor bolt.

The Upper and Lower Anchor Plates Are Precisely Matched

The upper anchor plate and the positioning anchor bolt are slowly raised and fixed directly above the lower anchor plate. The positioning anchor bolt and the matching bolt hole of the lower anchor plate are connected together. A gasket is placed below the lower anchor plate to fix the black nut, and the fixed torque is controlled at 300 N·m. FIG. 2 shows the exact matching of the upper and lower anchor plates.

Installation Work of Other Anchor Bolt Parts

After positioning anchor is fixed, the fixed anchor bolt is mainly based on the principles of diagonal sequence, ordinary bolt head through the first anchor plate, the other part through the anchor plate, based on the same principle, the other anchor fixed well, the bottom of the anchor bolt nut is fixed, with black coated PVC casing, and then add a layer of heat shrinkable tube, each floor installation gaskets, with black nut is fixed, the fixed torque control at 300 n. m.

Adjust and Check Anchor Bolt Assembly

  1. Adjust the concentricity of the upper and lower anchor plates. The Angle of the four bolts was measured by theodolite as 90°, which was taken as a reference. A pile was installed on the ground outside the wind power foundation at an interval of 90°, and was connected between the upper anchor plate and the pile with drag rope. The center line of the anchor bolt hole of the upper and lower anchor plate was regarded as a reference for adjusting the concentricity, and the standard length was within 3 mm.
  2. Adjust the level of anchor plate. The leveler is used to measure the levelness of the upper anchor plate. When the levelness does not meet the standard, the upper anchor plate shall be raised by jack and the nylon nut shall be further fixed to make the levelness meet the requirements.
  3. The excess length of the upper anchor plate at the anchor bolt head shall be controlled at L Within ± 1.5 mm.
  4. Heat the heat shrinkable tube, place the plug between the anchor bolt and the upper anchor plate anchor bolt hole, and fix the anchor bolt in the center of the anchor bolt hole.
Erecting Formwork and Pouring Concrete
Erecting Formwork and Pouring Concrete

Strapping Steel Rebars, Erecting Formwork and Pouring Concrete

  1. After finishing the adjustment work, the top and upper anchor plate of the steel bar are welded together through 4 steel bar anchor and bolt assemblies, which are strengthened according to the cross shape. The bottom and the embedded parts of the anchor cage foundation are welded together, and the cross spot welding of the 4 steel bars is done to strengthen the firmness of the anchor and bolt assemblies.
  2. Before concrete pouring, the upper anchor plate shall be tested for its levelness for the second time, and the levelness shall be no more than 2mm.
  3. When pouring concrete, the upper anchor plate and anchor bolt are sealed with plastic to prevent contamination.

Reliable Mining Roof Bolts Support for Your Mining Project

Mining Roof Bolts

Mining Roof Bolts Case Introduction

The mine engineering design annual production capacity is 1.8 million Ton, due to the complex geological structure in the minefield. In the design and construction of mining roof bolts support, support forms and parameters are selected based on experience or engineering analogy, so there are some problems, such as difficult roadway maintenance, low coal production rate and tight mining replacement. In order to solve these problems, take project mine roadway as the engineering background to carry out solutions based on the analysis of roadway deformation mechanism and support technical effect. The successful application of mining roof bolting, netting and cable combined support has important significance and practical application value for improving coal production rate, reducing support cost of mining roadway, and realizing high yield and high efficiency in mining roadway roof support.

In the construction and production of high-efficiency mines, the common mining roof bolts support has not been able to meet the requirements of mechanized large-scale production due to the fast construction speed. In order to solve the contradiction between the rapid excavation and the lagging of support, the combined support of high strength anchor bolt and anchor cable has been popularized and applied as the main support method. Mine roadway and semi-coal rock roadway are mainly mining rock bolted-net shotcrete, it is mainly bolted-net and anchor rock bolt + steel belt (or reinforced beam) support, general chamber also adopts rock bolt-net shotcrete + anchor cable support, only in special places (such as large ground pressure roof broken area) shed support. High strength roof bolt and cable combined support has the advantages of fast supporting speed, good effect and low cost.

Dimensions and Allowable Deviations of Hot-rolled Roof Bolts

Size Inner diameter Rib Height Rib Width Out of roundness Rib space
nominal size  allowable deviations nominal size  allowable deviations nominal size allowable deviations
Φ16 16 +0.5
+0.1
1.5 +0.4 1.0 ≤0.4 11.5 +0.5
Φ18 18 +0.5
+0.1
1.5 +0.4 1.3 ≤0.4 13.3 +0.5
Φ20 20 +0.5
+0.1
1.5 +0.4 1.3 ≤0.4 13.3 +0.5
Φ22 22 +0.5
-0.4
0.8 +0.3
-0.2
1.1 ≤0.4 12 +0.8

Main Factors Affecting Mining Roof Bolts Support

  1. The design method of mining roof bolts support is not scientific. Although its specification for coal roadway has been formulated, engineering analogy method is adopted in most of the design, and the support form and parameters are not reasonably determined. It is possible that the support strength is too much higher than the required level, the roof support structure cost is too much, for mining roof bolts are wasted. In soft, and other special geological conditions under the support strength may be insufficient, there is a possibility of danger, as roof collapse and other accidents may occur.
  2. The supporting material quality of mining roof bolt fails to reach the requirement. There might be various reasons, such as steel quality, thread quality of processing, resin coil quality are directly affected by the quality of support.
  3. The monitoring instrument and technology of mining roof bolts have high accuracy. The accuracy and practicability of the commonly used instruments are not perfect, which can not reflect the effect of bolt support completely.
  4. Under the existing technical conditions, the construction factor is the key link that directly affects the reliability of mining roof bolts support. The construction personnel does not have enough knowledge of the rock bolting support theory, or skills to install rock bolt properly, and the installation and operation quality management of the rock bolting cannot meet the design requirements. Such as sometimes only do the mining roof support and ignore the roadway side and floor, or some workers are not skilled enough and lacks sense of responsibility resulting in bolt and cable support strength reduction.
  5. In the construction of roadway uneven rock bolt anchor plate is not close to the rock surface, resulting in the failure of the mining rock bolt installed with no prestress. Different machines, tools and techniques used in the installation process lead to different pre-tensioning forces and different growth of support resistance after the installation of adjacent mining roof bolts, which will affect the support effect.

Mining Construction of Roof bolts

Rock Bolt for Tunnel Roof Support

During the installation of the resin bolt, the bolt must be pushed to the bottom of the hole to achieve the anchoring force. The agitator should be gently pushed vigorously, in order to quickly coagulant and resin stir evenly. When installing the nut of bolt support plate, the resin should reach a certain strength. The curing rate of resin and the growth rate of strength are accelerated with the increase in temperature. Practice shows that when the construction temperature is above 5 ℃, the supporting plate can be installed within minutes after mixing.

When the construction site temperature is below 5 ℃, the installation time should be postponed appropriately. The construction sequence is as follows: firstly construct the middle bolt, then construct the side bolt, dig a row spacing for each row, install a row of bolts, and make the jacking bolt and the side bolt work in parallel as far as possible.

  • According to the design requirements to excavate the roadway section, and then laid roof net, steel belt.
  • Use a single bolt drill to push the anchor hole to the design depth, place resin coil inside the hole, super-fast coil at the bottom of the hole, medium-fast coil at the outer part of the hole, and then use the assembled bolt to send the coil to the bottom of the manhole.
  • Lay the side net, set up the steel bar and the tray, tighten the nut with the plank hand, that is, complete the installation of a side bolt.

How to Install Roof bolts for Underground Mining

Construction tips for roof bolts install: from top to bottom, from back to front in turn.

  1. Clean the coal side to make it reach the design section size, and then determine the anchor hole position according to the design requirements.
  2. With the first hit the upper of the coal electric drill for bolt holes to design depth pack resin cartridge, the drill with connector and bolt, and start the drill, stirring side, until the bolt head to the bottom of the manhole, time is about 20 a 30 s, and then stop waiting for medicine curing, constraints, 30 s and then start the drill to tighten the nut, bolt installation. Lay the side net, set up the steel bar and the tray, tighten the nut with the plank hand, which is, complete the installation of a side bolt.

Anchor Cable Construction Tips

  1. Cut the steel hinge line according to the design length, remove rust and sludge (especially the internal anchoring section), install burr and retaining ring in the anchoring head section.
  2. Fix anchor cable hole position according to design requirement, use single anchor bolt drill, drill pipe and rotary bit to drill anchor cable hole to design depth.
  3. To hole placed resin cartridge, cartridge of super fast on the hole bottom, the medium cartridge placed outside the hole section, and then gently with the prepared steel strand pushing resin cartridge to the bottom of the hole, with stirring connector connect steel strand and drill, start the drill, stirring edge ahead, until to push resin cartridge to the bottom of the hole, such as back drill after 2 min, mixing connector, complete anchor cable anchorage.
  4. After resin anchoring and curing for 30 minutes, install jostles, trays and locks, and make them cling to the roof, hang tensioning, open the pump for tensioning, and observe the blasphemies of the pressure gauge, until pretension is designed, tension is stopped, jack is removed, and anchor cable is installed.

Test shows that rock bolt for mining roof with low initial anchor force cannot effectively control the displacement and deformation of surrounding rock. After the deformation, it only relies on the bracket of the net, beam and steel belt to prevent it from falling, which will increase the support cost. So by simply increasing the strength of roof bolt rebar, and neglecting to increase the primary anchor force, the strength of rock bolt rebar cannot be effectively exerted. Strictly control the mixing, solidification and waiting time of anchoring agent to ensure that the anchoring force meets the requirements of setting a standard, and the roles of composite beams and reinforced effect.

To make the anchorage rock bearing structure form as one structure, improves strata bearing capacity through changing the lower strata stress, effectively reduce the deformation of surrounding rock of roadway surrounding rock control early abscission layer, to improve the reliability of roadway roof support. After roadway excavation, the failure of surrounding rock gradually develops from the bottom to the roof, which shows that strengthening the support of the side walls plays an important role in the stability of the mining roof support. Prestressed rock bolt can effectively control the displacement of coal roof and the side walls. The higher initial anchor force of the rock bolt is main force to form “rigid” beam and “rigid” wall structure.

Rock Anchor Bolt Design and Production Line Equipments

Rock Anchor Bolt after Threading

Right-handed rock anchor bolt adopts the design of right spiral rib and one-way right screw thread, reinforced pitch and anchor bolt connection internal thread can be directly and effectively coordinated, it has the following advantages: simple connection and anchoring, strong adhesion, safety and reliability, etc. It is mainly used in underground rail track support engineering of coal mine, for ensuring smooth underground railway safety and coal mine construction industry. Except for low strength and poor safety of domestic old type rock anchor bolt, there are also higher strength and high tensile rock anchor bolt being developed.

Rock Anchor Bolt Production Line – Equipment Introduction

Here is a sample of small steel mill for rock anchor bolt production. Steel Mill adopts all rolling system, the air and gas – double heat furnace, use steel billet as raw material, with alternate arrangement of 6 roughing mills, and finishing mill group in all 6 high rigidity of short stress mills , and setting controlled cooling after rolling equipment, which is 120 m x 10 m step cooling equipment.

High Strength Rock Anchor Bolt Production

Here are list of difficulties and aspects in combination equipments in small steel mills for anchor bolt production:

  1. High strength rock anchor bolt steel has high-performance requirements. The raw material composition of steel rebar cannot reach the required yield strength and elongation, so it needs to be controlled in rolling process and heat treatment after rolling. The finished rock anchor bolt yield strength requires high carbon content, but it will lead to poor elongation. There are clear requirements for elongation in the standard, which requires post-rolling heat treatment. However, there is no post-rolling heat treatment equipment in small steel mills.
  2. The difficulty of rolling process development lies in the fact that steel rebar produced needs to be directly fitted with nuts, which means its size has to meet the deviation of standard requirements, and the threads on both sides should be exactly on the same spiral line. Therefore, groove width, expansion angle and radius of the base circle should be reasonable in the design of the threading process, and the cross rib spacing and included angle of the finished hole should be precise in both the design and processing.
  3. The middle and finishing mill groups without vertical roll rolling of continuous rolling production line, which requires torsion rolling; The second flow balance of rolled pieces cannot be controlled accurately, and the end – end difference will occur. The steelhead and tail have an extra part basically, which influence finished production rate.
  4. High processing precision is required for of finished rock anchor bolt products rolling groove; consistent transverse rib spacing between upper and lower rollers; consistent transverse rib spacing between the same roll; the actual pitch spacing of rolled products shall be consistent with the target value, and the design value of the transverse rib spacing shall be taken into account of impacting of sliding forward, cold shrinkage and others.
  5. Rolling mill, reducer quality ensures the upper and lower roll speed synchronization, no axial movement for rolling mill.

In order to solve the above problems completely before test run production of rock anchor bolt rebar, marking threads similar to right-handed rock anchor bolt steel transverse ribs were selected for test verification during production, so as to shorten the process development period and improve the success rate.

Design of Rock Anchor Bolt

  • According to the use characteristics and dimensions of high strength rock anchor bolt steel, the design ideas of finished pass and finished front pass are determined:
  • The finished product’s inner diameter height and width of free expansion surface shall meet the standard requirements; transverse rib filling degree is guaranteed on the premise, width of free expansion surface is as close as possible to the lower limit of the standard;
  • Accurately measure the influence of forwarding sliding and cold shrinkage of Kl under certain conditions, and make corresponding data compensation during design, control the spacing deviation of transverse ribs within 0.2mm after the steel bar is cooled;
  • Determine the diameter of Kl rolls of different specifications and the number of transverse ribs processed according to the front slip value, outlet speed of rolled pieces, the distance between transverse ribs and adjustment form to ensure the alignment effect and accuracy;
  • Adjust the angle of the axis of the transverse rib, which can directly fit with the nut of the same specification under the condition of the horizontal rib alignment.

Rock Anchor Bolt Grades and Mechanical Properties

Grade MG335 Yield Strength(MPa) Tensile Strength(MPa) Elongation(%)
Not Less Than
MG335 335 490 20
MG400 400 570 20
MG500 500 630 18
MG600 600 800 18

The proper calculation method of cross-rib alignment is determined through calculation and selection, so as the relationship between cross-rib phase error distance and adjustment parameters, the accurate rib alignment is realized through empirical data compensation, and the accuracy of roll turning and cross-rib machining is improved to create conditions for the successful manufacture of the high-strength rock anchor bolt.

Specifications of Rebar for Rock Bolt Tunnel Support

Rock bolt Tunnel support is an important direction of the development of coal roadway support. It is a technological revolution of coal roadway support. The progress of rock bolt tunnel support technology has accelerated the development of mining roadway industry. In the innovation of coal roadway technology, after years of research, Longton finally found the rock bolt support – extremely advantageous technology. The improvement of rebar rock bolt technology can greatly reduce the cost of coal roadway support, improve the safety mining work and improve the production efficiency to a new level.

Nowadays, rebar rock bolt tunnel support technology has become an indispensable technology in coal roadway support. In the supporting system, rebar rock bolt is the most widely used product. Here are some details of how high-quality rebar rock bolt is manufactured:

Mechanical Properties of Tunnel Rebar Rock Bolt

To understand the functions of the rebar rock bolt, you need to know exactly mechanical properties of rebar rock bolt.

Pull and Shear Tests on fully-grouted Rebar Rock Bolt

Test Stiffness (kN/mm) Yield load (kN) Peak load (kN) Load ratio (yield/peak) Displacement at peak load (mm) Rupture displacement (mm)
Pull 20 150 175 0.86 35 39
29 181 211 0.86 30 43
Shear 23 84 177 0.47 39 43
14 90 195 0.46 44 53

Anchoring Performance of Tunnel Rebar Rock bolt

Rebar Rock Bolt is Rolled from Rebar

The rebar itself has a good connection for the special screw structure, it will make the connection more tightly and not easy to fall off. And with chemical resin added, the connection becomes more seamless, resin will strengthen the strength of the connection, so that the rebar rock bolt has a strong anchoring ability.

Pure Bonding Force of Rebar Rock Bolt

This bond is mainly related to the spacing of threads and tooth height. For bolt surface has threads, when it starts to work, the rod body rotates along the thread, and resin will flow down the direction of the rod rotation, so that the gap will be filled, which can make the stirring effect. Moreover, the threaded teeth are trapezoidal, which makes the resin contact area larger, it becomes more sticky and effective. Moreover, for the rock rod body is all threaded and of sufficient length, the rebar rock bolt can slide along the rod body to achieve the ideal fixing force without worrying about rod length.

Resistance of Rebar Rock Bolt

Because of the special structure and length of the rebar rock bolt body, the force between thread and resin will increase. During stirring, when the resin flows down the thread, the rod body and the binder bond together, will create resistance to the rebar bolt, and only by overcoming this force can normal stirring be carried out.

Anchorage Methods of Rebar Rock Bolt

Different anchoring methods can achieve different anchoring effects. For example, full-length anchoring of rock bolt can effectively reduce the deformation of coal roadway and avoid the transfer of coal roadway position. This is how the force on the rod body is uniform when the full-length anchorage is used. Of course, if there is a full-length anchorage, there will be a local anchorage, and the local anchorage is mainly at the end, anchoring the end. This is a relatively uneven force.

Application of Rebar Rock Bolt

Rebar Rock Bolts in Mining Stoping Roadway

The use of rebar rock bolt in stoping roadway can greatly reduce the displacement of roof and floor as well as the two sides. Moreover, under the anchorage of the rebar rock bolt, the roof is well protected and will not be deformed or destroyed.

Rebar Rock Bolts in Mining Expansion Roadway

The use of rebar rock bolt support in mining roadway development will greatly increase the safety of roadway. For every project, safety is always the first priority. This kind of support texture is particularly good, not easy to damage, can greatly reduce the cost of maintenance. For it has advantages of operation is more convenient and higher production, it can bring huge economic benefits to customers. The full-length anchoring of rebar rock bolt can effectively improve the stiffness of bolt support system and limit the deformation of surrounding rock. The full-length anchoring bolt can provide anchoring force, improve the stiffness of the bolt support system, and when the stratum separation and deformation occur along its length range, reduce the deformation of surrounding rock. Because the full-length rebar anchor bolt support system has more advantages than resin anchor bolt, the safety and reliability of the support system is higher, therefore, it is the best form of mining roadway bolt supporting system at present.

Rebar Rock Bolts Used in Tunnel

Many projects constructions requires to dig tunnels, such as mining, building tunnels and so on. The excavation of the tunnel will easily loosen the rock structure, which will easily lead to disasters of landslides, it is a threat to people’s personal safety. However, the use of rebar rock bolt – resin anchors above the tunnels during excavation will strengthen the connections between the rocks and effectively prevent the rocks from slipping. So the use of rebar rock bolt keeps the people in the mines safe, so as the carts and machineries get through.

In a word, the appearance of rebar rock bolt has brought great convenience to many projects, and we should make good use of the benefits brought by this technology. However, the technology shall never stop, but also continue to research and innovation, I believe that with continuous efforts, Longton will offer more and more good rock anchor bolt technology to benefit more industries, if you need heat-treated high strength steel rod products, such as wind anchor cage bolt, anchor stud bolt, full thread bars, feel free to contact us now!

Structural Steel Tie Rod Application in Zunyi Science and Technology Museum

Structural Steel Tie Rod Project Introduction:

The construction project of Zunyi Science and Technology Museum has 3 floors, with a total construction area of 16598.58 m2 and a building height of 22.797m. The steel structure of the project includes steel columns, roofing steel truss, the steel structure of the exhibition hall at 12.45 meters, 80 structural steel tie rods on the exhibition ramp, an H-shaped steel beam, and a steel bridge of the ball screen film hall. A section steel column plane is divided into 10 points layout, divided into H section steel column, cross-section steel column.

Roof steel structure for large span cantilever which adopts truss structure. The trusses are divided into 3 parts, and each truss is provided with two supports (one end is sliding support, the other end is hinged support). A connection truss is arranged at the end of the main truss. The maximum cantilever length of the main truss is 18.395m, 20.825m and 12.082m. The chord of truss adopts a square steel pipe, and floor and roof board materials are steel and concrete. The third floor (12.45 meters in the exhibition hall) is hung with steel and concrete composite floor steel beam for hot-rolled H-beam. The large span of 28.8m is used above the ball screen cinema, and the steel beam is welded I-beam, which is supported on the surrounding frame column in the form of hinge. Walking ramp (ramp I and ramp) leading to the exhibition hall on the third floor, it has a span of 27.8m and is supported on the frame column on one side, and it is suspended from the steel structure roof on the other side by 80 structural tie rods. Large span, large overhang, and combination with concrete structure make the construction with steel structural tie rod more difficult.

Structural Steel Tie Rods with Upset and Rolled Threads EAU 2014

Nominal Diameter ØD1 Metric M39 M42 M45 M48 M52 M56 M60
Area, Core Diameter As [mm²] 976 1121 1306 1473 1758 2030 2361
Shaft Diameter d [mm] 36 39 42 45 38 41 44
Area, Shaft Ag [mm²] 1017 1194 1385 1590 1134 1320 1521

The high strength hot-rolled structural Steel tie rod used in Zunyi Science and Technology Museum has a diameter of 80mm, a length of 1L643m, 1L323m, and 1L418m, respectively, and tensile strength of not less than 650MPa. Three side-by-side and vertically connect the main box girder on the upper chord of ramp 1, ramp 3 and roof steel truss. High strength structural tie rod accessories mainly include: pull rod, adjusting sleeve (positive and negative screw), nut, backing plate, temporary U joint, etc.

Keys of Structural Steel Tie Rod Construction

  1. Single structural steel tie rod with a length of more than 11 meters passes through 3 reserved holes, and the upper and lower openings of reserved holes need to be installed with double nuts.
  2. The solution of construction problem is the prerequisite for structual tie rod construction to meet the design requirements.
  3. The concrete contact surface flatness between the backing plate and ramp inclined beam, and the included Angle between the nut and backing iron.
  4. During the assembly process, the structural steel tie rod surface coating treatment and thread protection.
  5. The sealing anticorrosion at the threaded joints of high strength structural tie rods should be given priority treatment.

Structural Steel Tie Rod Surface Treatment

This process is the key to ensure that the anti-corrosion life of the structural steel tie rod reaches the design requirements, and also directly affects the safety and stability of the whole structure. Before painting, the surface of the structural tie rod must be thoroughly cleaned of burrs, welding slag, spatters, dust accumulation, rust, oxide scale, oil stains and attachments. Due to the difficult surface shot peening, it is difficult to reach SA2.5 in a conventional way, so the mechanical sandblasting method is used for thorough dusting. The structural steel tie rod shall be coated with a water-borne inorganic zinc-rich primer except for the threaded connection part. The intermediate paint and top paint shall be the same. The primer shall be compatible with fireproof coating, and the paint shall have good adhesion to the substrate. The dry film thickness of each coat: 10 m primer, 100 m intermediate coat.

Before structural steel tie rod construction, it is necessary to coordinate with all departments to work on synchronously tracking, measuring, and controlling the embedded casing pipe, the position of the structural tie rod, ramp beam and the elevation of the top chord of truss.

Flatness Control of Structural Tie Rod Contact Surface

The contact surface is small. Place the level (without support) on the contact surface of an inclined beam of the ramp, rotate the level constantly to judge the flatness, and polish the uneven contact surface with the polishing equipment to ensure the flatness of the contact surface and ensure that there is no angle between the contact surface of the ramp and the inclined beam. If you are interested in other high strength steel rod products, contact us now for more details and the latest price!

Structural Tie Rod Install and Anti-Corrosion Treatment

Structural Tie Rod Application

Structural tie rod anti-corrosion treatment is very important for the life span of the building if it is done improperly, structural tie rod might be corrosion influenced, which will lead to more maintenance work. And this can be avoided by good anti-corrosion treatment work. The application of high-strength structural tie rod in this project meets the needs of large-span concrete beam structure, which reduces the steel quantity of the building structure, the building becomes more portable and beautiful. At the same time, steel structural tie rod lever itself has advantages of certain stiffness, convenient for construction and installation, short construction period, saving time and cost.

Installation of Structural Steel Tie Rod

  1. For single structural steel tie rod is more than 11 meters in length, and through the reserved hole, the reserved hole mouth up and down all need double nut and shim (bent truss beam under the mouth does not need), so the single structural steel rod is divided into 2 segments connection is made, namely the ramp between three and bent truss beam by adjusting sleeve 6 80 steel bar connection into three steel bar, in order to meet the design requirements
  2. The double nuts and iron cushion shall be placed in the corresponding embedded casing position in advance, and U-shaped joint shall be welded to steel pull rod end temporarily, so that the rod body does not damage galvanized layer on the surface of the steel pull rod during hoisting.
  3. Installation principle: the installation sequence of structural steel tie rods under the steel beam of the same axis shall be from high to low, from both ends to the middle direction.
  4.  Wire rope through the U-shaped joint hole, hoisting should be in place slowly, in advance to choose the structural steel tie rod emplacement path, and prevent scaffolding steel pipe, steel box girder to steel rod impact measures, especially on the connection of the adverse effect of thread.
  5. Steel rod in the process of hoisting, perforation in place, using hand chain hoist and lifting belt auxiliary positioning rod bottom end (perforation), artificial set of structural steel tie rod mat iron, double nut, adopt the method of vertical suspension to control the verticality of pull rod, and the error control within the permit, stay rod elevation, verticality are all meet the design requirements. The upper and lower orifice pads and double nuts of the 3 embedded sleeves in the ramp shall be installed and tightened successively.
  6. Special use special torque wrench turn adjusting sleeve and special fixture (to avoid damage of galvanized steel tie rod surface layer) are installed by the ramp between one and three ramp rod body, avoid with sleeve rotation, the regulating sleeve for the positive and negative screw thread, adjusting sleeve should be installed according to the positive and negative screw thread depth appropriate rotation on both ends of the sleeve, ensure the upper and lower end clearance rod body in the sleeve for about 28 mm, as steel bar stress adjustment allowance.
  7. The same method is used to lift the steel pull rod between the ramp no.3 and the main beam of upper chord successively. After steel pull rod is in place, a special clamp is used to jam the adjusting sleeve, steel pull rod at the upper end of the sleeve is rotated with a special torque wrench, and the depth control of steel pull rod is rotated at the same time, to ensure the end clearance of the two rod bodies within the sleeve is 28mm.
  8. The end contact surface of the structural steel tie rod of the main beam should be polished and level off before installing the contact surface of the iron cushion and the nut to ensure that there is no Angle between the iron cushion and the main beam.

Structural Tie Rods with Upset and Rolled Threads acc. to DIN EN 1993-5

Nominal Diameter ØD1 Metric M39 M42 M45 M48 M52 M56 M60
Stressed Area, Thread As [mm²] 976 1,121 1,306 1,473 1,758 2,030 2,362
Shaft Diameter d [mm] 36 39 42 45 38-39 41-42 44-46

Corrosion Resistance of Structural Steel Tie Rod End Thread Sealing

The structural steel tie rod used in this project adopts the same coating process for surface anti-corrosion, except the end connection thread, so the sealing anti-corrosion at the thread is the key part of the structural steel tie rod anti-corrosion.

This project adopts the neutral room temperature vulcanized high-grade sealant for anti-corrosion. This kind of sealant has good adhesion to a steel beam and zinc-rich primer, good weather resistance, water-resistance, and high and low-temperature property. Its anti-corrosion life can reach to over 30 years, and the service temperature is 65℃ to 300℃.

Steel tie rod installation (threaded connection is not adjusted), after the sleeve, nut, mat iron screw tooth surface and combining with the end to clean up, thoroughly remove grease, rust, and debris on the surface of the sealant with glue gun play at the end of thread surface, as well as the combination of components and shim and oblique beam concrete interface, evenly with flat to be closed.

Structural Tie rod Surface Anti-corrosion Post Treatment

For structural tie rod parts that have been used as antirust primers but have been damaged, re-embroidered, peeled, etc., and parts that have not been used as antirust primers, they should be first polished and cleaned manually. Then, water-based inorganic zinc-rich primers should be used as antirust primers with a dry film thickness of 100um, and then primers, intermediate paints, and topcoats should be sprayed as required to meet the design requirements.

If you happen to be inneed of structural steel tie rod or threaded stud of high tensile strength, send email now for more details now!

M48 Grade 8.8 Anchor Bolts Supplied for Wind Mill of China Resources

WindAnchor Cage Foundation

Great news, one of the many projects Longton Group participated in, China Resources Sha Yangmaliang Wind Farm Phase I, 20 units, Phase II, 25 units, and its capacity is 2.5WM, has been completed.

Project Details:

A few days ago, Hubei Provincial Development and Reform Commission approved China Resources Shayang Maliang Wind Farm Phase II project.

The construction site of the project is Shayang County, Jingmen City, with a construction scale of 100,000 kilowatts, 40 wind turbines with a single-unit capacity of 2.5 megawatts, and related supporting facilities. The annual designed on-grid electricity is 209.5 million kilowatt-hours. Lonteng Group supplied the M48 Anchor Bolt assembly to all 45 wind turbine foundations, and helped with onshore anchor cage foundation construction.

If you need anchor cage assembly such as wind anchor bolt and anchor plate, feel free to contact us now!

Anchor Bolt Foundation for

Maliang Wind Farm

Wind Mill Projects and Market Influenced by Covid-19

Affected by the new coronavirus, wind farm projects and enterprises are in a state of shutdown or half-stop, and the industry as a whole is in a period of rush installation, so the impact of epidemic on the industry is more obvious. Because the epidemic situation is radiating outwards with Hubei as the center, it has a great impact on construction period of rush-install projects in southern region (mostly low-speed projects).

On January 30, National Energy Administration issued the “Notice on Effectively Performing Electricity Guarantee Services for Epidemic Prevention and Control and Current Electricity Safety Production”. The notification requires that all units should thoroughly extend Spring Festival holiday, shortened planned construction period, and epidemic prevention and control period. The actual situation such as restricted personnel flow is planned in advance to deploy and resume work after the holiday. Electric power enterprises must adhere to the time and safety and quality, scientifically determine the time node for resumption of production, revise the construction operation plan in time, re-determine the reasonable construction period, and strictly prohibit the rush of progress and the rush period.

Overview of Useful Instructions on Rock Bolt Install

Rock Bolt Rebar Manufacture

What is Anchor Rock Bolt

Anchor rock bolt are solid or hollow steel rock bolts that are drilled into rock mass during excavation of the surrounding rock to avoid loose collapse of rock mass, which serves to reinforce and connect the soil body as a whole. The mortar or other materials are used to consolidate between rocks and set with steel backing plates

Tips for Rock Bolt Install

Rock Bolt Install Tips

  1. Rock bolt construction should be carried out after initial shotcrete, anchor rock bolt is driven into the hole with special machinery, and a special impactor should be equipped when using a general air-powered rock drill. The drill hole should be round and straight, and in line with the surrounding rock wall or rock layer where it is located. The main structural plane is in vertical direction.
  2. Lay the position according to design requirements, the allowable deviation of hole position is not more than 10cm, and the insertion length of rock bolt body should not be shorter than 95% of design length.

  3. When rock bolt body – high strength rebar is inserted into anchor hole, the position should be kept in the middle and insertion depth should meet design requirements.

  4. The mortar filled in the mortar anchor hole should be full and dense, and appropriate amount of micro-expansive agent and quick-setting agent can be added to the mortar or cement slurry.
  5. After anchor rod is installed and mortar filled is finally set, pallet should be installed immediately and nut should be tightened.

Common problems on Rock Bolt Worksite

  1. The number and length of anchor rock bolts are lower than the design value, and the distance between anchor bolts is large. The U-shaped welding is not adopted between the lock bolt and the steel frame. The on-site inspection shall separate the advanced small catheter, advanced anchor rod, hollow anchor rod, and lock foot anchor pipe (rod) in detail.
  2. The raw material of anchor rock bolt does not meet the standard. Wall thickness and weighing inspection of anchor rod should be checked on site.
  3. The phenomenon that hollow grouting bolt designed is not grouted or replaced with mortar bolts.

  4. The angle of rock bolt penetration does not meet design requirements.

Rock Bolt Rebar Material of European Standards 42CrMo4

High Tensile Rock Bolt

Rock Anchor and Rock Bolt

The material of rock bolt body mainly includes high-strength steel wire, steel strand, hot rolled rebar and other high-strength steel. It can stretch freely under tensile load. When this part of elongation is permanently fixed or “frozen”, a certain pre-compression stress is generated on rock mass or various structures.

Therefore, rock bolt body is the main part to realize medium anchoring by tension. At present, main materials used in prestressed rock bolts in mining are fine-rolled threaded steel bars.

Friction Between Rock Bolt Rebar

The connection of high-strength precision-rolled threaded steel rebar is to prevent mutual sliding of connecting parts by friction between contact surfaces. To make contact surface with sufficient friction, it is necessary to increase clamping force and increase the friction of contact surface. Clamping force between components is achieved by applying a pre-tension to rock bolts, so the connectors (finished rolled rebar, bolts, etc.) must be made of high-strength steel.

Threaded Rock Bolt Rebar

Precision-rolled threaded steel bar is a rigid prestressed anchor. It is a steel bar made of 40Si2MnV or 45SiMnV, which belongs to high-strength steel, and has a complete external thread on. At any cross-section, it can be connected or anchored with a connector or anchor with an internal precision rolled screw anchor. The use of this type of rock bolt body is convenient for construction and safe and reliable for anchoring.

European Standard of High Strength Steel Rock Bolt

Steel gradeYield
strength
[MPa]2)
European standards
S 355 J2+AR315 – 335EN 10025EN 10060EN 10204
42 CrMo4650EN 10083EN 10060EN 10204
34 CrNiMo6800EN 10083EN 10060EN 10204

As it is designed, rock bolts must be installed one meter into bedrock and one meter along sheet pile. Usually the length of rock bolts is therefore at least 3 meters or longer.

MSGLW 700 Rock Bolt Rebar

Typical rock bolt diameters vary between Ø 50 and Ø 90 mm. Contractors tend to prefer small diameters of rock bolts with high steel grades (42CrMo4 is most common), which reduces the weight, and consequently simplifies its handling which is normally done by hand.

These standards are most commonly used in Norway, however, other steel grades may be utilised. The differences in quality of rock bolts defined in different standards should normly be of little importance for this specific type of application.

Rock Bolt Application in Tunnel Roof Supporting System

Rock Bolt for Roof Bolting
Tunnel is an underground passage through a mountain, beneath a city or under a waterway or Tunnels are enclosed roadways, railways, waterways, etc. With vehicle, trains, ships, etc. access that is restricted to portals regardless of type of structure or method of construction.

Rock bolt used as roof bolt is a main method to provid safe working environment for miners, prevent ground falls and save human lives and properties from hazards. Roof bolting structure is scientificaly calculated by engineers according to the rock and earth conditions, it is a great improvement compared with the old standing support. As rock bolt rebar is the main force bearing part, it is of great importance to understand and use it wisely in mining underground support system.

Rock Bolt Anchoring
Mine Roof Bolting

Roof Bolt Development in Mining

Roof bolt specification include the rock bolt type, tensile strength, stress level,length, etc. Although engineers has experiences and knowlege to analyze the underground situation, the understanding is still in-efficient. Various types of rock bolts have been developed for now, and they all work in some specific conditions, it is hard to say which type is better.

  1.  Mining underground roof falls accident happens for more than 1000 times every year.
  2.  Inorder to fully research roof bolting system, engineers and institutes has been following evaluation of mining roof fall incident allover the country.
  3.  Rock bolt specifications and its stress levels can be used to consider the capacity, 3 basic ones are rock bolt length, rebar tension, grout length.

why Rock Bolt Design Matters in Mining

The portion where the work is carried out while its construction is called the face (heading) and all efforts are made in advancing this face as fast as possible till the end of tunnel is reached.

Rock bolts are the first line of defense protecting mineworkers from the hazards of ground falls. Because rock bolts utilize the inherent strength of the rock mass, they have many advantages when compared with earlier standing support systems. Due to their central importance, roof bolts have received more research attention than any other ground control topic, with the possible exception of coal pillars.

Rock Bolt Design and Function

Roof bolt design consists in specifying the proper bolt type, capacity, length, and pattern for a particular roof rock, stress level, and application. The interactions between these variables are very complex, and our understanding of their mechanics remains imperfect. Numerous roof bolt design methods have been proposed over the years, but none has gained widespread acceptance by the coal mining industry.

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