Method for increasing bearing capacity of existing engineering pile center drilling head expanding

Abstract

According to the method, a hole is drilled from the center of an engineering pile which is constructed and needs to be reinforced to the pile bottom, chambering below the pile bottom is carried out by adopting a high-pressure jet grouting and stirring combined or direct drilling method, and a reinforced concrete core grouting reinforcement body is additionally arranged in a cement soil pier body formed by jet grouting and stirring or a pier body combined pile hole formed by drilling, bottom expanding and concrete pouring. The bearing capacity of an original engineering pile is increased, and the aim of reinforcing the existing engineering pile is achieved. The foundation treatment and reinforcement method has the remarkable advantages that construction is convenient, the construction speed is high, and the manufacturing cost can be greatly saved.

Description

Technical Field

[0001] The present invention is a method applicable to reinforcing the already driven engineering piles to improve the pressure bearing or pull-out bearing capacity of the piles due to various reasons - a method for enhancing the bearing capacity of the existing engineering piles by central drilling and expanding the head. Background Art

[0002] In engineering construction, we often encounter various special situations that make the installed engineering piles unable to meet the design bearing capacity requirements: for example, the engineering piles have insufficient bearing capacity due to various improper construction reasons, the piles have insufficient bearing capacity due to engineering geological reasons, the original superstructure has been changed for various reasons, causing the piles to bear an increased design load or change from pressure bearing to pull-out bearing, and the existing buildings have uneven settlement due to underground piles, requiring reinforcement piles to stop sinking and correct deviation, etc. The above engineering accidents are usually difficult to handle, not only delaying the construction period but also costing more to deal with such problems; the development of a method for reinforcing existing engineering piles to improve the pressure bearing or pull-out bearing capacity of the piles is of extraordinary significance for the reinforcement treatment of pile accidents in engineering construction. Summary of the invention

[0003] The present invention is a method suitable for reinforcing completed engineering piles for various reasons to improve the pile's compressive or tensile bearing capacity - a method for enhancing the bearing capacity of existing engineering piles by drilling holes in the center and expanding the head. A hole is drilled in the center of an engineering pile that has been completed but needs to be reinforced to the pile bottom, and a high-pressure rotary spraying combined with stirring method is used to expand the hole below the pile bottom. The cement soil mound formed by rotary spraying and stirring is combined with additional reinforcement in the pile hole and a concrete core reinforcement body is used to achieve the purpose of reinforcing the existing engineering piles.

[0004] The present invention comprises two aspects:

[0005] First, after the construction of the engineering pile is completed, the engineering inspection determines that the pile bearing capacity does not meet the design requirements and needs to be reinforced. At this time, the upper structure has not yet been built and the pile has not yet been subjected to normal force. In this regard, the present invention provides a method for directly center drilling and expanding the pile to enhance the bearing capacity, which can greatly reduce the risks of construction delays and increased construction costs caused by conventional additional piling.

[0006] Second, when existing buildings are completed and put into use, they may encounter uneven settlement due to problems with engineering piles, and accidents such as tilting and cracking of buildings, which affect normal use or create safety risks, and must be reinforced and repaired; they may also often encounter situations where the original engineering piles are insufficient in compressive bearing capacity and need to be reinforced to increase the existing building's floor level; and there are also situations where the original anti-floating or pressure-bearing design does not meet the requirements due to changes in geological and hydrological conditions, which all require reinforcement. In response to this, the present invention provides a method for reinforcing and repairing existing engineering piles and improving their bearing capacity in a narrow indoor environment.

[0007] The beneficial effect of the present invention is that the method for enhancing the bearing capacity of existing engineering piles by central drilling and expanding the head can reinforce the engineering piles that do not meet the bearing capacity requirements to increase their bearing capacity and meet the design requirements without delaying the construction period and greatly increasing the construction cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1.1 Cross-sectional view of reinforcing the bottom of the pipe pile for high-pressure jet-jet cement soil mound body and setting a steel cage in the pile hole and pouring concrete into the core;

[0009] Figure 1.2 Cross-sectional view of reinforcing the bottom of the pipe pile with high-pressure jet cement-soil pier and setting a steel cage in the pile hole and partially pouring concrete into the core;

[0010] Figure 1.3 Drilling and enlarging the bottom hole of the pipe pile and setting the reinforced cage concrete core section;

[0011] Figure 1.4 Cross-sectional view of high-pressure jet grouting at the bottom of the pile, tamping and expanding the bottom, and setting the reinforced cage concrete core;

[0012] Figure 1.5 The cross-section diagram of the high-pressure rotary grouting expansion of the bottom of the pipe pile and the setting of steel rods or steel tube concrete core;

[0013] Figure 1.6 The bottom blasting and expansion of bored piles and the setting of steel rod or steel tube concrete core profile;

[0014] Figure 1.7 The top of the pile has been partially filled with core, and the bottom of the pile is reinforced with drilled high-pressure rotary spray cement soil mound;

[0015] Figure 2.1 To ensure that the side friction of the original pipe pile meets the requirements and to enhance the pull-out resistance of the pile body, the reinforced cross-section is shown;

[0016] Figure 2.2 The original pressure-bearing pipe pile has insufficient pull-out resistance, so the pile body pull-out resistance and pile side resistance reinforcement section are enhanced;

[0017] Figure 2.3 The original pressure-bearing pipe pile is adjusted to an anti-pulling pile, and the pile body and pile side are strengthened to resist the pull-out force (section 1);

[0018] Figure 2.4 The original pressure-bearing pipe pile is adjusted to an anti-pulling pile, and the pile body and pile side are strengthened to resist the pull-out force (section 2);

[0019] Figure 3.1 The reinforced cross-section diagram 1 is for bored cast-in-place piles with hard soil as the bearing layer to enhance the compressive bearing capacity;

[0020] Figure 3.2 The reinforced cross-section diagram 2 is for bored cast-in-place piles with hard soil as the bearing layer to enhance the compressive bearing capacity;

[0021] Figure 3.3 The reinforced cross-section diagram 3 is for bored cast-in-place piles with hard soil as the bearing layer to enhance the compressive bearing capacity;

[0022] Figure 3.4 Reinforcement profile 4 (blasting hole expansion) for bored piles with hard soil as the bearing layer to enhance the compressive bearing capacity;

[0023] Figure 4.1 This is a reinforced cross-section diagram of a bored pile with a hard soil layer as the bearing layer to enhance the pull-out bearing capacity of the pile body;

[0024] Figure 4.2 The reinforced cross-section diagram 1 is for bored cast-in-place piles with hard soil as the bearing layer, which can enhance the pull-out bearing capacity of the pile body and pile side;

[0025] Figure 4.3 For bored piles with hard soil as the bearing layer, the reinforcement section 2 is used to enhance the pull-out bearing capacity of the pile body and pile side;

[0026] Figure 4.4 For bored piles with hard soil as the bearing layer, the reinforcement section diagram 3 is used to enhance the pull-out bearing capacity of the pile body and pile side;

[0027] Figure 5.1 A reinforced cross-section diagram of a bored pile with hard rock as the bearing layer to enhance the concrete strength at the bottom of the pile;

[0028] Figure 5.2 For bored piles with hard rock as the bearing layer, add reinforcement profile of pile body reinforcement;

[0029] Figure 5.3 and Figure 5.4 A cross-sectional diagram of strengthening the bedrock strength at the bottom of a bored pile with a soft rock layer as the bearing layer;

[0030] Figure 5.5 A reinforced cross-section diagram of a bored pile with any rock layer as the bearing layer to enhance the compressive bearing capacity;

[0031] Figure 6 A reinforced cross-section diagram for increasing the pull-out bearing capacity of bored piles with rock as the bearing stratum;

[0032] Figure 7.1 and Figure 7.2 All of them are reinforced cross-section diagrams of pipe piles in construction projects with hard soil as the bearing layer, which increase the compressive bearing capacity of the pile end;

[0033] Figure 8.1 A reinforcement cross-section diagram for increasing the pull-out bearing capacity of pipe piles in construction projects where the bearing layer is a hard soil layer;

[0034] Figure 8.2A reinforcement profile diagram for increasing the pull-out bearing capacity of the pile side for pipe piles in construction projects with hard soil as the bearing layer;

[0035] Figure 8.3 A reinforcement profile diagram for increasing the pull-out bearing capacity of the pile body and pile side for pipe piles in construction projects with hard soil as the bearing layer;

[0036] Figure 9.1 A reinforced cross-section diagram of increasing the compressive bearing capacity of the pile body and pile end for bored cast-in-place piles in construction projects with hard soil as the bearing layer;

[0037] Figure 9.2 A reinforced cross-section diagram of increasing the compressive bearing capacity of the pile end for bored cast-in-place piles in construction projects with hard soil as the bearing layer;

[0039] Figure 10.1 A reinforced cross-section diagram of bored piles in construction projects with hard soil as the bearing layer to increase the pull-out bearing capacity of the pile body;

[0040] Figure 10.2 A reinforced cross-section diagram of increasing the pull-out bearing capacity of the pile body and pile side for bored cast-in-place piles in construction projects with hard soil as the bearing layer;

[0041] Figure 11.1 is a side elevation view of an expandable anchor;

[0042] Figure 11.2 is an oblique view of an expandable anchor;

[0043] Figure 11.3 Strengthen the single anchor head with steel rods / tubes to resist pull-out;

[0044] Figure 11.4 Strengthen the double anchor heads with pull-out steel rods / tubes;

[0045] Figure 11.5 Strengthen the pull-out steel rods / tubes for multiple anchor heads;

[0046] In the figure: 1-pipe pile, 2-concrete core, 3-pile bottom expanded cement soil mound body, 4-reinforcement bars such as steel cage, 5-pile bottom concrete expansion head, 6-ramming and expansion to form the pile bottom concrete expansion head, 7-pile bottom concrete pier body, 8-expanding the hole to form the concrete pier head by detonating explosives, 9-tensile steel pipe or steel rod, 10-cement soil mound body, 11-pile bottom fine stone concrete pier body, 12-pile bottom fine stone concrete pier body, 13-cast-in-place pile, 14-cement soil mound body, 15-steel rod or steel pipe, 16-pile bottom cement soil mound body, 17-cast-in-place pile bottom concrete pier head, 18-cast-in-place pile bottom explosive expansion formed by hole expansion, 19-reinforcement steel, 20-reinforcement Strong tensile steel bars or steel pipes, 21-special steel pipes, 22-cement soil mound body, 23-cement soil mound body formed by multiple rotary jet expansion, 24-concrete pier head, 25-reinforced steel core, 26-reinforced tensile steel core, 27-bottom plate and pedestal, 28-pile bottom expanded cement soil mound body, 29-reinforced steel pipes, 30-reinforced pull-out steel pipes, 31-pile bottom expanded cement soil mound body, 32-reinforced pull-out steel pipes, 33-expandable anchor head, 34-pull-out steel rods, 35-rotatable bending anchor, 36-rotating shaft, 37-fixing rod, 38-center slider, 39-center hinge shaft, 40-center pull rod, d-expandable anchor head outer diameter. DETAILED DESCRIPTION

[0047] Due to the different stress working conditions of existing piles, different bearing layers at the pile ends, different pile types, and different pile stress characteristics, the present invention has developed a targeted method for improving the bearing capacity of the most widely used prefabricated pipe piles (usually the bearing layer is a hard soil layer) and cast-in-place piles (usually the bearing layer is a hard soil layer or a rock layer). The specific points and implementation methods are as follows:

[0048] 1. After the construction of the engineering piles is completed, it is determined through testing that the pile bearing capacity does not meet the design requirements and needs to be reinforced. At this time, the superstructure has not yet been built and the piles have not yet been subjected to normal force. At this time, it is more convenient and beneficial to reinforce the piles.

[0049] 1.1. The present invention has developed a variety of implementation methods for improving the compressive bearing capacity of prefabricated reinforced concrete pipe piles 1 with a hard soil layer as the bearing layer at the pile end:

[0050] 1.1.1, when the pile head has not completed the conventional concrete core pouring treatment of anchor steel cage. There are several ways to improve the compressive bearing capacity:

[0051] The first is to use an ordinary high-pressure rotary jet pile machine for diameter expansion reinforcement. Use an ordinary high-pressure rotary jet pile machine to drill directly on the top of the pipe pile 1 with clean water until it passes through the bottom of the pipe pile to about 1m to 3m below the pile end. After lifting and lowering the rotary jet to expand the hole 2 to 4 times, use cement slurry to lift and lower the rotary jet to expand the hole several times until the slurry cement concentration emerging from the top of the pipe pile solidifies and reaches the strength requirement, forming a pile bottom expanded cement soil mound 3 to complete the reinforcement. If the compressive strength of the pipe pile itself is insufficient, reinforcing bars such as steel cages can be set in the cavity of the pipe pile 4 ( Figure 1.1 If the compressive strength of the pile can meet the reinforcement requirements, the top of the pile should be treated with a conventional concrete core with an anchor steel cage ( Figure 1.2 ).

[0052] The second method is to use an ordinary drilling rig combined with the pipe end tamping and expansion of the concrete head reinforcement method. Place a drill rod in the pipe pile and drill downward. The diameter of the drill bit should be smaller than the inner diameter of the pipe pile, and the value should be between 250mm and 450mm. The drill bit passes through the end of the pipe pile and drills downward for about 1 to 2m. After the hole is in place, lift and remove the drill rod, put in a mud pump to quickly drain the water and soil in the hole, and quickly pour dry hard concrete in batches (usually 1 to 4 batches, and the soil at the pile end should be divided into multiple batches). Then, use a through-the-heart hammer to tamp and expand the concrete expansion head 5 at the bottom of the pile in the cavity of the pipe pile with a free fall hammer to increase the bearing capacity of the pile end. After lifting and pulling out the drop hammer, put in the steel cage 4 (it may or may not be installed according to the strength of the pile body), and pour concrete in the pile hole to complete the reinforcement ( Figure 1.3 ).

[0053] The third is the ordinary high-pressure rotary spraying or rotary mixing spraying combined with pipe end tamping and expansion of concrete head reinforcement method. Use an ordinary high-pressure rotary spraying pile machine with clean water to drill directly on the top of the pipe pile until it passes through the bottom of the pipe pile to about 1m to 3m below. Lift and drop the rotary spraying hole 2 to 4 times, then lift and remove the drill rod, put in a mud pump to quickly drain the water and soil in the hole, and quickly pour dry hard concrete in batches (usually 1 to 4 batches, the soil at the pile end should be divided into multiple batches), and then use a through-heart hammer in the pile hole to tamp and expand with a free drop hammer to form a pile bottom concrete expansion head 6 to increase the bearing capacity of the pile end. After lifting and pulling out the drop hammer, put in the steel cage 4 (installed or not according to the strength of the pile body), and pour concrete in the pipe pile to complete the reinforcement ( Figure 1.4 ).

[0054] The fourth is the ordinary high-pressure rotary spraying or rotary mixing spraying combined with the concrete pipe end vibration reinforcement method. Use an ordinary high-pressure rotary spraying pile machine to drill directly at the top of the pile with clean water until it passes through the bottom of the pile to about 1m to 3m below. After lifting and lowering the rotary spraying hole 2 to 4 times, lift and remove the drill rod, and then insert the pouring and transporting fine stone concrete pipe with a vibrating head to the bottom of the hole. While pouring concrete, vibrate and lift to form the concrete pier at the bottom of the pile 7, and then pour concrete while lifting out the top of the pile, and vibrate into reinforcing steel rods or steel pipes to complete the reinforcement (4). Figure 1.5 ).

[0055] The fifth is the ordinary drilling and concrete blasting method to expand the hole into a pier head reinforcement method. Use an ordinary drilling rig to drill directly through the bottom of the pile and drill 1m to 2m downward. After the drill bit is pulled out, put in a mud pump to quickly drain the water and soil in the hole. Put strictly designed explosives at the bottom of the hole, put in reinforcing steel rods or steel pipes and other reinforcing bars 4 (depending on the strength of the pile body), and pour in concrete until it is full. Detonate the explosives to expand the hole to form a concrete pier head 8, and then fill it with concrete to complete the reinforcement ( Figure 1.6 ).

[0056] 1.1.2. When the concrete core 2 of the anchor steel cage has been poured at the head of the pile 1, there are several ways to improve the compressive bearing capacity:

[0057] First, the concrete core 2 with the anchor steel cage already set at the head of the pipe pile 1 is removed, and then the five methods in 1.1.1 above are used for processing.

[0058] Second, when the inner diameter of the concrete core 2 of the anchor steel cage on the top of the pipe pile 1 is relatively large, the concrete core 2 can be drilled through with a drill bit with a diameter greater than 250 mm, and then processed according to the five methods in 1.1.1 above.

[0059] Third, when the inner diameter of the concrete core 2 of the anchor steel cage on the top of the pile is relatively small, only a drill bit with a diameter of less than 200 mm can be used to drill through the conventional concrete core 2, and then the above-mentioned 1.1.1 is used for processing ( Figure 1.7 ).

[0060] 1.2. The method developed by the present invention for improving the pull-out bearing capacity of prefabricated reinforced concrete pipe piles with a hard soil layer as the bearing layer at the pile end:

[0061] 1.2.1. When the head of the pile 1 has not yet completed the conventional concrete core 2 treatment of the anchor steel cage, there are several methods to improve the pull-out bearing capacity:

[0062] First, the original pipe pile 1 is a pressure-bearing pile, and the reinforcement needs to have the function of an anti-pulling pile, and the friction resistance provided by the outer side of the pipe pile basically meets the design requirements. The high-pressure water gun is placed in the pipe pile 1 to flush the pipe wall to the bottom of the pipe pile, and the water in the pipe pile is drained. The anti-pulling reinforcement bar (reinforcement cage) 4 is quickly placed, concrete is poured in, and a vibrating rod is inserted to complete the reinforcement ( Figure 2.1 ).

[0063] Secondly, the original pipe pile 1 is a pressure-bearing pile that needs to function as an anti-pullout pile. However, the frictional resistance provided by the outside of the pipe pile is insufficient, and the anti-pullout force needs to be greatly increased. Ordinary high-pressure rotary jetting is used to drill through the bottom of the pipe pile 1 with clean water, and the clean water is continued to be rotary jetted up and down to a certain depth below the bottom of the pile (determined by the soil properties and the need to increase the anti-pullout force). Then, cement slurry is used for rotary jetting up and down to form a cement soil mound 10. The rotary jetting is continued until the cement slurry emerging from the top of the pipe pile 1 is condensed and the concentration meets the requirements. A specially made tensile steel pipe or steel rod 9 with multiple sections of extended anchor rods is placed, and the anchors at the bottom are deployed. The cross-sectional tensile strength of the tensile steel pipe or steel rod 9 combined with the original reinforcement of the pipe pile 1 should be able to meet the anti-pullout force requirements after reinforcement ( Figure 2.2 ).

[0064] Third, the original pipe pile 1 is a pressure-bearing pile and needs to be changed into a pull-out pile. However, the friction resistance provided by the outer side of the pipe pile is insufficient, and the pull-out resistance needs to be increased. Ordinary high-pressure rotary jetting is used to drill through the bottom of the pipe pile 1 with clean water, and the clean water is continued to be rotary jetted up and down to a certain depth below the pile bottom (determined by the soil properties and the need to increase the pull-out resistance). Then, cement slurry is used for rotary jetting up and down to form a cement soil mound 10. The rotary jetting is continued until the cement slurry emerges from the top of the pipe pile 1 and the concentration meets the requirements after solidification. Then, a casting and transporting fine stone concrete pipe with a vibrating head is inserted into the bottom of the hole, and the concrete is poured while vibrating and lifting to form a pile bottom concrete pier body 11. The transporting fine stone concrete pipe is lifted out, and a reinforcing tensile steel pipe or steel rod 9 is placed and vibrated into the pile bottom concrete pier body 11. The bottom anchor is deployed to complete the reinforcement ( Figure 2.3 ).

[0065] Fourth, the original pipe pile 1 is a pressure-bearing pile and needs to be changed into a pull-out pile. However, the friction resistance provided by the outside of the pipe pile is insufficient, and the pull-out resistance needs to be greatly increased. Use high-pressure rotary stirring and spraying to drill through the bottom of the pipe pile 1 with clean water. The drill bit is expanded to form a stirring rod and combined with the rotary nozzle of the stirring rod head, the clean water is continued to be stirred and sprayed up and down to a certain depth below the bottom of the pile (the specific depth is determined by the soil properties and the need to increase the pull-out resistance). Insert the pouring and transporting fine stone concrete pipe with a vibrating head into the bottom of the hole, and vibrate and lift the retracted stirring rod into the pipe pile 1 while pouring concrete, forming a pile bottom fine stone concrete pier body 12 at the bottom of the pipe pile 1. Lift out the transporting fine stone concrete pipe, put in the reinforced tensile steel pipe or steel rod 9 and vibrate it into the pile bottom fine stone concrete pier body 12, and unfold the bottom anchor. Drain the water and soil in the pipe pile 1, quickly pour in concrete and insert the vibrating rod to complete the reinforcement ( Figure 2.4 ).

[0066] 1.2.2. When the head of the pile 1 has been treated with conventional concrete core filling 2 with anchor steel cage, there are several methods to improve the pull-out bearing capacity:

[0067] First, the concrete core 2 of the pile head where the conventional anchor steel cage has been set is removed, and then the above 1.2.1 1 to 4 methods are followed.

[0068] Second, when the inner diameter of the concrete core 2 of the anchor steel cage on the top of the pipe pile 1 is relatively large, use a drill bit with a diameter greater than 250 mm to drill through the conventional concrete core 2, and then proceed according to the methods 1 to 4 of the above 1.2.1.

[0069] Third, when the inner diameter of the concrete core 2 of the anchor steel cage on the top of the pipe pile 1 is relatively small, use a drill bit with a diameter of less than 200mm to drill through the conventional concrete core, and then handle it according to the methods 1 and 2 in the above 1.2.1.

[0070] 1.3. The method for improving the compressive bearing capacity of the cast-in-place bored pile 13 with a hard soil layer as the bearing layer at the pile end developed by the present invention is specifically implemented by first drilling a hole downward at the center of the bored pile 13 with a drilling rig, and there are the following implementation methods:

[0071] First, the diameter of the drill hole is 100mm~150mm. The hole passes through the pile end. After the drill bit is pulled out, an ordinary jet-jet drill rod 1 is put in to jet downward with clean water for about>2m (determined by the soil properties and the need to increase the bearing capacity). Repeat the jet-jet up and down to expand the hole several times, and then jet the cement slurry up and down to further expand the hole to form a cement soil mound 14 (the number of up and down jet-jet is determined by the soil properties and the need to increase the compressive bearing capacity). Continue jet-jet until the cement slurry emerging from the top of the pile meets the requirements after solidification. If the bearing strength of the original pile body can meet the requirements after reinforcement, the reinforcement is completed; if the bearing strength of the original pile body cannot meet the requirements after reinforcement, a steel rod or steel pipe 15 is put into the drill hole to increase the bearing strength of the pile body to meet the requirements after reinforcement ( Figure 3.1 ).

[0072] Second, the diameter of the borehole is greater than 200mm. After the borehole passes through the bottom of the bored pile 13 by 1m, the drill bit is pulled out and a special retractable rotary stirring and spraying drill bit is put in. The drill bit is expanded to form a stirring rod and combined with the rotary spraying port of the stirring rod head, clean water is used to stir and spray downward to a depth greater than 2m below the bottom of the pile (determined by the soil properties and the need to increase the compressive bearing capacity). Then the cement slurry is sprayed, and the hole is repeatedly expanded by rotary spraying up and down to form a cement soil mound body 16 at the bottom of the pile (the number of up and down rotary spraying is determined by the soil properties and the need to increase the bearing capacity). The retracted stirring rod is lifted to allow the drill bit to enter the bored pile 13, and the drill bit is lifted out while spraying. If the bearing strength of the original pile body can meet the requirements after reinforcement, the reinforcement is completed; if the bearing strength of the original pile body cannot meet the requirements after reinforcement, a steel rod or steel pipe 15 is placed in the borehole to increase the bearing strength of the pile body to meet the requirements after reinforcement ( Figure 3.2 ).

[0073] Third, the diameter of the drill hole is greater than 200mm. After the hole passes through the pile end and drills downward for 1m, a special retractable rotary mixing and spraying drill bit is inserted after the drill bit is taken out. The drill bit is expanded to form a stirring rod and combined with the rotary spray port of the stirring rod head, clean water is used to stir and spray downward to a depth of more than 2m below the bottom of the pile (the specific depth is determined by the soil properties and the need to increase the compressive bearing capacity). Then insert the fine stone concrete conveying pipe with a vibrating head into the bottom of the hole, input fine stone concrete while vibrating and lifting to complete the concrete pier head 17 at the bottom of the cast-in-place pile 13. If the bearing strength of the original pile body can meet the requirements after reinforcement, the reinforcement is completed; if the bearing strength of the original pile body cannot meet the requirements after reinforcement, put a steel rod or steel pipe 15 into the conveying fine stone concrete pipe to increase the bearing strength of the pile body, continue to input fine stone concrete while vibrating and lifting out of the conveying concrete pipe ( Figure 3.3 ).

[0074] Fourth, the diameter of the drill hole is greater than 200mm. After the drill hole passes through the pile end and drills downward for 1m to 2m, after the drill bit is pulled out, a strictly designed explosive is placed at the bottom of the hole. Then, a fine stone concrete delivery pipe is inserted to the bottom of the hole. The delivery pipe is lifted while inputting fine stone concrete until it is full. The explosive is detonated to expand the hole to form a pier head 18, and then filled with concrete. If the original pile body's compressive strength can meet the requirements after reinforcement, the reinforcement is completed; if the original pile body's compressive strength cannot meet the requirements after reinforcement, a pile body reinforcement steel pipe 19 is placed in the drill hole, and concrete is poured through the reinforcement steel pipe 19. After the explosive is detonated to expand the hole, the reinforcement steel pipe 19 is left in the pile as a reinforcement body to meet the strength requirements after reinforcement ( Figure 3.4 ):

[0075] 1.4. The method for improving the pull-out bearing capacity of the cast-in-place bored pile 13 with a hard soil layer as the bearing layer at the pile end developed by the present invention is specifically implemented by first drilling a hole downward at the center of the bored pile 13 with a drilling rig, and there are the following implementation methods:

[0076] First, if the friction resistance of the original bored pile 13 can meet the requirements of the reinforcement pull-out resistance, the diameter of the drill hole is 100mm-150mm, and the drilling depth is usually more than 3 / 4 of the depth of the bored pile 13 (the specific drilling depth is determined by the reinforcement of the pile 13 and the distribution of friction resistance around the pile). After the drill bit is pulled out, the reinforcing tensile steel bar or steel pipe 20 is inserted, and the grouting pipe is inserted to the bottom of the hole, and the cement slurry is injected to complete the reinforcement ( Figure 4.1 ).

[0077] Secondly, if the frictional resistance of the original bored cast-in-place pile 13 cannot meet the requirements of the reinforcement pull-out resistance, the pull-out resistance needs to be increased. Use a drilling diameter of 100mm to 150mm, drill a hole through the bottom surface of the bored pile 13, remove the drill bit and put in an ordinary rotary jet drill bit. First, use clean water to rotary jet up and down several times (generally twice, which can be increased depending on the need for expansion) to lift and expand the hole. The drilling depth is >3m (specifically determined by the soil properties and the need to increase the pull-out bearing capacity). Then use cement slurry to rotary jet up and down multiple times to expand the hole at the bottom of the pile to form a cement soil mound 22, and continue to lift and rotary jet out of the top of the pile. Implant the special steel pipe 21 to the bottom and unfold the multiple anchor rods on the steel pipe, and wait for the cement slurry in the hole to solidify to complete the reinforcement. The special steel pipe 21 and the built-in steel bars or steel hinge wires and the reinforcement in the original bored cast-in-place pile jointly bear the pull-out resistance of the pile body, which matches the frictional resistance of the pile body after reinforcement ( Figure 4.2 ).

[0078] Third, if the friction resistance of the original bored pile 13 cannot meet the requirements of the reinforcement pull-out resistance, the pull-out resistance needs to be greatly increased. Use a drilling diameter of >200mm, drill through the pile end and drill downward about 1m, remove the drill bit and insert a special retractable rotary stirring and spraying drill bit, the drill bit expands to form a stirring rod and combines with the rotary spraying port of the stirring rod head, use clean water to stir and spray downward to a depth of more than 2m at the bottom of the pile (the specific depth is determined by the soil properties and the need to increase the compressive bearing capacity). First, repeatedly use clean water to spray up and down to expand the hole, and then use cement slurry to spray up and down on the bottom of the pile multiple times to expand the hole to form a cement soil mound 23, and continue to lift and spray out the top of the pile. Then sink the special steel pipe 21 to the bottom and unfold the anchor on the steel pipe to complete the reinforcement ( Figure 4.3 ).

[0079] Fourth, if the friction resistance of the original bored pile 13 cannot meet the requirements of reinforcement and anti-pulling, it is necessary to greatly increase the anti-pulling force. Use a borehole diameter of >200mm, drill down about 1m after the borehole passes through the pile end, put in a special retractable rotary stirring and spraying drill bit after the drill bit is raised, the drill bit is expanded to form a stirring rod and combined with the rotary spraying port of the stirring rod head, and spray with clean water up and down to a certain depth below the pile bottom >2m (specifically determined by the soil property and the need to increase the compressive bearing capacity). First, repeatedly use clean water up and down rotary spraying to expand the hole, and then insert the casting and transportation fine stone concrete pipe with a vibrating head into the bottom of the hole, while vibrating and tamping, lift and pour to form a concrete pier head 24, lift the retracted stirring rod drill bit into the cast-in-place pile 13 and lift out the pile top. Then sink the special steel pipe 21 to the pile bottom and vibrate into the concrete pier head 24, unfold the anchor on the steel pipe, and inject cement slurry into the borehole to be solidified to complete the reinforcement. The steel pipe and the internal steel bars or steel hinge wires together with the original bored pile reinforcement bear the pile pullout resistance, matching the friction resistance of the reinforced pile body ( Figure 4.4 ).

[0080] 1.5. The method for improving the compressive bearing capacity of the cast-in-place bored pile 13 with a rock layer as the bearing layer at the pile end developed by the present invention is specifically implemented by first drilling a hole downward at the center of the bored pile 13 with a drilling rig, and there are the following implementation methods:

[0081] First, when the bedrock is relatively hard, reinforcement mainly relies on improving the compressive strength of the pile body and strengthening the influence of sediment at the bottom of the pile. First, use an ordinary drilling rig to drill a hole downward in the center of the bored pile 13, using a drilling diameter of 100mm to 150mm. After the hole passes through the pile end, drill down about 1m, and insert the reinforcing steel core 25 after the drill bit is pulled out. Then, high-strength cement slurry is injected until the cement slurry concentration emerging from the top of the pile reaches the required concentration. If the compressive strength of the original pile body can meet the requirements after reinforcement, the reinforcing steel core 25 inserted can be only set at the bottom of the pile (mainly to improve the concrete strength of the pile bottom). Figure 5.1 ); If the original pile body pressure strength cannot meet the requirements after reinforcement, a reinforced compression steel core should be placed in the drilled hole directly to the top of the pile ( Figure 5.2 ). The inserted reinforcing steel core 25 can be a steel pipe, a steel rod or a steel section.

[0082] Second, the bedrock is relatively soft, and reinforcement mainly relies on improving the bedrock strength, eliminating the influence of pile bottom sediment and improving the compressive strength of the pile body. Use a drilling rig to drill a hole downward in the center of the bored pile 13, with a diameter of 100mm to 150mm. After the hole passes through the pile end, drill downward for about 2m to 3m. After the drill bit is pulled out, a reinforcing steel core 25 is placed, and then high-strength cement slurry is injected until the cement slurry concentration emerging from the pile top reaches the required concentration. The same method as above is used to place the reinforcing compressive steel core ( Figure 5.3 , 5.4 ).

[0083] Third, regardless of the hardness of the bedrock, if the above implementation still does not meet the requirements, the diameter of the drill hole can be >200mm, and the drill hole can pass through the end of the grouting pile 13 and the drill bit can be raised. A small diameter down-the-hole hammer is inserted to impact and drill downward into the rock layer >1m (the depth of penetration can be shallow or deep according to the hardness of the rock and is determined by the reinforcement needs), and then the same method as above is followed after the reinforced compression steel core 25 is inserted ( Figure 5.5 ).

[0084] 1.6. The method for improving the pull-out bearing capacity of the cast-in-place bored pile 13 with the pile end bearing layer being a rock layer developed by the present invention is specifically implemented by first drilling a hole downward at the center of the bored pile 13 with a drilling rig, and there are the following implementation methods:

[0085] First, when the original pile friction resistance can meet the pull-out bearing capacity requirements after reinforcement, the reinforcement is only to improve the pull-out strength of the pile. The implementation method is the same as the one in 1.4 above, only the reinforced tensile steel core 26 is placed in the hole.

[0086] Secondly, when reinforcing the original bored pile 13, in addition to improving the pull-out strength of the pile body, the friction resistance of the pile body should also be improved. First, use a drilling rig to drill a hole downward in the center of the bored pile 13, with a diameter of 100mm to 150mm. After the hole passes through the pile end, drill downward to a certain depth that should be sufficient to place the anchor of the reinforced tensile steel core 26. Inject high-strength cement slurry from the bottom of the hole until the cement slurry concentration emerging from the pile top reaches the required ( Figure 6 ).

[0087] 2. The upper building construction has been completed and entered the use stage. The underground engineering piles are already working under stress. At this time, the piles are sensitive to interference from the reinforcement construction, and all aspects of the reinforcement construction are inconvenient and unfavorable. First of all, the reinforcement construction of existing projects is carried out in a narrow and low-altitude environment, and the height and operating surface of the construction equipment are limited; the reinforcement implementation method must minimize the disturbance to the existing engineering piles to minimize the settlement of the pile body and affect the safety and normal use of the upper building. Therefore, in principle, the reinforcement of piles should be implemented in a dispersed and gradual manner, and the disturbance should be reduced for piles with a small number and high bearing capacity, and the reinforcement implementation design should be strictly implemented.

[0088] At present, the most widely used engineering piles in engineering are prefabricated reinforced concrete pipe piles (usually the bearing layer is a hard soil layer) and cast-in-place piles (usually the bearing layer is a hard soil layer or a rock layer). In existing buildings, underground pile cap foundations are divided into two categories: without a basement and with a basement. To reinforce existing engineering piles indoors, the floor should be excavated first to expose the pile cap and ground beam (without a basement) or directly in the basement according to the original construction drawings and the reinforcement design to determine the center position of the pile, and partially chisel the pile cap, ground beam or basement floor according to the reinforcement design requirements, and reinforce the pile foundation to meet the force requirements after the pile reinforcement increases the pressure or pull-out resistance. At the same time, reserve the reinforced pile head part during construction to prepare for the reinforcement of existing engineering piles and the end treatment after the pile reinforcement.

[0089] The reinforcement of engineering piles in existing buildings, targeting different engineering piles, the bearing soil properties of the pile bottom and the need to increase the pile stress properties, the specific implementation methods of the present invention are as follows:

[0090] 2.1. The method for improving the compressive bearing capacity of prefabricated reinforced concrete pipe piles with hard soil as the bearing layer at the pile end developed by the present invention is specifically implemented as follows:

[0091] Directly use a drill with a drill bit diameter of 100mm to 150mm on the top of the pipe pile 1, aim at the reserved hole position and drill downward until it passes through the bottom plate cap 27 and the concrete core 2 of the anchor steel cage on the top of the pipe pile 1. Use a high-pressure rotary jet pile driver to put the drill bit and drill rod and first use clean water to jet drill until it passes through the bottom of the pipe pile. Then use cement slurry to jet downward (control the pressure and drilling speed) to a certain depth (2m to 5m, which is determined by the soil properties. If there are many piles on the same cap and the soil is hard, a smaller depth can be selected). Then start the downward jet jet expansion operation. Specifically, continue to go down 2m to 5m and then repeatedly jet jet expansion in this section (usually 2 to 4 times) to form an expanded cement soil mound 28 at the bottom of the pile, and put the reinforcing steel pipe 29 to the bottom to complete the reinforcement of the pipe pile 1. If the compressive strength of the pipe pile itself is insufficient, the reinforcing compression steel pipe 28 can be extended to the top of the pile ( Figure 7.1 If the compressive strength of the pile 1 can meet the reinforcement requirements, the reinforced compression steel pipe 28 can only be raised to a certain distance inside the pile 1 ( Figure 7.2 ).

[0092] 2.2. The method for improving the pull-out bearing capacity of prefabricated reinforced concrete pipe piles with hard soil as the bearing layer at the pile end developed by the present invention is specifically implemented as follows:

[0093] First, the original pipe pile 1 is a pressure-bearing pile that needs to be reinforced to have the function of an anti-pulling pile, and the friction resistance provided by the outer side of the pipe pile basically meets the design requirements. According to the above, a drilling rig with a drill bit diameter of 100mm to 150mm and a jet pile machine are used to drill holes through the bottom plate cap 27 and the concrete core 2 of the anchor steel cage at the top of the pipe pile 1, and a high-pressure jet pile drill is inserted to jet cement slurry to the bottom of the pipe pile 1, and a reinforced anti-pulling steel pipe 30 is inserted to complete the reinforcement of the pipe pile 1 ( Figure 8.1 ).

[0094] Second, the original pipe pile 1 is a pressure-bearing pile that needs to bear the function of an anti-pulling pile, but the friction resistance provided by the outer side of the pipe pile is insufficient, and the anti-pulling force needs to be increased. According to the above 2.1 method, the drilling rig and the rotary jet pile driver drill holes through the bottom plate cap 27 and the concrete core 2 of the anchor steel cage at the top of the pipe pile 1 to form a pile bottom expanded diameter cement soil mound 28, and put the reinforcement steel pipe 30 to the bottom to complete the reinforcement of the pipe pile 1 ( Figure 8.2 ).

[0095] Third, the original pipe pile 1 is a pressure-bearing pile that needs to bear the function of an anti-pulling pile, but the friction resistance provided by the outer side of the pipe pile is insufficient, and the anti-pulling force needs to be greatly increased. First, use a drill bit with a diameter of about 200mm to drill a hole through the bottom plate cap 27 and the concrete core 2 of the anchor steel cage on the top of the pipe pile 1, and drill about 3m to 5m below the bottom of the pipe pile 1, pull out the drill bit, put in the high-pressure rotary spraying and mixing drill bit to the bottom, use cement slurry to stir and spray downward, form a stirring and mixing combination with the rotary spray at the end of the stirring rod, and spray downward about 1m to 3m, and repeatedly stir and spray up and down several times to form a pile bottom expanded diameter cement soil mound 31, put in the reinforced anti-pulling steel pipe 32 to the bottom, and unfold the bottom anchor to complete the reinforcement of the pipe pile 1 ( Figure 8.3 ).

[0096] 2.3. The method for improving the compressive bearing capacity of the cast-in-place bored pile 13 with hard soil as the bearing layer at the pile end developed by the present invention is specifically implemented as follows:

[0097] First, use a drilling rig with a drilling diameter of 100mm to 150mm, aim at the reserved hole position, drill downward through the bottom plate cap 27 until it passes through the bottom of the cast-in-place pile 13, then insert the jet grouting drill bit and jet downward to expand the hole to form a pile bottom expanded diameter cement soil mound 28, and insert the reinforcement steel pipe 29 to the bottom to complete the reinforcement of the cast-in-place pile 13. If the cast-in-place pile 13 itself has insufficient compressive strength, the reinforcement compression steel pipe 29 can be extended to the top of the pile ( Figure 9.1 ); If the compressive strength of the cast-in-place pile 13 can meet the reinforcement requirements, the reinforced compression steel pipe 28 can only rise to a certain distance within the cast-in-place pile 13 ( Figure 9.2 ).

[0098] 2.4. The method for improving the pull-out bearing capacity of the cast-in-place bored pile 13 with hard soil as the bearing layer at the pile end developed by the present invention is specifically implemented as follows:

[0099] First, the original cast-in-place pile 13 is a pressure-bearing pile, which needs to be reinforced to have the function of an anti-pulling pile, and the friction resistance provided by the outer side of the cast-in-place pile 13 basically meets the design requirements. According to the above, a drill with a drill bit diameter of 100mm to 150mm is used to drill a hole through the bottom plate cap 27 until it is about 1 / 4 of the pile length from the bottom of the cast-in-place pile 13, and a reinforced anti-pulling steel pipe 30 is placed to complete the reinforcement of the cast-in-place pile 13 ( Figure 10.1 ).

[0100] Second, the cast-in-place pile 13 is a pressure-bearing pile that needs to bear the function of an anti-pulling pile, and the friction resistance provided by the outer side of the cast-in-place pile is insufficient, so the anti-pulling force needs to be increased. According to the above, a drilling rig with a drill bit diameter of 100mm to 150mm and a rotary jet pile driver are used to drill holes through the bottom plate cap 27 and the cement soil mound 28 with a certain depth at the bottom of the pile, and a reinforcement steel pipe 30 is placed to the bottom to complete the reinforcement of the cast-in-place pile 13 ( Figure 10.2 ).

[0101] 2.5. The method for improving the compressive or tensile bearing capacity of a cast-in-place bored pile 13 with a rock bearing layer at the pile end developed by the present invention is implemented in the same manner as in 1.5 and 1.6.

[0102] 3. The above-mentioned existing engineering pile reinforcement and anti-pulling force enhancement uses specially made anti-pulling steel pipes or steel rods, numbered 9, 21 and 32, and the working principle is to insert the expandable anchor to enhance the anchoring force. The manufacturing is basically the same, and the simple expandable anchor head 33 ( Figure 11.1 and Figure 11.2 ), the only difference is the outer diameter d of the expandable anchor head 33, the diameter of the pull-out steel rod 34, and the composition of the entire reinforced pull-out steel pipe or steel rod (9, 21 and 32).

[0103] The expandable anchor head 33 is composed of two anti-pulling steel bars 34, two rotatable bending anchors 35, two rotating shafts 36, upper and lower fixing rods 37, a central slider 38, a central hinge shaft 39, and a central pull rod 40. The working principle is to pull the central pull rod 40 to lift the central slider 38 and drive the two rotatable bending anchors 35 to extend until they are stuck by the rotating shaft 36 ( Figure 11.1 and Figure 11.2 ).

[0104] The composition of the whole reinforced anti-pulling steel pipe or steel rod (9, 21 and 32) is determined according to the required anti-pulling force of reinforcement, the diameter of the reinforced borehole, the required anchoring requirements, the ease of implantation in the borehole (direct sinking, pressing, vibration pressing, etc.), the required stiffness of the reinforcement, etc., and can be specifically divided into two types: full steel rod type and steel pipe type, and each type can be single anchor head, double anchor head or multiple anchor heads ( Figure 11.3 , 11.4 ). For multiple anchor heads, the plane should be rotated 90 degrees and installed alternately, and the center tie rod 40 is connected in series; for the full steel bar type, if multiple anchor heads are used, a connecting steel ring 41 should be added to the pull-out steel bar 34. In order to increase the tensile strength of the cross section of the pull-out steel pipe or steel bar (9, 21 and 32), in addition to increasing the strength of the steel pipe or steel bar, the center tie rod 40 can be replaced by a high-strength steel strand.

Claims

1. A method for increasing the bearing capacity of existing engineering piles by drilling and expanding the center hole. Its characteristics are: For the completed engineering piles that need to be reinforced, a hole is drilled to the bottom of the pile, and the hole below the pile bottom is expanded by high-pressure rotary grouting combined with mixing. The cement soil mound formed by rotary grouting and mixing is combined with additional reinforcement in the pile hole and concrete core reinforcement is used to achieve the purpose of reinforcing the existing engineering piles.

2. According to claim 1, a method for increasing the bearing capacity of an existing engineering pile by central drilling and expansion, Its characteristics are: The engineering pile is a kind of hollow pipe pile and bored cast-in-place pile. The method for reinforcing the pile to improve the compressive bearing capacity is as follows: a hole with a diameter greater than 200 mm is drilled in the center of the pile through the pile end, and clear water is drilled in until the bottom of the pipe pile is 1m to 3m below by adopting a high-pressure rotary spraying and stirring method, and the hole is expanded by rotary spraying up and down, and the mud in the pile hole is drained, and then a casting and transporting fine stone concrete pipe with a vibrating head is inserted into the bottom of the hole, and concrete is poured while vibrating and lifting to form a concrete pier body at the bottom of the pile, and the pile top is lifted out, and a reinforcing steel rod is vibrated into the reinforcing steel rod to complete the reinforcement, thereby improving the compressive bearing capacity of the engineering pile.

3. According to claim 1, a method for increasing the bearing capacity of an existing engineering pile by central drilling and expansion, Its characteristics are: The engineering pile is a kind of pipe pile and bored cast-in-place pile. The method of reinforcing the pile to improve the compressive bearing capacity is as follows: a hole with a diameter greater than 200 mm is drilled in the center of the pile and passes through the pile end 1 to 2 m, explosives are put in, concrete is poured in, and the explosives are detonated to expand the hole to form a concrete pier head to complete the reinforcement and improve the compressive bearing capacity.

4. According to claim 1, a method for increasing the bearing capacity of an existing engineering pile by central drilling and expansion, Its characteristics are: The engineering pile is a bored pile with the bearing layer at the pile end as a rock layer. The method of reinforcing it to improve the compressive bearing capacity is: use a drilling rig to drill a 100mm to 150mm hole downward from the center of the bored pile, pass through the pile end about 1m to 3m, put in a reinforced steel core and inject high-strength cement slurry to complete the reinforcement and improve the compressive bearing capacity.

5. According to claim 1, a method for increasing the bearing capacity of an existing engineering pile by central drilling and expansion, Its characteristics are: The engineering pile is a kind of pipe pile and bored cast-in-place pile. The method of reinforcing it to improve the compressive bearing capacity is: using a high-pressure water gun to punch and drill holes to reach the pile bottom position, inserting anti-pulling reinforcement steel bars, and pouring fine stone concrete and cement slurry to complete the reinforcement to improve the anti-pulling bearing capacity.

6. According to claim 1, a method for increasing the bearing capacity of an existing engineering pile by central drilling and expansion, Its characteristics are: The engineering pile is a kind of pipe pile and bored cast-in-place pile. The method of reinforcing the pile to improve the pull-out bearing capacity is as follows: a hole with a diameter of more than 100 mm is drilled downward through the pile bottom by a drilling rig, a cement soil mound is formed at the pile bottom by using clean water and cement slurry in combination with a high-pressure rotary spraying and mixing method, and a steel rod and a steel pipe specially provided with an extended anchor are placed to complete the reinforcement and improve the pull-out bearing capacity.

7. According to claim 1, a method for increasing the bearing capacity of an existing engineering pile by central drilling and expansion, Its characteristics are: The engineering pile is a kind of pipe pile and bored cast-in-place pile. The method for reinforcing the pile to improve the pull-out bearing capacity is as follows: a hole with a diameter of more than 200 mm is drilled downward by a drilling rig through the pile bottom, and the pile bottom hole is expanded by using clean water and cement slurry in a high-pressure rotary spraying combined with a stirring method, and a casting and transporting fine stone concrete pipe with a vibrating head is inserted into the bottom of the hole, and concrete is poured while vibrating and lifting to form a concrete pier body at the pile bottom, and a specially made steel pipe with multiple sections of extended anchoring heads is placed to complete the reinforcement and improve the pull-out bearing capacity.

8. According to claim 1, a method for increasing the bearing capacity of an existing engineering pile by central drilling and expansion, Its characteristics are: The engineering pile is a bored cast-in-place pile, and the method of reinforcing it to improve the pull-out bearing capacity is: after drilling a hole with a diameter of 100mm to 150mm through the pile end with a drilling rig, drill downward to a depth that can meet the anchoring requirements for inserting a reinforced tensile steel core, insert the tensile steel core, and inject high-strength cement slurry to complete the reinforcement and improve the pull-out bearing capacity.

9. According to claim 4, a method for increasing the bearing capacity of an existing engineering pile by central drilling and expansion. Its characteristics are: The reinforced steel core is composed of two whole steel arms or a whole steel pipe at the upper part and a serially connected expandable anchor head at the lower part. The expansion direction of the expansion anchor pieces of the serially connected expandable anchor heads is staggered and distributed at intervals.

10. According to claim 9, a method for increasing the bearing capacity of an existing engineering pile by central drilling and expansion. Its characteristics are: The expandable anchor head is composed of two pull-out steel bars 34, two rotatable and bent anchor rods 35, two rotating shafts 36, upper and lower fixed rods 37, a central slider 38, a central hinge shaft 39, and a central pull rod 40. Its working principle is to pull the central pull rod 40 to lift the central slider 38 and drive the two rotatable and bent anchors 35 to extend until they are stuck by the rotating shaft 36.

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