Road shoulder micro pile reinforcing method and structure based on reconstructed and expanded expressway

Abstract

The invention discloses a road shoulder micro pile reinforcing method and structure based on a reconstructed and expanded expressway, and belongs to micro pile reinforcing structures. The method comprises the following steps that S1, pile positions are designed; s2, punching and chambering are conducted at the designed pile position; s3, steel floral tubes are inserted into the micro piles from the insertion hole sections; s4, external grouting is conducted; s5, pressure grouting is sequentially conducted on the positions, corresponding to the communicating holes in the bottom end and the communicating holes in the top end, in the steel floral tube in a segmented mode; s6, after cement is solidified, the auxiliary pipe extending out of the pavement layer is detached, and then plugging and leveling are conducted; and S7, the steps S2-S6 are repeated, and the next pile position is reinforced in a hole separation jump injection mode. By the adoption of the road shoulder micro pile reinforcing method and structure based on the reconstructed and expanded expressway, grouting reinforcement is conducted on a contact zone of a water stable layer and a roadbed layer and a lower soft soil body, gaps are filled, meanwhile, the physical and mechanical indexes of the soil body in the section are improved, a complete reinforcing zone is formed, and the overall stability and rigidity of a road surface are enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of road shoulder micropile reinforcement, and in particular to a road shoulder micropile reinforcement method and structure based on the reconstruction and expansion of expressways. Background Art

[0002] As the highway reconstruction and expansion project is in full swing, there are problems such as: the original highway shoulder will be located at the position of the heavy vehicle lane on the new road surface due to the widening and re-division of the original road surface. Due to the relatively weak structure layer under the original highway shoulder and the insufficient thickness of the water-stabilizing layer, the road surface's bearing capacity, deflection, modulus, service life and other indicators cannot meet the requirements of long-term use of the highway. Therefore, it is necessary to improve and reinforce the subgrade structure under the original hard shoulder.

[0003] There are two main types of existing shoulder pavements. One is a thin shoulder made mainly of asphalt pavement. Due to the good plasticity of asphalt, the thickness of the stress diffusion layer is insufficient and the modulus of the roadbed soil varies greatly, resulting in overall settlement and local uneven settlement. The other is a thin shoulder made mainly of concrete. Due to the high rigidity of concrete, the excessive shear stress caused by insufficient concrete thickness and the repeated tension between the pavement and the roadbed, the main form of damage is fracture and cracks.

[0004] In order to avoid settlement or cracking of the roadbed after the expansion of the expressway, the existing scheme adopts the method of layered backfilling after graded excavation. The specific construction method is: the general excavation depth is 2m, and the roadbed filler is backfilled and compacted in layers after excavation, and then the water-stable layer and the pavement layer are filled in layers. However, this method has the following obvious disadvantages: 1) During the roadbed excavation process, in order to ensure the normal operation of the original highway, the expanded highway is generally in a semi-construction and semi-open state. The shoulder of the expanded road is close to the original lane, and the margin is generally no more than 1m. If no protective measures are taken at the roadbed boundary during the excavation process, creep deformation or direct damage may occur under the action of dynamic loads, posing a serious threat to the safety of construction personnel and passing vehicles. If protective measures such as steel sheet piles are taken, although safety can be improved to a certain extent, construction organization is more difficult in the highway environment, and the construction joints caused by the withdrawal of steel sheet piles are difficult to handle, and the cost is high.

[0005] 2) Roadbed excavation generates a lot of waste materials, which are mainly roadbed fillers, water-stabilized gravel, asphalt or concrete mixtures. The abandoned slag will seriously pollute the surrounding environment. At the same time, this behavior also causes a lot of waste of resources and does not meet the requirements of low-carbon greening.

[0006] 3) During the layered compaction process of the roadbed, since the width of the shoulder area is generally small, conventionally around 2.5m, it is currently difficult to find suitable machinery for compaction of this long strip of foundation pit, and the construction quality is difficult to guarantee. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a method and structure for reinforcing the shoulders of highways based on the reconstruction and expansion of expressways. By grouting reinforcement of the contact zone between the water-stabilizing layer and the roadbed and the relatively soft soil below, the physical and mechanical indicators of the soil in this section are improved while filling the gaps, forming a complete reinforcement belt, and enhancing the overall stability and stiffness of the road surface.

[0008] To achieve the above object, the present invention provides a method for reinforcing a shoulder of a highway based on micro-pile construction and expansion, comprising the following steps: S1. Design pile positions: Design pile positions in a rectangular array in the area to be reinforced; S2, punching and expanding holes at the designed pile positions: first, punch holes in the pavement layer and the water-stable layer in sequence, and then expand holes in the roadbed, to obtain an inserting hole section and an expanding hole section that are connected up and down and concentrically arranged, the inserting hole section and the expanding hole section form a micropile, and the upper and lower ends of the inserting hole section are aligned with the pavement layer and the water-stable layer respectively, and the expanding hole section is aligned with the roadbed; S3, inserting the steel flower tube from the jack section into the micropile until the bottom end of the steel flower tube contacts the bottom inner wall of the reaming section, at which time the top of the steel flower tube is flush with the top of the reaming section, and the top of the steel flower tube also extends out of the jack section through the auxiliary tube, and the steel flower tube is arranged concentrically with the reaming section, the auxiliary tube is arranged concentrically with the jack section, and an external grouting cavity is left between the outer wall of the steel flower tube and the micropile; At the same time, multiple flow holes are opened on the side wall of the steel flower tube at positions corresponding to the bottom end and the top end of the roadbed, and plugs are stuck in the flow holes; S4, external grouting: grouting into the external grouting cavity until the external grouting cavity is filled, and waiting for the external cement to solidify; S5, grouting is performed in sections in sequence at the connecting holes at the bottom and the top of the steel tube, and the cement injected by pressure in layers flushes the plugging down and enters the external grouting cavity through the connecting holes, and at the same time, the cement injected at the corresponding connecting holes at the top penetrates into the contact zone between the water-stable layer and the roadbed; S6. Wait until the cement solidifies, remove the auxiliary pipes extending out of the pavement layer, seal and level them, and finally water them for maintenance; S7, repeat steps S2-S6, and reinforce the next pile position by skipping injection in alternate holes.

[0009] Preferably, in step S2, the drilling head used for punching comprises a first connecting rod having one end fixedly connected to the punching machine, a first drill bit frame having one side fixedly connected to the other end of the first connecting rod, and an impact tooth connected to the other side of the first drill bit frame; A first air inlet hole is provided at the center of the first connecting rod, and the first air inlet hole is connected to a first air outlet hole provided on a side of the first drill frame facing the impact teeth; The reaming head used for reaming comprises a second connecting rod connected to the drilling machine at one end, a second drill bit skeleton fixedly connected to the other end of the second connecting rod at one end, and a plurality of reaming wings radially slidably connected to the other end of the second drill bit skeleton, wherein the plurality of reaming wings are arranged in an annular array on the circumferential side of the second drill bit skeleton; A second air inlet hole is provided at the center of the second connecting rod, and the second air inlet hole is connected to a second air outlet hole provided at one end of the second drill frame close to the hole-expanding wing; It is achieved that during punching and expanding, air is blown toward the first air outlet hole and the second air outlet hole through the first air inlet hole and the second air inlet hole to blow out dust, and the dust is removed by using the dust suction equipment.

[0010] Preferably, the bottom end of the steel flower tube described in step S3 is provided with a plurality of flow holes, and the plurality of connecting holes provided at the bottom end of the steel flower tube are arranged linearly, and the plurality of flow holes provided at the top end of the side wall of the steel flower tube and the plurality of connecting holes at the bottom end are arranged in a circular array; the manufacturing steps are as follows: Take a pipe section with the same height as the expanded hole section as the basic pipe section, open flow holes at the bottom end of the steel flower pipe, the bottom end of the side wall and the top end of the side wall, insert plugs into the flow holes, and tap the internal thread on the inner wall of the top end of the steel flower pipe to connect the auxiliary pipe.

[0011] Preferably, the plug is made of water glass.

[0012] Preferably, step S4 specifically includes the following steps: Extend the catheter into the bottom of the external grouting cavity and inject cement into the catheter. Inject cement into the external grouting cavity from bottom to top. The cement uses PO42.5 cement with a water-cement ratio of 0.4 to 0.6 and solidifies after 7 to 10 hours.

[0013] Preferably, step S5 specifically includes the following steps: S51, wrapping an elastic water injection cavity outside the grouting pipe, and the elastic water injection cavity is connected with a water injection pipe; S52, placing the grouting pipe with the elastic water injection cavity into the steel flower pipe until the grouting port at the bottom end of the grouting pipe is aligned with the connecting hole at the bottom end; S53, injecting water into the elastic water injection cavity through the water injection pipe, so that the elastic water injection cavity expands until it fits with the inner wall of the tempered tube; S54, grouting the bottom of the tempered pipe through the grouting pipe, the cement at the bottom is flushed down and sealed, and then penetrates into the external grouting cavity through the connecting hole at the bottom, and waits for a set time until the grouting at the bottom solidifies; S55. Drain the water in the elastic water injection cavity, lift the grouting pipe upward until the grouting pipe is aligned with the connecting hole at the top, and inject grouting into the tempered pipe again through the grouting pipe. After the cement at the top is flushed down and sealed, it penetrates into the external grouting cavity from the connecting hole at the top, and penetrates into the contact zone between the water-stabilizing layer and the roadbed layer until the cement is flush with the top of the pavement layer. Pull out the grouting pipe and seal the auxiliary pipe.

[0014] Preferably, in step S53, the water injection pressure is 3.5 MPa to 4.5 MPa; In step S54 and step S55, the water-cement ratio of the grouting cement used is 0.8-1.1, the grouting splitting pressure is 3.8MPa-5.0MPa, and the grouting pressure after flushing and plugging is 0.8MPa-1.3MPa.

[0015] Preferably, in step S6, the process is continued for 8 to 12 hours, and cement slurry with a water-cement ratio of 0.4 to 0.6 is used for plugging and leveling.

[0016] A structure of a micro-pile reinforcement method for shoulders of highways based on reconstruction and expansion, comprising a micro-pile and a steel tube concentrically inserted into the micro-pile, wherein the micro-pile comprises an insertion hole section and an expansion hole section which are connected up and down and arranged concentrically, wherein the insertion hole section sequentially penetrates the pavement layer and the water-stable layer, the expansion hole section is arranged on the side of the roadbed layer facing the water-stable layer, and a contact zone is left between the water-stable layer and the roadbed layer; The bottom end of the steel flower pipe contacts the inner wall of the bottom end of the expansion section, the top end of the steel flower pipe is flush with the top end of the expansion section, and the top end of the steel flower pipe extends out of the insertion section through the auxiliary pipe; the steel flower pipe is provided with connecting holes at positions corresponding to the bottom end and the top end of the expansion section, and there is a blockage in the connecting holes; Cement is filled in layers inside the steel flower tube at positions corresponding to the communicating holes at the bottom and the communicating holes at the top, and the cement corresponding to the communicating holes at the top is flushed out of the communicating holes and then penetrates into the contact zone; The space between the outside of the steel flower tube and the micro piles is filled by external grouting.

[0017] Preferably, a plug is clamped in the communicating hole, and the plug is made of water glass.

[0018] The present invention has the following beneficial effects: 1. Through grouting reinforcement of the contact zone between the water-stable layer and the roadbed and the relatively soft soil at the bottom, the gaps are filled and the physical and mechanical indicators of the soil in this section are improved, forming a complete reinforcement belt and enhancing the overall stability and rigidity of the road surface; 2. The overall bearing capacity of the micropile is improved by grouting at the bottom of the micropile, while reducing settlement deformation. The force mechanism combines classical soil mechanics and pile foundation engineering. Compared with the existing technology, it has the characteristics of small construction disturbance, low-carbon greening, convenience, safety, reliability, controllable progress and low construction cost.

[0019] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a construction schematic diagram of a road shoulder micropile reinforcement method based on the reconstruction and expansion of expressways according to the present invention; Figure 2 It is a schematic diagram of a steel flower tube structure of a road shoulder micropile reinforcement method based on the reconstruction and expansion of expressways according to the present invention; Figure 3 It is a schematic diagram of the grouting pipe structure of a method for reinforcing a road shoulder micropile based on the reconstruction and expansion of an expressway according to the present invention; Figure 4 It is a structural schematic diagram of a drilling head of a method for reinforcing a road shoulder micropile based on the reconstruction and expansion of a highway according to the present invention; Figure 5 It is a schematic diagram of the structure of a hole expansion head of a road shoulder micropile reinforcement method based on the reconstruction and expansion of a highway according to the present invention; Figure 6 A pile position arrangement diagram of an embodiment of the present invention; Figure 7 It is a pile position arrangement diagram of a comparative example of the present invention.

[0021] Among them: 1. pavement layer; 2. water-stabilizing layer; 3. roadbed; 4. micro pile; 41. plug-in section; 42. expansion section; 5. elastic water injection cavity; 6. steel flower pipe; 61. connecting hole; 7. grouting pipe; 8. water injection pipe; 9. auxiliary pipe; 10. drilling head; 101. impact tooth; 102. first drill bit skeleton; 103. first connecting rod; 104. first air inlet; 11. expansion head; 111. second air inlet; 112. second connecting rod; 113. second drill bit skeleton; 114. expansion wing; 115. second air outlet. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0023] It should be noted that the terms "include", "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or devices.

[0024] Like reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0025] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0026] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] like Figure 1-Figure 5 As shown, a method for reinforcing a shoulder of a highway based on micro-pile construction and expansion includes the following steps: S1. Design pile positions: Design pile positions in a rectangular array in the area to be reinforced; S2. First, punch holes in the pavement layer 1 and the water-stabilizing layer 2 in turn, and then expand the roadbed 3 to obtain an insert section 41 and an expansion section 42 that are connected up and down and concentrically arranged. The insert section 41 and the expansion section 42 form a micropile 4, and the upper and lower ends of the insert section 41 are aligned with the pavement layer 1 and the water-stabilizing layer 2 respectively, and the expansion section 42 is aligned with the roadbed 3; the pavement layer 1 described in this embodiment is an asphalt layer or a concrete layer.

[0028] In step S2, the drilling head 10 used for punching includes a first connecting rod 103 fixedly connected to the puncher at one end, a first drill bit skeleton 102 fixedly connected to the other end of the first connecting rod 103 at one side, and an impact tooth 101 connected to the other side of the first drill bit skeleton 102; a first air inlet hole 104 is opened at the center of the first connecting rod 103, and the first air inlet hole 104 is connected to a first air outlet hole opened on the side of the first drill bit skeleton 102 facing the impact tooth 101; The reaming head 11 used for reaming comprises a second connecting rod 112 connected to a drilling rig at one end, a second drill bit skeleton 113 fixedly connected to the other end of the second connecting rod 112 at one end, and a plurality of reaming wings 114 radially slidably connected to the other end of the second drill bit skeleton 113, wherein the plurality of reaming wings 114 are arranged in a circular array on the circumferential side of the second drill bit skeleton 113; a second air inlet 111 is provided at the center of the second connecting rod 112, and the second air inlet 111 is connected to a second air outlet 115 provided at one end of the second drill bit skeleton 113 close to the reaming wings 114, and under the extrusion and rotation driving action of the drilling rig, the reaming wings 114 are opened to reame; It is achieved that during punching and expanding, air is blown toward the first air outlet hole 104 and the second air inlet hole 111 to blow out dust, and the dust is removed by using a dust suction device.

[0029] S3, insert the steel flower tube 6 (the steel flower tube 6 can be replaced by a high-strength PVC tube in a stratum with relatively low pressure) into the micropile 4 from the jack section 41 until the bottom end of the steel flower tube 6 contacts the bottom inner wall of the reaming section 42, at which time the top of the steel flower tube 6 is flush with the top of the reaming section 42, the top of the steel flower tube 6 also extends out of the jack section 41 through the auxiliary tube 9, and the steel flower tube 6 is concentrically arranged with the reaming section 42, the auxiliary tube 9 is concentrically arranged with the jack section 41, and an external grouting cavity is left between the outer wall of the steel flower tube 6 and the micropile 4; At the same time, a plurality of flow holes are provided on the side wall of the steel flower tube 6 and correspond to the bottom end of the roadbed 3 and the top end of the roadbed 3, respectively, and the flow holes are blocked; The bottom end of the steel flower tube 6 described in step S3 is provided with a plurality of flow holes, and the plurality of communication holes 61 provided at the bottom end of the steel flower tube 6 are arranged linearly, and the plurality of flow holes provided at the top end of the side wall of the steel flower tube 6 and the plurality of communication holes 61 at the bottom end are arranged in a circular array; the manufacturing steps are as follows: Take a pipe section with the same height as the expanded hole section 42 as the basic pipe section, open flow holes at the bottom end, the bottom end of the side wall and the top end of the side wall of the steel flower pipe 6 respectively, and plug the flow holes, and tap the internal thread on the inner wall of the top end of the steel flower pipe 6 to connect the auxiliary pipe 9.

[0030] The plug is made of water glass.

[0031] S4, external grouting: grouting into the external grouting cavity until the external grouting cavity is filled, and waiting for the external cement to solidify; Step S4 specifically includes the following steps: Extend the catheter into the bottom of the external grouting cavity and inject cement into the catheter. Inject cement into the external grouting cavity from bottom to top. The cement uses PO42.5 cement with a water-cement ratio of 0.4 to 0.6 and solidifies after 7 to 10 hours.

[0032] S5, grouting is performed in sections in sequence into the steel flower tube 6 and at the communicating holes 61 at the bottom and the communicating holes 61 at the top, respectively, and the cement injected by pressure layers flushes the plugging down and enters the external grouting cavity through the communicating holes 61, and at the same time, the cement injected at the communicating holes 61 at the top penetrates into the contact zone between the water-stable layer 2 and the roadbed 3; Step S5 specifically includes the following steps: S51, wrapping the elastic water injection cavity 5 outside the grouting pipe 7, and the elastic water injection cavity 5 is connected with the water injection pipe 8; S52, placing the grouting pipe 7 with the elastic water injection cavity 5 into the steel flower pipe 6 until the grouting port at the bottom end of the grouting pipe 7 is aligned with the connecting hole 61 at the bottom end; S53, injecting water into the elastic water injection chamber 5 through the water injection pipe 8, and the elastic water injection chamber 5 expands until it fits with the inner wall of the tempered pipe; In step S53, the water injection pressure is 3.5MPa to 4.5MPa; S54, grouting the bottom of the tempered pipe through the grouting pipe 7, the cement at the bottom is flushed down and sealed, and then penetrates into the external grouting cavity through the connecting hole 61 at the bottom, and waits for a set time until the grouting at the bottom solidifies; S55. Draw out the water in the elastic water injection cavity 5, lift the grouting pipe 7 upwards until the grouting pipe 7 is aligned with the connecting hole 61 at the top, and inject grout into the tempered pipe again through the grouting pipe 7. After the cement at the top is flushed down and blocked, it penetrates into the external grouting cavity through the connecting hole 61 at the top, and penetrates into the contact zone between the water-stabilizing layer 2 and the roadbed layer 3, until the cement is flush with the top of the pavement layer 1, pull out the grouting pipe 7 and seal the auxiliary pipe 9.

[0033] In step S54 and step S55, the water-cement ratio of the grouting cement used is 0.8-1.1, the grouting splitting pressure is 3.8MPa-5.0MPa, and the grouting pressure after flushing and plugging is 0.8MPa-1.3MPa.

[0034] S6, wait until the cement solidifies, remove the auxiliary pipe 9 extending out of the pavement layer 1, seal and level it, and finally water it for maintenance; In step S6, wait for 8 to 12 hours and use cement slurry with a water-cement ratio of 0.4 to 0.6 for plugging and leveling.

[0035] S7, repeat steps S2-S6, and reinforce the next pile position by skipping injection in alternate holes.

[0036] A structure of a method for reinforcing a shoulder micropile 4 based on the reconstruction and expansion of an expressway, comprising a micropile 4 and a steel flower tube 6 concentrically inserted into the micropile 4, wherein the micropile 4 comprises an inserting hole section 41 and an expanding hole section 42 which are connected up and down and arranged concentrically, wherein the inserting hole section 41 sequentially penetrates a pavement layer 1 and a water-stable layer 2, the expanding hole section 42 is arranged on a side of a roadbed 3 facing the water-stable layer 2, and a contact zone is left between the water-stable layer 2 and the roadbed 3; the bottom end of the steel flower tube 6 contacts the inner wall of the bottom end of the expanding hole section 42, and the steel flower tube 6 The top of the steel flower tube 6 is flush with the top of the expansion section 42, and the top of the steel flower tube 6 extends out of the jack section 41 through the auxiliary tube 9; the steel flower tube 6 is provided with connecting holes 61 at positions corresponding to the bottom and top of the expansion section 42, and there is a plug stuck in the connecting hole 61; the steel flower tube 6 is filled with cement in layers at positions corresponding to the connecting holes 61 at the bottom and the connecting holes 61 at the top, and the cement corresponding to the connecting holes 61 at the top is flushed out of the connecting holes 61 and then penetrates into the contact zone; the outside of the steel flower tube 6 and the micro pile 4 are filled by external grouting. A plug is stuck in the connecting hole 61, and the plug is made of water glass. The bottom of the steel flower tube 6 of this embodiment is also provided with multiple connecting tubes.

[0037] Verification Example This embodiment like Figure 6 As shown, the experiment was conducted in a high-speed test area from October to December 2023 as follows: Step 1: Design the pile position: Hole layout: Select micro piles with a diameter of 170mm and an expansion of 300mm, a total pile length of 1.0m, an expansion section length of 63mm, a pavement layer thickness of 37mm, a longitudinal hole spacing of 1100mm, and a transverse hole spacing of 800mm and 650mm; Step 2: Punch and expand holes at the designed pile positions: First, use a 170mm punching drill bit to punch a hole at 370mm, punching to the 370mm position; then use a 170mm 300mm reaming drill bit to reame the hole, and the length of the lower reaming section is 630mm; Step 3: First, prepare a steel tube with a diameter of 40-60mm. The length of the steel tube is equal to the length of the expansion section, which is 630mm. The length error is controlled within 50mm. There are no less than 2 grouting holes at the bottom of the steel tube, and no less than 8 connecting holes at the bottom and top of the side wall of the steel tube. All grouting holes are blocked with water glass. The length of the auxiliary tube is 60cm-100cm to ensure convenient construction and disassembly. Then put the prepared steel tube into the micropile, and ensure that the center line of the steel tube is in line with the center line of the micropile hole, the verticality is controlled within the range of plus or minus 5 degrees, and the overall deviation is controlled within the range of 2 cm; ensure that the grouting area at the top of the steel tube is within the contact zone between the water-stable layer and the roadbed, and ensure that the grouting liquid can penetrate into the contact zone; Step 4: External grouting: Use PO42.5 cement with a water-cement ratio of 0.4-0.6 for grouting, and use a conduit to grout from the bottom to the top. During the grouting process, ensure that there is no grout inside the steel flower tube; Step 5. After 7 to 10 hours (adjusted according to weather and temperature), the slurry on the outside of the steel pipe has a certain strength. Put a grouting pipe with a diameter of 30 to 40 mm inside the steel pipe, and the grouting port is 1 cm to 2 cm away from the bottom inner wall of the steel pipe. Use the water injection pipe to inject water into the elastic water injection cavity. The water injection pressure is controlled at 3.5 to 4.5 MPa, so that the elastic water injection cavity expands and opens, and fits the inner wall of the steel pipe to seal the steel pipe. Step 6: Grout the lower end and bottom of the steel pipe through the grouting pipe. The water-cement ratio is 0.8-1.1, and the grouting splitting pressure is controlled at 3.8MPa-5.0MPa. The slurry uses pressure to flush the water glass plug of the steel pipe. After flushing, the grouting pressure is maintained between 0.8MPa and 1.3MPa. After injecting 0.13-0.15 cubic meters of cement slurry, lift the grouting pipe to the auxiliary pipe position to ensure that the grouting port is at the connecting hole at the top of the steel pipe, and then grout (the grouting volume is controlled at 0.12-0.14 cubic meters, and the total amount of single pile grouting and splitting grouting is controlled at 0.25-0.28 cubic meters). After the grouting is completed, remove the grouting pipe and use a sealing plug to seal the hole. Step 7. After the grouting of one pile is completed, construct the next pile in the order of alternate holes, and finally complete all the micro-piles of the same batch. After 8 to 12 hours, remove the auxiliary pipe by twisting it to expose it to the road surface section. After removal, use cement slurry with a water-cement ratio of 0.4 to 0.6 to seal and level the small holes. After all is completed, water it for natural maintenance.

[0038] Test results: Since the spacing of 170mm to 300mm is within the range of 650 to 1100mm, the theoretically calculated bearing capacity is far greater than the design bearing capacity, so the detection is mainly carried out around the deformation index.

[0039] 1) Load plate test According to the modulus test results, the average deformation modulus of the un-grouted area is 522.3MPa, the average deformation modulus of the soil position between piles in the test area is 838.6MPa, and the average deformation modulus of the pile top position is 986.3MPa. The modulus of the soil position between piles has increased by 1.60 times, and the modulus of the pile top position has increased by 1.89 times. The comprehensive stress diffusion angle of the road surface and the water-stabilizing layer tested previously is about 39.1 degrees. It can be seen that in this embodiment, the overall soil index is strengthened, the stress is reasonably diffused, and it is properly concentrated at the pile position.

[0040] 2) Deflection test The completion value of the un-grouted area is between 18 and 35, with an average value of 25.5. The deflection settlement values ​​after grouting are shown in Table 1.

[0041] Table 1 Deflection statistics of the three test areas ;

[0042] It can be seen that the overall deflection has been greatly reduced and can meet the requirements of current standard design.

[0043] Comparative Example like Figure 7 As shown, the following experiments will be conducted in the high-speed test area 1 from October to December 2023: 1. Hole layout plan: Select micro piles with a diameter of 75mm, a total pile length of 1.0m, a hole expansion section length of 63mm, a pavement and structural layer thickness of 37mm, a longitudinal hole spacing of 800mm, and a transverse hole spacing of 800mm and 650mm. The grouting volume is divided into two sections for quantitative grouting based on calculations.

[0044] 2. Testing plan: Use pressure plate test and deflection test for testing.

[0045] 3. The specific plan is as follows: 1) Use a 75mm punching drill to punch holes to the 1000mm position; 2) Prepare steel flower pipes. The diameter of the steel flower pipes is 40-60mm ordinary steel pipes. The length of the steel pipe is equivalent to the length of the lower expansion section, which is 630mm. The length error is controlled within 50mm. There are no less than 2 grouting holes at the end of the steel flower pipe, and no less than 8 holes in the opening area at the top and bottom of the side wall of the grouting device. All grouting holes are temporarily blocked with water glass. The length of the auxiliary pipe of the steel flower pipe is controlled within the range of 60cm to 100cm to ensure convenient construction and disassembly; 3) Place the prepared steel tube into the expanded micropile hole, ensure that the center line of the steel tube is in line with the center line of the micropile hole, control the verticality within the range of plus or minus 5 degrees, and control the overall deviation within 1 cm; ensure that the grouting area of ​​the upper section of the steel tube is within the contact zone between the water-stable layer and the roadbed, and ensure that the grouting liquid can penetrate into the contact zone; 4) Grouting is performed on the outer area of ​​the micropile steel tube. PO42.5 cement is used for grouting (other types of cement can be used for special strata). The water-cement ratio is 0.4-0.6. Grouting is performed from the bottom to the top using a conduit. During the grouting process, ensure that there is no slurry inside the steel tube. 5) After 7 to 10 hours (adjusted according to weather and temperature conditions), when the slurry on the outside of the steel pipe has a certain strength, put a 30-40mm diameter grouting pipe inside the steel pipe, put the grouting port 1-2cm below the bottom of the steel pipe, and inject water into the elastic water injection cavity through the water injection pipe. The water injection pressure is controlled at 3.5-4.5MPa to ensure that the elastic water injection cavity expands and fits the steel pipe to seal the steel pipe; 6) Grout the lower end and bottom of the steel pipe through the grouting pipe, the water-cement ratio is 0.8-1.1, the grouting splitting pressure is controlled at 3.8-5.0MPa, the slurry uses pressure to flush the temporary water glass plugging of the grouting holes of the steel pipe, and the grouting pressure is maintained between 0.8-1.3MPa after flushing. After injecting 0.15-0.0.18 cubic meters of cement slurry, lift the grouting pipe to the auxiliary pipe position to ensure that the grouting port of the grouting pipe is in the grouting hole area of ​​the upper section of the steel pipe, and then grout the upper section with the same grouting steps as the lower end (the grouting volume is controlled at 0.14-0.16 cubic meters, and the total amount of single pile grouting and splitting grouting is controlled at 0.30-0.34 cubic meters). After the grouting is completed, remove the grouting pipe and immediately use a sealing plug to seal the hole; 7) After the grouting of one pile is completed, the next pile is constructed in the order of skipping grouting every other hole, and finally all the micro piles of the same batch are completed.

[0046] 9) After 8 to 12 hours, remove the auxiliary pipe by twisting it to expose it to the road surface; 10) After demolition, the small holes are sealed and leveled with cement slurry with a water-cement ratio of 0.4 to 0.6. After completion, water them for natural maintenance.

[0047] 6. Test results Since the 75mm micropiles are mainly controlled by bearing capacity and deformation indicators, the test is mainly carried out on these two indicators.

[0048] 1) Single pile static load test According to the static load test results, the ultimate bearing capacity of the pile body is 60KN when there is no secondary splitting grouting, the bearing capacity is 80KN when there is quantitative grouting, and the bearing capacity is 120KN when there is sufficient grouting. Since the model calculation shows that the bearing capacity of a single pile needs to reach more than 100KN, the entire comparison plan is based on the sufficient grouting plan. According to the static load test results of a single pile, the small-diameter non-expanded pile itself has relatively low indicators, and a large amount of grouting is required to make up for the shortcomings of the pile body itself.

[0049] 2) Load plate test (1) Modulus test results According to the modulus test results, the average deformation modulus of the un-grouting area is 522.3MPa, the average deformation modulus of the soil between piles in the test area is 701.5MPa, and the average deformation modulus of the pile top is 682.3MPa. The modulus of the soil between piles has increased by 1.34 times, and the modulus of the pile top has increased by 1.31 times. Although the overall indicators of small-diameter micropiles have been greatly improved, the improvement is not large, and the grouting volume is large, which cannot meet the design requirements. In addition, through model analysis and field tests, it can be seen that the micropiles themselves play a small role, and are mainly used to strengthen the soil, which causes defects in the model (the modulus of the soil between piles is greater than the modulus of the pile body because the stress diffused in the upper part of the soil between piles covers more of the pile body, resulting in a small difference).

[0050] (2) Deflection test The completion value of the un-grouted area is between 18 and 35, with an average value of 25.5. The deflection settlement values ​​after grouting are shown in Table 2.

[0051] Table 2 Deflection statistics of test area 1 ;

[0052] It can be seen that although the overall deflection has been reduced, the reduction is limited.

[0053] Conclusion: Through model calculation and test results analysis, the scheme described in the comparative example has an overall reinforcement effect on the weak shoulder, but the grouting volume is large, the construction cost is high, and the reinforcement effect is limited, so it is not suitable for adoption.

[0054] Therefore, the present invention adopts the above-mentioned shoulder micro-pile reinforcement method and structure based on the reconstruction and expansion of the expressway, and performs grouting reinforcement on the contact zone between the water-stabilizing layer and the roadbed and the relatively soft soil below, thereby filling the gaps and improving the physical and mechanical indicators of the soil in this section, forming a complete reinforcement belt, and enhancing the overall stability and stiffness of the road surface.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for reinforcing the shoulder of a highway based on micro-pile construction and expansion, characterized in that: The following steps are involved: S1. Design pile positions: Design pile positions in a rectangular array in the area to be reinforced; S2, punching and expanding holes at the designed pile positions: first, punch holes in the pavement layer and the water-stable layer in sequence, and then expand holes in the roadbed, to obtain an inserting hole section and an expanding hole section that are connected up and down and concentrically arranged, the inserting hole section and the expanding hole section form a micropile, and the upper and lower ends of the inserting hole section are aligned with the pavement layer and the water-stable layer respectively, and the expanding hole section is aligned with the roadbed; S3, inserting the steel flower tube from the jack section into the micropile until the bottom end of the steel flower tube contacts the bottom inner wall of the reaming section, at which time the top of the steel flower tube is flush with the top of the reaming section, and the top of the steel flower tube also extends out of the jack section through the auxiliary tube, and the steel flower tube is arranged concentrically with the reaming section, the auxiliary tube is arranged concentrically with the jack section, and an external grouting cavity is left between the outer wall of the steel flower tube and the micropile; At the same time, multiple flow holes are opened on the side wall of the steel flower tube at positions corresponding to the bottom end and the top end of the roadbed, and plugs are stuck in the flow holes; S4, external grouting: grouting into the external grouting cavity until the external grouting cavity is filled, and waiting for the external cement to solidify; S5, grouting is performed in sections in sequence at the connecting holes at the bottom and the top of the steel tube, and the cement injected by pressure in layers flushes the plugging down and enters the external grouting cavity through the connecting holes, and at the same time, the cement injected at the corresponding connecting holes at the top penetrates into the contact zone between the water-stable layer and the roadbed; S6. Wait until the cement solidifies, remove the auxiliary pipes extending out of the pavement layer, seal and level them, and finally water them for maintenance; S7, repeat steps S2-S6, and reinforce the next pile position by skipping injection in alternate holes.

2. A method for reinforcing a road shoulder with micro piles based on the reconstruction and expansion of a highway according to claim 1, characterized in that: In step S2, the drilling head used for punching includes a first connecting rod having one end fixedly connected to the punching machine, a first drill bit frame having one side fixedly connected to the other end of the first connecting rod, and an impact tooth connected to the other side of the first drill bit frame; A first air inlet hole is provided at the center of the first connecting rod, and the first air inlet hole is connected to a first air outlet hole provided on a side of the first drill frame facing the impact teeth; The reaming head used for reaming comprises a second connecting rod connected to the drilling machine at one end, a second drill bit skeleton fixedly connected to the other end of the second connecting rod at one end, and a plurality of reaming wings radially slidably connected to the other end of the second drill bit skeleton, wherein the plurality of reaming wings are arranged in an annular array on the circumferential side of the second drill bit skeleton; A second air inlet hole is provided at the center of the second connecting rod, and the second air inlet hole is connected to a second air outlet hole provided at one end of the second drill frame close to the hole-expanding wing; It is achieved that during punching and expanding, air is blown toward the first air outlet hole and the second air outlet hole through the first air inlet hole and the second air inlet hole to blow out dust, and the dust is removed by using the dust suction equipment.

3. A method for reinforcing a road shoulder with micro piles based on the reconstruction and expansion of a highway according to claim 1, characterized in that: The bottom end of the steel flower tube in step S3 is provided with a plurality of flow holes, and the plurality of communication holes provided at the bottom end of the steel flower tube are arranged linearly, and the plurality of flow holes provided at the top end of the side wall of the steel flower tube and the plurality of communication holes at the bottom end are arranged in a circular array; The production steps are as follows: Take a pipe section with the same height as the expanded hole section as the basic pipe section, open flow holes at the bottom end of the steel flower pipe, the bottom end of the side wall and the top end of the side wall, insert plugs into the flow holes, and tap the internal thread on the inner wall of the top end of the steel flower pipe to connect the auxiliary pipe.

4. A method for reinforcing a road shoulder with micro piles based on the reconstruction and expansion of a highway according to claim 3, characterized in that: The plug is made of water glass.

5. The method for reinforcing a road shoulder with micro piles based on the reconstruction and expansion of a highway according to claim 1, characterized in that: Step S4 specifically includes the following steps: Extend the catheter into the bottom of the external grouting cavity and inject cement into the catheter. Inject cement into the external grouting cavity from bottom to top. The cement uses PO42.5 cement with a water-cement ratio of 0.4 to 0.6 and solidifies after 7 to 10 hours.

6. The method for reinforcing a road shoulder with micro piles based on the reconstruction and expansion of a highway according to claim 1, characterized in that: Step S5 specifically includes the following steps: S51, wrapping an elastic water injection cavity outside the grouting pipe, and the elastic water injection cavity is connected with a water injection pipe; S52, placing the grouting pipe with the elastic water injection cavity into the steel flower pipe until the grouting port at the bottom end of the grouting pipe is aligned with the connecting hole at the bottom end; S53, injecting water into the elastic water injection cavity through the water injection pipe, so that the elastic water injection cavity expands until it fits with the inner wall of the tempered tube; S54, grouting the bottom of the tempered pipe through the grouting pipe, the cement at the bottom is flushed down and sealed, and then penetrates into the external grouting cavity through the connecting hole at the bottom, and waits for a set time until the grouting at the bottom solidifies; S55. Drain the water in the elastic water injection cavity, lift the grouting pipe upward until the grouting pipe is aligned with the connecting hole at the top, and inject grouting into the tempered pipe again through the grouting pipe. After the cement at the top is flushed down and sealed, it penetrates into the external grouting cavity from the connecting hole at the top, and penetrates into the contact zone between the water-stabilizing layer and the roadbed layer until the cement is flush with the top of the pavement layer. Pull out the grouting pipe and seal the auxiliary pipe.

7. A method for reinforcing a shoulder of a highway based on micro-pile construction and expansion according to claim 6, characterized in that: In step S53, the water injection pressure is 3.5MPa to 4.5MPa; In step S54 and step S55, the water-cement ratio of the grouting cement used is 0.8-1.1, the grouting splitting pressure is 3.8MPa-5.0MPa, and the grouting pressure after flushing and plugging is 0.8MPa-1.3MPa.

8. The method for reinforcing a road shoulder with micro piles based on the reconstruction and expansion of a highway according to claim 1, characterized in that: In step S6, wait for 8 to 12 hours and use cement slurry with a water-cement ratio of 0.4 to 0.6 for plugging and leveling.

9. The structure of the micro-pile reinforcement method for highway shoulders based on the reconstruction and expansion of highways according to any one of claims 1 to 8, characterized in that: It includes a micro pile and a steel flower tube concentrically inserted into the micro pile, wherein the micro pile includes an insertion hole section and an expansion hole section which are connected up and down and arranged concentrically, wherein the insertion hole section sequentially penetrates the pavement layer and the water-stable layer, the expansion hole section is arranged on the side of the road base layer facing the water-stable layer, and a contact zone is left between the water-stable layer and the road base layer; The bottom end of the steel flower pipe contacts the inner wall of the bottom end of the expansion section, the top end of the steel flower pipe is flush with the top end of the expansion section, and the top end of the steel flower pipe extends out of the insertion section through the auxiliary pipe; the steel flower pipe is provided with connecting holes at positions corresponding to the bottom end and the top end of the expansion section, and there is a blockage in the connecting holes; Cement is filled in layers inside the steel flower tube at positions corresponding to the communicating holes at the bottom and the communicating holes at the top, and the cement corresponding to the communicating holes at the top is flushed out of the communicating holes and then penetrates into the contact zone; The space between the outside of the steel flower tube and the micro piles is filled by external grouting.

10. A method for reinforcing a shoulder of a highway based on micro-pile construction and expansion according to claim 9, characterized in that: A plug is clamped in the communicating hole and is made of water glass.

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