A three-axis mixer for foundation pit segmented construction and construction method

Abstract

The invention discloses a three-axis mixer and construction method for segmented construction of foundation pits, and belongs to the technical field of foundation pit construction. The three-axis mixer and construction method for segmented construction of foundation pits drive the support shaft to rotate through a second motor, and the support shaft drives the cam to rotate. The cam can squeeze the roller body to drive the movable plate to move downward, so that the third spring is deformed. When the convex end of the cam is away from the roller body, the third spring drives the movable plate to reset, so that the third spring can cooperate with the cam to achieve the purpose of up and down movement, so that the drilling and stirring assembly can perform vibration drilling operation, which plays a role in assisting drilling, and the up and down movement of the bottom cavity can generate relative movement with the retaining ring, so that the transmission assembly maintains a one-way transmission slitting assembly, so that the connecting shaft drives the slice to rotate, so that the slice can play a slitting role on the hole wall, increase the looseness of the hole wall, and make the slitting and vibration increase the drilling efficiency, reduce the drilling resistance, and further improve the foundation pit construction efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of foundation pit construction, in particular to a three-shaft mixer for sectioned construction of a foundation pit and a construction method. Background Art

[0002] With the growth of urban population and economic development in my country, and the continuous expansion of urban space, more and more cities have started the process of rapid urban road transformation. In the process of transformation, existing underground pipelines often affect construction, and relocation lags behind. Inevitably, there is the problem of cross-construction of pipelines and foundation pits, which will have a great impact on foundation pit construction.

[0003] At present, temporary plugging methods such as SMW isolation piles and bored cast-in-place piles are usually used to segment narrow and long foundation pits in urban open-cut tunnels. There are still some problems in actual operation: the current segmentation method of urban open-cut tunnel foundation pits is usually set at the location where the foundation pit structure is subjected to force changes, and the actual pipeline impact is often not considered, resulting in the failure to close the open-cut tunnel foundation pit in time; in addition, the temporary plugging and removal of SMW isolation piles and bored cast-in-place piles is difficult, with high safety risks, and it is difficult to coordinate with the delayed relocation of pipelines for on-site adjustment construction, affecting the overall progress of the project. In addition, three-axis is often required in the segmentation of foundation pits. Mixing piles, while common three-axis mixing piles generally only have simple horizontal mixing and feeding functions. Since the soft soil varies from site to site and from layer to layer, there is a large amount of unpredictability. Therefore, during construction mixing, the mixing wing is set horizontally, so it is not easy to drill into the deep hard geology, and the clay particles are not easy to mix evenly, and it is easy to get stuck to the drill. In addition, during the drilling process, since the drill rod is long, the hollow drill rod is prone to shaking during movement, which affects the quality of the cement pile after forming. Moreover, since the grouting port is exposed to the outside, debris is easy to enter the pipeline inside the mixing shaft from the grouting port during drilling, causing pipeline blockage and affecting subsequent grouting treatment.

[0004] Therefore, it is of great significance to study a new three-axis mixer and construction method for segmented foundation pit construction to solve the above problems. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above and / or existing problems in existing foundation pit construction, the present invention is proposed.

[0007] Therefore, the technical problem to be solved by the present invention is that the current segmented method of urban open-cut tunnel foundation pit leads to the inability to close the open-cut tunnel foundation pit in time; in addition, the temporary plugging and removal of SMW method isolation piles and bored cast-in-place piles are difficult and have high safety risks, and the common three-axis mixing piles are not easy to drill during construction, and clay particles are not easy to mix evenly and are easy to get stuck to the drill; and during the drilling process, due to the long drill rod, the hollow drill rod is prone to shaking during movement, affecting the quality of the cement pile after forming, and because the grouting port is exposed to the outside, during the drilling process, debris is easy to enter the pipeline inside the mixing shaft from the grouting port, causing pipeline blockage, affecting the subsequent grouting treatment.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a three-axis mixer for foundation pit segmented construction, comprising a three-axis mixing mechanism, the three-axis mixing mechanism comprising a driving assembly, a vibration assembly is arranged below the driving assembly, three drilling mixing assemblies are connected to the driving assembly, a grouting assembly is arranged inside the drilling mixing assembly, a cleaning assembly is arranged below the drilling mixing assembly, and the driving assembly cooperates with the vibration assembly to control the drilling mixing assembly to smoothly perform the foundation pit drilling operation;

[0009] A sealing assembly is provided below the lower part of the lower drilling and stirring assembly, and two cutting assemblies are provided below the lower drilling and stirring assembly. The two cutting assemblies penetrate the lower drilling and stirring assembly, and a transmission assembly is connected to the upper transmission of the cutting assembly. The transmission assembly is provided below the grouting assembly. The cutting assembly moves up and down with the lower drilling and stirring assembly, so that the hole wall is cut after the cutting assembly and the transmission assembly are transmitted, thereby reducing the obstruction of the spiral shaft when drilling.

[0010] As a further solution of the present invention: the driving assembly includes a mounting plate, three second gears and two rotating shafts, the rotating shafts are rotatably mounted on the mounting plate through bearings, the rotating shafts are fixedly connected with first gears, the top end of one of the rotating shafts is fixedly connected to the output shaft of the first motor, the first motor is fixedly connected to the mounting plate through a bracket, and the two first gears are meshed with the three second gears.

[0011] As a further solution of the present invention: the vibration assembly includes two support shafts and a movable plate, the two support shafts are rotatably mounted on the mounting plate through two bearings, the two support shafts are transmission-connected through a chain transmission structure, one of the support shafts is fixedly connected to the output shaft of the second motor, and the second motor is mounted on one side of the mounting plate;

[0012] Both ends of the support shaft are fixedly connected with cams, a roller body is overlapped below the cam, the roller body is fixedly connected to the side of the movable plate, and two third springs are fixedly connected between the movable plate and the mounting plate.

[0013] As a further solution of the present invention: the cleaning component includes an assembly plate, a fan and three guide rings are installed on the assembly plate, a plurality of guide wheels are staggeredly installed inside the guide ring, an air blowing head is fixedly connected below the guide ring, the three air blowing heads are connected to the same air pipe, the air pipe passes through the assembly plate and is connected to the fan.

[0014] As a further solution of the present invention: the lower drilling and stirring assembly comprises a spiral shaft, the spiral shaft is provided with a guide ring and a blowing head, and the spiral shaft is rollingly connected to the guide wheel, the spiral shaft is rotatably mounted on the movable plate through a bearing, the bottom end of the spiral shaft is fixedly connected to a bottom cavity, the bottom of the bottom cavity is fixedly connected to a lower drill bit, two sides of the inner wall of the bottom cavity are fixedly connected to two inclined plane blocks, every two vertically corresponding inclined plane blocks are staggered up and down, and a plurality of grouting ports are arranged below the outside of the bottom cavity;

[0015] The interior of the spiral shaft is fixedly connected with a polygonal tube, and the interior of the polygonal tube is provided with a polygonal plate.

[0016] As a further solution of the present invention: the grouting assembly includes a shunt pipe, and the three ends of the shunt pipe are respectively connected to three slurry pipes, the slurry pipes are rotatably installed on the ports of the shunt pipe through bearings, the second gear is fixedly connected to the top of the slurry pipe, and the slurry pipe is also rotatably installed on the mounting plate through bearings, the slurry pipe is installed on a polygonal plate, and the bottom end of the slurry pipe is fixedly connected to a retaining ring, and the retaining ring is arranged in the bottom cavity.

[0017] As a further solution of the present invention: the sealing assembly includes a sealing ring, which is arranged in the bottom cavity, and a first spring is fixedly connected between the sealing ring and the bottom wall of the bottom cavity, and the sealing ring blocks the position of the grouting port.

[0018] As a further solution of the present invention: the slitting assembly includes a connecting shaft, which is rotatably mounted on the bottom cavity through a bearing, one end of the connecting shaft is fixedly connected to a plurality of slices, and the other end of the connecting shaft is fixedly connected to a third gear.

[0019] As a further solution of the present invention: the transmission assembly includes a bidirectional toothed plate and four telescopic rods, the bidirectional toothed plate is meshed with the third gear, both sides of the bidirectional toothed plate are fixedly connected with ball rods, one of the ball rods is overlapped with the inclined surface block, the ball rod slides in the hole sleeve, and the hole sleeve is fixedly connected above the retaining ring;

[0020] Both ends of each telescopic rod are fixedly connected with hinges, and a second spring is fixedly connected between the two hinges. The four hinges are hinged to the two-way toothed plate through pins, and every two hinges are hinged to two support bars respectively, and the support bars are fixedly connected above the retaining ring.

[0021] A construction method of a three-shaft mixer for segmented foundation pit construction comprises the following steps:

[0022] S1. Pipeline Survey

[0023] Cooperate with the construction unit to conduct detailed investigation and excavation of existing pipelines on site during the pre-construction preparation stage and compare them with the existing pipeline map to form complete pipeline investigation data with guiding significance for on-site construction;

[0024] S2, SMW method pile construction

[0025] Build a slurry mixing platform at the construction site, build a cement warehouse near the platform, and stir the slurry before starting the machine;

[0026] During grouting, two grouting pumps and two pipelines are used to mix and inject from the H port with a Y-type joint, and the double heads of the mixing pile are used for simultaneous grouting. After drilling to the bottom of the pile, the mixing is paused for 3 minutes to ensure the quality of the pile bottom;

[0027] Secondly, before the H-shaped steel is inserted, the surface must be coated with a friction reducer to facilitate its extraction and recovery after the main structure is constructed, and its pores must be filled with cement slurry;

[0028] S3, three-axis mixing pile blocking wall

[0029] According to the actual location of the pipeline, select an appropriate location with a safe distance of 5-10m from the pipeline, set up three-axis mixing piles as temporary blocking walls to block the groundwater excavated in stages in the longitudinal direction of the foundation pit;

[0030] S4, (non-affected section) foundation pit slope excavation

[0031] After the construction of the temporary blocking wall of the three-axis mixing pile is completed, the foundation pit of the non-impacted section of the urban open-cut tunnel foundation pit pipeline is closed, and dewatering operations, cap beam and support construction are carried out. After the conditions for excavation construction are met, the excavation construction of the non-impacted section foundation pit is carried out;

[0032] S5. Cold joint pile construction

[0033] The construction of three-axis mixing piles at the corresponding locations affected by pipelines was suspended. After the pipeline relocation was completed, the remaining pile foundations were constructed on site. Considering that the connection between the new and old SMW construction method piles was not firm and there was a risk of leakage, triple-tube high-pressure jet grouting piles were used to reinforce the cold joints of the new and old SMW construction method piles.

[0034] In order to ensure the construction quality, it is necessary to pre-drill holes and conduct random inspections on the inclination of the holes;

[0035] When the rotary jet grouting pipe is used for drilling, the two processes of drilling and inserting the pipe can be combined into one; when the first stage is penetrated into the soil, the injection or vibration of the jet pipe itself can be used for penetration;

[0036] After the drilling rig reaches the designed depth, the grouting pump is turned on, and then the grouting is performed from bottom to top, and the mud is cleaned and discharged at the same time. A trial spraying must be carried out first to ensure that everything is normal before the formal grouting pile can be carried out;

[0037] When the jet grouting is inserted into the predetermined depth, the jet grouting is carried out from bottom to top;

[0038] S6, (affected section) foundation pit slope excavation

[0039] After the pipeline relocation is completed, the old and new SMW piles are reinforced by cold-joint rotary jetting, and the dewatering wells, crown beams, support beams, etc. are constructed in the affected section foundation pit. When the excavation conditions are met, the slope excavation of the affected section foundation pit is started. The slope and excavation method are the same as the slope excavation of the (non-affected section) foundation pit. In the final stage of excavation, the temporary isolation and blocking wall of the three-axis mixing piles is excavated in layers simultaneously. The foundation pits of the pipeline affected area and the non-affected area are closed, and the subsequent main structure construction is carried out.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The three-axis mixer and construction method for the segmented construction of the foundation pit drive the support shaft to rotate through the second motor, and the support shaft drives the cam to rotate. The cam can squeeze the roller body to drive the movable plate to move downward, so that the third spring is deformed. When the convex end of the cam is away from the roller body, the third spring drives the movable plate to reset, so that the third spring can cooperate with the cam to achieve the purpose of up and down movement, so that the drilling and mixing assembly can perform vibration drilling operation, which plays a role in assisting drilling, and the up and down movement of the bottom cavity can generate relative movement with the retaining ring, so that the transmission assembly maintains a one-way transmission cutting assembly, so that the connecting shaft drives the slice to rotate, so that the slice can play a cutting role on the hole wall, increase the looseness of the hole wall, and make the cutting cooperate with the vibration to increase the drilling efficiency and reduce the drilling resistance, thereby further improving the foundation pit construction efficiency;

[0042] 2. The three-shaft mixer and construction method for the segmented construction of the foundation pit can play a role of limiting and guiding the spiral shaft through the guide wheel in the guide ring, and the guide wheel is arranged in an up-down staggered manner, so that the spiral pieces of the spiral shaft can be staggered to avoid affecting the drilling construction, so that the guide wheel can smoothly guide the spiral shaft to drill and prevent the spiral shaft from deviating. Secondly, when the spiral shaft is pulled out, the wind is delivered by the fan and discharged through the blowing head. Since the blowing head is arranged in a ring outside the spiral shaft, the air flow can evenly impact the surface of the spiral shaft, so as to play a role of cleaning the spiral shaft;

[0043] 3. The three-axis mixer and construction method for the segmented construction of the foundation pit can drive the lower drilling stirring assembly to vibrate through the vibration assembly, so that relative movement can be generated between the bottom cavity and the retaining ring. When the grouting pipe injects the grouting material into the space between the bottom cavity and the retaining ring, compression is generated between the two, thereby increasing the discharge pressure of the grouting material and the grouting pressure, so that the grouting material can be quickly discharged from the grouting port, thereby improving the glue spraying effect. Secondly, during the upward extraction process of the lower drilling stirring assembly, the lower drilling stirring assembly continues to vibrate, and the cutting assembly continues to cut the hole wall, thereby reducing the extraction resistance and the load of the lifting equipment, so that the lower drilling stirring assembly is easy to take out. Secondly, the vibration of the lower drilling stirring assembly can help shake off the impurities attached to the surface and loosen the attachments. In combination with the cleaning assembly, the cleaning effect of the lower drilling assembly can be greatly improved.

[0044] 4. The three-axis mixer and construction method for the segmented construction of the foundation pit are used. By adding a temporary blocking wall on one side of the pipeline and optimizing the design of the SMW method pile blocking wall position on the other side according to the actual situation, the pipeline-affected area is successfully separated from the rest of the foundation pit, ensuring that the tunnel foundation pit pump room is in the first section of the construction foundation pit, and the pump room foundation pit (key line) can enter the foundation pit excavation stage earlier, avoiding the problems of construction team idleness and large equipment entering the site multiple times. At the same time, after the pipeline is relocated, the affected SMW method retaining pile cold joints are reinforced with triple pipe high-pressure rotary spraying to stop water, successfully solving the problem of water leakage in the foundation pit affected by the pipeline, making the foundation pit safe and controllable. Secondly, after the pipeline is relocated, the affected section of the foundation pit enters the foundation pit excavation stage. During the excavation process, the three-axis mixing pile temporary blocking wall is synchronously excavated in layers, solving the safety hazards and construction delays of the later demolition of the conventional SMW method pile temporary blocking wall and the bored cast-in-place pile temporary blocking wall, ensuring the safety of the foundation pit construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0046] Figure 1 The present invention is a three-dimensional structural schematic diagram of a three-axis mixer for segmented foundation pit construction according to an embodiment of the present invention.

[0047] Figure 2 A schematic diagram of the rear-view stereoscopic structure of a three-shaft mixer for segmented foundation pit construction according to an embodiment of the present invention.

[0048] Figure 3The present invention is a three-dimensional structural schematic diagram of a vibration assembly in a three-axis mixer for segmented foundation pit construction according to an embodiment of the present invention.

[0049] Figure 4 A schematic structural diagram of a cleaning assembly in a three-shaft mixer for staged foundation pit construction according to an embodiment of the present invention, viewed from above.

[0050] Figure 5 A three-dimensional structural diagram of an assembly plate in a three-axis mixer for foundation pit segmented construction according to an embodiment of the present invention

[0051] Figure 6 A schematic structural diagram of the connection between a lower drilling and stirring assembly and a grouting assembly in a three-shaft mixer for segmented foundation pit construction according to an embodiment of the present invention.

[0052] Figure 7 The present invention is a schematic diagram of a three-dimensional structure of a cross-section of a lower drilling and mixing assembly in a three-shaft mixer for segmented foundation pit construction according to an embodiment of the present invention.

[0053] Figure 8 A schematic diagram of a three-dimensional structure of a partial cross section of a spiral shaft in a three-shaft mixer for staged foundation pit construction according to an embodiment of the present invention;

[0054] Fig. 9 A schematic diagram of a three-dimensional structure of a slurry delivery pipe in a three-axis mixer for staged foundation pit construction according to an embodiment of the present invention

[0055] Fig.10 A schematic diagram of a three-dimensional structure of a cross-section of a bottom chamber in a three-axis mixer for staged foundation pit construction according to an embodiment of the present invention;

[0056] Fig.11 A schematic structural diagram of the connection between a transmission assembly and a cutting assembly in a three-shaft mixer for segmented foundation pit construction according to an embodiment of the present invention.

[0057] In the figure: 100, three-axis stirring mechanism; 101, driving assembly; 1011, mounting plate; 1012, first gear; 1013, rotating shaft; 1014, bracket; 1015, first motor; 1016, second gear; 102, cleaning assembly; 1021, assembly plate; 1022, fan; 1023, guide ring; 1024, air blowing head; 1025, guide wheel; 1026, air pipe; 103, lower drilling stirring assembly; 1031, spiral shaft; 1032, polygonal cylinder; 1033, bottom cavity; 1034, lower drilling head; 1035, polygonal plate; 1036, grouting port; 1037, inclined block; 104, grouting assembly; 1041, diverter pipe ; 1042, slurry delivery pipe; 1043, retaining ring; 105, sealing assembly; 1051, sealing ring; 1052, first spring; 106, slitting assembly; 1061, third gear; 1062, connecting shaft; 1063, slice; 107, transmission assembly; 1071, two-way tooth plate; 1072, hole sleeve; 1073, ball rod; 1074, hinge; 1075, second spring; 1076, telescopic rod; 1077, support bar; 108, vibration assembly; 1081, second motor; 1082, chain transmission structure; 1083, cam; 1084, roller body; 1085, support shaft; 1086, movable plate; 1087, third spring. DETAILED DESCRIPTION

[0058] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0059] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0060] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0061] Furthermore, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0062] Example 1

[0063] like Figure 1-3 and Figure 6-11As shown, the present invention provides a technical solution: a three-axis mixer for foundation pit segmented construction, including a three-axis mixing mechanism 100, the three-axis mixing mechanism 100 includes a driving assembly 101, the driving assembly 101 includes a mounting plate 1011, three second gears 1016 and two rotating shafts 1013, the rotating shafts 1013 are rotatably mounted on the mounting plate 1011 through bearings, a first gear 1012 is fixedly connected to the rotating shaft 1013, the top end of one of the rotating shafts 1013 is fixedly connected to the output shaft of a first motor 1015, the first motor 1015 is fixedly connected to the mounting plate 1011 through a bracket 1014, the first motor 1015 can be fixed by the bracket 1014, so that the first motor 1015 can stably drive the rotating shaft 1013 to rotate The rotating shaft 1013 can drive the first gear 1012 and the second gear 1016 to transmit, thereby realizing power transmission, thereby driving the three slurry delivery pipes 1042 to rotate, the two first gears 1012 are meshed with the three second gears 1016, and a vibration component 108 is arranged below the driving component 101. The vibration component 108 includes two support shafts 1085 and a movable plate 1086. The two support shafts 1085 are rotatably mounted on the mounting plate 1011 through two bearings. The two support shafts 1085 are connected by a chain transmission structure 1082. The chain transmission structure 1082 can realize long-distance power transmission, thereby driving the two support shafts 1085 to rotate synchronously, and one of the support shafts 1085 is connected to the second motor The output shaft of 1081 is fixedly connected, the second motor 1081 is installed on one side of the mounting plate 1011, both ends of the support shaft 1085 are fixedly connected with cams 1083, and a roller body 1084 is overlapped below the cam 1083. The roller body 1084 can reduce the friction resistance between the cam 1083, thereby reducing wear and tear, and can maintain a smooth extrusion movement between the cam 1083 and the roller body 1084. The roller body 1084 is fixedly connected to the side of the movable plate 1086. Two third springs 1087 are fixedly connected between the movable plate 1086 and the mounting plate 1011. The movable plate 1086 can be driven to reset upward by the third spring 1087, and the cam 1083 can squeeze the roller body 1084 to drive the movable plate 1086 to move downward, so that The third spring 1087 cooperates with the cam 1083 to realize the vibration of the movable plate 1086, so that the screw shaft 1031 can perform vibration drilling operation. Three drilling and stirring components 103 are connected to the driving component 101. The drilling and stirring component 103 includes a screw shaft 1031. The screw shaft 1031 is penetrated by a guide ring 1023 and a blowing head 1024, and the screw shaft 1031 is rollingly connected to the guide wheel 1025. The screw shaft 1031 can be guided by the guide wheel 1025 to maintain the vertical drilling operation of the screw shaft 1031. The screw shaft 1031 is rotatably installed on the movable plate 1086 through a bearing. The bottom end of the screw shaft 1031 is fixedly connected to a bottom cavity 1033, and the bottom of the bottom cavity 1033 is fixedly connected to a lower drill bit 1034.Two inclined plane blocks 1037 are fixedly connected to both sides of the inner wall of the bottom cavity 1033. Every two vertically corresponding inclined plane blocks 1037 are staggered up and down. Through the staggered setting of the inclined plane blocks 1037, the two ball rods 1073 can be squeezed by the two inclined plane blocks 1037 alternately up and down, so as to realize the alternating movement of the two-way tooth plate 1071, so that the two tooth segments of the two-way tooth plate 1071 are alternately transmitted with the third gear 1061. A plurality of grouting ports 1036 are arranged at the lower part of the outside of the bottom cavity 1033. Through the setting of the grouting ports 1036, the grouting operation is facilitated. The interior of the spiral shaft 1031 is fixedly connected to the multilateral tube 1032. The multilateral A polygonal plate 1035 is provided inside the tube 1032. The polygonal structure of the polygonal tube 1032 and the polygonal plate 1035 allows the polygonal plate 1035 to rotate and drive the polygonal tube 1032 to drive the screw shaft 1031 to realize rotational movement, which is convenient for the screw shaft 1031 to perform drilling operations. At the same time, the polygonal tube 1032 can be movable on the polygonal plate 1035, so that the screw shaft 1031 can vibrate smoothly. A grouting assembly 104 is provided inside the drilling stirring assembly 103. A cleaning assembly 102 is installed below the drilling stirring assembly 103. The driving assembly 101 cooperates with the vibration assembly 108 to control the drilling stirring assembly 103 to perform the foundation pit drilling operations smoothly.

[0064] A sealing assembly 105 is provided below the interior of the lower drilling and stirring assembly 103. The sealing assembly 105 includes a sealing ring 1051. The sealing ring 1051 is provided in the bottom cavity 1033. A first spring 1052 is fixedly connected between the sealing ring 1051 and the bottom wall of the bottom cavity 1033. The first spring 1052 can maintain the position of the sealing ring 1051 so that the sealing ring 1051 can stably close the grouting port 1036. The sealing ring 1051 blocks the position of the grouting port 1036. Two cutting assemblies 106 are provided below the lower drilling and stirring assembly 103. The cutting assemblies 106 include a connecting shaft 1062. The connecting shaft 1062 is rotatably mounted on the bottom cavity 1033 through a bearing. One end of the connecting shaft 1062 is fixedly connected to a plurality of slices 1063. The other end of the connecting shaft 1062 is fixedly connected to the third gear 1061. The third gear 1061 and the two-way tooth plate 1071 can drive the connecting shaft 1062 to drive the slice 1063 to rotate, so that the slice 1063 can cut the hole wall, which is convenient for the drilling operation of the lower drill bit 1034. The two cutting components 106 are arranged through the lower drilling and stirring component 103. The cutting component 106 is connected to the transmission component 107. The transmission component 107 includes a two-way tooth plate 1071 and four telescopic rods 1076. The two-way tooth plate 1071 is meshed with the third gear 1061. Ball rods 1073 are fixedly connected on both sides of the two-way tooth plate 1071. One of the ball rods 1073 overlaps the inclined surface block 1037, and the ball rod 1073 slides on the hole sleeve 10 In the embodiment of the present invention, the hole sleeve 1072 is fixedly connected to the top of the retaining ring 1043, and the two ends of each telescopic rod 1076 are fixedly connected with a hinge 1074, and the two hinges 1074 are fixedly connected with a second spring 1075. The hinge 1074 can be turned through a pin to make the telescopic rod 1076 turn smoothly, so that the two-way tooth plate 1071 can translate smoothly, and at the same time, the second spring 1075 can be deformed. When the telescopic rod 1076 passes over the support bar 1077 and turns to the other side, the second spring 1075 can assist the two-way tooth plate 1071 to move, so that the two-way tooth plate 1071 can mesh with the third gear 1061 smoothly, and at the same time, the second spring 1075 can maintain the stable transmission of the two-way tooth plate 1071 and the third gear 1061. The connecting parts 1074 are hinged to the two-way tooth plate 1071 through the pin shaft. In addition, every two hinged parts 1074 are hinged to two support bars 1077 respectively. The support bar 1077 is fixedly connected to the top of the retaining ring 1043. The transmission assembly 107 is arranged below the grouting assembly 104. The grouting assembly 104 includes a shunt pipe 1041. The three ends of the shunt pipe 1041 are respectively connected to three slurry pipes 1042. The shunt pipe 1041 can guide the grouting material into the slurry pipe 1042, so that the slurry pipe 1042 can perform shunting and slurry delivery operations. The slurry pipe 1042 is rotatably installed on the port of the shunt pipe 1041 through a bearing. The slurry pipe 1042 can maintain stable rotation through the bearing. The second gear 1016 is fixedly connected to the top of the slurry pipe 1042.The slurry delivery pipe 1042 is rotatably mounted on the mounting plate 1011 through a bearing, and is installed through the polygonal plate 1035. The bottom end of the slurry delivery pipe 1042 is fixedly connected with a retaining ring 1043, and the retaining ring 1043 is arranged in the bottom cavity 1033. The cutting component 106 moves up and down following the drilling and stirring component 103, so that the cutting component 106 and the transmission component 107 are transmitted to perform hole wall cutting, thereby reducing the drilling blockage of the spiral shaft 1031.

[0065] In this embodiment, the support shaft 1085 is driven to rotate by the second motor 1081, and the support shaft 1085 drives the cam 1083 to rotate. The cam 1083 can squeeze the roller body 1084 to drive the movable plate 1086 to move downward, so that the third spring 1087 is deformed. When the convex end of the cam 1083 is away from the roller body 1084, the third spring 1087 drives the movable plate 1086 to reset, so that the third spring 1087 can cooperate with the cam 1083 to achieve the purpose of up and down movement, so that the drilling stirring assembly 103 can perform vibration drilling operation, play a role in assisting drilling, and the bottom cavity 1033 The up and down movement can generate relative movement with the retaining ring 1043, so that the inclined surface block 1037 and the ball rod 1073 can move relative to each other, and the two inclined surface blocks 1037 are staggered and separated up and down, so that the ball rod 1073 can be staggered and squeezed to drive the two-way tooth plate 1071 to alternately transmit with the third gear 1061, so that the third gear 1061 maintains unidirectional rotation, and the connecting shaft 1062 drives the slice 1063 to rotate, so that the slice 1063 can cut the hole wall, increase the looseness of the hole wall, and make the cutting and vibration increase the drilling efficiency, reduce the resistance of drilling, and further improve the efficiency of foundation pit construction.

[0066] Example 2

[0067] Combination Figure 4-5 , it is concluded that the cleaning component 102 includes an assembly plate 1021, on which a fan 1022 and three guide rings 1023 are installed, a plurality of guide wheels 1025 are staggeredly installed inside the guide ring 1023, a blowing head 1024 is fixedly connected below the guide ring 1023, the three blowing heads 1024 are connected to the same air pipe 1026, and the air pipe 1026 passes through the assembly plate 1021 and is connected to the fan 1022.

[0068] In this embodiment: the guide wheel 1025 in the guide ring 1023 can play a role of limiting and guiding the spiral shaft 1031, and the guide wheel 1025 is arranged in an up-down staggered manner, so that the spiral pieces of the spiral shaft 1031 can be staggered to avoid affecting the drilling construction, so that the guide wheel 1025 can smoothly guide the spiral shaft 1031 to drill, and prevent the spiral shaft 1031 from being deflected. Secondly, when the spiral shaft 1031 is pulled out, the wind is delivered by the fan 1022 and discharged through the blowing head 1024. Since the blowing head 1024 is arranged in a ring outside the spiral shaft 1031, the air flow can evenly impact the surface of the spiral shaft 1031, so as to clean the spiral shaft 1031.

[0069] Example 3

[0070] Combination Figure 1-3 and Figure 6-8 , it is concluded that the three-axis stirring mechanism 100 includes a driving component 101, a vibration component 108 is arranged below the driving component 101, three down-drilling stirring components 103 are connected to the driving component 101, a grouting component 104 is arranged inside the down-drilling stirring component 103, a cleaning component 102 is assembled below the down-drilling stirring component 103, two cutting components 106 are arranged below the down-drilling stirring component 103, the two cutting components 106 are arranged through the down-drilling stirring component 103, a transmission component 107 is connected to the cutting component 106 for transmission, and the transmission component 107 is arranged below the grouting component 104.

[0071] In this embodiment: the vibration component 108 can drive the lower drilling stirring component 103 to vibrate, so that relative movement can be generated between the bottom cavity 1033 and the retaining ring 1043. When the grouting pipe 1042 injects the grouting material into the space between the bottom cavity 1033 and the retaining ring 1043, compression is generated between the two, thereby increasing the discharge pressure of the grouting material and the spraying pressure, so that the grouting material can be quickly discharged from the grouting port 1036, thereby improving the spraying effect. Secondly, during the upward withdrawal process of the lower drilling stirring component 103, the lower drilling stirring component 103 continues to vibrate, and the cutting component 106 continues to cut the hole wall, thereby reducing the withdrawal resistance and reducing the load of the lifting equipment, so that the lower drilling stirring component 103 is easy to take out. Secondly, the vibration of the lower drilling stirring component 103 can help to shake off impurities attached to the surface and loosen the attachments. In combination with the cleaning component 102, the cleaning effect of the lower drilling component can be greatly improved.

[0072] A construction method of a three-shaft mixer for segmented foundation pit construction comprises the following steps:

[0073] S1. Pipeline Survey

[0074] Cooperate with the construction unit to conduct detailed investigation and excavation of existing pipelines on site during the pre-construction preparation stage and compare them with the existing pipeline map to form complete pipeline investigation data with guiding significance for on-site construction;

[0075] S2, SMW method pile construction

[0076] Build a slurry mixing platform at the construction site, build a cement warehouse near the platform, and stir the slurry before starting the machine;

[0077] During grouting, two grouting pumps and two pipelines are mixed and injected from the H port with a Y-type joint, and the double heads of the mixing pile are used for simultaneous grouting. After drilling to the bottom of the pile, the mixing is stopped for 3 minutes to ensure the quality of the pile bottom. If the pipeline is blocked, the pump is stopped immediately for treatment. After the treatment, the mixing drill is immediately lifted or sunk 0.5m before grouting. After 10 to 20 seconds, normal mixing is resumed to prevent pile breakage;

[0078] Secondly, before the H-shaped steel is inserted, the surface must be coated with a friction reducer to facilitate the extraction and recovery after the main structure is constructed. The pores must be filled with cement slurry. The H-shaped steel adopts HN700*300*13*24. The flatness and verticality of the steel must be ensured, and no distortion is allowed.

[0079] H-beam butt joints must be fully welded with 45-degree grooves on all four sides, and then a 400×400×16 steel plate must be welded on each side of the web, with a weld height of 10mm;

[0080] The retaining structure of the urban open-cut tunnel adopts SMW method piles. The SMW method piles adopt φ850@600 three-axis mixing piles + HN700*300*13*24 interval H-shaped steel. The SMW method piles of this project adopt the "one-hole construction method, four-mixing and two-spraying" method for cyclic construction; for three-axis mixing piles, during the whole process of drilling sinking and lifting, the screw rotates at a uniform speed, drills at a uniform speed, and lifts at a uniform speed. During the grouting process, the sinking speed is controlled between 0.5m / min and 0.8m / min, and water sinking is not allowed. The drill bit lifting speed is ≤1.0m / min to avoid negative pressure in the hole and cause settlement of the surrounding foundation. Secondly, the pile position deviation of the three-axis mixing pile and the steel should not exceed 50mm, and the verticality deviation should be less than 1 / 200; during the construction of cement-soil mixing piles, the pile driver should be in the middle, the plane allowable deviation should be 20mm, and the verticality of the column guide frame should not be greater than 1 / 250;

[0081] The overlap time between piles should not exceed 24 hours, otherwise high-pressure jet grouting piles should be used for reinforcement.

[0082] Stir and grout appropriately and continuously at the bottom of the pile, and keep original records of each pile formation;

[0083] Among them, cement soil mixing piles use P.O42.5 ordinary Portland cement, the water-cement ratio should be strictly controlled between 1.5 and 1.8, the cement content is ≥20%, the cement content in the air mixing stage is 6%, the 28-day unconfined compressive strength qu≥1.0MPa, the permeability coefficient is ≤1×10-7cm / s, bentonite should be added to the mixing pile construction in sandy soil, after the cement slurry is prepared, the stagnation time shall not exceed 2 hours, and it is strictly forbidden to use it if it exceeds 2 hours, and the construction interval of adjacent mixing piles in overlapping construction shall not exceed 24 hours;

[0084] S3, three-axis mixing pile blocking wall

[0085] According to the actual location of the pipeline, select an appropriate location with a safe distance of 5-10m from the pipeline, set up three-axis mixing piles as temporary blocking walls to block the groundwater excavated in stages in the longitudinal direction of the foundation pit;

[0086] The depth of the temporary plugging wall of the three-axis mixing pile is the same as the depth of the water-stop curtain on both sides of the longitudinal section of the corresponding pile number. It is reinforced to 12m below the bottom of the pit and the pile length is 22m. The three-axis mixing pile adopts the "one-hole method of sleeve connection, four-mixing and two-spraying" method for cyclic construction. The construction method is the same as the three-axis mixing pile construction part of the SMW method pile;

[0087] S4. Excavation of foundation pit slope in non-affected section

[0088] After the construction of the temporary blocking wall of the three-axis mixing pile is completed, the foundation pit of the non-impacted section of the urban open-cut tunnel foundation pit pipeline is closed, and dewatering operations, cap beam and support construction are carried out. After the conditions for excavation construction are met, the excavation construction of the non-impacted section foundation pit is carried out;

[0089] Before excavating the foundation pit, the slope should be reasonably designed according to geological survey reports, soil types, groundwater conditions, and engineering requirements. The foundation pit is about 10m deep, and three levels of slope are used for excavation. The height of each level is 3m, 3.5m, and 3.5m, and the slope is 1:1.5. The platform width at the ground is 4m, and the width of the slope platform is 2m. Pipe well dewatering is used in the foundation pit, and drainage wells are set up. A dewatering well is set up every 20m. The well wall pipe adopts Φ400 / 300mm cement gravel filter pipe, and the bottom is overlapped with a 1000mm long sand settling pipe. The filter pipe is wrapped with a layer of 40 mesh nylon mesh. The backfill sand and gravel particle size is 3-7mm. Longitudinal intercepting ditches are set around the foundation pit. At the same time, appropriate water level monitoring holes are set up inside and outside the foundation pit to monitor the groundwater level in the foundation pit. The groundwater level in the foundation pit should be reduced to 1m below the foundation pit surface before the foundation pit is excavated;

[0090] S5. Cold joint pile construction

[0091] The construction of three-axis mixing piles at the corresponding locations affected by pipelines was suspended. After the pipeline relocation was completed, the remaining pile foundations were constructed on site. Considering that the connection between the new and old SMW construction method piles was not firm and there was a risk of leakage, triple-tube high-pressure jet grouting piles were used to reinforce the cold joints of the new and old SMW construction method piles.

[0092] The cold joint piles are reinforced with three Φ800@500 high-pressure jet grouting piles, which are the same length as the SMW piles. The high-pressure jet grouting pile drill uses a special nozzle to drill into the predetermined position of the stratum, and then uses a high-pressure pulse pump to spray cement slurry through the injection device at the lower end of the drill rod to the soil at high speed in all directions. The impact force of the fluid is used to cut the soil layer, so that the soil within the jet range is damaged. At the same time, the drill rod rotates at a certain speed while slowly rising at a low speed, so that the soil and cement slurry are fully mixed and mixed. After cementation and hardening, a pile with a relatively uniform diameter and a certain strength is formed in the foundation, thereby reinforcing the stratum.

[0093] In order to ensure the construction quality, it is necessary to pre-drill the hole and conduct random inspections on the inclination of the hole. Since the quality of the hole has a great influence on the construction of cold-jointed piles, the construction must be carried out according to the technical parameters to ensure that the error between the center of the hole and the center of the pile position is less than 50mm, and the verticality error is less than 0.2%. Before drilling, the length of each drill rod should be measured and numbered in sequence with red paint, and the depth control red line should be marked on the wall of the top drill rod with red paint. The drilling depth control is based on the ground level measurement and the designed pile bottom elevation to determine the depth of the drill rod into the soil; the construction operation sequence of the jet grouting pile should adopt the method of hole separation, and the time interval between the injection grouting of adjacent holes should not be greater than 24h;

[0094] When the rotary jet grouting pipe is used for drilling, the two processes of drilling and inserting the pipe can be combined into one; when the first stage is penetrated into the soil, the injection or vibration of the jet pipe itself can be used for penetration;

[0095] After the drilling rig reaches the designed depth, the grouting pump is turned on, and then the grouting is performed from bottom to top, and the mud is cleaned and discharged at the same time. A trial spraying must be carried out first to ensure that everything is normal before the formal grouting pile can be carried out;

[0096] When the jet grouting is inserted into the predetermined depth, the jet grouting is carried out from bottom to top. During the grouting process, the on-duty personnel must always pay attention to check whether the parameters such as the initial setting time of the slurry, grouting flow rate, air volume, pressure, and rotation lifting speed meet the design requirements, and keep records at any time and draw process curves. When jet grouting, it should be sprayed evenly from bottom to top, and the position where the spraying is stopped should be 1m higher than the designed top surface of the curtain. During jet grouting, when the amount of grouting at the orifice is greater than 20% of the grouting amount, measures such as increasing the spraying pressure can be adopted. When the orifice does not return to the grouting due to slurry leakage, the grouting pipe should be stopped at the non-returning position to continue the jet grouting, and measures such as filling medium-coarse sand from the orifice and adding quick-setting agent to the grouting liquid should be adopted at the same time until the orifice returns to the grouting. When the jet grouting is stopped for some reason, when the grouting is continued, it should be overlapped with the grouting body before the spraying is stopped, and the overlap length is ≮500mm;

[0097] After the construction is completed, the grouting pipe and other equipment should be flushed clean, and no cement slurry should remain in the pipe or machine. Usually, the slurry is replaced with water and sprayed on the ground to drain all the slurry in the mud pump, grouting pipe and hose;

[0098] S6. Slope excavation of the affected section foundation pit

[0099] After the pipeline relocation is completed, the old and new SMW piles are reinforced by cold-joint rotary jetting, and the dewatering wells, crown beams, support beams, etc. are constructed in the affected section foundation pit. When the excavation conditions are met, the slope excavation of the affected section foundation pit is started. The slope and excavation method are the same as those of the non-affected section foundation pit. In the final stage of excavation, the temporary isolation and blocking wall of the three-axis mixing piles is excavated in layers simultaneously. The foundation pits of the pipeline affected area and the non-affected area are closed, and the subsequent main structure construction is carried out.

[0100] The working principle of the present invention is as follows: when the foundation pit drilling operation is performed, since the mounting plate 1011 is installed on the lifting device, the lifting device can lower the position of the driving assembly 101 and the drilling stirring assembly 103, and then the first motor 1015 drives the rotating shaft 1013 to rotate, and the rotating shaft 1013 drives the first gear 1012 to rotate, so that the first gear 1012 and the second gear 1016 can realize transmission, thereby rotating the slurry delivery pipe 1042, and the slurry delivery pipe 1042 drives the polygonal plate 1035 and the polygonal cylinder 1032 to rotate, so that the spiral shaft 1031 rotates, and the drilling is performed;

[0101] Then, the support shaft 1085 is driven to rotate by the second motor 1081, and the two support shafts 1085 are synchronously driven by the chain transmission structure 1082. The support shaft 1085 drives the cam 1083 to rotate, and the cam 1083 squeezes the roller body 1084 and the movable plate 1086 to move downward, and the movable plate 1086 drives the third spring 1087 to deform. When the convex surface of the cam 1083 turns away from the roller body 1084, the third spring 1087 drives the movable plate 1086 to reset upward until the cam 1083 squeezes the roller body 1084 again, so that the movable plate 1086 moves downward again, so that the cam 1083 cooperates with the third spring 1087 to drive the movable plate 1086 to move up and down, so that the movable plate 1086 drives the screw The spiral shaft 1031 vibrates, and the spiral shaft 1031 drives the drill bit 1034 to perform vibration drilling operation through the bottom cavity 1033. At the same time, the vibration of the bottom cavity 1033 can generate relative movement with the retaining ring 1043, so that the ball rod 1073 and the inclined surface block 1037 can generate relative movement, so that the two ball rods 1073 can alternately contact the inclined surface block 1037 up and down, so that the inclined surface extrusion of the inclined surface block 1037 can drive the ball rod 1073 to move, so that the tooth segments on both sides of the bidirectional tooth plate 1071 can alternately transmit with the third gear 1061, and the third gear 1061 can unidirectionally drive the connecting shaft 1062 to drive the slice 1063 to rotate, and the slice 1063 can cut the hole wall, so as to cooperate with the vibration to perform auxiliary drilling operation;

[0102] The lower drill bit 1034 is drilled to the designated position, and then connected to the grouting equipment through the shunt pipe 1041. The grouting equipment performs grouting through the shunt pipe 1041 and the grouting pipe 1042, so that the grouting material enters below the retaining ring 1043, and applies pressure to the sealing ring 1051, so that the sealing ring 1051 moves downward, the grouting port 1036 is opened, and then the grouting operation is performed outward. At the same time, due to the relative movement between the bottom cavity 1033 and the retaining ring 1043, the space can be compressed, thereby increasing the grouting pressure, and then the grouting operation is performed by pulling out the spiral shaft 1031 upward in sequence;

[0103] After the screw shaft 1031 extends out of the ground, the screw shaft 1031 vibrates to shake off impurities, and at the same time, the fan 1022 can blow air through the blowing head 1024, so that the airflow impacts the surface of the screw shaft 1031 for cleaning.

[0104] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, and parameter values ​​(e.g., temperature, pressure, etc.), installation arrangement, use of materials, color, directional changes, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present invention. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure of performing the function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to numerous modifications still falling within the scope of the appended claims.

[0105] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0106] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0107] It should be noted that the above embodiments are only used to illustrate the technical solutions 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 the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A three-shaft mixer for foundation pit segmented construction, characterized in that: The invention comprises a three-axis stirring mechanism (100), wherein the three-axis stirring mechanism (100) comprises a driving component (101), a vibration component (108) is arranged below the driving component (101), three drilling stirring components (103) are connected to the driving component (101), a grouting component (104) is arranged inside the drilling stirring component (103), a cleaning component (102) is arranged below the drilling stirring component (103), and the driving component (101) cooperates with the vibration component (108) to control the drilling stirring component (103) to smoothly perform the foundation pit drilling operation; A sealing component (105) is arranged below the lower part of the lower drilling and stirring component (103); two cutting components (106) are arranged below the lower drilling and stirring component (103); the two cutting components (106) are arranged through the lower drilling and stirring component (103); a transmission component (107) is connected to the cutting component (106); the transmission component (107) is arranged below the grouting component (104); the cutting component (106) moves up and down following the lower drilling and stirring component (103), so that the cutting component (106) and the transmission component (107) are transmitted to cut the hole wall, thereby reducing the drilling obstruction of the spiral shaft (1031).

2. A three-shaft mixer for foundation pit segmented construction as claimed in claim 1, characterized in that: The driving assembly (101) comprises a mounting plate (1011), three second gears (1016) and two rotating shafts (1013); the rotating shafts (1013) are rotatably mounted on the mounting plate (1011) via bearings; a first gear (1012) is fixedly connected to the rotating shaft (1013); a top end of one of the rotating shafts (1013) is fixedly connected to an output shaft of a first motor (1015); the first motor (1015) is fixedly connected to the mounting plate (1011) via a bracket (1014); and the two first gears (1012) are meshed with the three second gears (1016).

3. A three-shaft mixer for foundation pit segmented construction as claimed in claim 2, characterized in that: The vibration assembly (108) comprises two support shafts (1085) and a movable plate (1086); the two support shafts (1085) are rotatably mounted on the mounting plate (1011) via two bearings; the two support shafts (1085) are transmission-connected via a chain transmission structure (1082); one of the support shafts (1085) is fixedly connected to the output shaft of the second motor (1081); and the second motor (1081) is mounted on one side of the mounting plate (1011); Both ends of the support shaft (1085) are fixedly connected with cams (1083), a roller body (1084) is overlapped below the cam (1083), and the roller body (1084) is fixedly connected to the side of the movable plate (1086). Two third springs (1087) are fixedly connected between the movable plate (1086) and the mounting plate (1011).

4. A three-shaft mixer for foundation pit segmented construction as claimed in claim 3, characterized in that: The cleaning assembly (102) comprises an assembly plate (1021), on which a fan (1022) and three guide rings (1023) are mounted, a plurality of guide wheels (1025) are staggeredly mounted inside the guide ring (1023), an air blowing head (1024) is fixedly connected below the guide ring (1023), the three air blowing heads (1024) are connected to the same air supply pipe (1026), and the air supply pipe (1026) passes through the assembly plate (1021) and is connected to the fan (1022).

5. A three-shaft mixer for foundation pit segmented construction as claimed in claim 4, characterized in that: The lower drilling and stirring assembly (103) comprises a spiral shaft (1031), the spiral shaft (1031) is provided with a guide ring (1023) and a blowing head (1024), and the spiral shaft (1031) is rollingly connected to the guide wheel (1025), the spiral shaft (1031) is rotatably mounted on the movable plate (1086) via a bearing, the bottom end of the spiral shaft (1031) is fixedly connected to a bottom cavity (1033), the bottom of the bottom cavity (1033) is fixedly connected to a lower drill bit (1034), two inclined plane blocks (1037) are fixedly connected to both sides of the inner wall of the bottom cavity (1033), and every two vertically corresponding inclined plane blocks (1037) are staggered up and down, and a plurality of grouting ports (1036) are arranged below the outside of the bottom cavity (1033); The interior of the spiral shaft (1031) is fixedly connected to a polygonal cylinder (1032), and the interior of the polygonal cylinder (1032) is provided with a polygonal plate (1035).

6. A three-shaft mixer for staged foundation pit construction as claimed in claim 5, characterized in that: The grouting assembly (104) comprises a shunt pipe (1041), the three ends of the shunt pipe (1041) are respectively connected to three slurry delivery pipes (1042), the slurry delivery pipes (1042) are rotatably mounted on the ports of the shunt pipe (1041) via bearings, the second gear (1016) is fixedly connected above the slurry delivery pipe (1042), the slurry delivery pipe (1042) is also rotatably mounted on the mounting plate (1011) via bearings, the slurry delivery pipe (1042) is installed through the polygonal plate (1035), the bottom end of the slurry delivery pipe (1042) is fixedly connected to a retaining ring (1043), and the retaining ring (1043) is arranged in the bottom cavity (1033).

7. A three-shaft mixer for foundation pit segmented construction as claimed in claim 6, characterized in that: The sealing assembly (105) comprises a sealing ring (1051), wherein the sealing ring (1051) is arranged in the bottom cavity (1033), a first spring (1052) is fixedly connected between the sealing ring (1051) and the bottom wall of the bottom cavity (1033), and the sealing ring (1051) blocks the position of the grouting port (1036).

8. A three-shaft mixer for staged foundation pit construction as claimed in claim 7, characterized in that: The slitting assembly (106) comprises a connecting shaft (1062), wherein the connecting shaft (1062) is rotatably mounted on the bottom cavity (1033) via a bearing, one end of the connecting shaft (1062) is fixedly connected to a plurality of slices (1063), and the other end of the connecting shaft (1062) is fixedly connected to a third gear (1061).

9. A three-shaft mixer for staged foundation pit construction as claimed in claim 8, characterized in that: The transmission assembly (107) comprises a bidirectional toothed plate (1071) and four telescopic rods (1076), the bidirectional toothed plate (1071) meshing with the third gear (1061), both sides of the bidirectional toothed plate (1071) are fixedly connected with ball rods (1073), one of the ball rods (1073) overlaps the inclined plane block (1037), the ball rod (1073) slides in the hole sleeve (1072), and the hole sleeve (1072) is fixedly connected above the retaining ring (1043); Both ends of each telescopic rod (1076) are fixedly connected with hinges (1074), and a second spring (1075) is fixedly connected between the two hinges (1074). The four hinges (1074) are hinged to the bidirectional toothed plate (1071) through a pin shaft, and every two hinges (1074) are respectively hinged to two support bars (1077), and the support bars (1077) are fixedly connected to the top of the retaining ring (1043).

10. A construction method using a three-shaft mixer for staged foundation pit construction according to claim 9, characterized in that: The steps include: S1. Pipeline Survey Cooperate with the construction unit to conduct detailed investigation and excavation of existing pipelines on site during the pre-construction preparation stage and compare them with the existing pipeline map to form complete pipeline investigation data with guiding significance for on-site construction; S2, SMW method pile construction Build a slurry mixing platform at the construction site, build a cement warehouse near the platform, and stir the slurry before starting the machine; During grouting, two grouting pumps and two pipelines are used to mix and inject from the H port with a Y-type joint, and the double heads of the mixing pile are used for simultaneous grouting. After drilling to the bottom of the pile, the mixing is paused for 3 minutes to ensure the quality of the pile bottom; Secondly, before the H-shaped steel is inserted, the surface must be coated with a friction reducer to facilitate its extraction and recovery after the main structure is constructed, and its pores must be filled with cement slurry; S3, three-axis mixing pile blocking wall According to the actual location of the pipeline, select an appropriate location with a safe distance of 5-10m from the pipeline, set up three-axis mixing piles as temporary blocking walls to block the groundwater excavated in stages in the longitudinal direction of the foundation pit; S4, (non-affected section) foundation pit slope excavation After the construction of the temporary blocking wall of the three-axis mixing pile is completed, the foundation pit of the non-impacted section of the urban open-cut tunnel foundation pit pipeline is closed, and dewatering operations, cap beam and support construction are carried out. After the conditions for excavation construction are met, the excavation construction of the non-impacted section foundation pit is carried out; S5. Cold joint pile construction The construction of three-axis mixing piles at the corresponding locations affected by pipelines was suspended. After the pipeline relocation was completed, the remaining pile foundations were constructed on site. Considering that the connection between the new and old SMW construction method piles was not firm and there was a risk of leakage, triple-tube high-pressure jet grouting piles were used to reinforce the cold joints of the new and old SMW construction method piles. In order to ensure the construction quality, it is necessary to pre-drill holes and conduct random inspections on the inclination of the holes; When the rotary jet grouting pipe is used for drilling, the two processes of drilling and inserting the pipe can be combined into one; when the first stage is penetrated into the soil, the jet or vibration of the jet pipe itself can be used for penetration; After the drilling rig reaches the designed depth, the grouting pump is turned on, and then the grouting is performed from bottom to top, and the mud is cleaned and discharged at the same time. A trial spraying must be carried out first to ensure that everything is normal before the formal grouting pile can be carried out; When the jet grouting is inserted into the predetermined depth, the jet grouting is carried out from bottom to top; S6, (affected section) foundation pit slope excavation After the pipeline relocation is completed, the old and new SMW piles are reinforced by cold-joint rotary jetting, and the dewatering wells, crown beams, support beams, etc. are constructed in the affected section foundation pit. When the excavation conditions are met, the slope excavation of the affected section foundation pit is started. The slope and excavation method are the same as the slope excavation of the (non-affected section) foundation pit. In the final stage of excavation, the temporary isolation and blocking wall of the three-axis mixing piles is excavated in layers simultaneously. The foundation pits of the pipeline affected area and the non-affected area are closed, and the subsequent main structure construction is carried out.

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