DCM construction method for offshore deep cement-soil mixing piles with horizontal cantilevers

Abstract

The present invention discloses a method for constructing deep-seated cement-soil mixing piles at sea with horizontal cantilevers. The method comprises the following steps: navigating a DCM engineering vessel to a predetermined location; determining the construction method for each mixing pile based on stratum distribution data and the design and construction coordinates of each cement-soil mixing pile; employing a direct mixing construction method if the rock stratum slope at the construction location is less than a slope threshold; and employing a horizontal cantilever reinforced mixing construction method if the rock stratum slope at the construction location is greater than the slope threshold. Specifically, the method comprises: utilizing a variable-diameter drill bit mechanism in a drilling rig system to penetrate the rock stratum surface and drill to form a tapered hole located on the rock stratum surface, further constructing a horizontal cantilever pile hole, and using a four-axis DCM drill bit to perform downward mixing construction and grouting to form a mixing pile group. Advantages of the present invention include: a high degree of intelligence and automation, adaptability to diverse seabed rock stratum topography, and the ability to construct horizontal cantilevers on rock strata with steeper slopes, thereby improving stability.

Description

Technical Field

[0001] The invention belongs to the technical field of water cement mixing, and in particular relates to a DCM construction method of an offshore deep cement soil mixing pile with a horizontal cantilever. Background Art

[0002] When a tunnel passes through the seabed, the reinforcement of the soft seabed strata plays a vital role in the safety of the tunnel structure. For the reinforcement of soft seabed strata, the cement soil mixing pile DCM (deep cement mixing) method is generally used to achieve efficient and stable reinforcement effects, which can effectively ensure the smooth excavation of the shield and the quality of the formed tunnel.

[0003] The primary construction device for the DCM (cement-soil mixing) method is the DCM engineering vessel. This specialized vessel assists in the construction and installation of DCM piles. It is a highly automated, intelligent vessel that integrates cement storage, cement mixing, screw conveying, underwater shotcrete, and mixing. It can perform deep cement mixing at depths of up to 30 meters underwater, solidifying deep seabed foundations and playing an irreplaceable role in land reclamation.

[0004] The current cement soil mixing pile (DCM) construction method mainly involves using a drilling rig to inject cement slurry into the soft seabed strata that need to be improved to a certain depth. The drill bit blades of the drilling rig fully cut and mix the soil and then spray cement slurry into it to consolidate the soil and achieve a certain stability, as well as a certain shear and compressive strength.

[0005] The disadvantage of this DCM method is that there is a lack of effective connection between the cement-soil mixing piles and the rock layer below the soft seabed strata. Under the action of additional loads or earthquakes, the cement-soil mixing piles are prone to slippage or small-scale displacement on the surface of the rock layer with a relatively steep slope. Summary of the Invention

[0006] The object of the present invention is to provide a DCM construction method for deep-seated cement-soil mixing piles at sea with a horizontal cantilever in response to the above-mentioned deficiencies in the prior art. The DCM construction method utilizes a DCM engineering vessel and selects the construction method to be adopted based on different rock layer slope data, so that the mixing piles can be stably set on the steep rock layer of the seabed through the horizontal cantilever.

[0007] The purpose of the present invention is achieved by the following technical solutions:

[0008] A DCM construction method for offshore deep-seated cement-soil mixing piles with horizontal cantilevers, characterized in that the DCM construction method comprises the following steps:

[0009] S1: Conducting geological exploration of the seabed in the area to be reinforced to obtain stratum distribution data of the seabed, wherein the seabed comprises, from bottom to top, rock layers, clay layers, and silt layers;

[0010] S2: Driving the DCM engineering vessel to the predetermined location; the DCM engineering vessel includes a flat barge, a cement silo system, a mixing and storage slurry system, a slurry pump system, and a drilling rig system;

[0011] S3: Determining a construction method for each cement-soil mixing pile based on the stratum distribution data and the design construction coordinates of each mixing pile, wherein the construction method is one of direct mixing construction and horizontal cantilever reinforcement mixing construction;

[0012] S3.1: If the rock slope at the construction location is less than the slope threshold, direct mixing construction shall be used;

[0013] S3.2: If the slope of the rock formation at the construction location is greater than the slope threshold, the horizontal cantilever reinforcement mixing construction method is adopted. The horizontal cantilever reinforcement mixing construction method refers to: using the variable diameter drill bit mechanism in the drilling rig system to penetrate into the rock formation surface and drill to form a conical hole on the rock formation surface, the variable diameter drill bit mechanism has a telescopic drill bit, and the telescopic drill bit points to one side of the rock mass to perform oblique drilling to form a hole to further form a horizontal cantilever on the basis of the conical hole; then the variable diameter drill bit mechanism is lifted, and the four-axis DCM drill bit in the drilling rig system is used to perform downward mixing construction and grouting to form a mixing pile group.

[0014] The main body of the DCM engineering vessel is the flatbed barge, the cement silo system and the mixing and slurry storage system are interconnected and arranged on the flatbed barge, and the drilling rig system includes the variable-diameter drill bit mechanism, the four-axis DCM drill bit and a rotating frame. The rotating frame is arranged in a horizontal state and is rotatably connected to the front of the flatbed barge; the rotating frame is fan-shaped, and the variable-diameter drill bit mechanism and the four-axis DCM drill bit are vertically arranged at the front of the rotating frame.

[0015] A set of arc tracks is provided at the front of the flat barge, the front of the rotating frame is assembled on the arc tracks via running wheels, the rear of the rotating frame is fixed to the flat barge via a rotating shaft, and the running wheels are driven by a motor fixed under the rotating frame.

[0016] The variable diameter drill bit mechanism includes a first column bracket, a first pull rod, a first guide rail, a first slider, a first steel suspension beam, a first rotating motor, a first drill rod and a variable diameter drill bit. The first column bracket is vertically arranged at the front of the rotating frame. The upper end of the first pull rod is hinged to the upper end of the first column bracket, and the lower end is hinged to the rotating frame. The first guide rail is vertically arranged along the first column bracket and tightly fixed to each other. The first slider is slidably assembled on the first guide rail. The first steel suspension beam is fixed on the first slider and moves vertically with the first slider. The first rotating motor is fixed on the first steel suspension beam and drives the first drill rod to rotate. The variable diameter drill bit is arranged at the first drill The lower end of the rod, the variable diameter drill bit includes a drill bit, two long reamers and two hydraulic telescopic rods, the drill bit is arranged at the lower end of the first drill rod, the upper end of the long reamers is hinged to the first drill rod, and the hydraulic telescopic rod is arranged between the lower end of the long reamers and the first drill rod, and the hydraulic telescopic rod is used to drive the lower part of the long reamers to gradually expand outward to ream the rock formation to form the conical hole; and a telescopic drill bit is arranged in the groove on the long reamer, and the telescopic drill bit includes a hydraulic telescopic oil cylinder, a waterproof motor and a cantilever drill rod, and the hydraulic telescopic oil cylinder drives the waterproof motor and the cantilever drill rod to telescope back and forth in the groove to complete the operation of the horizontal cantilever.

[0017] The four-axis DCM drill bit includes a second column bracket, a second pull rod, a second guide rail, a second slider, a second steel suspension beam, several second rotating motors and several second drill rods. The second column bracket is vertically arranged at the front of the rotating frame. The upper end of the second pull rod is hinged to the upper end of the second column bracket and the lower end is hinged to the rotating frame. The second guide rail is vertically arranged along the second column bracket and fixed tightly to each other. The second slider is slidably assembled on the second guide rail. The second steel suspension beam is fixed on the second slider and moves vertically with the second slider. Each second rotating motor is fixed on the second steel suspension beam and drives the corresponding second drill rod to rotate respectively; a grouting pipeline is provided in the second drill rod, and the mixing and slurry storage system is rotatably connected to the upper end of the second drill rod through the grouting pipeline and pumps concrete slurry into the grouting pipeline in the second drill rod; a slurry outlet is provided on the drill bit of the second drill rod.

[0018] The horizontal cantilever reinforcement mixing construction includes the following steps:

[0019] The traveling wheel on the rotating frame is controlled to move along the arc track, so that the variable diameter drill bit mechanism on the rotating frame rotates with the rotating frame to a position to be constructed, so that the first drill rod is lowered to the surface of the rock formation, and then the drill bit of the variable diameter drill bit is controlled to drill into the rock formation. At the same time, the lower part of the elongated reamer is gradually lifted outward by the hydraulic telescopic rod to expand it outward until the drill bit drills to a predetermined depth. Thereafter, the elongated reamer is retracted inward by the hydraulic telescopic rod, and the first drill rod is lifted up to obtain the tapered hole. Thereafter, the telescopic drill bit in the groove of the elongated reamer is controlled to extend forward to drill and dig, so as to perform the horizontal cantilever operation.

[0020] The traveling wheels on the rotating frame are controlled to move along the arc track so that the four-axis DCM drill bit on the rotating frame rotates with the rotating frame to the position to be constructed, the second drill rod is controlled to drill down to the surface of the silt layer, and then the reamer blades on the second drill rod are opened and the drill is rotated to drill down. The drill bit on the second drill rod drills through the silt layer and the clay layer in sequence and reaches the conical hole in the rock layer. The drill bit on the second drill rod performs grouting to fill the conical hole and the horizontal cantilever to form a mixing pile located in the conical hole; then, several drillings and liftings are performed in the clay layer and grouting is performed to form a mixing pile in the clay layer; the drill bit on the second drill rod is continued to be lifted and grouting is continued to be performed to form a mixing pile located in the silt layer.

[0021] The direct mixing construction method includes the following steps: controlling the traveling wheels on the rotating frame to move along the arc track so that the four-axis DCM drill bit on the rotating frame rotates with the rotating frame to a position to be constructed, controlling the second drill rod to drill down to the surface of the silt layer, then starting the reamer blades on the second drill rod and rotating to drill, the drill bit on the second drill rod drills down through the silt layer and the clay layer in sequence to reach the surface of the rock layer, then drilling and lifting in the clay layer several times and performing grouting to form a mixing pile in the clay layer; continuing to lift the drill bit on the second drill rod and continuously performing grouting to form a mixing pile located in the silt layer.

[0022] The pile construction method in the clay layer comprises the following steps:

[0023] The drill bit on the second drill pipe drills 1 meter to the rock surface. During this stage, the grouting is at 1120 L / min, the drilling speed is 0.8 m / min, and the rotation speed is 30-36 rpm.

[0024] The drill bit on the second drill pipe was raised 4.1 m to the interface between the clay layer and the silt layer. During this stage, the upper shotcrete was 820 L / min, the lifting speed was 1 m / min, and the rotation speed was 30-36 rpm;

[0025] The drill bit on the second drill pipe drilled 3.5m. During this stage, the grouting was sprayed at 1120L / min, the drilling speed was 0.8m / min, and the rotation speed was 30-36rpm.

[0026] The drill bit on the second drill pipe drills 0.6m to the rock surface. During this stage, water injection and slurry squeezing are carried out at a speed of 1120L / min, a drilling speed of 0.8m / min, and a rotation speed of 30-36rpm.

[0027] The drill bit on the second drill rod is lifted for 1 m and then drilled down for 1 m, then lifted for another 1 m and then raised for 1 m. During this stage, the grouting is stopped, and the drilling and raising speed is 0.8 m / min, with a rotation speed of 30-36 rpm.

[0028] The advantages of the present invention are: high degree of intelligence and automation, adaptability to different seabed rock formations, good soil mixing effect, high construction efficiency, and ability to achieve ultra-deep reinforcement; by further constructing a horizontal cantilever on the basis of the conical hole, a stable connection with the steep rock formation is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A vertical cross-sectional view of the seabed topography distribution in the area to be reinforced in the present invention;

[0030] Figure 2 This is a schematic structural diagram of the DCM engineering ship of the present invention;

[0031] Figure 3 This is a plan view of the rotating frame on the DCM engineering ship of the present invention;

[0032] Figure 4 Schematic diagram of the variable diameter drill bit mechanism of the present invention;

[0033] Figure 5 Schematic diagram of the structure of the four-axis DCM drill bit of the present invention;

[0034] Figure 6 Schematic diagram of a mixing pile formed by direct mixing construction and a mixing pile formed by composite reinforcement mixing construction in the present invention;

[0035] Figure 7 This is a schematic diagram of the control during direct mixing construction in the present invention;

[0036] Figure 8 Detailed structural diagram of the variable diameter drill bit of the present invention;

[0037] Figure 9 For the present invention Figure 8 A-direction view in. DETAILED DESCRIPTION

[0038] The features of the present invention and other related features are further described in detail below through embodiments in conjunction with the accompanying drawings to facilitate understanding by those skilled in the art:

[0039] like Figure 1-9 , the symbols in the figure are: flat barge 1, cement silo system 2, mixing and storage system 3, slurry pump system 4, rotating shaft 5, rotating frame 6, traveling wheel 7, curved track 8, variable diameter drill mechanism 9, four-axis DCM drill bit 10, mixing pile 11, mixing pile 12, tapered hole 13, horizontal cantilever 14, hydraulic telescopic cylinder 15, waterproof motor 16, channel 17, cantilever drill rod 18;

[0040] First column support 901, first pull rod 902, first guide rail 903, first slide block 904, first steel suspension beam 905, first rotary motor 906, first drill rod 907, long strip reamer 908, hydraulic telescopic rod 909, and variable diameter drill bit 910;

[0041] The second column bracket 1001, the second pull rod 1002, the second guide rail 1003, the second slider 1004, the second steel suspension beam 1005, the second rotating motor 1006, the second drill rod 1007, the reamer blade 1008, and the drill bit 1009.

[0042] Example: Figure 1-9 As shown, this embodiment specifically relates to a DCM construction method for offshore deep cement-soil mixing piles with horizontal cantilevers, and the DCM construction method includes the following steps:

[0043] (S1) Figure 1 As shown, geological exploration is conducted on the seabed surface of the area to be reinforced to obtain the stratigraphic distribution data of the seabed surface. The seabed surface is composed of rock layers, clay layers and silt layers from bottom to top. In addition to the composition of each layer, the stratigraphic distribution data also includes the thickness of each layer and the elevation change of the upper surface of the rock layer. The elevation change of the upper surface of the rock layer will also reflect the slope of the upper surface of the rock layer from another angle.

[0044] (S2) Figure 2 As shown, the DCM engineering vessel is driven to the predetermined location, i.e., the location where the mixing pile 11 or the mixing pile 12 is to be installed. The DCM engineering vessel comprises a flat barge 1 and a cement silo system 2, a mixing slurry storage system 3, a slurry pump system 4, and a drilling rig system sequentially arranged and connected on the flat barge 1.

[0045] The main body of the DCM engineering ship is a flat barge 1. The cement silo system 2 and the mixing and slurry storage system 3 are connected to each other and are arranged on the flat barge 1. The drilling system includes a variable diameter drill bit mechanism 9, a four-axis DCM drill bit 10 and a rotating frame 6. Figure 3As shown, the rotating frame 6 is arranged in a horizontal state and is rotatably connected to the front of the flat barge 1; the rotating frame 6 is fan-shaped, and a variable diameter drill bit mechanism 9 and a four-axis DCM drill bit 10 are vertically arranged at the front of the rotating frame 6.

[0046] A set of curved tracks 8 is installed at the front of the flatbed barge 1. The front portion of the rotating frame 6 is mounted on the curved tracks 8 via running wheels 7. Furthermore, the rear portion of the rotating frame 6 is fixed to the flatbed barge 1 via a rotating shaft 5. The running wheels 7 are driven by a motor fixed below the rotating frame 6 (the motor is not shown in the figure, as it is a conventional drive). This arrangement of curved tracks 8, running wheels 7, and rotating shaft 5 allows for rotation within a certain range of angles. This allows the variable-diameter drill mechanism 9 and the four-axis DCM drill 10 to be adjusted in position without the flatbed barge 1 moving or turning.

[0047] like Figure 4 、 8 As shown in Figure 9, the variable diameter drill bit mechanism 9 includes a first column bracket 901, a first pull rod 902, a first guide rail 903, a first slider 904, a first steel suspension beam 905, a first rotary motor 906, a first drill rod 907 and a variable diameter drill bit 910. The first column bracket 901 is vertically fixed to the front of the rotating frame 6. The upper end of the first pull rod 902 is hinged to the upper end of the first column bracket 901, and the lower end is hinged to the rotating frame 6. The first guide rail 903 is vertically arranged along the first column bracket 901 and tightly fixed to each other. The first slider 904 is slidably assembled on the first guide rail 903. The lifting drive mode of the first slider 904 can be driven by a combination of a fixed pulley and a cable. The first steel suspension beam 905 is fixed to the first slider 904. And it moves vertically with the first slider 904. The first rotary motor 906 is fixed on the first steel suspension beam 905 and drives the first drill rod 907 to rotate. The variable diameter drill bit 910 is set at the lower end of the first drill rod 907. The variable diameter drill bit 910 includes a drill bit, two long strip reamers 908 and two hydraulic telescopic rods 909. The drill bit is set at the lower end of the drill rod 907. The upper end of the long strip reamers 908 is connected to the drill rod 907. A hydraulic telescopic rod 909 is set between the lower end of the long strip reamers 908 and the first drill rod 907. The hydraulic telescopic rod 909 and the long strip reamers 908 are connected in the form of a slider plus a hinge. The hydraulic telescopic rod 909 is used to drive the lower part of the long strip reamers 909 to gradually expand outward to ream and dig a tapered hole 13 on the rock formation. In addition, Figure 8 and 9As shown, a concave groove 17 is provided in the middle of the long strip reamer 908, and a telescopic drill bit is arranged in the groove 17. The telescopic drill bit includes a hydraulic telescopic cylinder 15, a waterproof motor 16 and a cantilever drill rod 18. The hydraulic telescopic cylinder 15 drives the waterproof motor 16 and the cantilever drill rod 18 to drill back and forth in the groove 17 to complete the operation of the horizontal cantilever 14. It should be noted that the horizontal cantilever 14 is not completely horizontal, but is in a tilted downward state.

[0048] like Figure 5 As shown, the four-axis DCM drill head 10 includes a second column bracket 1001, a second pull rod 1002, a second guide rail 1003, a second slider 1004, a second steel suspension beam 1005, four sets of second rotary motors 1006 and four second drill rods 1007. The second column bracket 1001 is vertically arranged in front of the rotating frame 6. The upper end of the second pull rod 1002 is hinged to the upper end of the second column bracket 1001 and the lower end is hinged to the rotating frame 6. The second guide rail 1003 is vertically arranged along the second column bracket 1001 and is tightly fixed to each other. The second slider 1004 is slidably assembled. On the second guide rail 1003, the second steel suspension beam 1005 is fixed on the second slider 1004 and moves vertically with the second slider 1004. Each second rotary motor 1006 is fixed on the second steel suspension beam 1005 and drives the corresponding second drill rod 1007 to rotate respectively; the second drill rod 1007 is provided with a grouting pipeline, and the mixing and slurry storage system is rotatably connected to the upper end of the second drill rod 1007 through the grouting pipeline and the slurry pump system 4 and pumps the cement slurry into the grouting pipeline in the second drill rod 1007; the drill bit 1009 of the second drill rod is provided with slurry holes, namely, an upper slurry hole and a lower slurry hole.

[0049] (S3) Determine a construction method for each cement-soil mixing pile based on the stratum distribution data and the design construction coordinates of each cement-soil mixing pile, wherein the construction method is one of direct mixing construction and horizontal cantilever reinforcement mixing construction.

[0050] S3.1: If the slope of the rock layer at the construction location is less than the slope threshold, direct mixing construction should be used. In short, if the rock layer surface slope is relatively gentle, direct mixing construction should be carried out. Specific methods include the following:

[0051] like Figure 6As shown, the traveling wheel 7 on the rotating frame 6 is controlled to move along the arc track 8 so that the four-axis DCM drill bit 10 on the rotating frame 6 rotates with the rotating frame 6 to the construction position, and the second drill rod 1007 is controlled to drill down to the surface of the silt layer. Then, the reamer blade 1008 on the second drill rod 1007 is opened and rotated to drill down. The drill bit 1009 on the second drill rod 1007 drills down through the silt layer and the clay layer in sequence and reaches the surface of the rock layer. Then, several drilling and lifting operations are performed in the clay layer and grouting is performed to form a mixing pile 11 in the clay layer; the drill bit 1009 on the second drill rod 1007 is continued to be lifted and grouting is continued to be performed to form a mixing pile 11 located in the silt layer.

[0052] like Figure 7 As shown, the control method of the drill bit 1009 of the second drill rod 1007 is as follows:

[0053] (1) The drill bit 1009 of the second drill pipe 1007 is drilled in the seawater above the silt layer without spraying, with a drilling speed of 0.2-2.0 m / min and a rotation speed of 17-24 rpm;

[0054] Drilling is performed in the silt layer without spraying, with a drilling speed of 0.2-1.5 m / min and a rotation speed of 12-30 rpm.

[0055] (2) The drill bit 1009 of the second drill rod 1007 drills down into the clay layer and sprays water until it meets the rock layer interface. The water spraying speed is 240-480 L / min, the drilling speed is 0.2-1.0 m / min, and the rotation speed is 12-30 rpm;

[0056] The drill bit 1009 of the second drill rod 1007 is lifted up by 1 m and sprayed downwards at a speed of 1120 L / min, a drilling speed of 0.8 m / min, and a rotation speed of 30-36 rpm.

[0057] The drill bit 1009 of the second drill rod 1007 drills 1 meter to the rock surface. During this stage, the grouting is sprayed at 1120 L / min, the drilling speed is 0.8 m / min, and the rotation speed is 30-36 rpm.

[0058] The drill bit 1009 of the second drill rod 1007 was raised 4.1 m to the interface between the clay layer and the silt layer. During this stage, the upper shotcrete was 820 L / min, the lifting speed was 1 m / min, and the rotation speed was 30-36 rpm.

[0059] The drill bit 1009 of the second drill rod 1007 drills 3.5 m. During this stage, the spraying speed is 1120 L / min, the drilling speed is 0.8 m / min, and the rotation speed is 30-36 rpm.

[0060] The drill bit 1009 of the second drill rod 1007 drills 0.6 m to the rock surface. During this stage, water injection and slurry squeezing are carried out at a speed of 1120 L / min, a drilling speed of 0.8 m / min, and a rotation speed of 30-36 rpm.

[0061] The drill bit 1009 of the second drill rod 1007 is lifted for 1 m and then drilled down for 1 m, then lifted for another 1 m and then continued to be lifted up for 1 m. During this stage, the grouting is stopped, and the drilling and lifting speed is 0.8 m / min, and the rotation speed is 30-36 rpm.

[0062] (3) The drill bit 1009 of the second drill rod 1007 is lifted up, and the upper and lower grouting are carried out at the same time. For details, please refer to the attached manual. Figure 7 The control parameters in .

[0063] S3.2: If the slope of the construction site is greater than the slope threshold, a composite reinforcement mixing method shall be used. In short, if the rock surface slope is steep, a horizontal cantilever reinforcement mixing method shall be used. The horizontal cantilever reinforcement mixing method is:

[0064] The traveling wheel 7 on the rotating frame 6 is controlled to move along the arc track 8, so that the variable diameter drill bit mechanism on the rotating frame 6 rotates with the rotating frame 6 to the construction position, so that the first drill rod 907 is lowered to the surface of the rock formation, and then the drill bit of the variable diameter drill bit 910 is controlled to drill into the rock formation. At the same time, the lower part of the long strip reamer 908 is gradually lifted outward by the hydraulic telescopic rod 909 to expand it outward until the drill bit drills to the predetermined depth; then the rotation is stopped and the drill bit is controlled to point to the high slope rock. The telescopic drill bit on the long strip reamer 908 on one side of the layer drills horizontally and obliquely downward, and the hydraulic telescopic cylinder 15 lifts the waterproof motor 16 and the cantilever drill rod 18 forward, so that the high-speed rotating drill bit drills into the rock formation, thereby forming the horizontal cantilever 14; after the drilling of the horizontal cantilever 14 is completed, the horizontal cantilever 14 is retracted inward and the long strip reamer 908 is retracted inward by the hydraulic telescopic rod 909, and the first drill rod 907 is lifted to obtain the tapered hole 13 and the horizontal cantilever 14;

[0065] The traveling wheels 7 on the rotating frame 6 are controlled to move along the arc track 8 so that the four-axis DCM drill bit 10 on the rotating frame 6 rotates with the rotating frame 6 to the construction position, and the second drill rod 1007 is controlled to drill down to the surface of the silt layer. Then, the reamer blade 1008 on the second drill rod 1007 is opened and rotated to drill. The drill bit 1009 on the second drill rod 1007 drills through the silt layer and the clay layer in sequence and reaches the tapered hole 13 in the rock layer. The drill bit 1009 on the second drill rod 1007 performs spraying and mixes with the broken rock mass to form a mixing pile 12 located in the tapered hole 13; then, several drilling and lifting operations are performed in the clay layer and spraying is performed to form the mixing pile 12 in the clay layer; the drill bit 1009 on the second drill rod 1007 is continued to be lifted and spraying is continued to form the mixing pile 12 located in the silt layer.

[0066] The beneficial effects of this embodiment are:

[0067] (1) High intelligence. The DCM pile construction control is implemented through the "DCM engineering vessel intelligent construction control system" and the "DCM engineering vessel construction positioning system". The system has various functions such as real-time monitoring, signal data acquisition, data analysis and summary and backup, and construction management. It can monitor construction parameters such as pile number, coordinates, pile length, and current in real time;

[0068] (2) High automation. The entire process from cement slurry material (cement, seawater) weighing and metering, production and mixing, storage, grouting and transportation, pile driver drill bit drilling, blade rotation, DCM pile bottom treatment, drill bit lifting, drill bit friction in the formation and drill bit flushing is completed automatically, reducing human operation errors and thus improving pile quality.

[0069] (3) High construction efficiency. Up to 12 Ø1300mm DCM piles can be constructed simultaneously, reducing the need for frequent machine moves and greatly improving operational efficiency.

[0070] (4) Good soil mixing effect. The mixing blades and the spray holes evenly arranged above and below the blades are configured. The mixing blades make the soil mixing more thorough, and the spray holes evenly arranged above and below allow the slurry to spread evenly in the mixing pile, better combining with the soil, and promoting uniform strength distribution of the mixing pile.

[0071] (5) Ultra-deep reinforcement. Equipped with a high-power four-axis DCM drilling rig and a stepless speed slurry pump. The drill rod can be extended to meet the needs of different construction depths. The slurry pump can adjust the flow and pressure of the slurry according to the requirements of the construction process to ensure construction quality.

Claims

1. A DCM construction method for offshore deep cement-soil mixing piles with horizontal cantilever, characterized in that The DCM construction method comprises the following steps: S1: Conducting geological exploration of the seabed in the area to be reinforced to obtain stratum distribution data of the seabed, wherein the seabed comprises, from bottom to top, rock layers, clay layers, and silt layers; S2: Driving the DCM engineering vessel to the predetermined location; the DCM engineering vessel includes a flat barge, a cement silo system, a mixing and storage slurry system, a slurry pump system, and a drilling rig system; S3: Determining a construction method for each cement-soil mixing pile based on the stratum distribution data and the design construction coordinates of each mixing pile, wherein the construction method is one of direct mixing construction and horizontal cantilever reinforcement mixing construction; S3.1: If the rock slope at the construction location is less than the slope threshold, direct mixing construction shall be used; S3.2: If the slope of the rock formation at the construction location is greater than the slope threshold, the horizontal cantilever reinforcement mixing construction method is adopted. The horizontal cantilever reinforcement mixing construction method refers to: using the variable diameter drill bit mechanism in the drilling rig system to penetrate into the rock formation surface and drill to form a conical hole on the rock formation surface, the variable diameter drill bit mechanism has a telescopic drill bit, and the telescopic drill bit points to one side of the rock mass to perform oblique drilling to form a hole to further form a horizontal cantilever on the basis of the conical hole; then the variable diameter drill bit mechanism is lifted, and the four-axis DCM drill bit in the drilling rig system is used to perform downward mixing construction and grouting to form a mixing pile group.

2. The DCM construction method of a deep-seated cement-soil mixing pile with a horizontal cantilever according to claim 1, characterized in that The main body of the DCM engineering vessel is the flatbed barge, the cement silo system and the mixing and slurry storage system are interconnected and arranged on the flatbed barge, and the drilling rig system includes the variable-diameter drill bit mechanism, the four-axis DCM drill bit and a rotating frame. The rotating frame is arranged in a horizontal state and is rotatably connected to the front of the flatbed barge; the rotating frame is fan-shaped, and the variable-diameter drill bit mechanism and the four-axis DCM drill bit are vertically arranged at the front of the rotating frame.

3. The DCM construction method of a deep-seated cement-soil mixing pile with a horizontal cantilever according to claim 2, characterized in that A set of arc tracks is provided at the front of the flat barge, the front of the rotating frame is assembled on the arc tracks via running wheels, the rear of the rotating frame is fixed to the flat barge via a rotating shaft, and the running wheels are driven by a motor fixed under the rotating frame.

4. The DCM construction method of a deep-seated cement-soil mixing pile with a horizontal cantilever according to claim 3, characterized in that The variable diameter drill bit mechanism includes a first column bracket, a first pull rod, a first guide rail, a first slider, a first steel suspension beam, a first rotating motor, a first drill rod and a variable diameter drill bit. The first column bracket is vertically arranged at the front of the rotating frame. The upper end of the first pull rod is hinged to the upper end of the first column bracket, and the lower end is hinged to the rotating frame. The first guide rail is vertically arranged along the first column bracket and tightly fixed to each other. The first slider is slidably assembled on the first guide rail. The first steel suspension beam is fixed on the first slider and moves vertically with the first slider. The first rotating motor is fixed on the first steel suspension beam and drives the first drill rod to rotate. The variable diameter drill bit is arranged at the first drill The lower end of the rod, the variable diameter drill bit includes a drill bit, two long reamers and two hydraulic telescopic rods, the drill bit is arranged at the lower end of the first drill rod, the upper end of the long reamers is hinged to the first drill rod, and the hydraulic telescopic rod is arranged between the lower end of the long reamers and the first drill rod, and the hydraulic telescopic rod is used to drive the lower part of the long reamers to gradually expand outward to ream the rock formation to form the conical hole; and a telescopic drill bit is arranged in the groove on the long reamer, and the telescopic drill bit includes a hydraulic telescopic oil cylinder, a waterproof motor and a cantilever drill rod, and the hydraulic telescopic oil cylinder drives the waterproof motor and the cantilever drill rod to telescope back and forth in the groove to complete the operation of the horizontal cantilever.

5. The DCM construction method of a deep-seated cement-soil mixing pile with a horizontal cantilever according to claim 4, characterized in that The four-axis DCM drill bit includes a second column bracket, a second pull rod, a second guide rail, a second slider, a second steel suspension beam, several second rotating motors and several second drill rods. The second column bracket is vertically arranged at the front of the rotating frame. The upper end of the second pull rod is hinged to the upper end of the second column bracket and the lower end is hinged to the rotating frame. The second guide rail is vertically arranged along the second column bracket and fixed tightly to each other. The second slider is slidably assembled on the second guide rail. The second steel suspension beam is fixed on the second slider and moves vertically with the second slider. Each second rotating motor is fixed on the second steel suspension beam and drives the corresponding second drill rod to rotate respectively; a grouting pipeline is provided in the second drill rod, and the mixing and slurry storage system is rotatably connected to the upper end of the second drill rod through the grouting pipeline and pumps concrete slurry into the grouting pipeline in the second drill rod; a slurry outlet is provided on the drill bit of the second drill rod.

6. The DCM construction method of a deep-seated cement-soil mixing pile with a horizontal cantilever according to claim 5, characterized in that The horizontal cantilever reinforcement mixing construction includes the following steps: The traveling wheel on the rotating frame is controlled to move along the arc track, so that the variable diameter drill bit mechanism on the rotating frame rotates with the rotating frame to a position to be constructed, so that the first drill rod is lowered to the surface of the rock formation, and then the drill bit of the variable diameter drill bit is controlled to drill into the rock formation. At the same time, the lower part of the elongated reamer is gradually lifted outward by the hydraulic telescopic rod to expand it outward until the drill bit drills to a predetermined depth. Thereafter, the elongated reamer is retracted inward by the hydraulic telescopic rod, and the first drill rod is lifted up to obtain the tapered hole. Thereafter, the telescopic drill bit in the groove of the elongated reamer is controlled to extend forward to drill and dig, so as to perform the horizontal cantilever operation. Controlling the traveling wheels on the rotating frame to move along the arc track so that the four-axis DCM drill bit on the rotating frame rotates with the rotating frame to a position to be constructed, controlling the second drill rod to penetrate to the surface of the silt layer, then opening the reamer blades on the second drill rod and rotating the drill, the drill bit on the second drill rod sequentially drilling through the silt layer and the clay layer to reach the tapered hole in the rock formation, and the drill bit on the second drill rod spraying grout to fill the tapered hole and the horizontal cantilever to form a mixing pile located in the tapered hole; Then, drilling and lifting are performed several times in the clay layer and grouting is performed to form a mixing pile in the clay layer; the drill bit on the second drill rod is continuously lifted and grouting is continuously performed to form a mixing pile located in the silt layer.

7. The DCM construction method of a deep-seated cement-soil mixing pile with a horizontal cantilever according to claim 5, characterized in that The direct mixing construction method includes the following steps: controlling the traveling wheels on the rotating frame to move along the arc track so that the four-axis DCM drill bit on the rotating frame rotates with the rotating frame to a position to be constructed, controlling the second drill rod to drill down to the surface of the silt layer, then starting the reamer blades on the second drill rod and rotating to drill, the drill bit on the second drill rod drills down through the silt layer and the clay layer in sequence to reach the surface of the rock layer, then drilling and lifting in the clay layer several times and performing grouting to form a mixing pile in the clay layer; continuing to lift the drill bit on the second drill rod and continuously performing grouting to form a mixing pile located in the silt layer.

8. The DCM construction method of a deep-seated cement-soil mixing pile with a horizontal cantilever according to claim 7, characterized in that The pile construction method in the clay layer comprises the following steps: The drill bit on the second drill pipe drills 1 meter to the rock surface. During this stage, the grouting is at 1120 L / min, the drilling speed is 0.8 m / min, and the rotation speed is 30-36 rpm. The drill bit on the second drill pipe was raised 4.1 m to the interface between the clay layer and the silt layer. During this stage, the upper shotcrete was 820 L / min, the lifting speed was 1 m / min, and the rotation speed was 30-36 rpm; The drill bit on the second drill pipe drilled 3.5m. During this stage, the grouting was sprayed at 1120L / min, the drilling speed was 0.8m / min, and the rotation speed was 30-36rpm. The drill bit on the second drill pipe drills 0.6m to the rock surface. During this stage, water injection and slurry squeezing are carried out at a speed of 1120L / min, a drilling speed of 0.8m / min, and a rotation speed of 30-36rpm. The drill bit on the second drill rod is lifted for 1 m and then drilled down for 1 m, then lifted for another 1 m and then raised for 1 m. During this stage, the grouting is stopped, and the drilling and raising speed is 0.8 m / min, with a rotation speed of 30-36 rpm.

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