Working platform for rotary drilling rig on soft soil foundation and using method thereof

Abstract

The present invention discloses an operating platform for a rotary drilling rig in a soft soil area and a method for using the same. The platform comprises three parts, namely a cushion foundation, a clay protection embankment and a rigid roadbed. The rigid roadbed adopts a prefabricated assembled concrete component, which is connected into a whole by a PBL key-type double-hinged connecting plate. A built-in guide pipe is buried in the component, and angle steel is provided to reinforce the edge of the component. The rigid roadbed is placed on the cushion foundation, and a clay protection embankment is provided around the rigid roadbed to form a temporary mud storage area with the rigid roadbed. The rigid roadbed effectively distributes the weight of the rotary drilling rig to the soft foundation, so that the bottom stress meets the bearing capacity requirements of the soft stratum, and at the same time alleviates the overall settlement of the operating platform; the built-in guide pipe and the temporary mud pool constitute a mud circulation system, which can effectively deal with the repeated overflow and backflow of mud in the rotary drilling process. The present invention has very significant economic and social benefits in municipal engineering in soft soil areas.

Description

Technical Field

[0001] The invention relates to the technical field of engineering construction, and in particular to a working platform for a rotary drilling rig on a soft soil foundation and a use method thereof. Background Art

[0002] With the increasing urbanization in my country, the urban population size has steadily increased, and urban expressways have become an important means to solve urban traffic congestion. Common urban expressways in China all adopt "ground road + main line elevated road", that is, the pedestal of the main line elevated road is located in the central dividing strip of the ground road. Usually, the construction scale of urban expressways is large, the number of bored piles is large, and the construction period is long. When the pile foundation involves embedded rock layers, gravel layers or pebble layers, the rotary drilling process has a higher economic advantage.

[0003] The rotary drilling rig required for the rotary drilling process is very heavy. The rotary drilling rigs widely used in the market are usually around 100 tons to 150 tons. The average stress of the crawler base exceeds 100kPa, which puts forward higher requirements on the work site:

[0004] For the expressway reconstruction project of existing roads, the rotary drilling rig can use the original road as the working platform;

[0005] For new construction projects in farmland areas, rotary drilling rigs cannot operate directly because the farmland surface soil has a high organic matter content (mainly peat soil and silty clay) and the foundation bearing capacity is weak.

[0006] In order to meet the operating requirements of a rotary drilling rig on soft foundation, a working platform is proposed. Summary of the invention

[0007] The main purpose of the present invention is to provide a solution of a working platform for a rotary drilling rig on a soft soil foundation and a method of using the same in order to solve the above-mentioned problems.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is: a working platform for a rotary drilling rig on a soft soil foundation, comprising a cushion foundation, a clay embankment and a rigid roadbed plate, characterized in that: the cushion foundation is located at the lowest part, the rigid roadbed plate is placed above the cushion foundation, the three sides of the rigid roadbed plate are surrounded by clay embankments, and the last side of the rigid roadbed plate coincides with a temporary construction passage; the clay embankments and the rigid roadbed plate on the three sides are provided with mud storage areas for storing mud, the rigid roadbed plate is composed of concrete components spliced ​​together, the concrete components are provided with PBL key-type double-hinged connecting plates at the splicing locations, the concrete components are provided with rigid roadbed plate joints at the splicing locations, the concrete components are provided with drilling holes, and the concrete components are provided with built-in guide pipes connected to the drilling holes.

[0009] The concrete component is provided with upper and lower layers of steel mesh, and two built-in guide pipes are provided in the long side direction of the concrete component; a single built-in guide pipe is provided in the short side direction of the concrete component, and the built-in guide pipe is located between the upper and lower layers of steel mesh.

[0010] The PBL key-type double-hinged connecting plate is provided with a connecting steel plate, and the connecting steel plate is provided with an anchor hole and a connecting hole. The anchor hole is arranged on the connecting steel plate on the inner side of the concrete member, and one anchor hole is arranged in the thickness direction of the concrete member. The connecting hole is arranged on the connecting steel plate on the outer side of the concrete member, and two connecting holes are arranged in the thickness direction of the concrete member.

[0011] At least three anchor holes are provided in the length direction of the concrete component, a connecting hole is provided in the length direction of the concrete component, an anchor steel bar fixed inside the concrete component is provided in the anchor hole, and a connecting steel bar located in the joint of the rigid roadbed is provided in the connecting hole. The connecting steel bar is used as a part to resist shear force.

[0012] The distance between each pair of the PBL key-type double-hinged connecting plates is not less than 0.8m and not more than 1.2m. This distance is the most suitable distance between one end of the shear-resistant parts. It is not necessary to assemble too many PBL key-type double-hinged connecting plates, and the shear-resistant effect of the connecting steel bars can be guaranteed. The spacing of the joints of the rigid roadbed plate is 10 to 20cm. This distance is for the convenience of installing the connecting steel bars and also for preventing the rigid roadbed plate from having obvious uneven settlement.

[0013] A PVC tube is installed in the built-in guide pipe, one end of which is connected to the drill hole, and the other end is connected to the mud storage area or the rigid roadbed joint. Closed stirrups are arranged around the built-in guide pipe, and the diameter of the closed stirrups is not less than 12 mm.

[0014] The upper and lower planes of the concrete member are both provided with hemming angle steels, and vertical reinforcing ribs and transverse reinforcing ribs are arranged at intervals along the length direction of the hemming angle steels. The vertical reinforcing ribs are arranged along the height direction of the concrete member, adopt a semi-circular structure, and connect the hemming angle steels of the upper and lower planes; the transverse reinforcing ribs are arranged along the plane direction of the concrete member, adopt an L-shaped structure, and are respectively welded to the upper and lower layers of steel mesh in their respective planes.

[0015] The cushion foundation is made of materials with low moisture content and low void ratio, and the thickness of the cushion foundation is 20 to 30 cm.

[0016] The clay embankment is made of low-permeability material and is in the shape of an earth dam. The height of the clay embankment is consistent with the height of the rigid roadbed. The volume of the mud storage area is at least 1.5 times the peak value of the mud overflow.

[0017] The method of use includes a use phase and a transition splicing phase;

[0018] The use phase includes the following steps:

[0019] Use the work platform to drill holes. When the drill bit of the drilling rig is placed in the drilling hole, the mud overflows through the built-in guide pipe to the mud storage area between the clay embankment and the rigid roadbed due to the occupation of the drill bucket and the drill rod. When the drill bit is lifted, the mud level in the drilling hole drops due to the removal of some of the drilled earth and the withdrawal of the drill bucket and the drill rod. At this time, the mud in the temporary mud storage area is replenished to the drilling hole through the built-in guide pipe. According to the principle of the communicating vessel, the mud level in the drilling hole is maintained close to the mud level in the mud storage area.

[0020] In order to make the rigid roadbed plate settle evenly as a whole, the drilling sequence of the rotary drilling rig must follow the principle of symmetrical operation, and drill in the order of edge first, then center, and midpoint first, then corner point;

[0021] The transition splicing stage includes the following steps:

[0022] A cushion foundation with a thickness of 20-30cm is built on the new working platform; the PBL key double hinge connection plate of the rigid roadbed of the previous pedestal is removed. When the PBL key double hinge connection plate is locked due to uneven settlement of the rigid roadbed, the steel bars of the PBL key double hinge connection plate are cut off with acetylene flame and then taken out; the concrete components of the rigid roadbed before the transfer are numbered, and the same pair of connection plates are given the same number based on the PBL key double hinge connection plate; a 70T truck crane is used to transfer each concrete component to another pedestal area in order; the same pair of connection plates are connected with steel bars, and each connection hole on each connection plate needs to be locked with shear steel bars; a clay embankment is set outside the rigid roadbed, and it enters the use stage again after completion. .

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] The rigid roadbed effectively distributes the weight of the rotary drilling rig to the soft foundation, so that the bottom stress meets the bearing capacity requirements of the soft stratum, and at the same time alleviates the overall settlement of the working platform; the built-in guide pipe and the temporary mud pool constitute a mud circulation system. If the mud is not replenished in time, the mud level at the hole mouth will drop sharply, causing the earthwork at the bottom of the casing to collapse (the bottom of the pit will rise and become unstable, as shown). The collapse of the hole top wall will cause the original ground to sink, accompanied by a sharp decline in the bearing capacity of the original ground foundation, the rotary drilling rig's stable operating platform will be lost, and the drilling rig will face the risk of overturning. This working platform can effectively avoid this danger, and at the same time can effectively deal with the repeated overflow and backflow of mud in the rotary drilling process, keeping the construction environment clean. The use of PBL keys instead of bolts effectively solves the problem of the rigid roadbed being stuck when the connecting parts sink unevenly. When a 70T truck crane is used, concrete components with lower costs are selected as the splicing parts and the manufacturing process of the concrete components is simpler. Therefore, the present invention has very significant economic and social benefits in municipal engineering in soft soil areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a top view of a working platform for a rotary drilling rig on soft soil;

[0026] Figure 2 It is a front view of a working platform for a rotary drilling rig on soft soil;

[0027] Figure 3 It is a working sequence diagram of a pile drilling rig with a working platform for a rotary drilling rig on a soft soil foundation;

[0028] Figure 4 yes Figure 1 AA section view;

[0029] Figure 5 yes Figure 1 BB section view;

[0030] Figure 6 yes Figure 3 A local C-direction view of

[0031] Figure 7 yes Figure 1 DD section view;

[0032] Figure 8 yes Figure 1 An enlarged view of a part E;

[0033] Fig. 9 It is a simple schematic diagram of the earth collapse at the bottom of the casing;

[0034] Fig.10 It is a schematic diagram of the flow direction of the mud liquid surface when the drilling rig moves downward;

[0035] Fig.11 It is a schematic diagram of the flow direction of the mud liquid surface when the drilling rig moves downward.

[0036] The names corresponding to the various figure marks are: cushion foundation 1; clay protection embankment 2; mud storage area 21; rigid roadbed plate 3; concrete component 31; rigid roadbed plate joint 32; PBL key double-hinged connecting plate 33; connecting steel plate 330; anchor hole 331; connecting hole 332; anchor steel bar 333; connecting steel bar 334; drilling hole position 34; built-in guide pipe 35; steel mesh 4; closed stirrups 43; temporary construction passage 5; edge angle steel 6; transverse reinforcement 61; vertical reinforcement 62; bottom surface elevation a; normal water head b; water head after raising the drill bit c; casing d; water penetration and earthwork trend f; drilling rig head movement direction 8; mud movement direction 9. DETAILED DESCRIPTION

[0037] The following description is used to disclose the specific content of the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0038] The embodiment of the present invention is a work platform for a rotary drilling rig on a soft soil foundation. To achieve the above purpose, the product mainly includes a cushion foundation 1, a clay protection embankment 2 and a rigid roadbed 3.

[0039] 1. Rigid road base

[0040] 1.1.1. Use concrete structure

[0041] The rigid roadbed plate 3 for rotary drilling rigs on soft soil foundations must have a certain thickness to meet the requirements of the soft foundation, and the thickness is preferably 30cm±5cm. On the one hand, if the thickness is too small, it is not enough to diffuse the stress of the rotary drilling rig crawler base of more than 100kPa to the soft foundation (otherwise the roadbed plate itself will bear a large internal force, greatly increasing material consumption); on the other hand, if the thickness is too large, the weight of the rigid roadbed plate 3 itself will be greatly increased, and the manufacturing cost and use cost will increase significantly, which will reduce the competitive advantage of the rigid roadbed plate solution and restrict the promotion of the rigid roadbed plate.

[0042] The structural forms of the rigid roadbed 1 can be mainly divided into three types: ① pure steel structure; ② steel-concrete composite structure; ③ concrete structure.

[0043] For the pure steel structure, in order to adapt to the concentrated load and fatigue effect on the surface of the rotary drilling rig crawler, the thickness of the steel plate should not be less than 20mm, and the overall steel consumption of the rigid roadbed is about 600kg / m2. Taking the 9-pile cap commonly used in municipal engineering as an example, the weight of a single pile is about 64.8 tons;

[0044] For the steel-concrete composite structure, the upper and lower layers are made of concrete slabs, and the middle layer is made of steel skeleton. The steel consumption can be reduced to 400kg / m2, and the weight of the 9-pile cap is about 71.3 tons.

[0045] For the concrete structure scheme, a two-way steel mesh is used, and the steel bar arrangement should be implemented in the mode of "small diameter, low spacing" (diameter should be φ12@120mm). The reinforcement ratio of a single layer of one-way steel bars is not less than 0.3% to meet the requirements of the specification. The steel consumption of the concrete structure scheme is about 200kg / m2, and the total weight is about 84.2 tons.

[0046] In addition, in the steel-concrete composite structure scheme, shear connectors need to be installed between the concrete slab and the steel frame, which has high manufacturing costs; the cutting and welding of the steel structure is large and the manufacturing difficulty is also not small; the concrete structure scheme has conventional processes and low manufacturing difficulty.

[0047] In terms of usage, the weight of the three schemes for the 9-pile cap is not much different (the total hoisting weight of the pure steel structure scheme is 77% of the concrete structure), and special measures are required to handle them.

[0048] project Pure steel structure solution Steel-concrete composite structure solution Concrete structure scheme Steel quantity (including steel bars) 600kg / m2 400kg / m2 200kg / m2 Overall weight (taking 9 pile caps as an example) 64.8 71.3 84.2 Manufacturing Difficulty Larger big Small

[0049] To sum up, the working platform adopts concrete structure.

[0050] 1.1.2. Use prefabricated assembled components

[0051] The rigid roadbed of the precast concrete component 31 is heavy, and has high requirements for on-site lifting machinery. Common truck cranes on construction sites are 25T and 70T. Among them, the rated lifting weight of a 70T truck crane at an operating radius of 12m is 12 tons. Therefore, the rigid roadbed of the precast concrete component 31 needs to be an assembled component, and the maximum weight of a single component does not exceed 12 tons.

[0052] 1.1.3. Use PBL key-type double-hinged connection plate

[0053] The plates of the precast concrete component 31 are connected by PBL key-type double-hinged connecting plates 33. Each pair of PBL key-type double-hinged connecting plates 33 includes two connecting steel plates 330, anchoring steel bars 333 in anchor holes 331, four connecting holes 332 and two connecting steel bars 334 inserted in the connecting holes for resisting shear force. It has the following characteristics:

[0054] 1) The connecting steel plate 330 of the PBL key-type double-hinged connecting plate 33 is divided into two types: anchor holes 331 and connecting holes 332. The anchor hole 331 is arranged on the connecting steel plate 330 on the inner side of the concrete member 31, and one is arranged along the thickness direction of the concrete member 31; the connecting holes 332 are arranged on the connecting steel plate 330 on the outer side of the concrete member 31, and two are arranged along the thickness direction of the concrete member 31;

[0055] 2) The anchor hole 331 is a typical PBL key structure. An anchor steel bar 333 fixed to the inner side of the concrete member 31 is inserted into the anchor hole 331. The diameter, spacing and diameter of the inner steel bar must meet the requirements of national standards. The shear bearing capacity of a single hole is not less than 20 tons. The number of anchor steel bars along the length direction of the concrete member 31 is not less than 3.

[0056] 3) The connection hole 332 is a typical double-hinged structure, that is, two holes are set along the thickness direction of the concrete member 31, and the connecting steel bars 334 are inserted inside as lateral shear members. This structure can bear vertical shear force, axial tension / compression and bending moment in the plane. The diameter and spacing of the connection hole 332 must meet the requirements of the "Steel Structure Design Code", and the diameter shall not exceed 30mm;

[0057] 4) The two connected prefabricated concrete components 31 are kept at a certain distance (preferably 10-20cm), and are connected in the middle by connecting steel bars 334 with a diameter of 20mm (the diameter can be less than 30mm), and the shear bearing capacity of a single hole should not be less than 15 tons; if the distance between the concrete components 31 is too small or even close, the temporary installation error on site is easy to cause the connection hole 332 to be misaligned. At this time, the connecting steel bar 334 can be inserted at a certain angle to facilitate the insertion of the connecting steel bar 334 into the connection hole 332; if bolt connection is adopted: when the connection hole 332 is within the misalignment error, only the diameter specification of the bolt that passes through the connection hole 332 can be reduced, thereby reducing the bearing capacity of the connection piece; and when the concrete component 31 on the rigid roadbed plate 3 has uneven settlement and causes the connection piece to be locked, even if the steel bar is cut off by acetylene flame, the bolt at the threaded connection is not easy to remove and the thread will be damaged, so it is not suitable to use bolt connection between the connection plates;

[0058] 5) The thickness of the connecting steel plate 330 shall not be less than 2cm to ensure its bearing capacity and rigidity requirements;

[0059] 6) The distance between two adjacent PBL key-type double-hinged connecting plates 33 shall not be less than 0.8m (needed for on-site steel bar insertion) and not more than 1.2m (needed for overall force bearing of concrete components);

[0060] 7) The gap between the prefabricated concrete components 31 is about 10 to 20 cm. If the gap is too small, there is insufficient space for the connecting steel bars 334 between the connecting plates to pass through; if the gap is too large, the integrity of the rigid roadbed plate 3 is reduced and uneven settlement is significant.

[0061] 1.1.4. Slits and built-in guide pipes

[0062] The mud capacity in the bored piles drilled by rotary drilling shows a "sawtooth growth": ① When the drill rod sinks, the mud overflows due to the space occupied by the drill bit (considering that the mud will not be filled in time when sinking) and the drill rod (the drill rod is a hollow component that can accommodate mud); ② After the drill rod is lifted, the returned mud not only needs to replenish the space occupied by the original drill bit and drill rod V1, but also needs to replenish the volume V2 of the earth excavation during this advance.

[0063] The diameter of the rotary drilling rig drill pipe is 508mm, with 4~5 inner tubes embedded inside. The minimum diameter of the inner tube is about 300mm, and the average wall thickness is 2.5cm. The drilling depth is 60m, and the required volume of the drill pipe itself is 1.885m 3 ; The drill bit diameter is 1.0m, the height is about 1.5m, and the required volume is 1.18m 3 Therefore, the total amount of mud overflow V1 is about 3.065m 3 Each drill bit penetration is calculated as 0.8m, and the mud return volume V2 required for 1.0m bored pile is 3.7m 3 .

[0064] If the mud is not replenished in time, the mud level at the hole mouth will drop sharply, causing the soil at the bottom of the casing to collapse (the bottom of the pit will rise and become unstable, such as Fig. 9 As shown in the figure, a represents the bottom elevation; b represents the normal water head; c represents the water head after the drill bit is raised; d represents the casing; and f represents the water penetration and the trend of earthwork). The collapse of the bottom retaining wall will cause the original ground to sink, accompanied by a sharp decline in the bearing capacity of the original ground foundation, the loss of the stable operating platform of the rotary drilling rig, and the risk of the drilling rig overturning - the smaller the diameter of the bored pile, the more significant the change in the liquid level caused by the loss of the same volume of mud.

[0065] Therefore, in order to accommodate the overflow mud during rotary drilling and replenish the mud level in the borehole in time, a mud balance system is set up according to the principle of communicating vessels:

[0066] 1) A temporary mud storage area 21 is set up around the working platform. The mud storage area 21 is filled with clay (anti-seepage), and its top mark is 0.1m~0.2m higher than the top mark of the rotary pile working platform. The capacity of the mud storage area 21 is not less than 1.5 times the peak mud return flow V2;

[0067] 2) Increase the buried depth of the steel casing. For a 1.0m bored pile, the casing length shall not be less than 5.0m (assuming the mud level sinks 1.5m); the opening area at the top of the steel casing shall not be less than 0.06m 2 The overflow hole has an overflow hole whose top elevation is 0.2~0.4m lower than the rotary drilling pile working platform.

[0068] In order to ensure the overflow and backflow of mud in the hole during drilling, a diversion pipe must be installed around each borehole. The diversion pipe solution and the rigid roadbed joint 32 solution complement each other:

[0069] When an external diversion channel is selected, the diversion channel is located at the center line of the borehole, so the concrete components are divided along the center line of the bored pile;

[0070] When the built-in guide groove is selected, the guide groove is still located at the center line of the borehole. At this time, the joints of the concrete components need to be set at the center line between the bored piles.

[0071] The biggest problem faced by the external diversion trough is that the concrete components have no effective connection in the external diversion trough area. On the soft soil foundation, when the rotary drilling rig with a capacity of more than 100 tons is operating, uneven settlement is prone to occur, which has an adverse effect on the overall stability of the working platform. Therefore, the present invention adopts an internally embedded internal diversion pipe 33, and the layout of the internal diversion pipe 33 has the following four characteristics:

[0072] 1) The embedded built-in guide pipe 33 adopts the principle of one-way arrangement, that is, after the flow pipe is arranged along the bridge, the built-in guide pipe 33 does not need to be arranged in the cross-bridge direction;

[0073] 2) The embedded internal guide pipe 33 adopts a linear series system, that is, it passes through several drill holes in one direction and then penetrates the entire plate in that direction. For a single drill hole, it can be bidirectionally drained or filled; when the center of the drill hole 34 is located at the rigid road base joint 32, there is no need to set the internal guide pipe 33 in the direction parallel to the rigid road base joint 32, and the rigid road base joint 32 plays the role of the internal guide pipe 33

[0074] 3) Considering the thickness of the plate and the flow restriction, the built-in guide pipe 33 uses two PVC pipes with a diameter of not less than 150mm~200mm on the concrete component 31, and the center distance of the PVC pipes is not less than 400mm;

[0075] 4) The PVC pipe (with built-in guide pipe 33) is reinforced by closed stirrups 43 with a diameter of not less than 12 mm and a spacing of not less than 100 mm.

[0076] 1.1.5. Use angle steel for edge protection

[0077] In order to ensure that the concrete components 31 around the working platform are not stripped by the crawler tracks of the rotary drilling rig, edge angle steels with specifications not exceeding L50 are set along the straight edge of the concrete components 31. The edge angle steels have the following requirements:

[0078] 1) Angle steel is set on both the upper and lower sides of the plate;

[0079] 2) A connecting steel bar is set every 40cm along the length direction of the angle steel. The connecting steel bars are divided into vertical reinforcement bars and transverse reinforcement bars. The vertical reinforcement bars are set along the height direction and adopt [structure to connect the upper and lower edge angle steels; the other transverse reinforcement bar is set along the plane direction and adopts L-shaped structure to connect the upper and lower steel mesh of the concrete component 31 by welding.

[0080] It is worth pointing out that the clear distance in the height direction of the hemming angle steel should be greater than the width of the PBL key-type double-hinge connecting steel plate. When the clear distance is insufficient, a notch needs to be reserved at the connecting steel plate of the hemming angle steel.

[0081] 1.2. Pad foundation

[0082] A cushion foundation 1 needs to be set between the rigid roadbed 3 and the original ground. The cushion foundation 1 needs to have the following two characteristics:

[0083] 1) The base is well matched (for sandy soil) or has low water content and low void ratio (for clay soil), which is convenient for compaction and ensures that the bottom surface of the rigid roadbed 1 is flat;

[0084] 2) The filling thickness is about 20~30cm, which is 1.5 times the expected settlement value of the rigid roadbed 1 in the soft soil foundation.

[0085] 1.3. Clay embankment

[0086] On the original ground, a clay embankment 2 with three sides is built around the rigid roadbed 3. The area enclosed between the clay embankment 2 and the rigid roadbed 1, and the remaining side of the rigid roadbed 3 is connected to the temporary construction passage 5, serving as a temporary mud storage area 21 during the rotary drilling operation. The enclosure structure has the following characteristics:

[0087] 1) Use clay or other materials with low water permeability to fill the area in the shape of an earth dam;

[0088] 2) The elevation of the retaining wall top is similar to the paving height of the rigid roadbed;

[0089] 3) The distance between the inner side of the enclosure and the edge of the rigid roadbed should be controlled at about 60 cm. If the spacing is too small, the mud storage capacity will be insufficient, resulting in mud outflow; if the spacing is too large, the amount of circulating mud will increase, which is not conducive to cost control and site management.

[0090] The method for using a working platform for a rotary drilling rig on a soft soil foundation of the present invention is specifically as follows:

[0091] 2. Usage

[0092] The use of the invention includes three parts: manufacturing, use and transition assembly.

[0093] 2.1. Production

[0094] In the pile cap area, a cushion foundation 1 with a thickness not exceeding 30 cm is filled, and a plain concrete leveling layer with a thickness not exceeding 5 cm is poured. After the strength reaches the requirement, tarpaulin is laid as the bottom membrane of the rigid roadbed plate 3.

[0095] Make an edge angle steel frame, and use steel bars to connect the upper and lower edge angle steels to serve as the outer frame of the rigid roadbed plate 3;

[0096] Tie the bottom steel bars of the rigid roadbed and use precast concrete pads to determine the thickness of the protective layer;

[0097] Install the connecting steel plate and PVC pipe. The connecting steel plate and the edge angle steel are temporarily fixed with spot welding. Both ends of the PVC pipe (with built-in guide pipe 35) are sealed with plastic film to avoid pipe blockage during concrete pouring.

[0098] Wooden formwork is used as the outer formwork of the rigid roadbed, and foam is used as the inner formwork - that is, the 10 cm gaps between concrete components 31 and the reserved drilling positions are filled with foam boards and interrupted at the PBL keyed double hinged connection plate 33;

[0099] During the concrete pouring, use stones to weigh down the foam formwork to prevent the foam from floating up;

[0100] The concrete curing time shall not be less than 72 hours, during which time it needs to be watered and cured. It can be used directly after its strength reaches 70%.

[0101] 2.2 Use phase

[0102] During the drilling stage, when the drill bit is lowered, the drilling head moves in a downward direction 8. Due to the occupation of the drill bucket and the drill rod, the mud moves in a direction 9 toward the outer mud storage area 21, and overflows through the built-in guide pipe 35 to the temporary mud storage area 21 between the clay embankment 2 and the rigid roadbed plate 3; when the drill bit is lifted, the drilling head moves in an upward direction 8. Due to the removal of some of the drilled earth and the withdrawal of the drill bucket and the drill rod, the mud level in the borehole position 34 drops. At this time, the mud moves in a direction 9 from the outer mud storage area 21 to the borehole, and the mud in the temporary mud storage area 21 is replenished into the borehole through the built-in guide pipe 33. According to the principle of communicating vessels, the mud level in the borehole is maintained close to the mud level in the mud storage area 33.

[0103] In addition, in order to make the rigid roadbed plate settle evenly as a whole, the drilling sequence of the rotary drilling rig must follow the principle of "symmetrical operation" and follow the order of edge first, center second, midpoint first, corner point second. Taking the 9-pile cap commonly used in municipal engineering as an example, the specific drilling sequence is as follows: Figure 3 shown.

[0104] 2.3. Transition assembly

[0105] After the construction of the bored piles of the previous foundation is completed, the concrete components 31 of the precast concrete rigid roadbed plate 1 are transferred one by one, and the order is as follows:

[0106] 1) Build a cushion foundation with a thickness of 20~30cm on the new working platform;

[0107] 2) Remove the connecting steel bars between the rigid roadbed plates of the previous cap; when the rigid roadbed plate 1 has uneven settlement and causes the steel bars to be locked, use acetylene flame to cut the steel bars and remove them;

[0108] 3) Number the concrete components 31 of the rigid roadbed plate 1 before the transfer respectively;

[0109] 4) Use a 70T truck crane to transfer each concrete component to another foundation area in sequence;

[0110] 5) Use steel bars to connect the same pair of connection plates, where each connection hole on each connection plate must be locked with shear steel bars;

[0111] 6) A clay embankment 2 is set outside the rigid roadbed, and the project enters the use stage after completion.

[0112] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A work platform for a rotary drilling rig on a soft soil foundation, comprising a cushion foundation (1), a clay protection embankment (2) and a rigid roadbed (3), characterized in that: The cushion foundation (1) is located at the lowest part, the rigid roadbed (3) is placed above the cushion foundation (1), the three sides of the rigid roadbed (3) are surrounded by clay embankments (2), and the last side of the rigid roadbed (3) coincides with the temporary construction passage (5); the clay embankments (2) and the rigid roadbed (3) on the three sides are provided with mud storage areas (21) for storing mud, the rigid roadbed (3) is composed of concrete components (31) spliced ​​together, the concrete components (31) are provided with PBL key-type double-hinged connection plates (33) at the splicing locations, and the concrete components (31) are provided with A rigid road base plate joint (32), the concrete components (31) are all provided with drilling holes (34), the concrete components (31) are provided with built-in flow guide pipes (35) connected to the drilling holes (34), the concrete components (31) are provided with upper and lower layers of steel mesh (4), the concrete components (31) are provided with two built-in flow guide pipes (35) in the long side direction of the concrete components (31); a single built-in flow guide pipe (35) is provided in the short side direction of the concrete components (31), the built-in flow guide pipe (35) is located between the upper and lower layers of steel mesh (4), the PBL key-type double-hinged connecting plate (33) is provided with a connecting steel plate (33 0), the connecting steel plate (330) is provided with an anchor hole (331) and a connecting hole (332), the anchor hole (331) is arranged on the connecting steel plate (330) on the inner side of the concrete component (31), and one anchor hole (331) is arranged in the thickness direction of the concrete component (31), the connecting hole (332) is arranged on the connecting steel plate (330) on the outer side of the concrete component (31), and two connecting holes (332) are arranged in the thickness direction of the concrete component (31), and at least three anchor holes (331) are arranged in the length direction of the concrete component (31), and the concrete component (31) A connection hole (332) is provided in the length direction of the concrete member (31), an anchoring steel bar (333) fixed inside the concrete member (31) is provided in the anchor hole (331), a connection steel bar (334) located in the rigid roadbed joint (32) is provided in the connection hole (332), a PVC pipe is installed in the built-in guide pipe (35), one end of the built-in guide pipe (35) is connected to the drilling hole (34), and the other end is connected to the mud storage area (21) or the rigid roadbed joint (32), and closed stirrups (43) are provided around the built-in guide pipe (35), and the diameter of the closed stirrups (43) is not less than 12 mm.

2. The working platform for a rotary drilling rig on soft soil according to claim 1, characterized in that: The spacing between each pair of the PBL key-type double-hinged connecting plates (33) is not less than 0.8 m and not more than 1.2 m, and the spacing between the rigid roadbed plate joints (32) is 10 to 20 cm.

3. The working platform for a rotary drilling rig on soft soil according to claim 1, characterized in that: The upper and lower planes of the concrete component (31) are both provided with edge angle steels (6), and vertical reinforcing ribs (62) and transverse reinforcing ribs (61) are arranged at intervals along the length direction of the edge angle steels (6), wherein the vertical reinforcing ribs (62) are arranged along the height direction of the concrete component (31), adopt a semi-circular structure, and connect the edge angle steels (6) of the upper and lower planes; the transverse reinforcing ribs (61) are arranged along the plane direction of the concrete component (31), adopt an L-shaped structure, and are respectively welded to the upper and lower steel meshes (4) in their respective planes.

4. The working platform for a rotary drilling rig on soft soil according to claim 1, characterized in that: The cushion foundation (1) is made of a material with low moisture content and low void ratio, and the thickness of the cushion foundation (1) is 20 to 30 cm.

5. The working platform for a rotary drilling rig on soft soil according to claim 1, characterized in that: The clay embankment (2) is made of a material with low water permeability and is in the shape of an earth dam. The height of the clay embankment (2) is consistent with the height of the rigid roadbed (3). The volume of the mud storage area (21) is at least 1.5 times the peak value of the mud overflow.

6. A method for using a working platform for a rotary drilling rig on a soft soil foundation, characterized in that: The method of use includes a use phase and a transition splicing phase; The use phase includes the following steps: The drilling platform is used to drill a hole. When the drill bit of the drilling rig is placed in the drilling hole position (34), the mud overflows through the built-in guide pipe (35) to the mud storage area (21) between the clay embankment (2) and the rigid roadbed (3) due to the occupation of the drill bucket and the drill rod. When the drill bit is lifted, the mud level in the drilling hole position (34) drops due to the removal of part of the drilled earth and the withdrawal of the drill bucket and the drill rod. At this time, the mud in the temporary mud storage area (21) is replenished to the drilling hole position (34) through the built-in guide pipe (35). According to the communicating vessel principle, the mud level in the drilling hole position (34) is maintained close to the mud level in the mud storage area (21). In order to make the rigid roadbed plate (3) settle evenly as a whole, the drilling sequence of the rotary drilling rig must comply with the principle of symmetrical operation, and drill in the order of edge first, then center, and midpoint first, then corner point; The transition splicing stage includes the following steps: A cushion foundation (1) with a thickness of 20 to 30 cm is built on the new working platform; the PBL key-type double-hinged connecting plate (33) of the rigid roadbed (3) of the previous pedestal is removed; when the PBL key-type double-hinged connecting plate (33) is locked due to uneven settlement of the rigid roadbed (3), the steel bars of the PBL key-type double-hinged connecting plate (33) are cut off with acetylene flame and then removed; the concrete components (31) of the rigid roadbed (3) before the transfer are numbered; a 70T truck crane is used to transfer each concrete component (31) in order to another pedestal area; steel bars are used to connect the same pair of connecting plates, wherein each connecting hole on each connecting plate needs to be provided with shear steel bars for locking; a clay embankment is set outside the rigid roadbed, and the pedestal is put into use again after completion.

Images