Foundation reinforcement method for offshore dump-fill geology

Abstract

The invention provides a foundation reinforcement method for an offshore dump-fill geology, and relates to the technical field of building construction, the offshore dump-fill geology at least sequentially comprises a backfill layer and a sludge layer from the earth surface to the bottom, and the method comprises the following steps that a drilling machine is started for drilling, and the hole bottom extends into the sludge layer; after drilling is completed, an outer sleeve is placed in the hole, the depth of the outer sleeve is smaller than that of the hole, and a through hole is formed in the side wall of the outer sleeve; a high-pressure injection process is adopted, an injection pipe is lowered to the hole bottom from the outer sleeve, an injection pile is formed upwards from the hole bottom, and the upper portion of the injection pile coincides with the outer sleeve to form a combination area; and a grouting pipe is lowered in the outer sleeve, the lower end of the grouting pipe penetrates into the combination area, a double-liquid grouting technology is adopted for grouting to form a grouting area, and combination of the grouting area and the jet pile is formed within the range of the combination area. According to the method, a high-pressure injection process and a double-liquid grouting process are organically combined, the characteristics of a complex stratum are fully utilized, and a stable foundation is formed.

Description

Technical Field

[0001] The present invention relates to the technical field of building construction, in particular to a foundation reinforcement method for offshore dump fill geology. Background Art

[0002] Traditional foundation reinforcement construction methods, such as the single high-pressure jet pile process, can handle some complex geological conditions. However, when dealing with soft soil and silt formations, it is difficult to achieve the expected pile-forming effect, resulting in insufficient foundation bearing capacity and affecting the safety and stability of the project.

[0003] Especially in the construction area of offshore dump fill geology, the geological conditions are complex, including at least two bottom layers with different properties: silt layer and backfill layer. Traditional high-pressure jet pile technology and grouting technology cannot achieve good pile formation effects, which greatly increases the difficulty of foundation reinforcement construction. Summary of the Invention

[0004] The purpose of the present invention is to provide a foundation reinforcement method for offshore dump fill geology, so as to solve the problem of poor construction effect of foundation reinforcement for offshore dump fill geology in the prior art.

[0005] In a first aspect, the present invention provides a method for reinforcing a foundation of offshore dump fill geology, wherein the offshore dump fill geology includes at least a backfill layer and a silt layer in sequence from the surface downward, comprising the following steps: Start drilling with the drilling rig, and extend the bottom of the hole into the silt layer; After the drilling is completed, an outer sleeve is placed in the hole. The depth of the outer sleeve is smaller than the depth of the hole, and a through hole is provided on the side wall of the outer sleeve. Using high-pressure jetting technology, the jet pipe is lowered from the outer casing to the bottom of the hole, and a jet pile is formed from the bottom of the hole upwards. The upper part of the jet pile overlaps with the outer casing to form a bonding area; A grouting pipe is lowered into the outer casing, and the lower end of the grouting pipe is inserted into the joint area. A double-liquid grouting process is used to perform grouting to form a grouting area, thereby forming a combination of the grouting area and the jet pile within the range of the joint area.

[0006] In an optional embodiment, the high-pressure spraying process adopts a rotary spraying process, including primary spraying and secondary spraying, and the lifting speed of the secondary spraying is greater than the lifting speed of the primary spraying.

[0007] In an optional embodiment, the weight ratio of cement: water glass: sulfate-resistant material in the high-pressure spraying process is 100:1.5:4.

[0008] In an optional embodiment, in the double-liquid grouting process, the grouting pipe is assembled into a segmented structure using multiple steel pipes, a spacer is provided between two adjacent steel pipes, and a slurry outlet hole is provided on the steel pipe.

[0009] In an optional embodiment, a plurality of groups of slurry outlet holes are circumferentially equidistantly provided on the steel pipe, and each group of slurry outlet holes is circumferentially symmetrically arranged.

[0010] In an optional embodiment, in the double-liquid grouting process, the grouting pressure is set according to each steel pipe segment, and the grouting pressure increases sequentially from shallow to deep.

[0011] In an optional embodiment, quantitative grouting is used in the double-liquid grouting process.

[0012] In an optional embodiment, in the dual-liquid grouting process, the water glass solution and the cement slurry solution are mixed by bottom hole mixing.

[0013] In an optional embodiment, in the double-liquid grouting process, the weight ratio of cement: water glass: sulfate-resistant material is 100:15:4.

[0014] In an optional embodiment, in the dual-liquid grouting process, the grouting diffusion radius is larger than the inner diameter of the outer casing.

[0015] The invention provides a method for reinforcing offshore dump fill geology, which has the following beneficial effects: 1. The present invention organically combines the high-pressure jetting process and the double-liquid grouting process. Jet piles are formed in the silt layer at the lower part of the hole by the high-pressure jetting process. The jet piles can be stably formed in the silt layer. The double-liquid grouting process is used to form a grouting area in the backfill layer at the upper part of the hole. The grouting area can be effectively combined with the backfill layer. At the same time, the grouting area is effectively combined with the jet piles in the bonding area, thereby forming a foundation reinforcement technology combining the jet piles with the grouting area, making full use of the characteristics of complex strata to form a stable foundation.

[0016] 2. The present invention does not require any equipment update and can directly utilize existing equipment for the high-pressure jetting process and the dual-liquid grouting process without requiring any equipment modification. The invention has low application costs and is easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 A flow chart of a foundation reinforcement method for offshore dump fill geology provided by an embodiment of the present invention; Figure 2 A structural schematic diagram of a foundation reinforcement method for offshore dump fill geology provided by an embodiment of the present invention.

[0019] Explanation of main component symbols: 100-backfill layer; 200-silt layer; 300-outer casing; 400-joining area; 500-grouting area; 600-jet pile. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0023] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like indicate positions or locations based on the positions shown in the accompanying drawings, or the positions or locations in which the inventive product is typically placed when in use. These terms are intended solely to facilitate the description of the present invention and to simplify the description, and are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third," etc., are used solely to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] Furthermore, terms such as "horizontal," "vertical," and "overhanging" do not necessarily imply that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0025] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0026] The following embodiments of the present invention are described in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0027] The embodiment of the present invention provides a method for reinforcing the foundation of offshore dump fill geology, such as Figure 1 and Figure 2 As shown, the offshore dump fill geology includes at least a backfill layer 100 and a silt layer 200 from the surface downward, and includes the following steps: Start drilling with a drilling rig, with the bottom of the hole extending into the silt layer 200; After the drilling is completed, an outer sleeve 300 is placed in the hole. The depth of the outer sleeve 300 is less than the depth of the hole, and a through hole is provided on the side wall of the outer sleeve 300. Using a high-pressure jetting process, the jetting pipe is lowered from the outer sleeve 300 to the bottom of the hole, and a jet pile 600 is formed from the bottom of the hole upwards. The upper part of the jet pile 600 overlaps with the outer sleeve 300 to form a bonding area 400; A grouting pipe is lowered into the outer casing 300 , and the lower end of the grouting pipe penetrates into the joint area 400 . A double-liquid grouting process is used to form a grouting area 500 , and a combination of the grouting area 500 and the jet pile 600 is formed within the range of the joint area 400 .

[0028] The foundation reinforcement method for offshore dump fill geology provided in this embodiment organically combines the high-pressure jetting process and the double-liquid grouting process. The jet pile 600 is formed by the high-pressure jetting process in the silt layer 200 at the lower part of the hole. The jet pile 600 can be stably formed in the silt layer 200. The grouting area 500 is formed by the double-liquid grouting process in the backfill layer 100 at the upper part of the hole. The grouting area 500 can form an effective combination with the backfill layer 100. At the same time, the grouting area 500 forms an effective combination with the jet pile 600 in the bonding area 400, thereby forming a foundation reinforcement technology combining the jet pile 600 with the grouting area 500, which fully utilizes the characteristics of complex strata to form a stable foundation.

[0029] The offshore dump fill geology foundation reinforcement method provided in this embodiment does not require equipment updates and can directly utilize the original equipment of the high-pressure jetting process and the double-liquid grouting process without equipment modification. The application cost is low and it is easy to promote and use.

[0030] In this embodiment, a drill bit with a diameter of 146 mm is used for drilling. The specific size of the drill bit is only a specific choice in this embodiment and does not constitute a limitation of the present invention. In actual applications, drill bits of other sizes can be selected according to needs.

[0031] In this embodiment, the high-pressure jetting process adopts a double-tube rotary jetting process, which specifically includes initial jetting and re-jetting, and the lifting speed of re-jetting is greater than the lifting speed of initial jetting. The pile diameter of the double-tube rotary jetting process is 800 mm and the pile length is 12 meters. Among the rotary jetting lifting speeds, the lifting speed of initial jetting is 0.1 meters per minute, the lifting speed of re-jetting is 0.15 meters per minute, and the lifting section length is 2 meters. The double-tube rotary jetting process sprays cement slurry solution and air respectively. In terms of the rotary jet slurry pressure of the cement slurry solution, the rotary jet slurry pressure of initial jetting and re-jetting is 4 MPa; in terms of the rotary jet pressure of air, the rotary jet pressure of initial jetting and re-jetting is 0.7 MPa. The weight ratio of cement: water glass: sulfate-resistant material is 100:1.5:4. In the bonding area 400, the cement slurry solution and air can overflow outside the outer sleeve 300 through the through hole of the outer sleeve 300, and the outer sleeve 300 will not affect the formation of the jet pile 600.

[0032] In this embodiment, water glass and anti-sulfate admixtures are added to traditional Portland cement, and the weight ratio of cement: water glass: anti-sulfate materials is 100:1.5:4, which improves the fluidity and erosion resistance of the slurry. Improving the fluidity of the slurry facilitates the formation of jet grouting piles, and improving the erosion resistance can also solve the erosion problem of offshore dumping sites.

[0033] In this embodiment, the outer sleeve 300 is made of PVC, and the diameter of the outer sleeve 300 is 110 mm.

[0034] In this embodiment, the grouting pipe is constructed using multiple steel pipes assembled into a segmented structure. Spacers are placed between adjacent steel pipes, and grouting holes are provided on each pipe. Multiple groups of grouting holes are circumferentially equidistantly arranged on the pipe, with each group of holes symmetrically positioned. Grouting pressure is set for each pipe segment, increasing from shallow to deep.

[0035] Specifically, the steel pipe is a one-inch galvanized steel pipe. The length of the first and second sections from top to bottom is 4.5 meters, and the length of the third section is 5 meters. The total depth of the grouting area 500 is consistent with the depth of the PVC sleeve in the hole, which is 14 meters. The grouting pressure of the first section of the steel pipe is 1 MPa. During the process, ensure that the pressure in the grouting pipe increases steadily until the grouting pressure of 1 MPa is reached. At a grouting pressure of 1 MPa, when the injection rate is less than 5 L / min, continue for 10 minutes to complete the single-stage grouting, and then gradually increase the grouting pressure to destroy the spacer, and the slurry enters the second section of the steel pipe. The grouting pressure of the second section of the steel pipe is 1.5 MPa, and the grouting pressure of the third section of the steel pipe is 2 MPa. The grouting process and end conditions of the second and third sections of the steel pipe are the same as those of the first end steel pipe. This embodiment adopts segmented grouting, which avoids repeated drilling and sweeping, and improves construction efficiency.

[0036] In this embodiment, the depth of the backfill layer 100 is 12 meters, the depth of the silt layer 200 is 12 meters, and the total depth of the grouting area 500 exceeds the depth of the backfill layer 100 by 2 meters, which constitutes the depth of the bonding area 400 .

[0037] In other embodiments, the depth of the combination can be specifically set according to the depth of the silt layer 200 and the backfill layer 100, but is preferably not less than one tenth of the length of the grouting area 500 or the jet pile 600, and more preferably not less than two tenths of the length of the grouting area 500 or the jet pile 600, so as to ensure the combining effect of the jet pile 600 and the grouting area 500.

[0038] In this embodiment, the dual-liquid grouting process uses a bottom-hole mixing method to mix a water glass solution and a cement slurry solution. The weight ratio of cement: water glass: sulfate-resistant material is 100:15:4. Quantitative grouting is used, with a grouting volume of 1.1 tons per meter and a slurry water-cement ratio of 0.8:1. The grouting diffusion radius is 0.95 meters. The weight ratio of cement: water glass: sulfate-resistant material is 100:15:4, which optimizes the slurry viscosity and gel time, achieving better diffusion and compaction effects.

[0039] In this embodiment, the outer side of the grouting pipe can be wrapped with geotextile, rubber strips and other materials to avoid clogging of the slurry outlet holes during the grouting process below.

[0040] In this embodiment, only the silt layer and the backfill layer are used as examples of complex geological conditions. In actual applications, when the geological conditions are more complex, such as artificial fill, Quaternary Holocene marine sedimentary layer, Quaternary Upper Pleistocene alluvial layer and the third lithologic section of the Yuntai Formation, the specific process provided in this embodiment can be applied according to the adaptive matching of the geological characteristics and the similar characteristics of the silt layer and the backfill layer, and this application does not impose any restrictions on this.

[0041] Finally, 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 above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for reinforcing a foundation of offshore dump fill geology, wherein the offshore dump fill geology comprises at least a backfill layer (100) and a silt layer (200) in sequence from the surface downward, characterized in that: The following steps are involved: Starting the drilling rig to drill a hole, with the bottom of the hole extending into the silt layer (200); After the drilling is completed, an outer sleeve (300) is placed in the hole, wherein the depth of the outer sleeve (300) is smaller than the depth of the hole, and a through hole is provided on the side wall of the outer sleeve (300); Using a high-pressure jetting process, the jetting pipe is lowered from the outer sleeve (300) to the bottom of the hole, and a jet pile (600) is formed from the bottom of the hole upwards. The upper part of the jet pile (600) overlaps with the outer sleeve (300) to form a bonding area (400); A grouting pipe is lowered into the outer casing (300), and the lower end of the grouting pipe penetrates into the joint area (400). Grouting is performed using a double-liquid grouting process to form a grouting area (500), and a combination of the grouting area (500) and the jet pile (600) is formed within the range of the joint area (400).

2. The offshore dump fill geology foundation reinforcement method according to claim 1, characterized in that: The high-pressure spraying process adopts a rotary spraying process, including primary spraying and secondary spraying, and the lifting speed of the secondary spraying is greater than the lifting speed of the primary spraying.

3. The offshore dump fill geology foundation reinforcement method according to claim 1, characterized in that: The weight ratio of cement: water glass: sulfate-resistant material in the high-pressure spraying process is 100:1.5:

4.

4. The offshore dump fill geology foundation reinforcement method according to claim 1, characterized in that: In the double-liquid grouting process, the grouting pipe is assembled into a segmented structure using multiple steel pipes, a spacer is provided between two adjacent steel pipes, and a slurry outlet hole is provided on the steel pipe.

5. The offshore dump fill geology foundation reinforcement method according to claim 4 is characterized in that: The steel pipe is provided with a plurality of groups of slurry outlet holes at equal intervals in the circumferential direction, and each group of slurry outlet holes is symmetrically arranged in the circumferential direction.

6. The offshore dump fill geology foundation reinforcement method according to claim 4, characterized in that: In the double-liquid grouting process, the grouting pressure is set in sections according to each steel pipe, and the grouting pressure increases from shallow to deep.

7. The offshore dump fill geology foundation reinforcement method according to claim 4, characterized in that: In the double-liquid grouting process, quantitative grouting is adopted.

8. The offshore dump fill geology foundation reinforcement method according to claim 4, characterized in that: In the dual-liquid grouting process, the water glass solution and the cement slurry solution are mixed by mixing at the bottom of the hole.

9. The offshore dump fill geology foundation reinforcement method according to claim 8, characterized in that: In the double-liquid grouting process, the weight ratio of cement: water glass: sulfate-resistant material is 100:15:

4.

10. The offshore dump fill geology foundation reinforcement method according to claim 4, characterized in that: In the dual-liquid grouting process, the grouting diffusion radius is greater than the inner diameter of the outer casing (300).

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