CN115949052B - CO2Device and method for reinforcing calcareous sand foundation - Google Patents
CO2Device and method for reinforcing calcareous sand foundation Download PDFInfo
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Abstract
The invention provides a device and a method for reinforcing a calcareous sand foundation by CO 2, belonging to the technical field of civil engineering foundation treatment. The device for reinforcing the calcareous sand foundation by the CO 2 comprises a CO 2 gas supply device and an aeration pipeline, wherein the CO 2 gas supply device is communicated with the aeration pipeline through an air outlet; the calcareous sand foundation to be reinforced comprises a calcareous sand stratum, a coral crushed stone permeable cushion layer and a natural stratum, wherein the coral crushed stone permeable cushion layer is arranged above the natural stratum, and the calcareous sand stratum is arranged above the coral crushed stone permeable cushion layer; the aeration pipeline is arranged in an interlayer of the coral broken stone permeable cushion layer, a plurality of aeration micropores are arranged on the aeration pipeline, and the average pore diameter of the aeration micropores ranges from 0.3 mm to 0.6mm. The method for reinforcing the calcareous sand foundation by the CO 2 is realized based on the device for reinforcing the calcareous sand foundation by the CO 2. The cement effect on the calcareous sand stratum is produced macroscopically, and the overall strength and liquefaction resistance of the calcareous sand foundation are improved.
Description
Technical Field
The invention relates to the technical field of civil engineering foundation treatment, in particular to a device and a method for reinforcing a calcareous sand foundation by CO 2.
Background
Unconsolidated and weakly cemented calcareous deposits are widely distributed on reef flat of coral island reefs and in lagoons, and are important materials in marine and coastal engineering construction. Unlike conventional Liu Yuandan quartz sand, the calcareous sand particles take CaCO 3 as a main component, and have physical and mechanical characteristics of pore development, high angle, low strength and easy breaking, so that the calcareous sand exposes a plurality of geotechnical engineering problems in engineering construction. In addition, the calcareous sand stratum is low in cementing degree, low in compactness and high in initial water content, and cannot be directly used for engineering construction, so that the calcareous sand stratum is required to be reinforced.
Disclosure of Invention
In view of the above, the present invention provides a device and a method for reinforcing a calcareous sand foundation with CO 2, which macroscopically has a cementing effect on the calcareous sand stratum, and improves the overall strength and liquefaction resistance of the calcareous sand foundation, so that the device and the method are more practical.
In order to achieve the first purpose, the technical scheme of the device for reinforcing the calcareous sand foundation by the CO 2 provided by the invention is as follows:
the device for reinforcing the calcareous sand foundation by the CO 2 provided by the invention comprises a CO 2 gas supply device and an aeration pipeline (13),
The CO 2 gas supply device is communicated with the aeration pipeline (13) through a gas outlet;
The to-be-reinforced calcareous sand foundation comprises a calcareous sand stratum (11), a coral crushed stone water-permeable cushion layer (12) and a natural stratum (14), wherein the coral crushed stone water-permeable cushion layer (12) is arranged above the natural stratum (14), and the calcareous sand stratum (11) is arranged above the coral crushed stone water-permeable cushion layer (12);
The aeration pipeline (13) is arranged in an interlayer of the coral macadam water-permeable cushion layer (12), a plurality of aeration micropores are formed in the aeration pipeline (13), and the average pore diameter of the aeration micropores ranges from 0.3 mm to 0.6mm.
The device for reinforcing the calcareous sand foundation by the CO 2 can be further realized by adopting the following technical measures.
Preferably, the CO 2 gas supply device comprises a CO 2 gas storage system (2) and a gas pressurizing and distributing system (3),
One end of the CO 2 gas storage system is communicated with one end of the gas pressurizing and distributing system, and the gas outlet is arranged at the other end of the gas pressurizing and distributing system.
Preferably, the device for reinforcing the calcareous sand foundation by the CO 2 further comprises a gas drying and purifying system (1), a gas pipeline (6) and a gas valve (7),
The air inlet end of the air transmission pipeline (6) is buried in the calcareous sand stratum (11);
the air valve (7) is arranged at the tail end of the air inlet end;
The gas transmission pipeline (6) is communicated with one end of the gas drying and purifying system (1) through a gas outlet end, and the other end of the gas drying and purifying system (1) is communicated with the CO 2 gas storage system (2).
Preferably, the device for reinforcing the calcareous sand foundation by the CO 2 also comprises a rocker arm spray gun (8) and a water suction pump (9),
The water inlet of the water suction pump (9) is arranged on the surface layer inside the calcareous sand stratum (11), and the lowest point of the water inlet of the water suction pump (9) is lower than the low tide level (5);
The water outlet of the water suction pump (9) is communicated with the inlet end of the rocker arm spray gun (8), and the setting position of the outlet end of the rocker arm spray gun (8) is higher than the stratum surface of the calcareous sand stratum (11).
Preferably, the aeration line (13) is made of a flexible polymer material.
Preferably, the flexible polymer material is neoprene.
As a preferred alternative to this,
The aeration pipeline is in a continuous distributed arrangement form;
Or alternatively
The CO 2 gas supply has a plurality of gas outlets,
The aeration pipeline is in a sectional arrangement mode, and each section of the aeration pipeline is communicated with one air outlet of the CO 2 gas supply device.
Preferably, the device for reinforcing the calcareous sand foundation by the CO 2 further comprises a transparent film (10),
The transparent film (10) is covered around the calcareous sand stratum (11) and the coral rubble water-permeable cushion layer (12).
Preferably, the aeration pipeline (13) is provided with a test point, and the test point is arranged at one or more positions of bending, branching, starting and ending of the aeration pipeline (13).
Preferably, the coral crushed stone water-permeable cushion layer (12) comprises circular or sub-circular calcareous sand, and the particle size of the calcareous sand ranges from 2mm to 5mm.
Preferably, the calcareous sand layer (11) is a calcareous sand layer (11) compacted by a vibratory compaction method.
In order to achieve the second purpose, the technical scheme of the method for reinforcing the calcareous sand foundation by the CO 2 provided by the invention is as follows:
The reaction mechanism of the method for reinforcing the calcareous sand foundation by the CO 2 based on the device for reinforcing the calcareous sand foundation by the CO 2 provided by the invention comprises the following steps:
Wherein,
In the formula (a), caCO 3 is the main chemical component of a solid medium in a calcareous sand foundation to be reinforced, CO 2 is generated by aeration through the aeration pipeline (13), and H 2 O exists in a seawater environment;
In the formula (b), ca 2+ is mainly solid CaCO 3 which is generated by dissolution, and SO 4 2- exists in a seawater environment;
In formula (c), ca 2+ is mainly solid CaCO 3, and HCO 3 - is produced in formula (a).
The beneficial effects of the invention include: the physical and mechanical properties of the calcareous sand foundation are obviously improved: the method is mainly characterized in the aspects of foundation bearing capacity, shear strength, liquefaction resistance and the like; (2) no environmental pollution: the essence of the four main chemical processes involved in the invention is that the original SO 4 2- and Ca 2+ in the seawater are utilized to form CaSO 4 sediment, and the other three reactions only carry out substance exchange in the interior of the sediment, SO that no pollutant released into the ocean and the atmospheric environment from the whole reaction system exists in theory; (3) energy conservation and environmental protection: as the only external reaction raw material in the invention, the important source of CO 2 gas is the waste gas generated by the thermal energy combustion of household garbage and the power generation of fossil energy on the adjacent artificial island, and the Carbon Capture and Utilization and Sequestration (CCUS) technology is combined, so that the production is carried out without consuming extra energy, thereby being beneficial to relieving the greenhouse effect caused by human activities; (4) economical, efficient, simple and feasible: the method utilizes the porous hose to chemically strengthen the way of exposing CO 2 gas into the calcareous sand foundation, has low raw material demand and easy transportation, does not need to be provided with large construction machinery, and is particularly suitable for strengthening the calcareous sand foundation in a large range; and (5) the prospect is wide: by means of huge economic and ecological benefits and development potential of the CCUS technology, large ships for transporting low-temperature liquid CO 2 internationally are under development at present, and CCUS regional cluster development including off-shore CO 2 sealing stations is promoted, so that large-scale popularization and application of the CO 2 reinforced calcareous sand foundation technology are facilitated.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to designate like parts throughout the figures. In the drawings:
Fig. 1 is a schematic diagram showing an arrangement of the apparatus for reinforcing a calcareous sand foundation by CO 2 according to the present invention.
Fig. 2 is a schematic view of the circulation of main substances inside the calcareous sand foundation of the present invention.
Fig. 3 is a schematic illustration of the planar arrangement of aeration lines and the selection of key test points in example 1.
Fig. 4 is a schematic illustration of the planar arrangement of aeration lines and the selection of key test points in example 2.
Reference numerals illustrate:
1. The gas drying and purifying system comprises a gas drying and purifying system 2, a CO 2 gas storage system 3, a gas pressurizing and distributing system 4, a high tide level 5, a low tide level 6, a gas pipeline 7, a gas valve 8, a rocker arm spray gun 9, a water suction pump 10, a transparent film 11, a calcareous sand stratum 12, a coral macadam permeable bedding layer 13, an aeration pipeline 14, a natural stratum 15, a solid medium 16, a liquid environment 17, a gas environment 18, caCO 3 cementing agent 19, caSO 4 cementing agent, 20, calcareous sand 21, SO 4 2-,22、Ca2+, 23, CO 3 2- produced by thermal decomposition reaction, 24, water 25, HCO 3 -, 26, CO 3 2- produced by dissolution of calcareous sand 27, CO 2 produced by thermal decomposition 28, CO 2 gas introduced into the calcareous sand stratum through an aeration pipeline 29, an aeration pipeline gas inlet 30, an aeration pipeline gas outlet 31, and a CO 2 gas flow direction.
Detailed Description
In view of the above, the present invention provides a device and a method for reinforcing a calcareous sand foundation with CO 2, which macroscopically has a cementing effect on the calcareous sand stratum, and improves the overall strength and liquefaction resistance of the calcareous sand foundation, so that the device and the method are more practical.
The inventor has long studied to find that:
The technology of microorganism induced CaCO 3 precipitation (MICP) is used for cementing and solidifying island reef calcareous sand by promoting the decomposition of marine original microorganisms on urea, so that the physical and mechanical properties of a calcareous sand foundation are enhanced, although the technology avoids the influence of exogenous microorganisms on the environment, the urea and hydrolysis products thereof can cause eutrophication and nitrate pollution of the marine ecological environment, and urea hydrolysis reaction participated by urease can be inhibited by urea byproducts such as seawater salinity, diamine shrinkage and the like, so that the strengthening effect is adversely affected. The calcareous sand foundation reinforcing technology is characterized in that a mixture of calcareous sand and water is acidified into a calcium bicarbonate solution by using CO 2 under a high-pressure environment, and injection and collection of the calcium bicarbonate solution and cementation of the calcareous sand foundation are realized through well drilling. The method has low reinforcement efficiency and high construction technology cost, is difficult to cement unsaturated calcareous sand above the sea surface, and is not suitable for large-scale reinforcement of calcareous sand foundations.
Island environments are usually far away from land, hydrogeological conditions are complex and changeable, engineering machinery and materials are difficult to transport, traditional construction technology is difficult to apply, and fragile coral reef ecological environments are likely to be damaged in a difficult recovery mode. Engineering practice shows that the calcareous sand stratum can meet the bearing capacity and sedimentation requirements of general engineering only through mechanical vibroflotation and compaction processes, however, unconsolidated calcareous sand has poor integrity, problems such as corrosion and liquefaction can occur under the action of dynamic factors such as waves, earthquakes and the like, and adverse effects are caused on the performance and safety of the upper engineering. In addition, the coral reef plays an extremely important role in maintaining the stability of the marine ecological environment, and at the same time, the coral reef is very sensitive to environmental changes, and particularly the degradation of the coral reef is remarkably aggravated since the industrial revolution. Therefore, it is necessary to avoid any adverse effect on the ecological environment of the coral reef during the foundation reinforcement process, and thus a method for reinforcing the calcareous sand foundation which is pollution-free to the marine ecological environment and is relatively economical and efficient is developed.
In order to further describe the technical means and effects adopted by the invention to achieve the preset aim, the following description refers to the specific implementation, structure, characteristics and effects of a device and a method for reinforcing a calcareous sand foundation by using CO 2 according to the invention, which are provided by the invention, with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.
The term "and/or" is herein merely an association relation describing an associated object, meaning that three relations may exist, e.g. a and/or B, specifically understood as: the composition may contain both a and B, and may contain a alone or B alone, and any of the above three cases may be provided.
Device for reinforcing calcareous sand foundation by CO 2
Referring to fig. 1, the apparatus for reinforcing a calcareous sand foundation by CO 2 according to an embodiment of the present invention includes a CO 2 gas supply device and an aeration line 13. The CO 2 gas supply device is communicated with the aeration pipeline 13 through a gas outlet; the calcareous sand foundation to be reinforced comprises a calcareous sand stratum 11, a coral macadam permeable cushion layer 12 and a natural stratum 14, wherein the coral macadam permeable cushion layer 12 is arranged above the natural stratum 14, and the calcareous sand stratum 11 is arranged above the coral macadam permeable cushion layer 12; the aeration pipeline 13 is arranged in the interlayer of the coral macadam permeable cushion layer 12, a plurality of aeration micropores are arranged on the aeration pipeline 13, and the average pore diameter of the aeration micropores ranges from 0.3mm to 0.6mm.
The device for reinforcing the calcareous sand foundation by the CO 2 has the beneficial effects that: the physical and mechanical properties of the calcareous sand foundation are obviously improved: the method is mainly characterized in the aspects of foundation bearing capacity, shear strength, liquefaction resistance and the like; (2) no environmental pollution: the essence of the four main chemical processes involved in the invention is that the original SO 4 2- and Ca 2+ in the seawater are utilized to form CaSO 4 sediment, and the other three reactions only carry out substance exchange in the interior of the sediment, SO that no pollutant released into the ocean and the atmospheric environment from the whole reaction system exists in theory; (3) energy conservation and environmental protection: as the only external reaction raw material in the invention, the important source of CO 2 gas is the waste gas generated by the heat energy combustion of household garbage and the power generation of fossil energy on the adjacent artificial island, and the Carbon Capture and Utilization and Sequestration (CCUS) technology is combined, so that the production is carried out without consuming extra energy, thereby being beneficial to relieving the 'enhanced greenhouse effect' caused by human activities; (4) economical, efficient, simple and feasible: the method utilizes the porous hose to chemically strengthen the calcareous sand foundation by exposing CO 2 gas, has low raw material demand and easy transportation, does not need to be provided with large construction machinery, and is particularly suitable for strengthening the calcareous sand foundation in a large range; and (5) the prospect is wide: by means of huge economic and ecological benefits and development potential of the CCUS technology, large ships for transporting low-temperature liquid CO 2 internationally are under development at present, and CCUS regional cluster development including off-shore CO 2 sealing stations is promoted, so that large-scale popularization and application of the CO 2 reinforced calcareous sand foundation technology are facilitated.
The device for reinforcing the calcareous sand foundation by the CO 2 further comprises a gas drying and purifying system 1, a gas transmission pipeline 6 and a gas valve 7. The air inlet end of the air conveying pipeline 6 is buried in the calcareous sand stratum 11; the air valve 7 is arranged at the tail end of the air inlet end; the gas transmission pipeline 6 is communicated with one end of the gas drying and purifying system 1 through a gas outlet end, and the other end of the gas drying and purifying system 1 is communicated with the CO 2 gas storage system 2.
The device for reinforcing the calcareous sand foundation by the CO 2 further comprises a rocker arm spray gun 8 and a water pump 9. The water inlet of the water pump 9 is arranged on the surface layer inside the calcareous sand stratum 11, and the lowest point of the water inlet of the water pump 9 is lower than the low tide level 5; the water outlet of the water pump 9 is communicated with the inlet end of the rocker arm spray gun 8, and the outlet end of the rocker arm spray gun 8 is arranged at a position higher than the stratum surface of the calcareous sand stratum 11.
Wherein the aeration line 13 is made of a flexible polymer material.
Wherein the flexible polymer material is neoprene.
Wherein the aeration pipeline is in a continuous distributed arrangement mode. Or the CO 2 gas supply device is provided with a plurality of gas outlets, the aeration pipeline is in a sectional arrangement mode, and each section of the aeration pipeline is communicated with one of the gas outlets of the CO 2 gas supply device.
Wherein, the device for reinforcing the calcareous sand foundation by CO 2 also comprises a transparent film 10. The transparent film 10 is covered around the calcareous sand stratum 11 and the coral rubble water permeable cushion layer 12. The transparent film 10 can prevent the CO 2 from diffusing into the atmosphere to cause pollution; and, at ambient temperature above 50℃, chemical reaction The transparent film 10 is able to use solar radiation energy to provide favorable temperature conditions for the reaction and to accelerate the decomposition of HCO 3 -.
Wherein the aeration line 13 is provided with test points, and the test points are arranged at one or more positions of bending, branching, starting and terminating of the aeration line 13.
Wherein the coral crushed stone water-permeable cushion layer 12 comprises circular or sub-circular calcareous sand, and the particle size of the calcareous sand ranges from 2 mm to 5mm.
Wherein the calcareous sand stratum 11 is the calcareous sand stratum 11 compacted by a vibration compaction method.
Method for reinforcing calcareous sand foundation by CO 2
Referring to fig. 2, a reaction mechanism of a method for reinforcing a calcareous sand foundation by using CO 2, which is implemented based on a device for reinforcing a calcareous sand foundation by using CO 2 provided by the embodiment of the present invention, includes:
Wherein,
In the formula (a), caCO 3 is the main chemical component of a solid medium in a calcareous sand foundation to be reinforced, CO 2 is generated by aeration through the aeration pipeline (13), and H 2 O exists in a seawater environment;
In the formula (b), ca 2+ is mainly solid CaCO 3 which is generated by dissolution, and SO 4 2- exists in a seawater environment;
In formula (c), ca 2+ is mainly solid CaCO 3, and HCO 3 - is produced in formula (a).
Wherein, as the main component of the calcareous sand, the solubility of CaCO 3 in liquid environment is mainly affected by the environment temperature, the partial pressure of CO 2 and the ion concentration, and compared with the environment of normal temperature and pressure, inert gas and pure water, the solubility of CaCO 3 in the environment of normal temperature and pressure, CO 2 and sea water is increased by about fifty times. When CO 2 gas is introduced into the seawater-CaCO 3 system in the form of tiny bubbles, the dissolution rate of CaCO 3 is obviously accelerated. The main reaction sites in the invention are relatively closed seawater environments inside the island, and the main reaction processes comprise: the reaction of dissolved CO 2 in water and CO 3 2- promotes the dissolution of solid CaCO 3, increases the concentration of HCO 3 - and Ca 2+ in seawater, forms CaSO 4 sediment with SO 4 2- in seawater environment by one part of Ca 2+, sprays the surface seawater rich in HCO 3 - onto the surface of calcareous sand, forms new CaCO 3 sediment through thermal decomposition reaction with the loss of moisture, and simultaneously, CO 2 gas generated by decomposition can be recycled together with CO 2 gas overflowed from the sea surface, SO that adverse effects on ecological environment are avoided to the greatest extent.
The method for reinforcing the calcareous sand foundation by using the CO 2 has the beneficial effects that: the physical and mechanical properties of the calcareous sand foundation are obviously improved: the method is mainly characterized in the aspects of foundation bearing capacity, shear strength, liquefaction resistance and the like; (2) no environmental pollution: the essence of the four main chemical processes involved in the invention is that the original SO 4 2- and Ca 2+ in the seawater are utilized to form CaSO 4 sediment, and the other three reactions only carry out substance exchange in the interior of the sediment, SO that no pollutant released into the ocean and the atmospheric environment from the whole reaction system exists in theory; (3) energy conservation and environmental protection: as the only external reaction raw material in the invention, the important source of CO 2 gas is the waste gas generated by the heat energy combustion of household garbage and the power generation of fossil energy on the adjacent artificial island, and the Carbon Capture and Utilization and Sequestration (CCUS) technology is combined, so that the production is carried out without consuming extra energy, thereby being beneficial to relieving the 'enhanced greenhouse effect' caused by human activities; (4) economical, efficient, simple and feasible: the method utilizes the porous hose to chemically strengthen the calcareous sand foundation by exposing CO 2 gas, has low raw material demand and easy transportation, does not need to be provided with large construction machinery, and is particularly suitable for strengthening the calcareous sand foundation in a large range; and (5) the prospect is wide: by means of huge economic and ecological benefits and development potential of the CCUS technology, large ships for transporting low-temperature liquid CO 2 internationally are under development at present, and CCUS regional cluster development including off-shore CO 2 sealing stations is promoted, so that large-scale popularization and application of the CO 2 reinforced calcareous sand foundation technology are facilitated.
The device and the method for reinforcing the calcareous sand foundation by the CO 2 provided by the invention are implemented,
(1) Preparing water, electricity, ventilation, leveling site and other construction earlier stages, and installing, paving and debugging equipment according to design requirements;
(2) Selecting representative test points on an aeration pipeline in combination with the actual condition of an engineering site, taking air as test gas, measuring aeration quantity (the volume of gas in the pipeline escaping to the outside through micropores uniformly distributed on the pipe wall in unit time) at each point under the condition of different total air inflow (speed), and primarily determining the reasonable range of the air inflow pressure and the air inflow of the aeration pipeline;
(3) Paving coral sand permeable cushions, uniformly distributing coral gravel soil on the upper side and the lower side of an aeration pipeline, and compacting the calcareous sand cushions by adopting a vibration compaction method;
(4) After the construction of the upper calcareous sand stratum is completed, introducing CO 2 gas into an aeration pipeline, and adjusting and determining parameters such as optimal air inlet pressure, optimal air inflow and the like for reinforcing the calcareous sand stratum in a reasonable range by combining the on-site hydrogeological conditions and the dissipation condition of the surface CO 2 gas;
(5) And stably introducing CO 2 gas into the pipeline according to the finally determined air inlet parameters, extracting surface seawater in the calcareous sand stratum, and spraying the surface seawater to the surface of the calcareous sand stratum at certain time intervals by using a rocker arm spray gun.
Further, the equipment in the step (1) mainly comprises a gas storage system, a gas pressurizing and distributing system, a microporous aeration pipeline and a flow monitoring system. Wherein the microporous aeration pipe is made of flexible polymer materials. Compared with the rigid material, the flexible aeration pipe has the advantages of simple connection structure, flexible layout form, good aeration uniformity, light weight, no pollution and corrosion resistance, but when the flexible aeration pipe is used in a calcareous sand foundation, the aeration pipe can block the passage of internal air flow due to extrusion and adhesion of calcareous sand particles.
Further, the debugging of each system in the step (1) is mainly aimed at guaranteeing the usability and stability of the aeration system.
Furthermore, the representative test points in the step (2) are mainly based on the arrangement form of the pipelines, and are usually selected at the positions where the gas circulation conditions of the aeration pipelines such as bending, branching, starting, terminating and the like can be changed suddenly, and the aeration amount of any other point can be deduced through real-time monitoring data of the adjacent test points.
Further, the reasonable range of the air inlet parameters in the step (2) respectively determines the maximum value and the minimum value of the required air inlet parameters by simultaneously meeting two conditions of safe, stable, uniform and effective air inlet process.
Furthermore, the material of the permeable cushion layer in the step (3) is preferably calcareous sand with a circular or sub-circular shape and a particle size in the range of 2-5mm, and the calcareous sand is classified as round gravel in gravelly soil according to the geotechnical engineering investigation standard of GB50021-2001 (2009). The coral gravel soil cushion layer not only can greatly reduce engineering disturbance to which an aeration pipeline is subjected, establishes a channel for efficient migration of seawater and bubbles in a stratum, but also can separate a micropore aeration pipe from fine powder sand in the stratum, and effectively relieves the blocking phenomenon of the micropore aeration pipe.
Further, the optimal air intake parameters in the step (4) are determined by reducing the escape of ineffective carbon dioxide gas from the sea surface to the gas environment as much as possible on the basis of ensuring the effectiveness and safety of aeration.
Further, the seawater in the formation in step (5) is enriched with high concentration of bicarbonate after a series of reactions, HCO 3 - can be thermally decomposed at room temperature, and the thermal decomposition process is significantly accelerated when the temperature reaches about 50 ℃. The bicarbonate in the seawater can be rapidly decomposed to form CaCO 3 sediment by using the higher surface temperature in summer in low latitude areas, and the unsaturated calcareous sand foundation is cemented.
Example 1
The engineering field is located in a certain coral island reef in tropical sea area, the natural ground is flush with sea level in low tide, the tide difference is 2m, a rectangular area with the reinforcing range of 100m multiplied by 200m is designed, and the calcareous sand stratum thickness is 6m. The aerator pipe is made of neoprene, the average pore diameter of the micropores is 0.3-0.6mm, and the diameter of the bubbles is about 1mm.
Step one, preparing works of water supply, power supply, ventilation and the like in the construction early stage are finished, and the land is dug to be filled up and filled down and leveled. And (3) installing a gas pressurizing and distributing system, a microporous aeration pipeline and a flow monitoring system according to related technical requirements, connecting with a CO 2 gas storage system, testing whether the system and each subsystem can work normally or not, and testing whether the interconnection between each subsystem is good or not, and performing the second step after the test is passed.
Step two, paving microporous aeration pipelines on the surface of a natural stratum, wherein the axis of the pipeline is 100mm higher than the ground, the pipeline direction is parallel or orthogonal to the field boundary, the microporous aeration pipelines are arranged at intervals of 2.5m in the direction parallel to the long side, the distance from the field boundary is 1-2m, and the plane arrangement form of the aeration pipelines and the selection of key test points are shown in figure 3.
Step three, paving coral round gravel permeable cushion layers with the grain diameter of 5mm and the thickness of 200mm, wherein the upper side and the lower side of a plane where a pipeline is positioned are respectively 100mm, compacting the coral gravel soil cushion layers by using a small tyre road roller, and repeatedly compacting for 2-3 times.
Fourthly, when the calcareous sand stratum is constructed to the designed elevation, the site is leveled again, the stratum surface is drilled between the natural stratum surface and the low tide level, small water pumping machinery and rocker arm spray guns are distributed according to regular triangles, and the distance between the adjacent spray guns is 50m.
And fifthly, after the drainage consolidation process of the calcareous sand stratum under the action of dead weight is initially completed, paving a transparent film on the temporary surface of the stratum, and arranging a gas outlet and connecting a CO 2 gas storage system.
Step six, introducing CO 2 gas into the aeration system during the period that the sea surface is higher than the plane of the aeration pipeline at night, wherein the air inlet pressure is 5atm, the air inlet amount is 800m 3/h, the corresponding aeration amount is about 0.1m 3/(h.m), and meanwhile, the CO 2 gas collected by the film is dried and purified and then is conveyed back to the gas storage system; and stopping introducing CO 2 gas during the period that the sea surface is lower than the plane of the aeration pipeline in daytime, collecting the film, extracting surface seawater in the calcareous sand stratum, spraying the seawater to the surface of the calcareous sand stratum by using a rocker arm spray gun to increase the water content of the stratum, paving the film on the ground surface again after the spraying is finished, collecting a small amount of CO 2 gas generated by thermal decomposition by the film during the intermittent spraying, and conveying the film back to the gas storage system after the drying and purifying treatment. The time interval between two adjacent spraying can be properly adjusted according to the surface temperature, usually 1-3h, and the surface temperature takes a smaller value when the surface temperature is high and takes a larger value when the surface temperature is low.
Example 2
The situation and steps of this embodiment are basically the same as those of embodiment 1, except that in this embodiment, the aeration pipeline is arranged in a sectional manner, referring to fig. 4, in the system, the CO 2 gas is redistributed, and is respectively introduced into a plurality of gas inlets, and after the CO 2 gas is collected and summarized from a plurality of gas outlets, the gas is input into the gas storage system after drying and purifying treatment. Accordingly, the intake pressure at the intake port in step six of the present embodiment is reduced to 2atm, and the intake air amount is reduced to 50m 3/h.
Example 3
The situation and steps of this embodiment are basically the same as those of embodiment 1, except that the natural ground where the engineering site is located in this embodiment is still close to or exposed to the sea surface even during the high tide level, the reaction efficiency in the sea water phase is low or cannot be performed, and a closed sea water-calcareous sand reaction system needs to be added in the adjacent sea area to replace the relatively closed sea water environment in the stratum. Therefore, in the embodiment, the parts related to the microporous aeration pipes and the permeable cushion layers in the first, second and third steps are omitted, and the sixth step is changed into continuously introducing CO 2 gas into the closed reaction system through the gas pressurizing system in the whole day time range, extracting the reacted seawater and spraying the seawater on the surface of the stratum by using a sprinkler.
Example 4
The situation and steps of this embodiment are basically the same as those of embodiment 2, except that in this embodiment, a separate closed seawater reaction system is not required to be added in the adjacent sea area, but the interval between aeration pipelines in the second step is increased to 5m, the air inlet pressure in the sixth step is reduced to 3atm, the air inlet amount is reduced to 150m 3/h, CO 2 gas is introduced into the unsaturated calcareous sand stratum at certain time intervals, and meanwhile, seawater is extracted and sprayed onto the surface of the calcareous sand stratum, so that the water content of the calcareous sand stratum is kept to be not lower than 20%.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (12)
1. A method for reinforcing a calcareous sand foundation by CO 2 is characterized in that a device for reinforcing the calcareous sand foundation by CO 2 applied in the method for reinforcing the calcareous sand foundation by CO 2 comprises a CO 2 gas supply device and an aeration pipeline (13),
The CO 2 gas supply device is communicated with the aeration pipeline (13) through a gas outlet;
The calcareous sand foundation to be reinforced comprises a calcareous sand stratum (11), a coral crushed stone water-permeable cushion layer (12) and a natural stratum (14), wherein the coral crushed stone water-permeable cushion layer (12) is arranged above the natural stratum (14), and the calcareous sand stratum (11) is arranged above the coral crushed stone water-permeable cushion layer (12);
The aeration pipeline (13) is arranged in an interlayer of the coral macadam water-permeable cushion layer (12), a plurality of aeration micropores are formed in the aeration pipeline (13), and the average pore diameter of the aeration micropores ranges from 0.3 mm to 0.6mm.
2. The method for reinforcing a calcareous sand foundation of claim 1, wherein the CO 2 gas supply device comprises a CO 2 gas storage system (2), a gas pressurizing and distributing system (3),
One end of the CO 2 gas storage system is communicated with one end of the gas pressurizing and distributing system, and the gas outlet is arranged at the other end of the gas pressurizing and distributing system.
3. The method for reinforcing a calcareous sand foundation by CO 2 according to claim 2, further comprising a gas drying and purifying system (1), a gas pipeline (6) and a gas valve (7),
The air inlet end of the air transmission pipeline (6) is buried in the calcareous sand stratum (11);
the air valve (7) is arranged at the tail end of the air inlet end;
The gas transmission pipeline (6) is communicated with one end of the gas drying and purifying system (1) through a gas outlet end, and the other end of the gas drying and purifying system (1) is communicated with the CO 2 gas storage system (2).
4. The method for reinforcing a calcareous sand foundation by CO 2 according to claim 1, further comprising a rocker arm lance (8) and a water pump (9),
The water inlet of the water suction pump (9) is arranged on the surface layer inside the calcareous sand stratum (11), and the lowest point of the water inlet of the water suction pump (9) is lower than the low tide level (5);
The water outlet of the water suction pump (9) is communicated with the inlet end of the rocker arm spray gun (8), and the setting position of the outlet end of the rocker arm spray gun (8) is higher than the stratum surface of the calcareous sand stratum (11).
5. The method for reinforcing a calcareous sand foundation by CO 2 according to claim 1, characterized in that the aeration line (13) is made of a flexible polymeric material.
6. The method of reinforcing a calcareous sand foundation of claim 5, wherein the flexible polymeric material is neoprene.
7. The method for reinforcing a calcareous sand foundation of claim 1, wherein the CO 2 is selected from the group consisting of,
The aeration pipeline is in a continuous distributed arrangement form;
Or alternatively
The CO 2 gas supply has a plurality of gas outlets,
The aeration pipeline is in a sectional arrangement mode, and each section of the aeration pipeline is communicated with one air outlet of the CO 2 gas supply device.
8. The method for reinforcing a calcareous sand foundation according to claim 1, characterized in that it further comprises a transparent film (10),
The transparent film (10) is covered around the calcareous sand stratum (11) and the coral rubble water-permeable cushion layer (12).
9. The method for reinforcing a calcareous sand foundation by CO 2 according to claim 1, characterized in that the aeration line (13) is provided with test points, which are located at one or more of the bending, branching, starting and ending positions of the aeration line (13).
10. A method of reinforcing a calcareous sand foundation with CO 2 as claimed in claim 1, wherein the coral crushed stone water-permeable mat (12) comprises a circular or sub-circular calcareous sand having a particle size ranging from 2 to 5mm.
11. The method of reinforcing a calcareous sand foundation with CO 2 according to claim 1, wherein the calcareous sand formation (11) is a calcareous sand formation (11) compacted by a vibratory compaction method.
12. The method of reinforcing a calcareous sand foundation of claim 1, wherein the reaction mechanism of the method of reinforcing a calcareous sand foundation of CO 2 comprises:
Wherein,
In the formula (a), caCO 3 is the main chemical component of a solid medium in a calcareous sand foundation to be reinforced, CO 2 is generated by aeration through the aeration pipeline (13), and H 2 O exists in a seawater environment;
In the formula (b), ca 2+ is mainly solid CaCO 3 which is generated by dissolution, and SO 4 2- exists in a seawater environment;
In formula (c), ca 2+ is mainly solid CaCO 3, and HCO 3 - is produced in formula (a).
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| JPS546309A (en) * | 1977-06-16 | 1979-01-18 | Mamoru Akashi | Method of stabilizing nature of soil |
| JP4940462B1 (en) * | 2011-02-10 | 2012-05-30 | 強化土エンジニヤリング株式会社 | Ground improvement method |
| CN107905213A (en) * | 2017-11-24 | 2018-04-13 | 中国矿业大学 | Calcareous sand ground base carbon dioxide reinforcement technique |
| CN212506221U (en) * | 2020-03-13 | 2021-02-09 | 中国电建集团华东勘测设计研究院有限公司 | Calcareous sandy soil foundation biological reinforcement test device |
| CN115075221A (en) * | 2022-07-15 | 2022-09-20 | 中国科学院武汉岩土力学研究所 | Quick curing method for calcareous sand |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS546309A (en) * | 1977-06-16 | 1979-01-18 | Mamoru Akashi | Method of stabilizing nature of soil |
| JP4940462B1 (en) * | 2011-02-10 | 2012-05-30 | 強化土エンジニヤリング株式会社 | Ground improvement method |
| CN107905213A (en) * | 2017-11-24 | 2018-04-13 | 中国矿业大学 | Calcareous sand ground base carbon dioxide reinforcement technique |
| CN212506221U (en) * | 2020-03-13 | 2021-02-09 | 中国电建集团华东勘测设计研究院有限公司 | Calcareous sandy soil foundation biological reinforcement test device |
| CN115075221A (en) * | 2022-07-15 | 2022-09-20 | 中国科学院武汉岩土力学研究所 | Quick curing method for calcareous sand |
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