A two-stage physical and chemical composite method for embankment construction

Abstract

The present invention provides a two-stage physical and chemical composite method for filling embankments. The method of the present invention includes two stages: flocculation-vacuum preloading dehydration and chemical curing, and the two stages have a temporal sequence; the curing agent involved in chemical curing has very low activity under normal circumstances, and mixing it in high-water content mud can leave sufficient time for full dehydration in the flocculation-vacuum preloading dehydration stage; after the flocculation-vacuum preloading dehydration stage is completed, a chemical stimulant is pressure-injected through the grouting pipe at the bottom of the cofferdam, and the chemical stimulant is induced to directional seepage in the block induction method, uniformly stimulating the activity of the curing agent, and promoting the chemical curing reaction stage. The present invention significantly improves the dehydration effect of the flocculation-vacuum preloading treatment mud in the first stage by greatly extending the window period of the curing reaction of the curing agent, while not affecting the chemical curing modification effect of the second stage. The high-water content waste mud after treatment can meet the mechanical property requirements of embankment filling.

Description

Technical Field

[0001] The invention belongs to the fields of geotechnical engineering and water conservancy engineering, and in particular relates to a two-stage physical and chemical composite method for filling embankments. Background Art

[0002] Over the past decade or so, the use of cement-stabilized marine silt as embankment fill has gained increasing attention and popularity. This application solves the problem of the lack of ideal fill materials for local embankment filling projects and allows the economical disposal of large amounts of waste mud generated by dredging channels or underground excavation projects without the need to open new dumping sites. However, the large amount of waste mud generated by dredging channels or underground excavation projects usually has an extremely high water content (120% to 250%). Existing studies generally show that the use of cement and other cementitious materials for solidification without dehydration treatment is ineffective or extremely costly. Therefore, scholars have proposed a method for treating large amounts of high-water-content mud by combining flocculation and dehydration with chemical solidification - the "flocculation-solidification-low-level vacuum preloading combined method", also known as the "physical and chemical composite method."

[0003] The core concept of the physical and chemical composite method is: (1) the added flocculant can play a flocculation and conditioning role, significantly improving the microstructure, permeability and dewatering performance of high-water content mud; (2) using the time window before the solidification reaction fully progresses, vacuum pressure is applied to quickly filter out the water in the high-water content mud mixture, significantly reducing the water content and porosity in a short period of time; (3) the chemical reaction of the late solidifying agent is fully carried out in the dehydrated and more dense medium, greatly improving the mechanical properties after treatment. This method can recycle large volumes of silt resources for embankment filling projects, which is feasible and advanced in theory and practice. However, during the implementation process, it was found that the time window before the solidification reaction fully progresses is usually less than 7 days, or even within 3 days. In this short time window, the vacuum preloading dehydration method cannot achieve a low water content in the high-water content mud, which significantly affects the mechanical properties of the modified mud filler after subsequent chemical solidification. Therefore, there is an urgent need to improve the current "physical and chemical composite method" and develop a new high-water content mud modification technology that can not only improve the dehydration effect in the vacuum preloading dehydration stage, but also give full play to the chemical solidification effect. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art by providing a two-stage physicochemical composite method for embankment construction to address these issues. This method significantly extends the curing reaction window of the curing agent (i.e., precursor), significantly improving the dehydration efficiency of the slurry during the first stage of flocculation and vacuum preloading. Furthermore, by inducing the migration of the chemical stimulant within the lower-water-content mixture through partitioning, it ensures uniform chemical curing and enhances the chemical curing modification effect of the second stage. The treated high-water-content waste slurry meets the mechanical requirements of embankment fill.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] The present invention provides a two-stage physical and chemical composite method for embankment filling, comprising the following steps:

[0007] S1. Build a first layer of cofferdam and install a grouting pipe at the bottom of the first layer of cofferdam, wherein the grouting pipe is provided with a plurality of grouting holes;

[0008] S2. Install a first drainage system on the side wall of the first cofferdam, the first drainage system being connected to a first drainage pipe outside the cofferdam;

[0009] S3. Install a second drainage system at the bottom of the first cofferdam, wherein the second drainage system is connected to a second drainage pipe outside the cofferdam, and a second valve is installed in the second drainage pipe;

[0010] S4, pouring the slurry mixed with the precursor and flocculant into the first cofferdam;

[0011] S5. Connect the second drain pipe to the second vacuum pump, open the second valve, and perform flocculation-vacuum pre-pressing dehydration on the mud;

[0012] S6. Continue to build a second layer of cofferdam on the first layer of cofferdam and repeat steps S2 to S5; build the third to n-1th layers of cofferdam on the second layer of cofferdam and repeat steps S2 to S5;

[0013] Continue to build the nth layer of cofferdam on the n-1th layer of cofferdam to reach the embankment height, and set a third drainage system on the top of the mud in the nth layer of cofferdam, and repeat steps S2 to S5 until the flocculation-vacuum preloading dehydration of the mud in the entire embankment height is completed; n is a positive integer ≥ 3;

[0014] Wherein, the third drainage system is connected to the third drainage pipe outside the cofferdam, and a third valve is provided in the third drainage pipe;

[0015] S7, injecting a chemical stimulant into the grouting pipe, opening the first valve in the first drain pipe corresponding to the first cofferdam, and simultaneously closing the first valves in the first drain pipes corresponding to the other cofferdams, as well as the second valves and third valves in the second drain pipes of all cofferdams, connecting the first drain pipe to a first vacuum pump, starting the first vacuum pump, and inducing the chemical stimulant to migrate toward the side wall of the first cofferdam; when the ion concentration or pH value in the first drain pipe is close to the ion concentration or pH value of the chemical stimulant, closing the first valve in the first drain pipe;

[0016] Open the first valve in the first drainage pipe corresponding to the second cofferdam, and at the same time close the first valves in the first drainage pipes corresponding to other cofferdams and the second valves and third valves in the second drainage pipes of all cofferdams, connect the first drainage pipe to the first vacuum pump, start the first vacuum pump, and induce the chemical stimulant to migrate to the side wall of the second cofferdam; repeat the same method to induce the chemical stimulant to migrate to the side wall of the n-th cofferdam, when the ion concentration or pH value in the first drainage pipe corresponding to the n-th cofferdam is close to the ion concentration or pH value of the chemical stimulant, close the first valve in the first drainage pipe corresponding to the n-th cofferdam, and at the same time open the third valve, connect the third drainage pipe to the third vacuum pump, start the third vacuum pump, and induce the chemical stimulant to stimulate the remaining unstimulated areas from bottom to top, so that the chemical stimulant in the mud in each part of the cofferdam contacts the precursor, thereby exerting a chemical solidification effect.

[0017] Preferably, the flocculant includes an organic flocculant or an inorganic flocculant;

[0018] At least one of the organic flocculant polyacrylamide and the composite flocculant of polyacrylamide and calcium oxide;

[0019] The inorganic flocculant includes at least one of polyaluminum chloride and polyferric chloride.

[0020] Preferably, the precursor includes at least one of slag powder, fly ash, red mud, and metakaolin;

[0021] And / or, the chemical stimulant includes at least one of NaOH, water glass, and Ca(OH)2.

[0022] Preferably, after the first layer of cofferdam is constructed, a first non-woven geotextile is laid at the bottom of the first layer of cofferdam, and the grouting pipe and the second drainage system are both located on the first non-woven geotextile;

[0023] The grouting pipe is located in the middle of the bottom of the first cofferdam, and a plastic film is laid within a certain range below the grouting pipe to prevent pollution to the soil below.

[0024] Preferably, step S4 is specifically as follows:

[0025] Pour the slurry mixed with the precursor and flocculant into the first cofferdam layer, and then lay a sealing membrane on top of the slurry;

[0026] Step S5 is specifically as follows:

[0027] Connect the second drain pipe to the second vacuum pump, open the second valve, perform flocculation-vacuum pre-pressing dehydration on the mud, and roll up the sealing film after the vacuum dehydration is completed.

[0028] Preferably, before dehydrating the mud in the n-th cofferdam, a second non-woven geotextile is laid on top of the mud in the n-th cofferdam, the third drainage system is located on the second non-woven geotextile, and a sealing membrane is laid on the third drainage system.

[0029] Preferably, the flocculant is an organic flocculant, and the mass of the organic flocculant is 0.04% to 0.2% of the mass of the soil particles in the mud;

[0030] Alternatively, the flocculant is an inorganic flocculant, and the mass of the inorganic flocculant is 0.5% to 3% of the mass of the soil particles in the mud;

[0031] The mass of the precursor is 10% to 20% of the mass of the soil particles in the mud;

[0032] The injection amount of the chemical activator is 60% to 80% of the mass of the precursor.

[0033] Preferably, the first drainage system includes third non-woven geotextiles arranged opposite to each other and a plurality of first permeable panels located between the third non-woven geotextiles, and the first drainage pipe is connected to the plurality of first permeable panels;

[0034] The second drainage system includes fourth non-woven geotextiles arranged opposite to each other and a plurality of second permeable panels located between the fourth non-woven geotextiles, and the second drainage pipe is connected to the plurality of second permeable panels.

[0035] Preferably, the third drainage system includes fifth non-woven geotextiles that are arranged opposite to each other and a plurality of third permeable panels located between the fifth non-woven geotextiles, and the third drainage pipe is connected to the plurality of third permeable panels.

[0036] Preferably, the first drain pipe and the third drain pipe are both provided with an ion concentration sensor and a pH sensor;

[0037] When the ion concentration sensor in the first drain pipe or the third drain pipe monitors that the ion concentration is 80% to 100% of the ion concentration of the chemical stimulant or the pH sensor monitors that the pH value is 80% to 100% of the pH of the chemical stimulant, the first valve in the first drain pipe is closed or the third valve in the third drain pipe is closed.

[0038] The two-stage physical and chemical composite method for embankment filling of the present invention has the following advantages compared with the prior art:

[0039] 1. The two-stage physical and chemical composite embankment filling technology of the present invention introduces a low-activity curing agent to highly separate the two stages of flocculation-vacuum preloading dehydration and chemical curing. This overcomes the negative impact of the early chemical curing reaction on the dehydration effect during the flocculation-vacuum preloading dehydration process in traditional waste mud dehydration and curing treatment methods, leaving a sufficient window period for the first stage of flocculation-vacuum preloading dehydration technology to fully dehydrate high-water-content mud.

[0040] 2. In the second stage of the present invention, a chemical stimulant is introduced to fully stimulate the chemical activity of the low-activity curing agent within the system. A block-by-block induction chemical stimulation method is proposed to achieve directional induction of the seepage of the chemical stimulant within the mud. This ensures the uniformity and controllability of the chemical stimulation of the precursor within the system and fully utilizes the chemical curing effect.

[0041] 3. The present invention monitors the ion concentration and pH at the sidewall and top of the cofferdam to ensure the seepage direction of the chemical stimulant and the stimulating effect of the chemical stimulant, while accurately controlling the amount of stimulant used, thus avoiding environmental pollution caused by excessive overflow of the chemical stimulant;

[0042] 4. The two-stage physical and chemical composite method of embankment filling technology of the present invention stimulates the pre-added precursor, which not only greatly improves the degree of vacuum preloading dehydration, but also ensures the chemical solidification effect of the mud after dehydration, and realizes the optimal solidification effect of the mud at a lower water content. The modified mud meets the mechanical property requirements for embankment engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 This is a schematic diagram of the working process of the flocculation-vacuum preloading and dehydration stage of the two-stage physical and chemical composite method for embankment filling of the present invention;

[0045] Figure 2 This is a schematic diagram of the working process of the partitioned block induced chemical excitation curing stage of the present invention;

[0046] Figure 3 This is a longitudinal cross-sectional structural diagram of the cofferdam of the present invention;

[0047] Figure 4 Schematic diagram of the connection structure between the second drainage system and the second drainage pipe of the present invention;

[0048] Figure 5 It is a structural schematic diagram of the second drainage system of the present invention.

[0049] Figures 1 to 5 The meaning of the numbers are: high-water-content mud to be treated-1, cofferdam-11, grouting pipe-12, grouting hole-121, first drainage system-14, first drainage pipe-15, first valve-16, ion concentration sensor-17, second drainage system-2, first vacuum pump-13, second vacuum pump-25, precursor unloading device-6, first agitator-3, second agitator-5, mud mixture 10, second drainage pipe 23, second valve 24, grouting pump-19, sealing membrane 7, third drainage system 18, third drainage pipe 181, third valve 182, fourth non-woven geotextile 21, second permeable board 22, chemical stimulant 20. DETAILED DESCRIPTION

[0050] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0051] For a better understanding of the present invention and not to limit the scope of the present invention, all numbers used in this application to express amounts, percentages, and other numerical values ​​should be understood as modified by the word "about" in all cases. Therefore, unless otherwise specified, the numerical parameters listed in the specification and the appended claims are approximate values, which may vary depending on the desired properties to be obtained. Each numerical parameter should at least be regarded as obtained based on the reported significant figures and by conventional rounding methods.

[0052] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of this application, the term "including" means "including but not limited to". Various embodiments of the present invention may be presented in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be understood as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0053] The present invention provides a two-stage physical and chemical composite method for embankment filling, comprising two stages: flocculation-vacuum preloading dehydration and chemical solidification. The two stages are sequential in time and include the following steps:

[0054] S1. Build a first layer of cofferdam and install a grouting pipe at the bottom of the first layer of cofferdam, wherein the grouting pipe is provided with a plurality of grouting holes;

[0055] S2. Install a first drainage system on the side wall of the first cofferdam, the first drainage system being connected to a first drainage pipe outside the cofferdam;

[0056] S3. A second drainage system is provided at the bottom of the first cofferdam, the second drainage system being connected to a second drainage pipe outside the cofferdam, and a second valve being provided in the second drainage pipe;

[0057] S4, pouring the slurry mixed with the precursor and flocculant into the first layer of silt cofferdam;

[0058] S5. Connect the second drain pipe to the second vacuum pump, open the second valve, and perform flocculation-vacuum pre-pressing dehydration on the mud;

[0059] S6. Continue to build a second layer of cofferdam on the first layer of cofferdam and repeat steps S2 to S5; build the third to n-1th layers of cofferdam on the second layer of cofferdam and repeat steps S2 to S5;

[0060] Continue to build the nth layer of cofferdam on the n-1th layer of cofferdam to reach the embankment height, and set a third drainage system on the top of the mud in the nth layer of cofferdam, and repeat steps S2 to S5 until the flocculation-vacuum preloading dehydration of the mud in the entire embankment height is completed; n is a positive integer ≥ 3;

[0061] The third drainage system is connected to the third drainage pipe outside the cofferdam, and a third valve is provided in the third drainage pipe;

[0062] S7, injecting a chemical stimulant into the grouting pipe, opening the first valve in the first drain pipe corresponding to the first cofferdam, and simultaneously closing the first valves in the first drain pipes corresponding to the other cofferdams and the second valves and third valves in the second drain pipes of all cofferdams, connecting the first drain pipe to a first vacuum pump, starting the first vacuum pump, and inducing the chemical stimulant to migrate toward the side wall of the first cofferdam; when the ion concentration or pH in the first drain pipe is close to the ion concentration or pH of the chemical stimulant, closing the first valve in the first drain pipe;

[0063] Open the first valve in the first drainage pipe corresponding to the second cofferdam, and simultaneously close the first valves in the first drainage pipes corresponding to other cofferdams and the second valves and third valves in the second drainage pipes of all cofferdams, connect the first drainage pipe to the first vacuum pump, start the first vacuum pump, and induce the chemical stimulant to migrate to the side wall of the second cofferdam;

[0064] Repeat the same method as above to induce the chemical stimulant to migrate to the side wall of the nth layer of cofferdam;

[0065] When the ion concentration or pH value in the first drainage pipe corresponding to the n-th cofferdam is close to the ion concentration or pH value of the chemical stimulant, the first valve in the first drainage pipe corresponding to the n-th cofferdam is closed, and the third valve is opened at the same time. The third drainage pipe is connected to the third vacuum pump, and the third vacuum pump is started to induce the chemical stimulant to stimulate the remaining unstimulated areas from bottom to top, so that the chemical stimulant in each part of the mud in the cofferdam contacts the precursor and exerts a chemical solidification effect.

[0066] The two-stage physical and chemical composite method for embankment filling of the present invention comprises steps S1 to S6 as stage one: flocculation-vacuum preloading and dehydration, and S7 as stage two: chemical solidification; stage one: flocculation-vacuum preloading and dehydration is achieved by flocculation conditioning and vacuum preloading; specifically, Figure 1As shown, the cofferdam 11 is constructed in layers according to the designed height. First, the first layer of cofferdam is constructed, and a grouting pipe 12 is set at the bottom of the first layer of cofferdam. The grouting pipe 12 is provided with multiple grouting holes 121. A first drainage system 14 is set on the side wall of the first layer of silt cofferdam, and the first drainage system 14 is connected to the first drainage pipe 15 outside the cofferdam. A second drainage system 2 is set at the bottom of the first layer of cofferdam, and the second drainage system 2 is connected to the second drainage pipe outside the cofferdam. A second valve is provided in the second drainage pipe; specifically, the first drainage system 14 and the second drainage system 2 are relatively independent, and are independently controlled by the first vacuum pump 13 and the second vacuum pump 25 respectively.The mud mixed with the precursor and the flocculant is poured into the first layer of the silt cofferdam; specifically, the mud 1 is transported to the first pipeline, the precursor is added to the first pipeline through the precursor feeding device 6, the mud 1 and the precursor are transported to the first agitator 3 for mixing and stirring, and then transported to the second pipeline again, the flocculant is added to the second pipeline through the flocculant feeding device 4, the precursor, flocculant and mud are transported to the second agitator 5 for mixing and mixing to obtain a mud mixture 10 mixed with the precursor and the flocculant, that is, a mud mixed with the precursor and the flocculant; the mud mixture 10 is poured into the first layer of the silt cofferdam, and a sealing film is laid on the top surface of the mud mixed with the precursor and the flocculant, and the second drainage pipe 23 is connected to the second vacuum pump 25. Open the second valve 24 (the first valve 16 can be opened or closed at this time) to perform flocculation-vacuum pre-pressing dehydration on the mud; apply vacuum pressure inside the mud to be treated by vacuum filtration to promote rapid dehydration of the mud mixture, roll up the sealing film after the vacuum filtration is completed, and start to build the next layer of cofferdam until the predetermined embankment height is reached; specifically, continue to build the second layer of cofferdam on the first layer of cofferdam, lay the first drainage system and the corresponding first drainage pipe on the side wall of the second layer of cofferdam, and set the second drainage system and the second drainage pipe at the bottom of the second layer of cofferdam, and again pour the mud mixed with the precursor and flocculant into the second layer of silt cofferdam, and lay the sealing film on the top surface of the mud mixed with the precursor and flocculant, and then The second drainage pipe 23 corresponding to the cofferdam is connected to the second vacuum pump 25, and the second valve 24 is opened (the first valve can be opened or closed at this time), and the mud is flocculated and vacuum pre-pressed for dehydration; according to the same method, the third to n-1th cofferdams are built on the second cofferdam, and a second drainage system and a second drainage pipe are set at the bottom of the n-1th cofferdam, and the mud mixed with the precursor and the flocculant is poured into the n-1th silt cofferdam again, and a sealing film is laid on the top surface of the mud mixed with the precursor and the flocculant, and the second drainage pipe 23 corresponding to the n-1th cofferdam is connected to the second vacuum pump 25, and the second valve 24 is opened (the first valve can be opened or closed at this time), and the mud is flocculated and vacuum pre-pressed for dehydration, so as to complete the process. Flocculation-vacuum preloading and dehydration of the mud in pairs from the first to the nth cofferdams; continue to build the nth cofferdam on the n-1th cofferdam to reach the embankment height, and set a third drainage system on the top of the mud in the nth cofferdam (it can be understood that the nth cofferdam is the topmost cofferdam), and follow the same method as above until the flocculation-vacuum preloading and dehydration of the mud in the entire embankment height is completed; n is a positive integer ≥3; wherein, the third drainage system is connected to the third drainage pipe 181 outside the cofferdam, and the third valve 182 is provided in the third drainage pipe 181; Stage 2: chemical curing; The chemical curing stage involves the selection of a curing agent (i.e., a precursor), which is added together with the flocculant during the flocculation conditioning process and is evenly mixed in the mud to be treated.The characteristic of the curing agent is that it has controllable curing reaction, that is, its activity under normal environment is very low, and it hardly plays a role in curing, which can leave a sufficient time window for the flocculation-vacuum preloading dehydration stage. After the time required for the flocculation-vacuum preloading dehydration stage is over, by injecting a chemical stimulant and controlling the chemical stimulant to fully contact the precursor through technical means, the activity of the precursor is greatly improved, and a uniform and controllable curing effect is achieved in the chemical curing stage. In order to achieve the control effect on the curing effect of the curing agent in stage two, the focus is on ensuring uniform and sufficient contact of the chemical stimulant with the precursor; the present invention proposes a scheme for inducing the chemical stimulant in blocks to achieve the above-mentioned needs, that is, by inducing the chemical stimulant to achieve block migration inside the mud after dehydration, the curing agent is controlled to complete a uniform curing effect inside the mud. Specifically, the second stage is: injecting chemical stimulant into the grouting pipe 12, opening the first valve 16 in the first drain pipe 15 corresponding to the first cofferdam, and at the same time closing the first valves in the first drain pipes corresponding to other cofferdams and the second valves 24 and the third valve 182 in the second drain pipes 23 of all cofferdams, connecting the first drain pipe 15 to the first vacuum pump 13, starting the first vacuum pump 13, under the action of vacuum negative pressure, the chemical stimulant preferentially migrates to the side wall of the first cofferdam, fully stimulating the activity of the curing agent (i.e., precursor) in the first cofferdam, and entering the chemical curing stage; when the ion concentration or pH in the first drain pipe is close to the ion concentration or pH of the chemical stimulant, then closing the first valve in the first drain pipe; opening the first valve in the first drain pipe corresponding to the second cofferdam, and at the same time closing the first valves in the first drain pipes corresponding to other cofferdams and the second valves and the third valves in the second drain pipes of all cofferdams, connecting the first drain pipe to the first vacuum pump, starting the first vacuum pump, inducing the chemical stimulant to migrate to the second cofferdam The chemical stimulant migrates to the side wall of the cofferdam, fully stimulating the activity of the curing agent (i.e., precursor) in the second cofferdam and entering the chemical curing stage; repeating the same method as above to induce the chemical stimulant to migrate to the side wall of the n-1th cofferdam; further, opening the first valve in the first drain pipe corresponding to the nth cofferdam, and at the same time closing the first valve in the first drain pipe corresponding to other cofferdams and the second valve and the third valve in the second drain pipe of all cofferdams, connecting the first drain pipe corresponding to the nth cofferdam to the first vacuum pump, starting the first vacuum pump, inducing the chemical stimulant to migrate to the side wall of the nth cofferdam, when the ion concentration or pH value in the first drain pipe corresponding to the nth cofferdam is close to the ion concentration or pH value of the chemical stimulant, closing the first valve in the first drain pipe corresponding to the nth cofferdam, and at the same time opening the third valve, connecting the third drain pipe to the third vacuum pump, starting the third vacuum pump, inducing the chemical stimulant to stimulate the remaining unstimulated areas from bottom to top, so that the chemical stimulant in each part of the mud in the cofferdam contacts with the precursor, and exerting a chemical curing effect.

[0067] The present invention discloses a two-stage physicochemical composite embankment construction technology, comprising two stages: flocculation-vacuum preloading dehydration and chemical curing. The two stages are sequentially timed. The curing agent involved in chemical curing has very low activity under normal circumstances. Mixing it with high-water-content mud allows sufficient time for complete dehydration during the flocculation-vacuum preloading dehydration stage. After the flocculation-vacuum preloading dehydration stage, a chemical stimulant is pressure-injected through the grouting pipe at the bottom of the cofferdam. The chemical stimulant is induced to flow in a block-by-block manner, uniformly stimulating the activity of the curing agent and promoting the chemical curing reaction stage. Monitoring is also used to accurately determine the stimulating effect of the current block and the start time of the next block, thereby avoiding environmental pollution caused by stimulant overflow. The present invention significantly improves the dehydration effect of the mud treated in the first stage of flocculation-vacuum preloading by significantly extending the window period of the curing agent curing reaction, while not affecting the chemical curing modification effect of the second stage. The treated high-water-content waste mud can meet the mechanical property requirements of embankment construction.

[0068] For further reference, Figure 2 As shown, it shows a schematic diagram of the solution to solidify the slurry in the cofferdam by controlling the opening or closing of the first valve 16 and simultaneously closing the second valve 24 and opening or closing the third valve 182. Figure 2 The figure shows the gradual solidification of the slurry in areas a, b, c, and d within the cofferdam. Specifically, a third drainage system is installed on top of the slurry within the nth cofferdam. To achieve solidification in areas c and d, relying solely on the first drainage system is not feasible. To achieve this, third valve 182 in third drainage pipe 181 is opened, connecting the third drainage pipe to a third vacuum pump. This induces the chemical stimulant to migrate upward toward areas c and d, where it chemically solidifies. The vacuum pump and grouting pump are then turned off. Curing is then performed for 7 to 28 days, depending on the strength requirements, to allow the chemically stimulated precursor to continue chemically solidifying within the relatively dense, dehydrated mixture. The treated, high-water-content slurry meets the mechanical requirements for embankment fill.

[0069] In some embodiments, the chemical activator 20 is placed in a container and injected into the grouting pipe 12 through the grouting pump 19 .

[0070] In some embodiments, the flocculant comprises an organic flocculant or an inorganic flocculant;

[0071] In some embodiments, at least one of an organic flocculant polyacrylamide and a composite flocculant of polyacrylamide and calcium oxide;

[0072] In some embodiments, the inorganic flocculant includes at least one of polyaluminum chloride and polyferric chloride.

[0073] In some embodiments, the precursor includes at least one of slag powder, fly ash, red mud, and metakaolin.

[0074] In some embodiments, the chemical activator includes at least one of NaOH, water glass, and Ca(OH)2.

[0075] In the above embodiment, the precursor hardly undergoes a solidification reaction during the flocculation-vacuum preloading dehydration stage, which reserves sufficient time for mud dehydration; in the chemical solidification stage, a chemical activity stimulator corresponding to the low-activity solidifying agent is introduced to stimulate the chemical activity of the solidifying agent, so that the chemical solidification effect is fully exerted in the low-water content mud mixture that has been fully dehydrated by the flocculation-vacuum preloading technology.

[0076] In some embodiments, after the first layer of silt cofferdam is constructed, a first non-woven geotextile is laid at the bottom of the first layer of silt cofferdam, and the grouting pipe and the second drainage system 2 are both located on the first non-woven geotextile.

[0077] In some embodiments, the grouting pipe is located in the middle of the bottom of the first layer of silt cofferdam, and a plastic film is laid within a certain range below the grouting pipe to prevent contamination of the soil below.

[0078] In some embodiments, step S4 is specifically as follows:

[0079] Pour the slurry mixed with precursor and flocculant into the first layer of silt cofferdam, and then lay a sealing membrane on top of the slurry.

[0080] In some embodiments, step S5 is specifically as follows:

[0081] Connect the second drain pipe 23 to the second vacuum pump 25, open the second valve 24, perform flocculation-vacuum pre-pressing dehydration on the mud, and roll up the sealing film after the vacuum dehydration is completed.

[0082] In some embodiments, before dehydrating the mud in the nth layer of silt cofferdam, a second non-woven geotextile is laid on top of the mud in the nth layer of cofferdam, the third drainage system is located on the second non-woven geotextile, and a sealing membrane 7 is laid on the third drainage system.

[0083] Specifically, in the above embodiment, the nth layer of cofferdam is continued to be built on the n-1th layer of cofferdam to reach the embankment height, n is a positive integer ≥ 3, for example, n is 3, 4, 5, 6, 7, 8, 9, 10..., the specific value of n is determined according to the embankment height, and the third drainage system is set at the top of the nth layer of cofferdam, that is, the top of the topmost cofferdam. For example, if n = 10, the third drainage system is set at the top of the 10th layer of cofferdam.

[0084] In some embodiments, the flocculant is an organic flocculant, and the mass of the organic flocculant is 0.04% to 0.2% of the mass of the soil particles in the mud. Specifically, the mud is composed of water and soil particles.

[0085] In some embodiments, the flocculant is an inorganic flocculant, and the mass of the inorganic flocculant is 0.5% to 3% of the mass of the soil particles in the mud.

[0086] In some embodiments, the mass of the precursor is 10% to 20% of the mass of the soil particles in the slurry.

[0087] In some embodiments, the injection amount of the chemical activator is 60% to 80% of the mass of the precursor.

[0088] In some embodiments, the flocculant is a polyacrylamide organic flocculant, the mass of which is 0.125% of the mass of the soil particles in the mud. The organic flocculant is first dissolved in water, and the mass ratio of the flocculant to water is 1:500; the precursor is slag powder and fly ash, the mass of the precursor is 15% of the mass of the soil particles in the mud, wherein the mass ratio of the slag powder to the fly ash is 10:90; the chemical activator is a mixed activator of NaOH and water glass, the mass of which is 75% of the mass of the precursor, wherein the volume ratio of NaOH to water glass is 40:60, the NaOH concentration is 10 mol / L, and the water glass modulus is 3.3. After flocculation and vacuum preloading, internal pressure is generally below 101 kPa, typically around 80 to 90 kPa, due to potential damage to the sealing membrane and loss of vacuum pressure by the cofferdam. Laboratory tests show that slurry with an initial moisture content of 180% drops to 120% after the first stage of dehydration, a 60% reduction from the initial moisture content. At this moisture content, the 7-day strength of slag powder and fly ash-solidified mud without chemical activators measured by cross-plate shear tests is only approximately 20 kPa, while the 7-day strength of cement-solidified mud under the same conditions reaches 350 kPa; the 7-day strength of slag powder and fly ash-solidified mud with chemical activators reaches 550 kPa. This comparison shows that, compared with traditional cement-solidified mud, slag powder and fly ash-solidified mud without chemical activators undergo virtually no solidification reaction, thus providing a sufficient window for full dehydration in the first stage.

[0089] In some embodiments, the first drainage system 14 includes relatively arranged third non-woven geotextiles and multiple first permeable boards located between the third non-woven geotextiles. The first drainage pipe connects the multiple first permeable boards. Specifically, the multiple first permeable boards are arranged from bottom to top along the side wall of the cofferdam.

[0090] In some embodiments, the second drainage system 2 includes a fourth non-woven geotextile 21 and a plurality of second permeable panels 22 located between the fourth non-woven geotextiles. The second drainage pipe 23 is connected to the plurality of second permeable panels 22. Figures 4-5 As shown, multiple second permeable plates 22 are arranged along the front and rear directions of the cofferdam, and the multiple second permeable plates 22 are all connected to the second drainage pipe 23. A second valve 24 is provided on the second drainage pipe 23, and the second drainage pipe 23 is connected to the second vacuum pump 25. When the second vacuum pump 25 and the second valve 24 are opened, the mud is flocculated and vacuum pre-pressed for dehydration.

[0091] In some embodiments, the third drainage system includes relatively arranged fifth non-woven geotextiles and third permeable panels located between the fifth non-woven geotextiles. The third drainage pipe 181 connects multiple third permeable panels. Specifically, multiple third permeable panels are arranged in the left and right directions at the top.

[0092] Specifically, in the above embodiments, the first drainage system, the second drainage system, and the third drainage system have similar structures, and all include relatively arranged non-woven geotextiles and multiple permeable boards located between the non-woven geotextiles. It can be understood that the non-woven geotextiles are permeable to water, and the permeable boards are porous and can also be permeable to water.

[0093] For further reference, Figure 3 As shown, it is a cross-sectional structural diagram of the cofferdam. The third drainage system is above the second drainage system. The multiple third permeable panels of the third drainage system are vertical to the multiple second permeable panels of the second drainage system in space. The multiple second permeable panels of the second drainage system 2 are arranged at a spacing of 70 to 90 cm. The multiple second permeable panels in the upper and lower cofferdams are staggered, and the spacing between the second permeable panels in the upper and lower cofferdams is 70 to 90 cm.

[0094] In some embodiments, as Figure 3 As shown, a large number of small grouting holes 121 are evenly punched on the surface of the grouting pipe 12, allowing the grouting pump 19 to pressurize the chemical stimulant 20 and diffuse it into the dehydrated mud mixture.

[0095] In some embodiments, an ion concentration sensor 17 and a pH sensor are provided in the first drain pipe 15 and the third drain pipe 181. The ion concentration sensor 17 is used to monitor the ion concentration in the first drain pipe 15 or the third drain pipe 181, and the pH sensor is used to monitor the pH value in the first drain pipe 15 or the third drain pipe 181. When the ion concentration sensor in the first drain pipe or the third drain pipe monitors that the ion concentration is 80% to 100% of the ion concentration of the chemical stimulant or the pH sensor monitors that the pH value is 80% to 100% of the pH of the chemical stimulant, the first valve in the first drain pipe is closed or the third valve in the third drain pipe is closed. Specifically, the ions monitored by the ion concentration sensor are the ions corresponding to the chemical stimulant. For example, when the chemical stimulant is NaOH, the ion concentration sensor monitors Na + Ion concentration, if the chemical stimulant is Ca(OH)2, the ion concentration sensor monitors Ca2+ Ion concentration.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A two-stage physical and chemical composite method for embankment filling, characterized in that: The following steps are involved: S1. Build a first layer of cofferdam and install a grouting pipe at the bottom of the first layer of cofferdam, wherein the grouting pipe is provided with a plurality of grouting holes; S2. Setting a first drainage system on the side wall of the cofferdam, wherein the first drainage system is connected to a first drainage pipe outside the cofferdam; S3. Install a second drainage system at the bottom of the cofferdam, wherein the second drainage system is connected to a second drainage pipe outside the cofferdam, and a second valve is installed in the second drainage pipe; S4, pouring the slurry mixed with the precursor and flocculant into the cofferdam layer; S5. Connect the second drain pipe to the second vacuum pump, open the second valve, and perform flocculation-vacuum pre-pressing dehydration on the mud; S6. Continue to build a second layer of cofferdam on the first layer of cofferdam and repeat steps S2 to S5; build the third to n-1th layers of cofferdam on the second layer of cofferdam and repeat steps S2 to S5; Continue to build the nth layer of cofferdam on the n-1th layer of cofferdam to reach the embankment height, and set a third drainage system on the top of the mud in the nth layer of cofferdam, and repeat steps S2 to S5 until the flocculation-vacuum preloading dehydration of the mud in the entire embankment height is completed; n is a positive integer ≥ 3; Wherein, the third drainage system is connected to the third drainage pipe outside the cofferdam, and a third valve is provided in the third drainage pipe; S7, injecting a chemical stimulant into the grouting pipe, opening the first valve in the first drain pipe corresponding to the first cofferdam, and simultaneously closing the first valves in the first drain pipes corresponding to the other cofferdams, as well as the second valves and third valves in the second drain pipes of all cofferdams, connecting the first drain pipe to a first vacuum pump, starting the first vacuum pump, and inducing the chemical stimulant to migrate toward the side wall of the first cofferdam; when the ion concentration or pH value in the first drain pipe is close to the ion concentration or pH value of the chemical stimulant, closing the first valve in the first drain pipe; Open the first valve in the first drainage pipe corresponding to the second cofferdam, and at the same time close the first valves in the first drainage pipes corresponding to other cofferdams and the second valves and third valves in the second drainage pipes of all cofferdams, connect the first drainage pipe to the first vacuum pump, start the first vacuum pump, and induce the chemical stimulant to migrate to the side wall of the second cofferdam; repeat the same method to induce the chemical stimulant to migrate to the side wall of the n-th cofferdam, when the ion concentration or pH value in the first drainage pipe corresponding to the n-th cofferdam is close to the ion concentration or pH value of the chemical stimulant, close the first valve in the first drainage pipe corresponding to the n-th cofferdam, and at the same time open the third valve, connect the third drainage pipe to the third vacuum pump, start the third vacuum pump, and induce the chemical stimulant to stimulate the remaining unstimulated areas from bottom to top, so that the chemical stimulant in the mud in each part of the cofferdam contacts the precursor, thereby exerting a chemical solidification effect.

2. The two-stage physical and chemical composite method for embankment filling according to claim 1 is characterized in that: The flocculant includes an organic flocculant or an inorganic flocculant; The organic flocculant includes at least one of polyacrylamide and a composite flocculant of polyacrylamide and calcium oxide; The inorganic flocculant includes at least one of polyaluminum chloride and polyferric chloride.

3. The two-stage physical and chemical composite method for embankment filling according to claim 1, characterized in that: The precursor includes at least one of slag powder, fly ash, red mud, and metakaolin; And / or, the chemical stimulant includes at least one of NaOH, water glass, and Ca(OH)2.

4. The two-stage physical and chemical composite method for embankment filling according to claim 1, characterized in that: After the first layer of cofferdam is constructed, a first non-woven geotextile is laid at the bottom of the first layer of cofferdam, and the grouting pipe and the second drainage system are both located on the first non-woven geotextile; The grouting pipe is located in the middle of the first layer of cofferdam.

5. The two-stage physical and chemical composite method for embankment filling according to claim 1, characterized in that: Step S4 is specifically as follows: Pour the slurry mixed with the precursor and flocculant into the first cofferdam layer, and then lay a sealing membrane on top of the slurry; Step S5 is specifically as follows: Connect the second drain pipe to the second vacuum pump, open the second valve, perform flocculation-vacuum pre-pressing dehydration on the mud, and roll up the sealing film after the vacuum dehydration is completed.

6. The two-stage physical and chemical composite method for embankment construction according to claim 1, characterized in that: Before dehydrating the mud in the n-th cofferdam, a second non-woven geotextile is laid on the top of the mud in the n-th cofferdam. The third drainage system is located on the second non-woven geotextile and a sealing membrane is laid on the third drainage system.

7. The two-stage physical and chemical composite method for embankment construction according to claim 2, characterized in that: The flocculant is an organic flocculant, and the mass of the organic flocculant is 0.04% to 0.2% of the mass of the soil particles in the mud; Alternatively, the flocculant is an inorganic flocculant, and the mass of the inorganic flocculant is 0.5% to 3% of the mass of the soil particles in the mud; The mass of the precursor is 10% to 20% of the mass of the soil particles in the mud; The injection amount of the chemical activator is 60% to 80% of the mass of the precursor.

8. The two-stage physical and chemical composite method for embankment construction according to claim 1, characterized in that: The first drainage system includes third non-woven geotextiles arranged opposite to each other and a plurality of first permeable panels located between the third non-woven geotextiles, and the first drainage pipe is connected to the plurality of first permeable panels; The second drainage system includes fourth non-woven geotextiles arranged opposite to each other and a plurality of second permeable panels located between the fourth non-woven geotextiles, and the second drainage pipe is connected to the plurality of second permeable panels.

9. The two-stage physical and chemical composite method for embankment filling according to claim 1, characterized in that: The third drainage system includes fifth non-woven geotextiles arranged opposite to each other and a plurality of third permeable panels located between the fifth non-woven geotextiles. The third drainage pipe is connected to the plurality of third permeable panels.

10. The two-stage physical and chemical composite method for embankment construction according to claim 6, characterized in that: The first drain pipe and the third drain pipe are both provided with an ion concentration sensor and a pH sensor; When the ion concentration sensor in the first drain pipe or the third drain pipe monitors that the ion concentration is 80% to 100% of the ion concentration of the chemical stimulant or the pH sensor monitors that the pH value is 80% to 100% of the pH of the chemical stimulant, the first valve in the first drain pipe is closed or the third valve in the third drain pipe is closed.

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