Method for reducing frost heaving and salt heaving of roadbed

Abstract

The invention relates to the technical field of roadbed engineering, in particular to a method for reducing frost heaving and salt heaving of a roadbed. According to the method, a waterproof cushion layer is arranged on a foundation, and a roadbed is arranged on the waterproof cushion layer; the components of the roadbed comprise a neutralizer of sulfate and / or sulfite. According to the method for reducing frost heaving and salt heaving of the roadbed, the waterproof cushion layer is arranged, water of the foundation can be prevented from moving upwards and entering the roadbed, and therefore frost heaving is effectively reduced; the neutralizer of the sulfate and / or the sulfite is added into the components of the roadbed, the sulfate and / or the sulfite can be neutralized, precipitates are formed, soluble salt containing sulfate radicals and sulfite radicals is prevented from being migrated, and therefore salt expansion is effectively reduced; the method is simple in step, low in cost, high in construction efficiency and easy to popularize in the cold region where the salinized soil is widely distributed.

Description

Technical Field

[0001] The invention relates to the technical field of roadbed engineering, and in particular to a method for reducing frost heave and salt heave of a roadbed. Background Art

[0002] Saline soil is a general term for saline soil, alkaline soil and various salinized and alkaline soils, in which the content of soluble salt is greater than 0.3%. In saline soil areas, when carrying out road construction, local saline soil is generally used as the filler for the roadbed.

[0003] However, when saline soil is used as filler for roadbed, it is prone to problems such as dissolution, salt swelling, and corrosion. Salt swelling of saline soil is mainly caused by the precipitation of sodium sulfite (Na2SO3) or sodium sulfate (Na2SO4) crystals, which form hydrates and cause volume expansion.

[0004] These situations will not only make the road construction process more difficult, but also reduce the quality of the road, and in serious cases will cause some safety hazards. Saline soil is widely distributed, and is also widely distributed in cold areas with lower temperatures. For cold areas, the winter temperature can be as low as minus 20 degrees Celsius or even lower. Under low temperature conditions, moisture in the roadbed will precipitate, leading to frost heave problems. At the same time, the precipitated moisture will cause a greater amount of soluble salt in the saline soil to dissolve, making problems such as salt heave more serious.

[0005] At present, the general method for improving saline soil is to use coal slag to treat the alkaline components in it, but there is no particularly effective method for treating the salt components. At the same time, there is currently no method that can solve both frost heave and salt heave at the same time. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for reducing frost heave and salt heave of roadbed, so as to solve the serious problem of frost heave and salt heave of roadbed in cold regions.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] The invention provides a method for reducing frost heave and salt heave of roadbed, comprising arranging a waterproof cushion layer on the foundation and arranging a roadbed on the waterproof cushion layer; the components of the roadbed include a neutralizer of sulfate and / or sulfite.

[0009] Based on the above technical solution, the present invention can also be improved as follows.

[0010] Furthermore, the components of the roadbed include saline soil, and the mass percentage of the saline soil is greater than or equal to 0.2%.

[0011] Furthermore, before setting up the roadbed, the concentration of sulfate and / or sulfite in the saline soil is detected, and the amount of the neutralizer is determined according to the concentration of sulfate and / or sulfite.

[0012] Furthermore, the detection process is: obtaining a soil sample and preparing a soil sample solution, and measuring the salt content in the soil sample solution; the measuring method is one of a conductivity measurement method, a titration method or a weighing method.

[0013] Furthermore, the neutralizing agent is a CaCl2 solution, in which the molar ratio of CaCl2 to sulfate and / or sulfite is 1:1.

[0014] Furthermore, the method also includes the step of spraying the CaCl2 solution onto a roadbed filler, and compacting the roadbed filler on the waterproof cushion layer to obtain the roadbed.

[0015] Furthermore, the waterproof cushion layer comprises calcium oxide.

[0016] Furthermore, the waterproof cushion layer is a quicklime cushion layer.

[0017] Furthermore, in the quicklime cushion layer, the particle size of the quicklime is less than 2 mm.

[0018] Furthermore, the thickness of the quicklime cushion layer is 5 to 10 cm, and the thickness of the roadbed is 1 to 9 cm.

[0019] The beneficial effects of the present invention are:

[0020] (1) The method for reducing frost heave and salt heave of the roadbed of the present invention can prevent the moisture of the foundation from migrating upward and entering the roadbed by providing a waterproof cushion layer, thereby effectively reducing frost heave;

[0021] (2) The method for reducing frost heave and salt swelling of roadbed of the present invention comprises adding a sulfate and / or sulfite neutralizer to the components of the roadbed, which can neutralize the sulfate and / or sulfite and form a precipitate, thereby preventing the migration of soluble salts containing sulfate and sulfite, thereby effectively reducing salt swelling;

[0022] (3) In the method for reducing frost heave and salt heave of roadbed of the present invention, the waterproof cushion layer comprises calcium oxide, which generates calcium sulfite precipitation while reducing water migration and thus reducing frost heave, forming a natural water-insulating layer, further preventing water and salt migration, and thus preventing and controlling the occurrence of salt heave and frost heave of roadbed in cold regions;

[0023] (4) The method for reducing frost heave and salt heave of roadbed of the present invention has simple steps, low cost, high construction efficiency, and is easy to promote in cold areas where saline soil is widely distributed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The method for reducing frost heave and salt heave of roadbed of the present invention is a construction flow chart of Example 1;

[0025] Figure 2 This is a cross-sectional view of the foundation, roadbed and quicklime cushion layer of Example 1 of the method for reducing frost heave and salt heave of roadbed according to the present invention. DETAILED DESCRIPTION

[0026] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0027] The method for reducing frost heave and salt heave of roadbed of the present invention comprises arranging a waterproof cushion layer on the foundation and arranging a roadbed on the waterproof cushion layer; the components of the roadbed include a neutralizer of sulfate and / or sulfite.

[0028] The method for reducing frost heave and salt swelling of a roadbed of the present invention can prevent moisture in the foundation from migrating upward and entering the roadbed, thereby effectively reducing frost heave; and adding a sulfate and / or sulfite neutralizer to the components of the roadbed can neutralize the sulfate and / or sulfite and form a precipitate, thereby preventing the migration of soluble salts containing sulfate and sulfite, thereby effectively reducing salt swelling.

[0029] Theoretically, the method of the present invention can be applied to the situation that the roadbed contains sulfate and / or sulfite under any conditions. In some areas or during the construction process, although saline soil is not used as the main component of the roadbed, it is still unavoidable that some soluble salt components may be mixed in it.

[0030] However, the above situation is relatively rare. The present invention is mainly aimed at the saline soil areas in cold regions, and uses saline soil as the main component of the roadbed. Therefore, the components of the roadbed of the present invention also include saline soil.

[0031] Preferably, the saline soil contains sulfate and / or sulfite.

[0032] Preferably, before setting the roadbed, the concentration of sulfate and / or sulfite in the saline soil is first detected, and the amount of neutralizer is determined according to the concentration of sulfate and / or sulfite; this can effectively improve the anti-swelling effect, save the amount of neutralizer, and improve the treatment efficiency of the neutralizer.

[0033] Preferably, the detection process is:

[0034] Salt content detection steps:

[0035] (1) Soil sampling: Select representative saline soil on the roadbed and sample at a depth of 0.2 m. The sampling points should be evenly distributed across the entire roadbed section to ensure the representativeness of the sample. After sampling, mix the soil samples evenly to reduce errors.

[0036] (2) Soil solution extraction: Extract the salt from the sample. Common extraction methods include saturated soil solution method, saturated soil suspension method and soil leaching method. These methods are suitable for soils with different salt contents. The sample is mixed with water in a certain proportion, stirred and then left to stand or soak, and then the supernatant is taken for testing.

[0037] (3) Salt content determination: The salt content can be determined indirectly by measuring the conductivity of the soil solution, or by evaporating the soil solution to dryness and then weighing the residual salt mass. In addition, the content of specific ions in the soil solution, such as chloride ions or sulfate ions, can also be determined by titration.

[0038] (4) Calculation of results: Calculate the water-soluble salt content in the sample according to the experimental principles and experimental steps. This usually involves measuring the total amount of salt in the solution after the soil sample is mixed with water, or inferring the salt content by measuring conductivity or other physical and chemical parameters.

[0039] Preferably, the neutralizing agent is a CaCl2 solution, and the molar ratio of CaCl2 to sulfate and / or sulfite is 1:1.

[0040] Using CaCl2 as a neutralizer can effectively convert sulfate and / or sulfite in saline soil into precipitation. Specifically, CaCl2 can react with sulfate or sulfite in the following chemical reactions:

[0041] Na2SO3+CaCl2=2NaCl+CaSO3↓

[0042] Na2SO4+CaCl2=2NaCl+CaSO4↓

[0043] Through the above reaction, SO3 in saline soil can be -2 and SO4 -2 Chemical precipitation is formed, thus fundamentally eliminating the influence of salt expansion. The formed Ca2SO3 or Ca2SO4 solid sediments can not only serve as a roadbed solidification adhesive to improve the roadbed strength and deformation resistance, but also form a natural waterproof layer to reduce the migration and penetration of water in the roadbed and weaken the frost heave effect. In addition, when CaCl2 solution is used as an improver, the solubility of the new product of the chemical reaction, chloride (Nacl), is 4 to 8 times that of sulfate in the range of 0℃ to 10℃, which can effectively reduce the precipitation of chloride crystals, and at the same time reduce the freezing temperature of the roadbed and reduce frost heave.

[0044] Preferably, the method further comprises the step of spraying a CaCl2 solution onto the roadbed filler, and compacting the roadbed filler on the waterproof cushion layer to obtain a roadbed; this allows the CaCl2 solution to be evenly mixed with the roadbed filler, further improving the treatment effect.

[0045] Preferably, the waterproof cushion layer includes calcium oxide, which can react with moisture in the foundation to produce calcium hydroxide. At the same time, the waterproof cushion layer may also contain gravel, sand and other ingredients, all of which can assist in water isolation.

[0046] The specific reaction process of calcium oxide is:

[0047] CaO+H2O=Ca(OH)2

[0048] 2NaHSO3+Ca(OH)2→Na2SO3+2H2O+CaSO3

[0049] Na2SO3+Ca(OH)2=CaSO3↓+2NaOH

[0050] Na2SO4+Ca(OH)2=CaSO4↓+2NaOH

[0051] It can be seen that while calcium oxide reduces water migration and thus reduces frost heave, it also generates calcium sulfite precipitation, forming a natural waterproof layer, which further blocks water and salt migration and thus prevents the occurrence of salt heave and frost heave of roadbed in cold regions.

[0052] Preferably, the waterproof cushion layer is a quicklime cushion layer; the use of a quicklime cushion layer can effectively achieve waterproofing, and quicklime is low in price and easy to obtain.

[0053] Preferably, in the quicklime cushion layer, the particle size of the quicklime is less than 2 mm; further preferably, the particle size of the quicklime is 0.01 to 2 mm.

[0054] Preferably, the thickness of the quicklime cushion layer is 5 to 10 cm, and the thickness of the roadbed is 1 to 9 cm.

[0055] More preferably, the thickness of the quicklime cushion layer is 5 cm, and the thickness of the roadbed is 1 to 3 m.

[0056] Further preferably, the thickness of the quicklime cushion layer is 10 cm, and the thickness of the roadbed is greater than 3 m.

[0057] The present invention is illustrated below by means of specific examples.

[0058] Example

[0059] This embodiment adopts the method of the present invention to treat the saline soil roadbed of the Sanshiliyingfang bypass highway on G219 line in Xinjiang, and the treatment steps are as follows:

[0060] S1. Detection of sulfate and sulfite content in saline soil.

[0061] S2. Determine the amount of CaCl2 and prepare CaCl2 solution.

[0062] S3, spraying the roadbed filler with CaCl2 to obtain a treated roadbed filler.

[0063] S4. Lay a quicklime cushion layer on the foundation.

[0064] S5, laying the treated roadbed filler on the quicklime cushion layer and compacting it to obtain a roadbed. The cross-sectional view of the foundation, roadbed and quicklime cushion layer of this embodiment is as follows: Figure 2 shown.

[0065] The detailed description of the above steps is as follows:

[0066] The roadbed filler of this embodiment uses saline soil widely distributed in the region as the main raw material. Before construction, the sulfate and sulfite content in the saline soil is tested, and the measured result shows that the salt content is 1.2%.

[0067] According to the above results, the dosage of CaCl2 solid is determined to be 12g / kg saline soil. According to the specific mass of saline soil, the corresponding mass of CaCl2 solid is prepared into solution.

[0068] There is no specific limit to the concentration of the CaCl2 solution. Generally, it can be diluted to a sprayable state. However, if the solution contains too much water, the water content of the roadbed will be too high. Therefore, in this embodiment, the CaCl2 solution is prepared into a 0.12 g / ml solution.

[0069] The CaCl2 solution is sprayed on the roadbed filler and fully reacted to obtain the treated roadbed filler.

[0070] In this embodiment, a quicklime cushion layer is used as a waterproof cushion layer. After the quicklime cushion layer is laid on the foundation, the roadbed filler treated as above is laid on the quicklime cushion layer and compacted.

[0071] In this embodiment, the particle size range of the quicklime in the quicklime cushion layer is less than 2 mm, the thickness of the quicklime cushion layer is 5 cm, and the thickness of the roadbed is 1.5 m.

[0072] Under the condition of -10°C, the frost heave and salt heave conditions of the roadbed of this embodiment were tested, and the test results showed that the total amount of frost heave and salt heave was 15 mm.

[0073] Comparative Example 1

[0074] In this comparative example, the saline soil roadbed of the Sanshiliyingfang bypass road on line G219 in Xinjiang is treated. In the treatment steps, fly ash is used as a cushion layer, and the roadbed is laid on the fly ash cushion layer. The other steps are the same as those in the embodiment.

[0075] Under the same conditions as in the example, the frost heave and salt heave conditions of the roadbed in this comparative example were tested, and the test results showed that the total amount of frost heave and salt heave was 32 mm.

[0076] From the above comparison, it can be seen that fly ash has a certain anti-freeze and salt expansion effect, but it is significantly lower than the embodiment, and when the temperature is lower than -10°C, its effect is significantly reduced, indicating that this method cannot meet the conditions in cold regions.

[0077] Comparative Example 2

[0078] In this comparative example, the saline soil roadbed of the Sanshiliyingfang bypass road on G219 line in Xinjiang is treated. In the treatment steps, no cushion layer is used, and the roadbed is laid directly on the foundation. The other steps are the same as those in the embodiment.

[0079] Under the same conditions as those in the embodiment, the frost heave and salt heave conditions of the roadbed in this comparative example were tested, and the test results showed that the total frost heave and salt heave were 43 mm.

[0080] From the above comparison, it can be seen that without using a cushion layer, the anti-frost expansion effect of this comparative example is extremely poor, the anti-salt expansion effect is also significantly reduced, and when the temperature is lower than -10°C, the effect is significantly reduced, indicating that this method cannot meet the conditions of cold regions.

[0081] Comparative Example 3

[0082] In this comparative example, the saline soil roadbed of the Sanshiliyingfang bypass road on G219 line in Xinjiang was treated. In the treatment steps, the same quicklime cushion layer as in the embodiment was used, but the roadbed auxiliary materials were not treated, and the other steps were the same as in the embodiment.

[0083] Under the same conditions as those in the embodiment, the frost heave and salt heave conditions of the roadbed in this comparative example were tested, and the test results showed that the total amount of frost heave and salt heave was -28 mm.

[0084] From the above comparison, it can be seen that without treating the roadbed, the anti-salt expansion effect of this comparative example is extremely poor, the anti-freeze expansion effect is also significantly reduced, and when the temperature is lower than -10°C, the effect is significantly reduced, indicating that this method cannot meet the conditions of cold areas.

[0085] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0086] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0087] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0088] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0089] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0090] 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for reducing frost heave and salt heave of roadbed, characterized in that: A waterproof cushion layer is arranged on the foundation, and a roadbed is arranged on the waterproof cushion layer; the components of the roadbed include a neutralizer of sulfate and / or sulfite.

2. A method for reducing frost heave and salt heave of roadbed according to claim 1, characterized in that: The roadbed comprises saline soil, and the mass percentage of salt content of the saline soil is greater than or equal to 0.2%.

3. A method for reducing frost heave and salt heave of roadbed according to claim 2, characterized in that: Before setting the roadbed, the concentration of sulfate and / or sulfite in the saline soil is first detected, and the amount of the neutralizer is determined according to the concentration of sulfate and / or sulfite.

4. A method for reducing frost heave and salt heave of roadbed according to claim 3, characterized in that: The detection process is: obtaining a soil sample and preparing a soil sample solution, and measuring the salt content in the soil sample solution; the measuring method is one of a conductivity measuring method, a titration method or a weighing method.

5. A method for reducing frost heave and salt heave of roadbed according to claim 3, characterized in that: The neutralizing agent is a CaCl2 solution, in which the molar ratio of CaCl2 to sulfate and / or sulfite is 1:

1.

6. A method for reducing frost heave and salt heave of roadbed according to claim 5, characterized in that: The method also includes the step of spraying the CaCl2 solution onto the roadbed filler, and after spraying, compacting the roadbed filler on the waterproof cushion layer to obtain the roadbed.

7. A method for reducing frost heave and salt heave of roadbed according to any one of claims 1 to 6, characterized in that: The waterproof cushion layer comprises calcium oxide.

8. A method for reducing frost heave and salt heave of roadbed according to claim 7, characterized in that: The waterproof cushion layer is a quicklime cushion layer.

9. A method for reducing frost heave and salt heave of roadbed according to claim 8, characterized in that: In the quicklime cushion layer, the particle size of the quicklime is less than 2 mm.

10. A method for reducing frost heave and salt heave of roadbed according to claim 8, characterized in that: The thickness of the quicklime cushion layer is 5 to 10 cm, and the thickness of the roadbed is 1 to 9 cm.

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