A method for temporary roadbed hardening for seasonally frozen ground
By injecting soluble calcium salt and sodium silicate solution into the surface of seasonally frozen soil to form grouting stone bodies, the problem of high cost of temporary road reinforcement is solved, achieving low-cost and rapid frozen soil solidification, which is suitable for roadbed hardening before construction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA FIRST HIGHWAY ENGINEERING CO LTD
- Filing Date
- 2024-03-15
- Publication Date
- 2026-07-07
AI Technical Summary
Existing methods for reinforcing seasonally frozen soil are too costly for temporary roads and each has its own problems, especially in effectively addressing traffic difficulties caused by frozen soil thawing during construction.
By adding soluble calcium salts and sodium silicate solutions to the surface of seasonally frozen soil, their reaction forms grouting stone bodies, hardening the temporary roadbed. A modified seeder is used to inject grout into the frozen soil, ensuring a rapid reaction and the formation of a solid roadbed.
It enables low-cost and rapid solidification of seasonally frozen soil, avoids thaw collapse, reduces reliance on large construction equipment, is suitable for construction before the frozen soil thaws, and does not affect the frozen soil thawing process.
Smart Images
Figure CN118147962B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of foundation technology for formation on frozen foundations, and in particular to a method for hardening temporary roadbeds in seasonally frozen soil. Background Technology
[0002] Seasonally frozen soil refers to soil or rock layers that, over a certain period (usually about six months), partially freeze in winter and completely thaw in summer. This type of frozen soil is directly affected by seasonal changes, exhibiting significant temperature fluctuations. While seasonally frozen soil is frozen, construction can proceed directly without additional work. However, once the seasonally frozen soil thaws, it forms mud, making it impassable for vehicles and other construction equipment, requiring reinforcement.
[0003] Currently, the main methods for reinforcing seasonally frozen soil are replacement and insulation. Replacement involves replacing the active layer of frozen soil (the part of the frozen soil that will completely thaw) with materials such as coarse sand and gravel, while insulation involves installing an insulation layer on the soil surface. Of course, in addition to replacement and insulation, there is also drainage, but this method has very limited applicability.
[0004] However, these reinforcement methods are not suitable for structures like temporary roads. Temporary roads are roads used for temporary material transportation during construction, such as dirt roads along highway / railway / construction sites for transporting various building materials and excavated soil. For temporary roads, both replacement and insulation methods are too costly (both material and labor costs are high). Furthermore, replacement methods face the problem of being extremely difficult to implement at any time. If construction is underway in a frozen state, removing the frozen soil is very difficult; if construction is underway in a thawing state, large construction machinery cannot be used. Insulation methods also suffer from poor effectiveness (only maintaining the frozen state for a short time) and are not conducive to vehicle traffic (due to the insulation materials). Summary of the Invention
[0005] This invention provides a method for hardening temporary roadbeds in seasonally frozen soil.
[0006] The technical problem to be solved is that existing methods of reinforcing seasonally frozen soil are too costly for temporary roads, and each method has its own set of problems.
[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for hardening the subgrade of temporary roads in seasonally frozen soil, wherein the subgrade of temporary roads is formed by hardening the surface of seasonally frozen soil, wherein the temporary roads are dirt roads used for transporting building materials and excavated soil near construction sites of highways, railways, and buildings, and the hardening method includes the following steps:
[0008] Step 1: Remove debris from the frozen soil surface that may obstruct vehicle movement;
[0009] Step 2: Before the active layer of the frozen soil begins to thaw, add soluble calcium salts to the surface layer of the frozen soil along the direction of road extension and let them come into contact with the frozen soil; at the same time, at a location adjacent to the location where the soluble calcium salts were injected into the active layer of the frozen soil, inject sodium silicate solution into the surface layer of the frozen soil along the direction of road extension. The active layer of the frozen soil comes into contact with the soluble calcium salts and melts, reacting with the sodium silicate solution to form a grouting stone body, thus completing the hardening of the temporary road surface.
[0010] Furthermore, in step two, soluble calcium salts and sodium silicate are injected into the frozen soil as saturated solutions. The soluble calcium salts and solutions are referred to as calcium slurry, and the saturated sodium silicate solution is referred to as silica slurry. If there is a meadow on the surface of the frozen soil, the slurry injection position is at least 5 cm below the meadow.
[0011] Furthermore, in step two, the soluble calcium salts and sodium silicate injected into the frozen soil meet the following conditions:
[0012] Condition 1: When the total number of moles of soluble calcium salt injected into the frozen soil is reduced by the number of moles of carbonate ions in the soil solution in the active layer of the frozen soil, the solidification temperature of the remaining soluble calcium salt dissolved in the sum of the free water contained in the active layer of the frozen soil, the water contained in the calcium slurry, and the water contained in the silica slurry is lower than the air temperature at the time of construction.
[0013] Condition 2: The total volume of calcium slurry and silica slurry is 100-130% of the total void volume in the active layer of frozen soil;
[0014] Condition 3: Sodium silicate in excess (10-20%).
[0015] Furthermore, in step two, a modified seeder is used to inject two types of slurry into the frozen soil. In the modified seeder, the seed metering device and furrow opener are replaced with a traveling grouting unit, and the seed-fertilizer box is replaced with a slurry storage tank. The traveling grouting unit includes a row of soil-breaking angle steel connected as one unit by a spacing adjustment screw. The soil-breaking angle steel is an angle steel with its edges pointing towards the bottom and tilting forward in the direction of the seeder's movement. A grouting pipe connected to the slurry storage tank is tied to a groove on the back of the soil-breaking angle steel. After all the grouting pipes are connected to a main pipe, they are connected to the slurry storage tank via a grouting pump. Locking nuts for adjusting the spacing of the soil-breaking angle steel are respectively installed on the left and right sides of the spacing adjustment screw.
[0016] Soluble calcium salt solution and sodium silicate solution are stored in two different grout storage tanks, and the grouting pipes corresponding to the two adjacent excavation angle steels are connected to the different grout storage tanks.
[0017] Furthermore, stiffening ribs are welded to the edges of the ground-breaking angle steel, and the stiffening ribs are steel bars, which are combined with the ground-breaking angle steel to form a triangular frame; the bottom of the ground-breaking angle steel is cut into a pointed tip in the horizontal direction for ground breaking, and is re-cut after each construction is completed.
[0018] Furthermore, in use, the distance between two adjacent excavation angle steels should not exceed the slurry diffusion radius.
[0019] Furthermore, step two is carried out when the active layer of the permafrost is frozen and the temperature is not lower than minus 5 degrees Celsius.
[0020] Furthermore, the soluble calcium salt is calcium chloride or calcium formate. When the frozen soil is clayey frozen soil, the soluble calcium salt is calcium formate.
[0021] Compared with existing technologies, the temporary roadbed hardening method for seasonally frozen soil proposed in this invention has the following advantages:
[0022] This invention rationally utilizes the characteristic that temporary roads only need to eliminate thaw settlement, not frost heave (the entire construction process not only fails to eliminate frost heave but actually exacerbates it, while frost heave has no effect on temporary roads). Using mobile grouting equipment, soluble calcium salts and sodium silicate are injected together into the frozen seasonal permafrost. The soluble calcium salts not only melt the permafrost at low temperatures, similar to de-icing salt, allowing the permafrost to participate in the subsequent solidification process, but also react with sodium silicate to solidify the melted permafrost into a grout-formed aggregate. This allows for rapid solidification of seasonal permafrost at a lower cost (both labor and material costs), preventing further thaw settlement. Furthermore, the use of the mobile grouting equipment is separate from the process of permafrost thawing and solidification. Steps requiring large construction machinery are all performed while the permafrost is in a solidified state, unaffected by thawing. Attached Figure Description
[0023] Figure 1 This is a structural diagram of a single traveling grouting unit, with arrows indicating its direction of movement during use.
[0024] Figure 2 This is a schematic diagram of the structure after the grouting unit is assembled.
[0025] In the diagram, 1-Grouting unit, 11-Soil breaking angle steel, 12-Stiffening rib, 13-Grouting pipe, 2-Spacing adjusting screw, 3-Locking nut. Detailed Implementation
[0026] A method for rapid hardening of temporary pavements in seasonally frozen soil is provided, which forms the roadbed of temporary roads by hardening the surface of seasonally frozen soil.
[0027] The temporary roads mentioned here refer to dirt roads used for transporting various building materials and excavated soil along construction sites of highways, railways, and buildings. These roads are simply leveled and not paved. On seasonally frozen ground, they are quite firm and suitable for vehicles if construction is carried out in winter. However, once temperatures rise, they will thaw and subside, so reinforcement is necessary before they melt due to rising temperatures. Of course, if the seasonally frozen ground has already thawed at the beginning, this invention is not applicable, and replacement or paving methods are required.
[0028] The hardening method includes the following steps:
[0029] Step 1: Remove debris from the frozen soil surface that may obstruct vehicle movement;
[0030] This step primarily removes large rocks and other debris that may obstruct vehicle and machinery operation; it does not require removing turf or similar debris. Permafrost differs significantly from regular ground conditions. Directly applying salt would make it difficult for either of the two types of salt described below to come into contact with the ice in the permafrost. Therefore, it is necessary to inject the two types of salt directly into the permafrost using a method similar to seeding with a planter. Because this is required, the previous step necessitates clearing away any debris that might impede the injection machinery.
[0031] Step 2: Before the active layer of the frozen soil begins to thaw, add soluble calcium salts to the surface layer of the frozen soil along the direction of road extension and let them come into contact with the frozen soil; at the same time, at a location adjacent to the location where the soluble calcium salts were injected into the active layer of the frozen soil, inject sodium silicate solution into the surface layer of the frozen soil along the direction of road extension. The active layer of the frozen soil comes into contact with the soluble calcium salts and melts, reacting with the sodium silicate solution to form a grouting stone body, thus completing the hardening of the temporary road surface.
[0032] Unlike conventional two-component grouting, the reaction between the two soluble calcium salts and sodium silicate is very fast. If injected into the same location, the reaction will not have enough time to diffuse before it reacts. Therefore, grouting needs to be carried out at different locations.
[0033] In step two, soluble calcium salts and sodium silicate are injected into the frozen soil as saturated solutions to reduce water content. The soluble calcium salt and solution are referred to as calcium slurry, and the saturated sodium silicate solution is referred to as silicate slurry. If there is a meadow on the frozen soil surface, the slurry injection position is at least 5 cm below the meadow to avoid the meadow affecting the slurry injection and to reduce damage to the meadow.
[0034] In step two, the soluble calcium salts and sodium silicate injected into the frozen soil must meet the following conditions:
[0035] Condition 1: When the total number of moles of soluble calcium salt injected into the frozen soil is reduced by the number of moles of carbonate ions in the soil solution in the active layer of the frozen soil, the solidification temperature of the remaining soluble calcium salt dissolved in the sum of the free water contained in the active layer of the frozen soil, the water contained in the calcium slurry, and the water contained in the silica slurry is lower than the air temperature at the time of construction.
[0036] This condition primarily ensures that the permafrost can thaw. The number of moles of carbonate ions is subtracted because carbonate ions in the soil solution consume some soluble calcium salts. The total volume of the active permafrost layer is calculated by multiplying the thickness of the active permafrost layer (measured in the field) by the area of the temporary road. Multiplying this by the amount of free water per unit volume of the active permafrost layer (measured after thawing) yields the total amount of free water contained in the active permafrost layer. The total volume of the active permafrost layer is then multiplied by the number of moles of carbonate ions per unit volume of the soil solution within the active permafrost layer (measured after thawing) to obtain the total number of moles of carbonate ions in the soil solution within the active permafrost layer.
[0037] Condition 2: The total volume of calcium slurry and silica slurry is 100-130% of the total void volume in the active layer of frozen soil;
[0038] There is no need to consider the formation expansion caused by excessive grouting here, so excessive grouting is allowed to ensure the curing effect, but too much grouting will cause significant waste.
[0039] Condition 3: Sodium silicate in excess (10-20%). "Excess" here means that after the soluble calcium salts have reacted completely, 10-20% remains. Sodium silicate readily reacts with other substances in the soil or undergoes hydrolysis, thus requiring an excess. It is best to use sodium silicate with a lower modulus to ensure smooth grouting at low temperatures.
[0040] In step two, a modified seeder is used to inject two types of slurry into the frozen soil. In the modified seeder, the seed metering device and furrow opener are replaced with a traveling grouting unit, and the seed-fertilizer box is replaced with a slurry storage tank. The traveling grouting unit includes a row of soil-breaking angle steel connected as one unit by a spacing adjustment screw. The soil-breaking angle steel is an angle steel with its edges pointing towards the bottom and tilting forward in the direction of the seeder's movement. A grouting pipe connected to the slurry storage tank is tied to a groove on the back of the soil-breaking angle steel. After all the grouting pipes are connected to a main pipe, they are connected to the slurry storage tank via a grouting pump. Locking nuts for adjusting the spacing of the soil-breaking angle steel are respectively installed on the left and right sides of the spacing adjustment screw.
[0041] Soluble calcium salt solution and sodium silicate solution are stored in two different grout storage tanks, and the grouting pipes corresponding to the two adjacent excavation angle steels are connected to the different grout storage tanks.
[0042] To facilitate implementation, various components commonly found on construction sites were used to modify commercially available seeders to achieve mobile grouting.
[0043] The edges of the ground-breaking angle steel are welded with stiffening ribs, which are steel bars, and are combined with the ground-breaking angle steel to form a triangular frame; the bottom of the ground-breaking angle steel is cut horizontally to form a pointed tip for ground breaking, and is re-cut after each construction is completed.
[0044] The reason for using a soil-breaking angle steel instead of a furrow opener like a seeder is that it experiences significant wear when moving and grouting on frozen soil. The soil-breaking angle steel can be sharpened after each use by cutting it. In contrast, a furrow opener would wear down to unusable condition after only a few uses.
[0045] When in use, the distance between two adjacent excavation angle steels should not be greater than the slurry diffusion radius (obtained by on-site measurement).
[0046] Step two is carried out when the active layer of the permafrost is frozen and the temperature is not lower than -5 degrees Celsius. In other words, it is carried out when the permafrost is about to thaw, under which condition 1 is easily met.
[0047] Soluble calcium salts are calcium chloride or calcium formate, two commonly used calcium salts in construction. When the frozen soil is clayey, the soluble calcium salt is calcium formate.
[0048] The reason for using calcium formate when the frozen soil is clayey is to avoid soil salinization.
[0049] Among the various ions that enter the soil along with the grout, silicate and calcium ions will inevitably form insoluble substances, while sodium ions, which enter the soil along with silicate ions, will be encapsulated within the grouting aggregate. Formate and chloride ions can be released, but formate ions are easily metabolized by organisms to form carbon dioxide or carbonate ions, which readily form insoluble substances in the soil. Chloride ions, however, are different; they hardly form insoluble substances in the soil and remain in the soil solution, increasing the salt concentration. If the soil drainage is good, this has little impact, but if the frozen soil is clayey and drainage is poor, salinization is likely.
[0050] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for hardening the subgrade of temporary roads in seasonally frozen soil, comprising hardening the surface of seasonally frozen soil to form the subgrade of temporary roads, wherein the temporary roads are dirt roads used for transporting building materials and excavated soil near construction sites of highways, railways, and buildings, characterized in that: The hardening method includes the following steps: Step 1: Remove debris from the frozen soil surface that may obstruct vehicle movement; Step 2: Before the active layer of the frozen soil begins to thaw, add soluble calcium salts into the surface layer of the frozen soil along the direction of road extension and let them come into contact with the frozen soil; at the same time, at a location adjacent to the location where the soluble calcium salts were injected into the active layer of the frozen soil, inject sodium silicate solution into the surface layer of the frozen soil along the direction of road extension. The active layer of the frozen soil comes into contact with the soluble calcium salts and melts, reacting with the sodium silicate solution to form a grouting stone body, thus completing the hardening of the temporary road surface; Soluble calcium salts and sodium silicate are injected into the permafrost as saturated solutions. The soluble calcium salt and solution are referred to as calcium slurry, and the saturated sodium silicate solution is referred to as silica slurry. If there is a meadow on the surface of the permafrost, the slurry injection position is at least 5 cm below the meadow. A modified seeder was used to inject two types of slurry into the frozen soil. In the modified seeder, the seed metering device and furrow opener were replaced with a traveling grouting unit, and the seed-fertilizer box was replaced with a slurry storage tank. The traveling grouting unit includes a row of soil-breaking angle steel connected as one unit by a spacing adjustment screw. The soil-breaking angle steel is an angle steel with its edges pointing towards the bottom and tilting forward in the direction of the seeder's movement. A grouting pipe connected to the slurry storage tank is tied to a groove on the back of the soil-breaking angle steel. After all the grouting pipes are connected to a main pipe, they are connected to the slurry storage tank via a grouting pump. Locking nuts for adjusting the spacing of the soil-breaking angle steel are respectively installed on the left and right sides of the spacing adjustment screw. Soluble calcium salt solution and sodium silicate solution are stored in two different grout storage tanks, and the grouting pipes corresponding to the two adjacent excavation angle steels are connected to the different grout storage tanks.
2. The method for hardening temporary roadbeds in seasonally frozen soil according to claim 1, characterized in that: In step two, the calcium slurry and silica slurry must meet the following conditions: Condition 1: When the total number of moles of soluble calcium salt injected into the frozen soil is reduced by the number of moles of carbonate ions in the soil solution in the active layer of the frozen soil, the solidification temperature of the remaining soluble calcium salt dissolved in the sum of the free water contained in the active layer of the frozen soil, the water contained in the calcium slurry, and the water contained in the silica slurry is lower than the air temperature at the time of construction. Condition 2: The total volume of calcium slurry and silica slurry is 100-130% of the total void volume in the active layer of frozen soil; Condition 3: Sodium silicate in excess of 10-20%.
3. The method for hardening temporary roadbeds in seasonally frozen soil according to claim 1, characterized in that: The ground-breaking angle steel has stiffening ribs welded to its edges. The stiffening ribs are steel bars and are combined with the ground-breaking angle steel to form a triangular frame. The bottom of the ground-breaking angle steel is cut horizontally to form a pointed tip for breaking ground, and is re-cut after each construction is completed.
4. A method for hardening temporary roadbeds in seasonally frozen soil according to claim 1, characterized in that: When in use, the distance between two adjacent excavation angle steels should not be greater than the slurry diffusion radius.
5. A method for hardening temporary roadbeds in seasonally frozen soil according to claim 1, characterized in that: Step two is carried out when the active layer of the permafrost is frozen and the temperature is not lower than -5 degrees Celsius.
6. A method for hardening temporary roadbeds in seasonally frozen soil according to claim 1, characterized in that: The soluble calcium salt is calcium chloride or calcium formate. When the frozen soil is cohesive frozen soil, the soluble calcium salt is calcium formate.