Foam light soil bridge head high fill embankment and construction process thereof

Abstract

The application relates to the field of bridge-head filling embankment, and particularly discloses a foamed light soil bridge-head high filling embankment and a construction process thereof. The foamed light soil bridge-head high filling embankment comprises an isolation layer and a foamed light soil layer, and a protective wall is arranged in the foamed light soil layer. The foamed light soil layer is formed by pouring foamed light soil, and the foamed light soil comprises the following raw materials in parts by weight: 100 parts of Portland cement, 60-64 parts of water, 4-6.8 parts of foam, 21-35 parts of a modifier, and the preparation raw materials of the modifier comprise a cationic polymer and improved soil, and the weight ratio of the cationic polymer to the improved soil is 1: (6-20). The construction process is as follows: S1, excavating a roadbed and a slope; S2, laying the isolation layer; S3, pouring a stratum protective wall; S4, pouring the foamed light soil; S5, maintenance; and S6, repeating S3-S5. The application has the effects of improving the pouring uniformity of the foamed light soil and reducing the probability of uneven settlement of the embankment.

Description

Technical Field

[0001] This application relates to the field of bridge abutment embankment subgrade, and in particular to a foamed lightweight soil bridge abutment high embankment subgrade and its construction technology. Background Technology

[0002] In my country, where the terrain is predominantly mountainous and varied, the construction of highways is often constrained by topography, geomorphology, and hydrogeological conditions, inevitably requiring the construction of high embankments on existing roads and bridges. During the construction of transition sections for high embankment bridges, geotechnical problems such as poor stability and uneven settlement are frequently encountered.

[0003] In related technologies, reducing the superstructure load, such as by using lightweight fillers, reduces the additional stress on the foundation, thereby solving the problems of stability and uneven settlement of the roadbed in the transition section between roads and bridges. Foamed lightweight soil is a commonly used lightweight material. It has the characteristics of being lightweight, earthquake-resistant, sound-insulating, heat-insulating, non-toxic, and harmless, effectively reducing the superstructure load and lowering the risks brought by natural disasters such as earthquakes.

[0004] In the mountainous areas of southeastern my country, the soil is mainly composed of stony soil, and is a mixture of carbonate rock and clay. Due to the different densities and properties of carbonate rock and clay, there are significant differences in soil density. When pouring foamed lightweight soil, some foamed lightweight soil enters the gaps between the carbonate rocks, while some is blocked by clay. This results in uneven pouring volume of the foamed lightweight soil. After curing, the uniformity and compressive strength of the foamed lightweight soil decrease, leading to reduced stability of high embankment roadbeds at bridgeheads and a higher likelihood of uneven settlement. Summary of the Invention

[0005] In order to improve the uniformity of foamed lightweight soil pouring and reduce the probability of uneven settlement of the roadbed, this application provides a foamed lightweight soil bridge abutment high embankment and its construction technology.

[0006] Firstly, the technical solution for a foamed lightweight soil bridge approach high embankment subgrade provided in this application is as follows:

[0007] A foamed lightweight soil bridgehead high embankment roadbed consists of an isolation layer and a foamed lightweight soil layer from bottom to top, with a protective wall running through the foamed lightweight soil layer;

[0008] The foamed lightweight soil layer is formed by casting foamed lightweight soil, which includes the following raw materials in parts by weight: 100 parts silicate cement; 60-64 parts water; 4-6.8 parts foam; and 21-35 parts modifier.

[0009] The raw materials for preparing the modifier include cationic polymer and modified soil, with a weight ratio of cationic polymer to modified soil of 1:(6-20).

[0010] By adopting the above technical solutions, the cationic polymer is used in combination with the improved soil. The cationic polymer is adsorbed on the surface of the improved soil, reducing the probability of the improved soil absorbing water and swelling. The modifier, silicate cement, water, and foam are used together to form a three-dimensional network structure, which improves the stability of the foamed lightweight soil and reduces the probability of foam rupture, thereby reducing the probability of self-settlement of the foamed lightweight soil. The modified foamed lightweight soil, combined with the isolation layer, makes it less likely for the foamed lightweight soil to penetrate into the pores of the surrounding soil, improving the uniformity of the foamed lightweight soil pouring. After the foamed lightweight soil is cured and formed, its uniformity and compressive strength are improved, the stability of the high embankment subgrade at the bridgehead is improved, and the probability of uneven settlement of the subgrade is reduced.

[0011] Optionally, the cationic polymer is selected from long-chain polyacrylamide.

[0012] By adopting the above technical solution, the amide groups of long-chain polyacrylamide adsorb and bond with the modified soil particles, forming a bridging structure between the modified soil particles, reducing the probability of the modified soil absorbing water and turning into clay. Under mechanical action, the modified soil particles bonded by long-chain polyacrylamide mix with silicate cement particles to form a network, improving the stability of foamed concrete. After filling, the foamed lightweight soil is less prone to segregation and fills the pores of the original subgrade, improving the uniformity of foamed lightweight soil pouring. After curing, the uniformity and compressive strength of the foamed lightweight soil are improved, enhancing the stability of the high embankment subgrade at bridgeheads and reducing the probability of uneven subgrade settlement. During curing, water penetrates the foamed lightweight soil. Under the composite three-dimensional combination of long-chain polyacrylamide, silicate particles, and modified soil, the foamed lightweight soil is less prone to defoaming and settling, improving its uniformity.

[0013] Optionally, the improved soil includes foundation treatment soil and a pH adjuster, wherein the weight ratio of the foundation treatment soil to the pH adjuster is 5:(1-2).

[0014] By adopting the above technical solution, the local foundation soil is a mixture of carbonate rock and clay. When excavating the roadbed, the excavated soil is treated and its pH value is adjusted by a pH adjuster, and then reused, which improves the utilization rate of resources.

[0015] Optionally, the preparation of the foundation treatment soil includes the following steps: during the excavation of the roadbed, the excavated soil is crushed, calcined, and ground to obtain the foundation treatment soil.

[0016] By adopting the above technical solutions, after crushing, calcining, and grinding, the organic matter in the soil is reduced, decreasing the probability of the soil becoming soft and losing its supporting strength under the action of microorganisms. During calcination, the clay loses water and shrinks in volume, while the carbonate rock decomposes to release carbon dioxide and produce minerals such as calcium silicate and aluminum silicate. The molten minerals fill the voids inside the soil, resulting in a lower porosity in the foundation treatment soil and an improved compressive strength. After calcination and grinding, the water absorption capacity of the foundation treatment soil is reduced, decreasing the water absorption and swelling rate of the foamed lightweight soil and improving its volume stability. The foundation treatment soil after calcination and grinding is slightly alkaline; after treatment with a pH adjuster, the resulting improved soil is neutral to acidic, reducing the adverse effects of the improved soil on foam stability. The surface of the calcined carbonate rock carries a negative charge, facilitating the adsorption of cationic polymers to form a bridging structure, thus improving the stability of the foamed lightweight soil.

[0017] Optionally, the pH adjuster comprises ash and gravelly soil, wherein the weight ratio of ash to gravelly soil is (5-12):1.

[0018] By adopting the above technical solutions, the foundation treatment soil is alkaline, which reduces the stability of the foam in the foamed lightweight soil. Using pumice soil to adjust the foundation treatment soil improves its permeability, reduces its alkalinity, and enhances the stability of the foamed lightweight soil. However, pumice soil is heavy, difficult to dry, and has an acidity of around 4.5. Ash is used as a neutralizing agent to assist in adjusting the acidity and alkalinity of the foundation treatment soil and acts as a fulcrum in the network structure formed by long-chain polyacrylamide, improving the stability of the three-dimensional composite network structure.

[0019] Optionally, the ash is selected from pine needle ash.

[0020] By adopting the above technical solution, the residual oil and wax in the pine needle ash improves the bonding strength between the stone soil particles and the foundation treatment soil particles. The pine needle ash, stone soil particles and foundation treatment soil are combined to form reinforcement points on the long-chain polyacrylamide, which improves the stability of the three-dimensional composite structure, thereby improving the stability of the foamed lightweight soil and reducing the probability of uneven settlement of the roadbed.

[0021] Optionally, the isolation layer is made of galvanized steel wire mesh and impermeable geomembrane.

[0022] By adopting the above technical solution, galvanized steel wire mesh and impermeable geomembrane serve as an isolation layer, improving the subgrade strength and reducing the probability of water seeping into the subgrade. This reduces the probability of segregation, infiltration, and settlement of the foamed lightweight soil, thereby reducing the probability of uneven settlement of the subgrade.

[0023] Secondly, the construction technology for a foamed lightweight soil bridge approach high embankment subgrade provided in this application adopts the following technical solution:

[0024] A construction process for a foamed lightweight soil bridge approach high embankment subgrade includes the following steps:

[0025] S1. Excavation of the roadbed and slope;

[0026] S2. Lay the isolation layer;

[0027] S3. Construct the protective wall;

[0028] S4. Pour foamed lightweight soil, with the pouring height of the foamed lightweight soil lower than the height of the retaining wall;

[0029] S5, Maintenance;

[0030] S6. Repeat S3-S5 until the foamed lightweight soil bridgehead high embankment subgrade is laid.

[0031] By adopting the above technical solutions, an isolation layer is laid before pouring foamed lightweight soil, which improves the strength of the roadbed and reduces the probability of uneven settlement of the roadbed; the setting of the protective wall reduces the probability of irregular settlement and loss of foamed lightweight soil and improves the stability of the roadbed.

[0032] Optionally, the slope can be set in a stepped shape, with the upper surface of the steps sloping towards the bridge.

[0033] By adopting the above technical solutions, the contact area between the slope and the foamed lightweight soil is increased, the probability of the foamed lightweight soil shifting is reduced, and the stability of the roadbed is improved.

[0034] In summary, this application includes at least one of the following beneficial technical effects:

[0035] 1. When foamed lightweight soil is poured, the curing and hardening speeds are different. The surface layer of foamed lightweight soil solidifies first under the influence of wind speed, temperature, etc., while the inner foamed lightweight soil gradually solidifies. At this time, some of the foamed lightweight soil in contact with the original soil enters the gaps between the carbonate rocks, resulting in pores in the foamed lightweight soil layer. This application reduces the probability of foamed lightweight soil seeping into the original soil after pouring by combining foamed lightweight soil, isolation layer, and protective wall, improves the uniformity of foamed lightweight soil pouring, and improves the uniformity and compressive strength of foamed lightweight soil after curing. This improves the stability of high embankment roadbed at bridgeheads and reduces the probability of uneven settlement of the roadbed.

[0036] 2. The soil excavated on-site is processed to obtain improved soil. The improved soil and long-chain polyacrylamide adsorb each other to form a modifier with a three-dimensional network structure. This modifier is added to silicate cement to form a composite three-dimensional network structure, which improves the stability of foamed lightweight soil. The foamed lightweight soil is not easy to segregate and penetrate into the surrounding soil, which improves the uniformity of foamed lightweight soil pouring. After the foamed lightweight soil is cured and formed, its uniformity and compressive strength are improved, the stability of the high embankment subgrade at the bridgehead is improved, and the probability of uneven settlement of the subgrade is reduced.

[0037] 3. After crushing, calcining and grinding, the organic matter in the soil excavated on-site is reduced, the water absorption rate is lowered and the self-density is increased, thereby improving the compressive strength of the soil. After treatment with pH adjuster, the improved soil is neutral and acidic, which reduces the adverse effects of the improved soil on foam stability. Detailed Implementation

[0038] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0039] Unless otherwise specified, the following examples shall be conducted under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all raw materials used in the following examples shall be commercially available.

[0040] The silicate cement is selected from ordinary commercially available P.O42.5 silicate cement.

[0041] The foaming agent is a compound foaming agent of animal and plant proteins, a yellow liquid with a foaming ratio of 25 times, a dilution ratio of 40 times, a pH value of 6.5, and a foam density of 0.04 g / cm³. 3 Foaming agent density (g / cm³) 3 It meets the index requirements in "JC / T2199-2013 Foaming Agent for Foamed Concrete".

[0042] Pine needle ash is the substance collected mainly as ash after pine needles are burned.

[0043] The Shiguzi soil was taken from Sichuan, dried and ground into 600-mesh powder, with a pH value of 4.8±0.2.

[0044] Preparation Example

[0045] Preparation Example 1

[0046] S1. When excavating the roadbed, the excavated soil is crushed. After crushing, the particle size is less than 10cm. It is then placed in a conventional calcination equipment and calcined at 800℃ for 20 minutes. After natural cooling, it is ground to obtain the target roadbed treatment soil with a particle size of 400.

[0047] S2. Mix 5 kg of pine needle ash and 1 kg of stone soil evenly as a pH adjuster. Take 6 kg of the pH adjuster and mix it evenly with 30 kg of the foundation treatment soil obtained in S1 to obtain the improved soil.

[0048] S3. Mix 1 kg of long-chain polyacrylamide with 20 kg of modified soil prepared in S2. Stir at 1200 rpm and 50°C for 20 min, adding 1 L of water three times during the process. After stirring, maintain the temperature at 20°C and 60% humidity for 24 h, then dry at 20°C to obtain the modifier.

[0049] Preparation Example 2

[0050] S1. When excavating the roadbed, the excavated soil is crushed. After crushing, the particle size is less than 10cm. It is then placed in a conventional calcination equipment and calcined at 800℃ for 20 minutes. After natural cooling, it is ground to obtain the target roadbed treatment soil with a particle size of 400.

[0051] S2. Mix 9 kg of pine needle ash and 1 kg of stone soil evenly as a pH adjuster. Take 9.5 kg of the pH adjuster and mix it evenly with 30 kg of the foundation treatment soil obtained in S1 to obtain the improved soil.

[0052] S3. Mix 3 kg of long-chain polyacrylamide with 25 kg of modified soil prepared in S2. Stir at 1200 rpm and 55°C for 15 min, adding 1 L of water three times during the process. After stirring, maintain the temperature at 20°C and 60% humidity for 24 h, then dry at 20°C to obtain the modifier.

[0053] Preparation Example 3

[0054] S1. When excavating the roadbed, the excavated soil is crushed. After crushing, the particle size is less than 10cm. It is then placed in a conventional calcination equipment and calcined at 800℃ for 20 minutes. After natural cooling, it is ground to obtain the target roadbed treatment soil with a particle size of 400.

[0055] S2. Mix 12 kg of pine needle ash and 1 kg of stone soil evenly as a pH adjuster. Take 12 kg of the pH adjuster and mix it evenly with 30 kg of the foundation treatment soil obtained in S1 to obtain the improved soil.

[0056] S3. Mix 5 kg of long-chain polyacrylamide with 30 kg of modified soil prepared in S2. Stir at 1200 rpm and 60°C for 10 min, adding 1 L of water three times during the process. After stirring, maintain the temperature at 20°C and 60% humidity for 24 h, then dry at 20°C to obtain the modifier.

[0057] Preparation Example 4

[0058] The difference from Preparation Example 2 is that the amount of long-chain polyacrylamide added is 1 kg.

[0059] Preparation Example 5

[0060] The difference from Preparation Example 2 is that the amount of long-chain polyacrylamide added is 5 kg.

[0061] Preparation Example 6

[0062] The difference from Preparation Example 2 is that in S2, the amount of pine needle ash added is 7.9 kg, the amount of stone soil added is 1.6 kg, and the weight ratio of pine needle ash to stone soil is approximately 5:1.

[0063] Preparation Example 7

[0064] The difference from Preparation Example 2 is that in S2, the amount of pine needle ash added is 8.77 kg, the amount of stone soil added is 0.73 kg, and the weight ratio of pine needle ash to stone soil is approximately 12:1.

[0065] Preparation Example 8

[0066] The difference from Preparation Example 2 is that 28 kg of long-chain polyacrylamide was used as a modifier.

[0067] Preparation Example 9

[0068] S1. When excavating the roadbed, the excavated soil is crushed and then ground to obtain foundation treatment soil with a particle size of 400.

[0069] S2. Mix 3 kg of long-chain polyacrylamide with 25 kg of foundation treatment soil prepared in S1. Stir at 1200 rpm and 55°C for 15 min, adding 1 L of water three times during the process. After stirring, maintain the temperature at 20°C and 60% humidity for 24 h, then dry at 20°C to obtain the modifier.

[0070] Preparation Example 10

[0071] The difference from Preparation Example 2 is that no pH adjuster was added. The specific steps are as follows:

[0072] S1. When excavating the roadbed, the excavated soil is crushed. After crushing, the particle size is less than 10cm. It is then placed in a conventional calcination equipment and calcined at 800℃ for 20 minutes. After natural cooling, it is ground to obtain improved soil with a particle size of 400 mesh.

[0073] S2. Mix 3 kg of long-chain polyacrylamide with 25 kg of modified soil prepared in S1. Stir at 1200 rpm and 55°C for 15 min, adding 1 L of water three times during the process. After stirring, maintain the temperature at 20°C and 60% humidity for 24 h, then dry at 20°C to obtain the modifier.

[0074] Preparation Example 11

[0075] The difference from Preparation Example 2 is that pine needle ash was not added to the pH adjuster, and 9.5 kg of stone soil was used as the pH adjuster.

[0076] Preparation Example 12

[0077] The difference from Preparation Example 2 is that no stone soil was added to the pH adjuster, and 9.5 kg of pine needle ash was used as the pH adjuster.

[0078] Preparation Example 13

[0079] The difference from Preparation Example 2 is that no long-chain polyacrylamide was added.

[0080] Table 1 Raw material list for the preparation example

[0081]

[0082]

[0083] Example

[0084] Example 1

[0085] S1. The foaming agent is diluted 40 times to form a foaming liquid. It is then placed in an air compressor, and compressed air is introduced into the foaming liquid to form foam.

[0086] S2. Mix 100 kg of silicate cement and 21 kg of the modifier prepared in Example 1, stir at 700 rpm for 2 min, then add 60 kg of water and stir at 1400 rpm for 3 min to obtain the slurry.

[0087] S3. Take 4 kg of the foam prepared in S1 and put it into the slurry prepared in S2. Stir at 700 rpm for 2 minutes to obtain foamed lightweight soil.

[0088] Example 2

[0089] S1. The foaming agent is diluted 40 times to form a foaming liquid. It is then placed in an air compressor, and compressed air is introduced into the foaming liquid to form foam.

[0090] S2. Mix 100 kg of silicate cement and 28 kg of the modifier prepared in Example 2, stir at 700 rpm for 2 min, then add 62 kg of water and stir at 1400 rpm for 3 min to obtain the slurry.

[0091] S3. Take 5.9 kg of the foam prepared in S1 and put it into the slurry prepared in S2. Stir at 700 rpm for 2 minutes to obtain foamed lightweight soil.

[0092] Example 3

[0093] S1. The foaming agent is diluted 40 times to form a foaming liquid. It is then placed in an air compressor, and compressed air is introduced into the foaming liquid to form foam.

[0094] S2. Mix 100 kg of silicate cement and 35 kg of the modifier prepared in Preparation Example 3, stir at 700 rpm for 2 min, then add 64 kg of water and stir at 1400 rpm for 3 min to obtain the slurry.

[0095] S3. Take 6.8 kg of the foam prepared in S1 and put it into the slurry prepared in S2. Stir at 700 rpm for 2 minutes to obtain foamed lightweight soil.

[0096] Examples 4-7

[0097] The difference from Example 2 is that the modifiers prepared in Preparation Examples 4 to 7 were added sequentially.

[0098] Example 8

[0099] S1. The bottom of the roadbed is excavated with a slope. The slope is set in a stepped shape with a step height of 1m±0.01m and a step width of 1m±0.01m. The upper surface of the step is inclined at a 2% slope towards the bridge. The foamed lightweight soil pouring area is inverted trapezoidal.

[0100] S2. Clean the roadbed surface, and lay galvanized steel wire mesh and HDPE geomembrane in sequence on the roadbed to form an isolation layer. The galvanized steel wire mesh is fixed with U-shaped nails, and the joints are tied with wire and fixed with U-shaped nails.

[0101] S3. Place the protective panel on the slope surface. The protective panel should be 20cm thick, the foundation should be buried at a depth of not less than 1.5m, and the outer edge width should be not less than 2m. Pour the protective panel with C30 cement concrete to form a protective wall.

[0102] S4. The foamed lightweight soil prepared in Example 2 is poured using a pumping method, with a layer thickness of 50cm. The pouring height of each layer of foamed lightweight soil is 30cm ± 5cm lower than the protective panel.

[0103] S5. Sprinkle water for 72 hours. During the curing period, it is strictly forbidden to load the surface.

[0104] S6. Repeat S4-S6, pouring and curing the foamed lightweight soil in layers until the foamed lightweight soil bridgehead high embankment subgrade is completed.

[0105] Comparative Example

[0106] Comparative Example 1

[0107] The difference from Example 2 is that no modifier was added.

[0108] Comparative Examples 2-7

[0109] The difference from Example 2 is that the modifiers prepared in Preparation Examples 8 to 13 were added sequentially.

[0110] Table 2 Raw material list for the examples and comparative examples

[0111]

[0112]

[0113] Performance testing

[0114] Test methods

[0115] 1. The 28-day unconfined compressive strength (MPa) of foamed lightweight soil was determined by referring to the method of "T0148-1993 Unconfined Compressive Strength Test of Fine-Grained Soil" in "JTGE40-2007 Highway Geotechnical Test Procedure". The test results are detailed in Table 3.

[0116] 2. Settlement rate of foamed lightweight soil under earthquake and vehicle loads

[0117] (1) Using a 300mm×300mm×100mm mold, pour foamed lightweight soil, cure it at 25℃ and 60% humidity for 7 days, and then demold to obtain the specimen;

[0118] (2) Place the specimen into the rutting tester for asphalt mixture rutting test, set the test temperature to 25℃, wheel pressure to 0.3MPa, and total load to 780N; the wheel rolls back and forth for 10 seconds. ^3 Afterwards, the specimen was removed, placed in a mold, and a load of 780N was applied above it. The mold was then placed on a concrete vibration platform and vibrated at 200Hz for 10 minutes. The specimen was then removed and compacted in a roller for 10 minutes. ^3 Remove the sample;

[0119] (3) Calculate the settlement rate: Settlement rate (%) = (Test height before test - Specimen height after test) / Specimen height before test × 100%

[0120] The height of the specimen after the test is the vertical width from the lowest point of the upper surface of the specimen to the lower surface of the specimen.

[0121] Table 3. Test results data for each embodiment and comparative example.

[0122]

[0123] Based on Examples 1, 2, and 3 and Table 3, foamed lightweight soil with low settlement rate and high compressive strength was prepared by adjusting the amount of silicate cement, water, foam, and modifier added, as well as the type of modifier.

[0124] The preparation steps of the modifier are as follows: pine needle ash is mixed with stone mill soil as a pH adjuster; the foundation soil taken locally is crushed, calcined and ground, and then mixed with the pH adjuster to obtain improved soil; the improved soil is mixed with long-chain polyacrylamide to prepare the modifier.

[0125] The difference between Examples 2, 4, and 5 lies in the different weight ratios of long-chain polyacrylamide to improved soil in the modifier used. In Example 2, the amount of long-chain polyacrylamide added was 3 kg, and the weight ratio of long-chain polyacrylamide to improved soil was 3:25. In Example 4, the amount of long-chain polyacrylamide added was 1 kg, and the weight ratio of long-chain polyacrylamide to improved soil was 1:25. In Example 2, the amount of long-chain polyacrylamide added was 5 kg, and the weight ratio of long-chain polyacrylamide to improved soil was 1:5. As can be seen from Table 3, with the increase of the weight ratio of long-chain polyacrylamide to improved soil in the modifier, the 28-day unconfined compressive strength of the foamed lightweight soil first increased and then decreased, and the settlement of the foamed lightweight soil first decreased and then increased.

[0126] The difference between Examples 2, 6, and 7 lies in the different weight ratios of pine needle ash and pumice soil in the pH adjuster. In Example 2, the weight ratio of pine needle ash to pumice soil is 9:1; in Example 7, the weight ratio of pine needle ash to pumice soil is approximately 5:1; and in Example 8, the weight ratio of pine needle ash to pumice soil is approximately 12:1. As can be seen from Table 3, with the increase of the weight ratio of pine needle ash to pumice soil in the pH adjuster, the 28-day unconfined compressive strength of the foamed lightweight soil first increases and then decreases, while the settlement of the foamed lightweight soil first decreases and then increases.

[0127] Compared to Example 2, the difference in Comparative Example 1 is that no modifier was added. As can be seen from Table 3, the addition of the modifier effectively improved the 28-day unconfined compressive strength and reduced the sedimentation rate.

[0128] Compared to Comparative Example 1, Comparative Example 2 differs in that it includes the addition of long-chain polyacrylamide. As shown in Table 3, the addition of long-chain polyacrylamide increases the 28-day unconfined compressive strength of the foamed lightweight soil and reduces its settlement rate. Furthermore, as seen in Example 2, the addition of long-chain polyacrylamide alone increases the 28-day unconfined compressive strength of the foamed lightweight soil by approximately 21% and reduces the settlement rate by approximately 29%; the addition of a modifier prepared from long-chain polyacrylamide and improved soil increases the 28-day unconfined compressive strength of the foamed lightweight soil by approximately 2.5 times and reduces the settlement rate by approximately 91.6%.

[0129] Compared to Comparative Example 3, the difference in Comparative Example 4 is that the uncalcined foundation soil was replaced with improved soil. As can be seen from Table 3, without the addition of pH adjuster, the addition of improved soil increased the 28-day unconfined compressive strength of foamed lightweight soil, but not significantly; at the same time, it increased the settlement rate of foamed lightweight soil.

[0130] As can be seen from Example 2 and Comparative Example 4, and Table 3, the use of pH adjuster improved the 28-day unconfined compressive strength of foamed lightweight soil and reduced the settlement rate of foamed lightweight soil.

[0131] No pH adjuster was added to the improved soil used in Comparative Example 4. In Comparative Example 5, only sago palm soil was used as a pH adjuster in the improved soil used in Comparative Example 6. In Example 2, pine needle ash and sago palm soil were mixed in a 9:1 ratio and used as a pH adjuster in the improved soil used in Example 2. As can be seen from Table 3, pine needle ash and sago palm soil worked synergistically to effectively improve the 28-day unconfined compressive strength of foamed lightweight soil and reduce the settlement rate of foamed lightweight soil.

[0132] The difference between Comparative Example 1 and Comparative Example 7 is that the modifier used in Comparative Example 7 added modified soil alone. As can be seen from Table 3, adding modified soil alone increases the 28-day unconfined compressive strength of foamed lightweight soil by about 1.3 times and reduces the settlement rate by about 43%. As can be seen from Example 2 and Comparative Example 2, the synergistic use of long-chain polyacrylamide and modified soil has a significant effect on improving the 28-day unconfined compressive strength of foamed lightweight soil and reducing the settlement rate of foamed lightweight soil.

[0133] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A foamed lightweight soil bridge abutment high embankment roadbed, characterized in that, From bottom to top, there is an isolation layer and a foamed lightweight soil layer, and a protective wall is installed inside the foamed lightweight soil layer; The foamed lightweight soil layer is formed by casting foamed lightweight soil, which includes the following raw materials in parts by weight: 100 parts silicate cement; 60-64 parts water; Foam 4-6.8 parts; Modifier 21-35 parts; The raw materials for preparing the modifier include cationic polymer and modified soil, with a weight ratio of cationic polymer to modified soil of 1:(6-20). The cationic polymer is selected from long-chain polyacrylamide. The modified soil includes foundation treatment soil and pH adjuster, with a weight ratio of foundation treatment soil to pH adjuster of 5:(1-2). The preparation of the foundation treatment soil includes the following steps: during the excavation of the roadbed, the excavated soil is crushed, calcined, and ground to obtain the foundation treatment soil.

2. The foamed lightweight soil bridge abutment high embankment roadbed according to claim 1, characterized in that, The pH adjuster comprises ash and gravelly soil, wherein the weight ratio of the ash and gravelly soil is (5-12):

1.

3. The foamed lightweight soil bridge abutment high embankment roadbed according to claim 2, characterized in that, The ash is selected from pine needle ash.

4. The foamed lightweight soil bridge abutment high embankment roadbed according to claim 1, characterized in that, The isolation layer is made of galvanized steel wire mesh and impermeable geomembrane.

5. The foamed lightweight soil bridge abutment high embankment roadbed according to claim 1, characterized in that, The protective wall is made of cement concrete cast protective panels.

6. A construction method for a high embankment subgrade at bridge abutments using foamed lightweight soil according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Excavation of the roadbed and slope; S2. Lay the isolation layer; S3. Construct the protective wall; S4. Pour foamed lightweight soil, with the pouring height of the foamed lightweight soil lower than the height of the retaining wall; S5, Maintenance; S6. Repeat S3-S5 until the foamed lightweight soil bridgehead high embankment subgrade is laid.

7. The construction technology of foamed lightweight soil bridge abutment high embankment subgrade according to claim 6, characterized in that, The slope is designed in a stepped shape, with the upper surface of the steps inclined away from the foundation pit.

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