Modified riverbed soil for embankment and modified riverbed soil subgrade

Abstract

This application relates to the field of embankment subgrades, specifically disclosing modified riverbed soil for embankment and modified riverbed soil subgrades. The modified riverbed soil for embankment comprises the following raw materials in parts by weight: 100 parts riverbed soil; 4-8 parts cement; and 2-4 parts water-absorbing carrier. The water-absorbing carrier includes water-absorbing resin and porous support nests, with the water-absorbing resin loaded on the porous support nests. The modified riverbed soil subgrade is constructed by laying the aforementioned modified riverbed soil. This application has the effect of shortening the riverbed soil treatment time and improving the efficiency of subgrade construction.

Description

Technical Field

[0001] This application relates to the field of embankment subgrade and its materials, and in particular to a modified riverbed soil for embankment and a modified riverbed soil subgrade. Background Technology

[0002] With the continuous improvement of my country's transportation network and the continuous increase in residents' income, the traffic volume on highways has increased, and the pressure on highway traffic has increased. In particular, when the original highways were designed as two-lane highways in both directions, congestion and traffic accidents are very likely to occur. In order to alleviate traffic pressure and improve road capacity, highways are generally widened.

[0003] In highway widening projects, when located in plains areas with no nearby construction sites, soil sources are often scarce, yet the designed fill volume is large, making it impossible for the project to be self-sufficient. One related technique is to use soil from riverbeds as fill. However, riverbed soil has a high water content and cannot be directly used for roadbed filling; it requires tilling and drying before use, which is time-consuming and severely restricts construction progress. Summary of the Invention

[0004] In order to shorten the treatment time of riverbed soil and improve the construction efficiency of roadbed, this application provides a modified riverbed soil for embankment and a modified riverbed soil roadbed.

[0005] Firstly, this application provides a technical solution for modified riverbed soil used in embankment filling, which adopts the following approach:

[0006] The modified riverbed soil for filling includes the following raw materials in parts by weight: 100 parts riverbed soil; 4-8 parts cement; 2-4 parts water-absorbing carrier; the water-absorbing carrier includes water-absorbing resin and porous support nest, and the water-absorbing resin is loaded on the porous support nest.

[0007] By employing the above technical solution, riverbed soil, cement, and absorbent carrier are mixed. Cement hydration consumes free water and forms CSH gel, improving the cohesiveness of the riverbed soil. The absorbent carrier includes porous support nests loaded with absorbent resin. These nests protect the resin, and after absorption and expansion, the porous support nests limit this expansion, acting as a support and reducing the probability of resin breakage due to compression. Simultaneously, as aggregate, they improve the compressive strength of the modified riverbed soil. Under the action of CSH gel, the porous support nests bond with the dehydrated riverbed soil, forming modified riverbed soil with high bearing capacity and high compressive strength. With the combined use of cement and absorbent carrier, the water in the riverbed soil is utilized and converted, reducing the moisture content of the modified riverbed soil. Compared to sun-drying the riverbed soil to reduce moisture content, the combination of cement and absorbent carrier shortens the riverbed soil treatment time and improves roadbed construction efficiency.

[0008] Optionally, the weight ratio of the absorbent resin to the porous support nest is 16:(25-30).

[0009] By adopting the above technical solution, when the weight ratio of absorbent resin to porous support nest is too large, the absorbent resin is prone to detaching from the porous support nest, increasing the water absorption capacity of the absorbent carrier but reducing its compressive strength. By adopting the above ratio, the absorbent carrier balances both water absorption capacity and compressive strength.

[0010] Optionally, the absorbent carrier further includes low-melting-point fibers and low-melting-point elastomers, and the weight ratio of the porous support nest, low-melting-point fibers and low-melting-point elastomers is 75:(25-30):(10-24).

[0011] By adopting the above technical solution, during the modification of riverbed soil, the water-absorbing resin is easily detached from the porous support nest. At this time, low-melting-point fibers and low-melting-point elastomers are used. At an appropriate temperature, the low-melting-point fibers partially soften and become sticky, and the low-melting-point elastomer softens, forming a three-dimensional network elastic structure on the surface loaded with water-absorbing resin. The water-absorbing resin absorbs water and expands, and the three-dimensional network structure is stretched open, binding the water-absorbing resin after it has absorbed water and expanded. The water-absorbing resin is not easy to detach from the porous support nest. After the modified riverbed soil is filled, the porous support nest acts as aggregate, and the water-absorbing resin is wrapped and not easily broken, thereby improving the compressive strength of the modified riverbed soil.

[0012] Optionally, the low-melting-point fiber is selected from polyethylene fiber.

[0013] By adopting the above technical solution, polyethylene fibers exhibit excellent wear resistance and flexibility. The three-dimensional network elastic structure formed with the low-melting-point elastomer is not easily worn or broken, thus improving the fixation strength of the absorbent resin. The melting point of polyethylene fibers is 110-130℃, and even when heated to the point where the polyethylene fibers become sticky, the absorbent resin and porous support network are not easily damaged.

[0014] Optionally, the low-melting-point elastomer is selected from thermoplastic polyurethane.

[0015] By adopting the above technical solution, thermoplastic polyurethane has a melting point of around 120℃ and good toughness and wear resistance. When combined with low-melting-point fibers, the resulting three-dimensional network elastic structure is not easily worn or broken, thus improving the fixation strength of the absorbent resin. Even when heated to a tacky state, the absorbent resin and porous support nests are not easily damaged.

[0016] Optionally, the porous support nest is obtained by crushing nut shells and washing them with alkali.

[0017] By adopting the above technical solution, the lignocellulose material in the nut shell swells after alkali washing, which reduces the degree of polymerization and crystallinity of cellulose, increases the internal surface area of ​​the nut shell, increases the porosity of the nut shell, and facilitates the loading of water-absorbing resin.

[0018] Optionally, the nut shell is selected from macadamia nut shells.

[0019] By adopting the above technical solution, the macadamia nut shell has high hardness, which improves the compressive strength of the water-absorbing carrier, thereby improving the compressive strength of the modified riverbed soil.

[0020] Optionally, the alkaline washing solution is selected from a 0.2-0.7M sodium hydroxide solution.

[0021] By employing the above technical solution, after alkaline washing with a 0.2-0.7M sodium hydroxide solution, the surface of macadamia nut shells exhibits signs of layering, but does not peel off. Surface roughness and porosity increase, facilitating the loading of water-absorbing resin. If the sodium hydroxide concentration is too low, layering is unlikely to occur on the macadamia nut surface; if the sodium hydroxide solution concentration is too high, the macadamia nut shells suffer severe corrosion, resulting in reduced compressive strength. With increasing sodium hydroxide solution concentration, the hydrophilicity of the macadamia nut shell surface first decreases and then increases. At a sodium hydroxide solution concentration of 0.2-0.7M, the macadamia nut shells exhibit a tendency towards hydrophobicity. This hydrophobicity, combined with the water-absorbing resin, facilitates moisture absorption by the resin, shortening the treatment time for riverbed soil.

[0022] Optionally, the superabsorbent resin is selected from one of polyacrylamide resins, acrylic superabsorbent resins, isobutylene-maleic anhydride superabsorbent resins, and low-crosslinked sodium polyacrylate superabsorbent resins.

[0023] By adopting the above technical solution, the water-absorbing resin, in combination with macadamia nut shells, improves the compressive strength of the modified riverbed soil based on the treatment time of the riverbed soil on the left side. Preferably, the water-absorbing resin is selected from sodium polyacrylate limited crosslinking polymer, which has high water absorption performance, good water absorption stability, and resistance to microbial erosion, thus improving the stability of the water-absorbing carrier.

[0024] Secondly, the modified riverbed subgrade provided in this application adopts the following technical solution:

[0025] The modified riverbed subgrade is constructed by paving the aforementioned fill with modified riverbed soil.

[0026] By employing the above technical solution, the free water is solidified using water-absorbing resin, reducing the fluidity of the modified riverbed soil. Simultaneously, modified nut shells, low-melting-point fibers, and low-melting-point elastomers bind and protect the water-absorbing resin after absorption, reducing the probability of compression breakage and improving the compressive strength of the modified riverbed soil. Roadbeds paved with this modified riverbed soil exhibit high compressive strength and good stability.

[0027] In summary, this application includes at least one of the following beneficial technical effects:

[0028] 1. After mixing riverbed soil, cement, and absorbent carrier, the cement hydrates, consuming water and forming CSH gel, which improves the cohesiveness of the riverbed soil. The absorbent carrier fixes free water, reducing the mobility of the modified riverbed soil and improving its stability. Compared to sun-drying the riverbed soil to reduce its moisture content, the combined use of cement and absorbent carrier shortens the treatment time. 2. Porous support nests loaded with absorbent resin protect the resin. After the resin absorbs and expands, the porous support nests limit its expansion and, acting as aggregate, increase the compressive strength of the modified riverbed soil. The resin is less prone to breakage due to compression. Under the action of CSH gel, the porous support nests bond with the dehydrated riverbed soil, forming a modified riverbed soil with high bearing capacity and high compressive strength.

[0029] 3. During the modification of riverbed soil, water-absorbing resin is prone to detaching from the porous support nest. At this time, low-melting-point fibers and low-melting-point elastomers are used. At appropriate temperatures, the low-melting-point fibers partially soften and become sticky, and the low-melting-point elastomers soften, forming a three-dimensional network elastic structure on the surface loaded with water-absorbing resin. The water-absorbing resin absorbs water and swells, and the three-dimensional network structure is stretched open, binding the water-absorbing resin after it has absorbed water and swelled. The water-absorbing resin is not easy to detach from the porous support nest. After the modified riverbed soil is used for backfilling, the porous support nest acts as aggregate, and the water-absorbing resin is wrapped and not easily broken, thereby improving the compressive strength of the modified riverbed soil. Detailed Implementation

[0030] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0031] 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.

[0032] The natural water content of the riverbed soil is (92±0.5)%, the plastic limit is 38.6%, the liquid limit is 72.2%, the plasticity index is 34, the relative density is 2.70, and the clay content is 16%.

[0033] The cement is selected from brand PO42.5 ordinary Portland cement, powder, with a density of 3190 kg / m³. 3 The compressive strengths at 3d, 7d, and 28d were 20.1 MPa, 35.4 MPa, and 46.4 MPa, respectively.

[0034] The water-absorbing resin is a limited cross-linked polymer of sodium polyacrylate with a particle size of 300 mesh and a theoretical maximum water absorption (deionized water) rate of 800 g / g.

[0035] The melting temperature of thermoplastic polyurethane is 120℃; the melting temperature of polyethylene fiber is 125℃.

[0036] Example

[0037] Example 1

[0038] S1. Preparation of the absorbent carrier, the steps are as follows:

[0039] (1) The macadamia nut shells were mechanically crushed and sieved to obtain particles smaller than 5 cm and larger than 1 cm. The particles were washed with 0.2 M sodium hydroxide solution at a temperature of 55 °C, a pressure of 0.5 MPa, and a time of 18 min. After washing with water, the modified nut shells were obtained, namely, porous support nests.

[0040] (2) Take 2.5 kg of the modified nut shell prepared in step (1), add 1.6 kg of water-absorbing resin, 1 kg of polyethylene fiber and 0.8 kg of thermoplastic polyurethane, dry mix for 2 min, heat to 118℃, stir for 20 min, cool and then shake and sieve to obtain water-absorbing carriers smaller than 5 cm.

[0041] S2. Mix 100kg of riverbed soil, 4kg of cement and 4kg of the water-absorbing carrier prepared by S1 evenly, and let it stand for 2h in an environment of (20±2)℃ and (65±2)% to obtain modified riverbed soil.

[0042] Example 2

[0043] S1. Preparation of the absorbent carrier, the steps are as follows:

[0044] (1) The macadamia nut shells were mechanically crushed and sieved to obtain particles smaller than 5 cm and larger than 1 cm. The particles were washed with 0.5 M sodium hydroxide solution at a temperature of 55 °C, a pressure of 0.5 MPa, and a time of 15 min. After washing with water, the modified nut shells were obtained, namely, porous support nests.

[0045] (2) Take 2kg of the modified nut shell prepared in step (1), add 1.2kg of water-absorbing resin, 0.7kg of polyethylene fiber and 0.5kg of thermoplastic polyurethane, dry mix for 2min, heat to 118℃, stir for 20min, cool and then shake and sieve to obtain water-absorbing carriers less than 5cm.

[0046] S2. Mix 100kg of riverbed soil, 6kg of cement and 3kg of the water-absorbing carrier prepared by S1 evenly, and let it stand for 2h in an environment of (20±2)℃ and (65±2)% to obtain modified riverbed soil.

[0047] Example 3

[0048] S1. Preparation of the absorbent carrier, the steps are as follows:

[0049] (1) The macadamia nut shells were mechanically crushed and sieved to obtain particles smaller than 5 cm and larger than 1 cm. The particles were washed with 0.7 M sodium hydroxide solution at a temperature of 55 ℃, a pressure of 0.5 MPa, and a time of 15 min. After washing with water, the modified nut shells, i.e., porous support nests, were obtained.

[0050] (2) Take 1.5 kg of the modified nut shell prepared in step (1), add 0.8 kg of water-absorbing resin, 0.5 kg of polyethylene fiber and 0.2 kg of thermoplastic polyurethane, dry mix for 2 min, heat to 118℃, stir for 20 min, cool and then shake and sieve to obtain water-absorbing carriers smaller than 5 cm.

[0051] S2. Mix 100kg of riverbed soil, 8kg of cement and 2kg of the water-absorbing carrier prepared by S1 evenly, and let it stand for 2h in an environment of (20±2)℃ and (65±2)% to obtain modified riverbed soil.

[0052] Example 4

[0053] The difference from Example 2 is that the amount of cement added in S2 is 4 kg.

[0054] Example 5

[0055] The difference from Example 2 is that the amount of cement added in S2 is 8 kg.

[0056] Example 6

[0057] The difference from Example 2 is that the amount of water-absorbing carrier added in S2 is 2kg.

[0058] Example 7

[0059] The difference from Example 2 is that the amount of water-absorbing carrier added in S2 is 4 kg.

[0060] Example 8

[0061] The difference from Example 2 is that the amount of water-absorbing resin added in step (2) is 0.8 kg.

[0062] Example 9

[0063] The difference from Example 2 is that the amount of water-absorbing resin added in step (2) is 1.6 kg.

[0064] Example 10

[0065] The difference from Example 2 is that the amount of polyethylene fiber added in step (2) is 0.5 kg.

[0066] Example 11

[0067] The difference from Example 2 is that the amount of polyethylene fiber added in step (2) is 1 kg.

[0068] Example 12

[0069] The difference from Example 2 is that the amount of thermoplastic polyurethane added in step (2) is 0.2 kg.

[0070] Example 13

[0071] The difference from Example 2 is that the amount of thermoplastic polyurethane added in step (2) is 0.8 kg.

[0072] Table 1 Raw material list for Examples 1-13

[0073]

[0074]

[0075] Example 14

[0076] The difference from Example 2 is that the concentration of sodium hydroxide solution in step (1) is 0.2M.

[0077] Example 15

[0078] The difference from Example 2 is that the concentration of sodium hydroxide solution in step (1) is 0.7M.

[0079] Example 16

[0080] A modified riverbed soil subgrade is constructed by paving with the modified riverbed soil prepared in Example 2, and the process is as follows:

[0081] (1) Level the construction area and remove debris from the construction surface;

[0082] (2) The subgrade filling and compaction process is adopted. The thickness of the modified riverbed soil in each loose layer is controlled within 50cm, and the compaction degree is controlled above 90%. The compaction is carried out by vibratory roller equipment, and the roller is rolled 2-6 times. In this embodiment, the roller is rolled 3 times.

[0083] Comparative Example

[0084] Comparative Example 1

[0085] 100 kg of riverbed soil was turned over and dried in a laboratory at a temperature of (25±2)℃ and a humidity of (35±2)%. The soil was spread to a thickness of 5 cm and turned over automatically every 4 hours. The heat source was an incandescent lamp, which was kept on 24 hours a day. The lamps were placed 2 m vertically from the riverbed soil and were set to 1 lamp per 5 m. 2 Riverbed soil was collected after the water content was no more than 4%.

[0086] Comparative Example 2

[0087] The difference from Example 2 is that no cement was added.

[0088] Comparative Example 3

[0089] The difference from Example 2 is that no absorbent carrier was added.

[0090] Comparative Example 4

[0091] The difference from Example 2 is that no absorbent carrier was prepared, and the absorbent carrier was replaced with absorbent resin.

[0092] Comparative Example 5

[0093] The difference from Example 2 is that polyethylene fiber and thermoplastic polyurethane were not added during the preparation of the absorbent carrier.

[0094] Comparative Example 6

[0095] The difference from Example 2 is that no polyethylene fiber was added during the preparation of the absorbent carrier.

[0096] Comparative Example 7

[0097] The difference from Example 2 is that thermoplastic polyurethane was not added during the preparation of the absorbent carrier.

[0098] Comparative Example 8

[0099] The difference from Example 2 is that the macadamia nut shells were not treated with alkali. The preparation steps of the modified nut shells are as follows: (1) The macadamia nut shells are mechanically crushed, and after sieving, particles smaller than 5cm and larger than 1cm are taken as modified nut shells, i.e., porous support nests.

[0100] Performance testing

[0101] Test methods

[0102] 1. The bearing ratio of riverbed soil or modified riverbed soil was tested using the method of "T0134-2019 Bearing Ratio (CBR) Test" in "JTG 3430—2020 Highway Geotechnical Test Specifications". The compaction degree was controlled at 93%. The specimens were formed by static compaction in one step. The test results are detailed in Table 2.

[0103] 2. The unconfined compressive strength (MPa) and compressive resilient modulus (MPa) of riverbed soil or modified riverbed soil were determined using the methods in "JTG E51—2009 Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering". The test results are detailed in Table 2.

[0104] Table 2. Test results data for each embodiment and comparative example.

[0105]

[0106]

[0107] Based on Examples 1, 2, and 3 and Table 2, modified riverbed soil for embankment with high bearing capacity, high unconfined compressive strength, and appropriate compressive resilient modulus was prepared by adjusting the weight ratio of riverbed soil, cement, and absorbent carrier, as well as the type of absorbent carrier.

[0108] Combining Examples 2, 4, and 5, the difference lies in the amount of cement added. In Example 2, the amount of cement added is 6 kg, accounting for approximately 6%; in Example 4, the amount of cement added is 4 kg, accounting for approximately 4%; and in Example 5, the amount of cement added is 8 kg, accounting for approximately 7%. As can be seen from Table 2, the modified riverbed soil prepared in Example 2 has the highest unconfined compressive strength and the largest compressive resilient modulus, while the modified riverbed soil prepared in Example 5 has the largest bearing ratio. That is, as the amount of cement added increases, the bearing ratio of the modified synthetic riverbed soil increases, the unconfined compressive strength first increases and then decreases, and the compressive resilient modulus first increases and then decreases. With an increased cement content, more CSH gel is produced by cement hydration, which improves the bonding strength between the absorbent carrier and the riverbed soil particles, thus increasing the bearing capacity of the modified riverbed soil. The cement hydration products fix adjacent absorbent carriers, making it difficult for them to shift relative to each other, which facilitates the absorbent carrier's role as aggregate. However, the absorbent carrier is partially encapsulated by CSH gel, which reduces its water absorption rate, increases the moisture content of the modified riverbed soil, and reduces its stability.

[0109] Combining Examples 2, 6, and 7, the difference lies in the amount of water-absorbing carrier added: 3 kg in Example 2, 2 kg in Example 6, and 4 kg in Example 7. As shown in Table 2, with the increase of water-absorbing carrier addition, the bearing capacity of the modified synthetic riverbed soil decreases, the unconfined compressive strength increases, and the compressive resilient modulus first increases and then decreases. The structure of the water-absorbing carrier consists of a modified nut shell loaded with water-absorbing resin encased in a three-dimensional network elastic structure formed by polyethylene fibers and thermoplastic polyurethane. The polyethylene fibers and thermoplastic polyurethane prevent the water-absorbing resin from easily detaching from the modified nut shell. When the water-absorbing carrier contacts the riverbed soil, the resin absorbs water through the gaps in the three-dimensional network elastic structure, increasing the resin volume. The three-dimensional network elastic structure deforms but is not easily broken. When the modified riverbed soil is compressed, the modified nut shell supports and protects the resin, reducing the probability of resin breakage, and ensuring the dimensional stability and resistance to deformation of the modified riverbed soil.

[0110] The difference between Examples 2, 8, and 9 lies in the amount of water-absorbing resin added during the preparation of the absorbent carrier. In Example 2, the amount of water-absorbing resin added is 1.2 kg, and the weight ratio of water-absorbing resin, modified nut shell, polyethylene fiber, and thermoplastic polyurethane is 1.2:2:0.7:0.5. In Example 8, the amount of water-absorbing resin added is 0.8 kg, and the weight ratio of water-absorbing resin, modified nut shell, polyethylene fiber, and thermoplastic polyurethane is 0.8:2:0.7:0.5. In Example 9, the amount of water-absorbing resin added is 1.6 kg, and the weight ratio of water-absorbing resin, modified nut shell, polyethylene fiber, and thermoplastic polyurethane is 1.6:2:0.7:0.5. As can be seen from Table 2, with the increase of the proportion of water-absorbing resin in the absorbent carrier, the bearing capacity of the modified synthetic riverbed soil first increases and then decreases, the unconfined compressive strength decreases, and the compressive resilient modulus first increases and then decreases.

[0111] The differences between Examples 2, 10, and 11 lie in the amount of polyethylene fiber added during the preparation of the absorbent carrier. In Example 2, the amount of polyethylene fiber added is 0.7 kg, and the weight ratio of modified nut shell, polyethylene fiber, and thermoplastic polyurethane is 2:0.7:0.5. In Example 10, the amount of polyethylene fiber added is 0.5 kg, and the weight ratio of modified nut shell, polyethylene fiber, and thermoplastic polyurethane is 2:0.5:0.5. In Example 11, the amount of polyethylene fiber added is 1 kg, and the weight ratio of modified nut shell, polyethylene fiber, and thermoplastic polyurethane is 2:1:0.5. As can be seen from Table 2, with the increase of the proportion of polyethylene fiber in the absorbent carrier, the bearing capacity of the modified synthetic riverbed soil first increases and then decreases, the unconfined compressive strength first increases and then decreases, and the compressive resilient modulus first increases and then decreases. Polyethylene fibers disperse the soluble components, reducing stress concentration and improving the compressive strength and compressive resilience modulus of the sample; however, polyethylene fibers hinder the dispersion of the absorbent carrier and the absorption of water by the absorbent resin, thus reducing the stability of the modified riverbed soil.

[0112] The difference between Examples 2, 12, and 13 lies in the amount of thermoplastic polyurethane added during the preparation of the absorbent carrier. In Example 2, the amount of thermoplastic polyurethane added is 0.5 kg, and the weight ratio of modified nut shells, polyethylene fibers, and thermoplastic polyurethane is 2:0.7:0.5. In Example 12, the amount of thermoplastic polyurethane added is 0.2 kg, and the weight ratio of modified nut shells, polyethylene fibers, and thermoplastic polyurethane is 2:0.7:0.2. In Example 13, the amount of thermoplastic polyurethane added is 0.8 kg, and the weight ratio of modified nut shells, polyethylene fibers, and thermoplastic polyurethane is 2:0.7:0.8. As can be seen from Table 2, with the increase of the proportion of thermoplastic polyurethane in the absorbent carrier, the bearing capacity of the modified synthetic riverbed soil first increases and then decreases, the unconfined compressive strength first increases and then decreases, and the compressive resilient modulus first increases and then decreases.

[0113] The difference between Examples 2, 14, and 15 lies in the concentration of sodium hydroxide solution used in preparing the modified nut shells. In Example 2, the concentration of sodium hydroxide solution was 0.5M; in Example 14, it was 0.2M; and in Example 15, it was 0.8M. As can be seen from Table 2, with the increase of sodium hydroxide solution concentration, the unconfined compressive strength of the modified synthetic riverbed soil decreased, while the compressive resilient modulus increased.

[0114] Comparative Example 1 uses the sun-drying method to treat riverbed soil. Combined with Example 2 and Table 2, it can be seen that even though the sun-dried riverbed soil has the same moisture content as the modified riverbed soil prepared in this application, the modified riverbed soil prepared in this application has a shorter treatment time, higher bearing capacity, and higher unconfined compressive strength.

[0115] Compared to Example 2, Comparative Example 2 did not add cement. As can be seen from Table 2, the addition of cement effectively improved the bearing capacity, unconfined compressive strength and compressive resilient modulus of the modified riverbed soil.

[0116] Compared to Example 2, Comparative Example 3 did not add a water-absorbing carrier. As can be seen from Table 2, the addition of the water-absorbing carrier effectively improved the unconfined compressive strength and compressive resilient modulus of the modified riverbed soil.

[0117] Compared to Comparative Example 3, Comparative Example 4 used water-absorbing resin as the water-absorbing carrier. As can be seen from Table 2, adding water-absorbing resin alone reduced the bearing capacity of the modified riverbed soil, as well as the unconfined compressive strength and compressive resilient modulus.

[0118] Compared to Comparative Example 4, Comparative Example 5 uses a mixture of water-absorbing resin and modified nut shells as the water-absorbing carrier. As shown in Table 2, the addition of modified nut shells effectively improves the unconfined compressive strength. However, as shown in Example 2, the absence of polyethylene fiber and thermoplastic polyurethane reduces the bearing capacity, compressive resilience modulus, and unconfined compressive strength of the modified riverbed soil.

[0119] Based on Comparative Examples 5, 6, and 7, and in conjunction with Table 2, it can be seen that the addition of polyethylene fiber or thermoplastic polyurethane both improved the bearing capacity, unconfined compressive strength, and compressive resilient modulus of the modified riverbed soil. Furthermore, based on Example 2, it can be seen that neither polyethylene fiber nor thermoplastic polyurethane alone was as effective as the combination of both.

[0120] The difference between Example 2 and Comparative Example 8 lies in whether the modified nut shells were prepared by alkali washing. Comparative Example 8 was not alkali washed. As can be seen from Table 2, the use of alkali washing process improved the unconfined compressive strength of the modified riverbed soil.

[0121] 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. Modified riverbed soil for fill, characterized in that, The raw materials include the following parts by weight: 100 parts riverbed soil; 4-8 parts cement; 2-4 parts water-absorbing carrier; the water-absorbing carrier includes water-absorbing resin and porous support nest, the water-absorbing resin is loaded on the porous support nest; the weight ratio of water-absorbing resin to porous support nest is 16:(25-30). The absorbent carrier further includes low-melting-point fibers and low-melting-point elastomers, wherein the weight ratio of the porous support nest, low-melting-point fibers, and low-melting-point elastomers is 75:(25-30):(10-24); the low-melting-point fibers are selected from polyethylene fibers; and the low-melting-point elastomers are selected from thermoplastic polyurethanes. The porous support nest is obtained by crushing nut shells and washing them with alkali.

2. The modified riverbed soil for embankment filling according to claim 1, characterized in that, The nut shells are selected from macadamia nut shells.

3. The modified riverbed soil for embankment construction according to claim 2, characterized in that, The alkaline washing solution is selected from a 0.2-0.7M sodium hydroxide solution.

4. The modified riverbed soil for embankment filling according to claim 1, characterized in that, The superabsorbent resin is selected from one of the following: polyacrylamide resin, acrylic superabsorbent resin, isobutylene-maleic anhydride superabsorbent resin, and low-crosslinked sodium polyacrylate superabsorbent resin.

5. Modified riverbed soil subgrade, characterized in that, It is paved with modified riverbed soil as described in any one of claims 1-3.

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