Foundation trench backfill material, preparation method and application thereof

Abstract

The application relates to the technical field of foundation trench backfilling, and particularly discloses a foundation trench backfilling material and a preparation method and application thereof. The foundation trench backfilling material disclosed by the application comprises the following components in parts by weight: shield slag 24-30 parts; sand 29-42 parts; cement 8-15 parts; a solidifying agent 0.01-0.5 parts and water 25-28 parts; the solidifying agent comprises silicon dioxide, epoxy resin and styrene-acrylic emulsion in a weight ratio of (30-40):(10-18):(0.5-1.5). The application further discloses a preparation method and application of the foundation trench backfilling material. The foundation trench backfilling material obtained by the technical scheme provided by the application has good fluidity, high compressive resistance and good durability.

Description

Technical Field

[0001] This application relates to the technical field of foundation trench backfilling, specifically to a foundation trench backfilling material, its preparation method, and its application. Background Technology

[0002] With the rapid development of urbanization and urban rail transit, shield tunneling technology has become a key technology for the construction of subways and major tunnels. The shield tunneling process generates a large amount of excavated soil, which is generally transported off-site by dump trucks or discarded, failing to achieve effective utilization. Furthermore, improper handling of shield tunneling excavated soil can easily cause environmental pollution.

[0003] To fully utilize tunnel boring machine (TBM) excavation soil while reducing environmental pollution, existing research has focused on recycling and improving this soil for use in foundation trench backfill materials. However, for foundation trench backfilling projects, the fluidity and compressive strength of the backfill material directly affect the stability of the foundation pit. Failure to implement quality control can negatively impact the stability of the foundation pit structure, potentially leading to its destruction.

[0004] Therefore, in the process of using tunnel boring machine (TBM) excavation soil as backfill material for foundation trenches, how to ensure the fluidity and compressive strength of the backfill material in order to improve the stability of the foundation pit and internal structures during the backfilling process is an urgent problem to be solved. Summary of the Invention

[0005] In order to ensure the fluidity and compressive strength of the foundation trench backfill material, and to improve the stability of the foundation pit and internal structures during the foundation trench backfilling process, this application provides a foundation trench backfill material, its preparation method and application.

[0006] In one aspect, this application provides a foundation trench backfill material comprising the following components in parts by weight: 24-30 parts of shield tunneling excavation soil; 29-42 parts of sand; 8-15 parts of cement; 0.01-0.5 parts of curing agent; and 25-28 parts of water;

[0007] The curing agent comprises silica, epoxy resin and styrene-acrylic emulsion in a weight ratio of (30-40):(10-18):(0.5-1.5).

[0008] This application utilizes silica, epoxy resin, and styrene-acrylic emulsion in the above weight ratio as an organic-inorganic composite curing agent to prepare a foundation trench backfill material with shield tunnel slag, sand, cement, and water. The obtained foundation trench backfill material exhibits excellent consistency, compressive strength, and durability, indicating that the foundation trench backfill material has good fluidity and self-compacting properties, and also has high compressive strength after foundation trench backfilling and curing.

[0009] The technical solution of this application uses tunnel boring machine (TBM) slag and sand as the main materials, and cement as the gelling material. Cement acts as a binder and also improves the compressive strength of the backfill material. This application utilizes silica, epoxy resin, and styrene-acrylic emulsion as an organic-inorganic composite curing agent. The small particle size of silica can fill the gaps between the components of the curing agent, improving the self-compacting degree and bonding effect of the backfill material, thereby increasing its compressive strength. Simultaneously, cement hydration produces calcium hydroxide, which reacts exothermically with the silica in the curing agent, further accelerating the cement hydration reaction and reducing the setting time of the backfill material. In addition, under the action of the curing agent provided in this application, the system has a high viscosity, forming good adhesion between shield tunnel slag, sand and cement particles, thereby reducing the probability of sand and gravel flying, increasing the specific surface area of ​​the trench backfill material, reducing the gaps between sand and gravel particles, and thus increasing the density between sand and gravel particles. This can significantly improve the compressive strength of the trench backfill material, while ensuring the stability of the trench backfill material, thereby improving the durability of the trench backfill material.

[0010] Preferably, the backfill material for the foundation trench comprises the following components in parts by weight: 24-27 parts of shield tunneling excavation soil; 33-42 parts of sand; 8-12 parts of cement; 0.1-0.5 parts of curing agent and 25-28 parts of water.

[0011] In one specific implementation plan, the amount of tunnel boring machine excavated soil added can be 24 parts, 27 parts, or 30 parts.

[0012] In some specific implementation schemes, the amount of tunnel boring machine excavated soil added can be 24-27 parts.

[0013] In one specific implementation, the amount of sand added can be 29 parts, 33 parts, or 42 parts.

[0014] In some specific implementations, the amount of sand added can also be 29-33 parts.

[0015] In one specific implementation, the amount of cement added can be 8 parts, 12 parts, or 15 parts.

[0016] In some specific implementations, the amount of cement added can also be 12-15 parts.

[0017] In one specific implementation, the amount of curing agent added can be 0.05 parts, 0.1 parts, or 0.5 parts.

[0018] In some specific implementations, the amount of curing agent added may be 0.05-0.1 parts.

[0019] Experimental analysis shows that by controlling the amount of each component added to the foundation trench backfill material within the above-mentioned range, the fluidity, compressive strength and durability of the foundation trench backfill material can be further improved.

[0020] Preferably, the method for preparing the shield tunneling slag is as follows: the shield tunneling mud is screened stepwise to remove gravel and sand, then a flocculant is added for flocculation, and the shield tunneling slag is obtained by pumping water and squeezing.

[0021] Furthermore, the flocculant is a nonionic polyacrylamide type flocculant, and the dosage of the flocculant is 0.01-0.05 wt%.

[0022] In one specific implementation, the amount of flocculant used can be 0.01 wt%, 0.025 wt%, or 0.05 wt%.

[0023] In some specific implementations, the amount of the flocculant can also be 0.01-0.025 wt% or 0.025-0.05 wt%.

[0024] Experimental analysis shows that by controlling the amount of flocculant within the above-mentioned range, the compressive strength and corrosion resistance coefficient of the obtained foundation trench backfill material are significantly improved.

[0025] Furthermore, the particle size of the tunnel boring machine excavated soil is ≤0.25mm, and the moisture content is 5-8wt%.

[0026] Preferably, the curing agent comprises silica, epoxy resin and styrene-acrylic emulsion in a weight ratio of (35-40):(10-14):(0.5-1).

[0027] Experimental analysis shows that by controlling the weight ratio of silica, epoxy resin and styrene-acrylic emulsion in the curing agent to the above range, this application can further improve the fluidity, compressive strength and durability of the backfill material for the foundation trench.

[0028] Preferably, the sand has a particle size of 0.25-1 mm.

[0029] Preferably, the cement is one or more of ordinary Portland cement or sulfoaluminate cement with a PO ≥ 42.5.

[0030] Secondly, this application provides a method for preparing the aforementioned foundation trench backfill material, specifically including the following steps:

[0031] Dissolve each component of the curing agent in the water according to the specified ratio to obtain a curing agent solution for later use. Then, pour the shield tunnel slag, the sand, and the cement into a mixer and mix them evenly. Then, add the prepared curing agent solution and stir for 3-5 minutes to obtain the foundation trench backfill material.

[0032] Thirdly, this application provides the application of the aforementioned foundation trench backfill material in the foundation or foundation trench construction environment.

[0033] In summary, the technical solution of this application has the following effects:

[0034] This application improves the excavated soil from shield tunneling, enabling it to meet the requirements for trench backfilling. This fully utilizes the excavated soil during shield tunneling, effectively uses soil resources, reduces environmental pollution, and significantly lowers transportation and construction costs for trench backfilling. It also provides a reference for the smooth construction of trench backfilling.

[0035] The technical solution of this application uses shield tunneling slag and sand as the main materials, cement as the gelling material, and utilizes silica, epoxy resin and styrene-acrylic emulsion as organic-inorganic composite curing agents, which makes the system have high viscosity and good adhesion between shield tunneling slag, sand and cement particles. This increases the specific surface area of ​​the trench backfill material, reduces the gaps between sand and gravel particles, and thus increases the density between sand and gravel particles. This can significantly improve the compressive strength of the trench backfill material, while ensuring the stability of the trench backfill material, thereby improving the durability of the trench backfill material.

[0036] This application optimizes the preparation method of shield tunnel slag by screening the addition amount of each component in the foundation trench backfill material, and further improves the fluidity, compressive strength and durability of the foundation trench backfill material by screening the weight ratio of silica, epoxy resin and styrene-acrylic emulsion in the curing agent. Detailed Implementation

[0037] The present application will be further described in detail below with reference to embodiments, comparative examples and performance test results. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0038] Preparation Example

[0039] Preparation Example 1

[0040] This preparation example provides a shield tunneling excavation material.

[0041] The preparation method of shield tunneling excavated soil in this example is as follows:

[0042] The tunnel boring machine slurry (sourced from Beijing Municipal Road and Bridge Management and Maintenance Group Co., Ltd.) is screened in stages to remove gravel and sand (the first screening removes gravel with a particle size greater than 2mm, and the second screening removes sand with a particle size of 2-0.25mm). After screening, the slurry enters a sedimentation tank through pipelines, and 0.03wt% of non-ionic polyacrylamide flocculant is added. After flocculation, water is pumped out and squeezed to reduce the moisture content, resulting in tunnel boring machine slag with a particle size ≤0.25mm and a moisture content of 6.54wt%.

[0043] Preparation Example 2

[0044] This preparation example provides a shield tunneling excavation material.

[0045] The difference between this preparation example and Preparation Example 1 is that the amount of nonionic polyacrylamide flocculant used is 0.008 wt%.

[0046] Preparation Example 3

[0047] This preparation example provides a shield tunneling excavation material.

[0048] The difference between this preparation example and Preparation Example 1 is that the amount of nonionic polyacrylamide flocculant used is 0.01 wt%.

[0049] Preparation Example 4

[0050] This preparation example provides a shield tunneling excavation material.

[0051] The difference between this preparation example and Preparation Example 1 is that the amount of nonionic polyacrylamide flocculant used is 0.05 wt%.

[0052] Preparation Example 5

[0053] This preparation example provides a shield tunneling excavation material.

[0054] The difference between this preparation example and Preparation Example 1 is that the amount of nonionic polyacrylamide flocculant used is 0.06 wt%.

[0055] Preparation Example 6

[0056] This preparation example provides a shield tunneling excavation material.

[0057] The preparation method of shield tunneling excavated soil in this example is as follows:

[0058] The tunnel boring machine slurry (sourced from Beijing Municipal Road and Bridge Management and Maintenance Group Co., Ltd.) is screened in stages to remove gravel and sand (the first screening removes gravel with a particle size greater than 2mm, and the second screening removes sand with a particle size of 2-0.25mm). After screening, the slurry enters a sedimentation tank through pipelines, where it is pumped out and squeezed to reduce the moisture content, resulting in tunnel boring machine slag with a particle size ≤0.25mm and a moisture content of 6.54wt%.

[0059] Example

[0060] Examples 1-5

[0061] Examples 1-5 each provide a backfill material for foundation trenches.

[0062] The difference in the above embodiments is that the amount of each component added to the foundation trench backfill material is shown in Table 1.

[0063] The preparation method of the foundation trench backfill material is as follows:

[0064] 3.5g of silica, 1.4g of epoxy resin, and 0.1g of styrene-acrylic emulsion (purchased from Jiangsu Shengda New Material Technology Co., Ltd.) were mixed evenly to obtain a curing agent (the weight ratio of silica, epoxy resin, and styrene-acrylic emulsion was 35:14:1). According to Table 1, the corresponding amount of curing agent was weighed and dissolved in water to obtain a curing agent solution for later use. Then, the shield tunneling slag, sand with a particle size of 0.5±0.2mm, and ordinary silicate cement with PO≥42.5 were poured into a mixer according to the proportions in Table 1 and mixed evenly. Then, the prepared curing agent solution was added and stirred for 5 minutes to obtain the backfill material for the foundation trench.

[0065] Table 1 shows the addition amounts of each component in the backfill material of the foundation trench in Examples 1-5.

[0066]

[0067] Examples 6-10

[0068] Examples 6-10 each provide a foundation trench backfill material.

[0069] The difference between the above embodiments and Embodiment 3 is that the source of the tunnel boring machine excavation soil is as shown in Table 2.

[0070] Table 2 shows the sources of tunnel boring machine excavation in Examples 3 and 6-10.

[0071] Example Sources of tunnel boring machine excavation Example Sources of tunnel boring machine excavation 3 Preparation Example 1 8 Preparation Example 4 6 Preparation Example 2 9 Preparation Example 5 7 Preparation Example 3 10 Preparation Example 6

[0072] Examples 11-15

[0073] Examples 11-15 each provide a backfill material for foundation trenches.

[0074] The difference between the above embodiments and Embodiment 3 is that the weight ratio of silica, epoxy resin and styrene-acrylic emulsion in the curing agent is as shown in Table 3.

[0075] Table 3 shows the weight ratios of silica, epoxy resin, and styrene-acrylic emulsion in Examples 3, 11-15.

[0076]

[0077]

[0078] Comparative Example

[0079] Comparative Example 1

[0080] This comparative example provides a foundation trench backfill material.

[0081] The difference between this comparative example and Example 3 is that sodium silicate is used instead of silicon dioxide, that is, the curing agent includes sodium silicate, epoxy resin and styrene-acrylic emulsion in a weight ratio of 35:14:1.

[0082] Comparative Example 2

[0083] This comparative example provides a backfill material for foundation trenches.

[0084] The difference between this comparative example and Example 3 is that silicone-acrylic emulsion is used instead of styrene-acrylic emulsion, that is, the curing agent includes sodium silicate, epoxy resin and silicone-acrylic emulsion in a weight ratio of 35:14:1.

[0085] Comparative Examples 3-5

[0086] Comparative Examples 3-5 each provide a backfill material for foundation trenches.

[0087] The difference between the above comparative example and Example 3 is that the weight ratio of silica, epoxy resin and styrene-acrylic emulsion in the curing agent is as shown in Table 4.

[0088] Table 4 shows the weight ratios of silica, epoxy resin, and styrene-acrylic emulsion in Comparative Examples 3-5.

[0089]

[0090] The performance testing was conducted using the backfill materials provided in Examples 1-15 and Comparative Examples 1-5 as the test objects, and the consistency (flowability) of the backfill materials and the compressive strength and durability after backfilling were tested.

[0091] (1) Consistency test: The fluidity of the backfill material mixture was determined according to the consistency test method in GB / T17669.4-1999 "Determination of Physical Properties of Building Gypsum Paste". The test mold was a stainless steel cylinder with an inner diameter of 50±0.1mm and a height of 100±0.1mm.

[0092] (2) Compressive strength and durability test:

[0093] Under the same conditions, 20 foundation trenches of the same size and shape were backfilled using the foundation trench backfill materials provided in Examples 1-15 and Comparative Examples 1-5. After backfilling, a film covering method was used for moisture retention and maintenance, and water was sprayed regularly every day to keep the trenches moist.

[0094] Compressive strength: The compressive strength of the backfill material at 3d, 7d and 28d was determined according to the compressive strength test method of GB / T50123-2019 "Standard for Geotechnical Test Methods".

[0095] Durability: The compressive strength of the backfill material after 30 sulfate attacks during 28 days of standard curing was determined according to the sulfate attack test method in GB / T50082-2019 "Standard Test Method for Long-term Performance and Durability of Ordinary Soil Concrete". The compressive strength corrosion resistance coefficient was obtained according to Formula 1 to characterize the durability of the backfill material.

[0096] K = (S 1 / S0)×100% Formula 1

[0097] Where: K—compressive strength corrosion resistance coefficient (%); S0—compressive strength of backfill material after 28 days of standard curing (MPa); S1—compressive strength of backfill material after 30 sulfate erosions after 28 days of standard curing (MPa).

[0098] Test results are shown in Table 5.

[0099] Table 5 Performance test results of the trench backfill materials in Examples 1-15 and Comparative Examples 1-5

[0100]

[0101]

[0102] As shown in Table 5, the test results of this application utilize silica, epoxy resin, and styrene-acrylic emulsion in a weight ratio of (30-40):(10-18):(0.5-1.5) as curing agents to prepare trench backfill material with shield tunnel slag, sand, cement, and water. The consistency of this trench backfill material is 90-118, and its 3-day compressive strength after backfilling and curing is between 2.15-2.66 MPa, its 7-day compressive strength is between 3.59-4.24 MPa, and its 28-day compressive strength is between 4.72-5.32 MPa, with a corrosion resistance coefficient exceeding 90.25%. The above test results indicate that the trench backfill material obtained using the technical solution provided in this application exhibits excellent consistency, compressive strength, and durability, demonstrating good fluidity and self-compacting properties, and high compressive strength after trench backfilling and curing.

[0103] By comparing the test results of Example 3 with those of Comparative Examples 1-2, it can be seen that when sodium silicate is used instead of silica or silicone-acrylic emulsion is used instead of styrene-acrylic emulsion as the curing agent in the curing agent formulation, the consistency of the prepared trench backfill material is lower than 68, the 3-day compressive strength after trench backfilling and curing is between 0.86-1.21 MPa, the 7-day compressive strength is between 1.29-1.54 MPa, the 28-day compressive strength is between 1.25-2.32 MPa, and the corrosion resistance coefficient is lower than 87%. In contrast, this application selects silica, epoxy resin, and styrene-acrylic emulsion as curing agents, and the prepared trench backfill material has excellent consistency, compressive strength, and corrosion resistance coefficient. That is, the formulation provided in this application can obtain trench backfill material with excellent fluidity, compressive strength, and durability.

[0104] Furthermore, by comparing the test results of Examples 3, 11-15 with those of Comparative Examples 3-5, it can be seen that the weight ratio of silica, epoxy resin and styrene-acrylic emulsion in the curing agent controlled by this application is (30-40):(10-18):(0.5-1.5), which can further improve the fluidity, compressive strength and durability of the trench backfill material.

[0105] By comparing the test results of Examples 1-5, this application further controls the weight of the components in the trench backfill material to 24-27 parts shield tunnel slag, 33-42 parts sand, 8-12 parts cement, 0.1-0.5 parts curing agent and 25-28 parts water, which can further improve the fluidity, compressive strength and durability of the trench backfill material.

[0106] Comparing the test results of Examples 3 and 6-10, in Example 10 of this application, when no flocculant was added during the preparation of shield tunneling slag using shield tunneling mud, the 3-day compressive strength of the backfill material after curing was 2.15 MPa, the 7-day compressive strength was 3.64 MPa, the 28-day compressive strength was 4.78 MPa, and the corrosion resistance coefficient was 95.61%. In Examples 6 or 9, the amount of flocculant used in the preparation of shield tunneling slag using shield tunneling mud was lower (below 0.01 wt%) or higher (…). When the flocculant content is higher than 0.05 wt%, the 3-day compressive strength of the backfill material after curing is between 2.31 and 2.34 MPa, the 7-day compressive strength is between 3.82 and 3.84 MPa, and the 28-day compressive strength is between 4.83 and 4.89 MPa, with a corrosion resistance coefficient lower than 96.27%. However, in Examples 3 and 7-8, during the preparation of shield tunneling excavation soil using shield tunneling slurry, the flocculant dosage was controlled at 0.01-0.05 wt%, resulting in significantly improved compressive strength and corrosion resistance coefficient of the obtained backfill material. Therefore, this application selects to control the flocculant dosage within the above-mentioned range during the preparation of shield tunneling excavation soil using shield tunneling slurry.

[0107] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A foundation trench backfill material, characterized by, The components include the following weight parts: shield slag 24-30 parts; sand 29-42 parts; cement 8-15 parts; curing agent 0.01-0.5 parts and water 25-28 parts; The curing agent is composed of silica, epoxy resin and styrene-acrylic emulsion in a weight ratio of (35-40):(10-14):(0.5-1); The preparation method of the shield slag is as follows: the shield mud is subjected to step-by-step screening to remove gravel and sand, then a flocculating agent is added for flocculation, and the shield slag is obtained by pumping and extrusion; the flocculating agent is a non-ionic polyacrylamide flocculating agent, and the amount of the flocculating agent is 0.01-0.05wt%.

2. The foundation trench backfill material of claim 1, wherein, The components include the following weight parts: shield slag 24-27 parts; sand 33-42 parts; cement 8-12 parts; curing agent 0.1-0.5 parts and water 25-28 parts.

3. The foundation trench backfill material of claim 1, wherein, The particle size of the shield slag is ≤0.25mm, and the water content is 5-8wt%.

4. The foundation trench backfill material of claim 1, wherein, The particle size of the sand is 0.25-1mm.

5. The foundation trench backfill material of claim 1, wherein, The cement is one or more of P.O≥42.5 ordinary Portland cement or sulphoaluminate cement.

6. The method of preparing a foundation trench backfill material according to any one of claims 1 to 5, wherein Specifically includes the following steps: Each component in the curing agent is dissolved in the water according to the proportion to obtain a curing agent solution for standby, then the shield slag, the sand and the cement are poured into a mixer and mixed uniformly, then the prepared curing agent solution is added, and stirred for 3-5min; the base trench backfill material is obtained.

7. The base trench backfill material according to any one of claims 1-5 in the application of foundation or base trench construction environment.

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