Earth-rockfill dam termite nest bionic simulation material and preparation method thereof

Abstract

The application discloses a kind of earth-rock dam termite nest bionics simulation materials and preparation method thereof, it is related to water conservancy engineering geotechnical material and termite disaster prevention and control technical field, the bionics simulation material is composed of mixed aggregate, basic cementing agent, auxiliary cementing agent and composite reinforcing fiber;The mixed aggregate is the dry mixture of sand and clay, and the dry mass ratio of sand and clay is 1:2;The basic cementing agent is composed of dry glue powder and pregelatinized starch according to dry mass ratio 1:2;The auxiliary cementing agent is polyvinyl alcohol PVA aqueous solution with mass concentration 1%;The composite reinforcing fiber is composed of dry fine cellulose and woody coarse fiber, and woody coarse fiber accounts for 50% of the total dry mass of composite reinforcing fiber;The application is prepared by three-step progressive strategy of aggregate gradation optimization, cementing system modification and coarse and fine fiber composite reinforcement, and the bionic material highly consistent with natural nest wall meets the demand of earth-rock dam termite disaster mechanism model test.

Description

Technical Field

[0001] This invention relates to the field of geotechnical materials for water conservancy projects and termite disaster prevention technology, specifically to a biomimetic simulation material for termite nests in earth-rock dams and its preparation method. Background Technology

[0002] Earth-rock dams are one of the most widely used dam types in my country's water conservancy projects, undertaking important functions such as flood control, irrigation, water supply, and power generation. Termite infestation is a major hidden danger threatening the long-term safe operation of earth-rock dams. Termites construct complex nest systems inside the dam body, with the outer nest walls providing the main structural support, while the interior is a loose and porous cavity structure. The presence of termite nests can damage the structural integrity of the dam, weaken its seepage resistance, and cause leakage, piping, or even dam failure, resulting in enormous loss of life and property.

[0003] Physical model testing is the most intuitive and effective research method for revealing the termite-causing mechanism of earth-rock dams. It can realistically reproduce the evolution process and damage mode of termite nests under the coupling effect of the stress field and seepage field of the dam body. The engineering characteristics of biomimetic simulation materials and their matching degree with natural termite nest walls directly determine the accuracy, reliability, and scientific nature of the model test results, and are the core foundation for conducting high-quality physical model tests.

[0004] However, research on materials for simulating termite nests in earth-rock dams, both domestically and internationally, is still in its early stages, and existing materials generally suffer from the following prominent defects: First, the aggregate system design is unreasonable, often using single clay or sand as aggregate, which fails to form a stable skeleton-filling structure. This results in low material density, large drying shrinkage, and a tendency to produce drying shrinkage cracks, making it difficult to prepare complex ant tunnel and nest models. Furthermore, the models are prone to breakage and damage during the dam's filling and compaction process. Second, the performance of the cementing system differs significantly from that of natural nest walls. Existing materials either have excessively strong cementing properties, making it difficult to soften and disintegrate upon contact with water, thus failing to simulate the hydrophysical damage process of nest walls, or have excessively weak cementing properties, rapidly disintegrating upon contact with water. First, the material's structure is flawed; second, the reinforcement system is incomplete, often using single fine fibers as reinforcement components, making it difficult to form an effective spatial bridging network. This results in poor crack resistance and toughness, failing to meet the structural stability requirements of long-term seepage tests. Third, the overall performance matching is low; existing materials can only approximate natural nest walls in a single indicator, unable to accurately simulate multiple dimensions such as physical indicators, mechanical properties, hydrological characteristics, and microstructure. This leads to model tests failing to accurately reproduce the mechanical behavior and hydrological response of termite nests within the dam body, resulting in significant discrepancies between test results and actual engineering conditions. This severely restricts in-depth research on the termite-causing mechanism of earth-rock dams. Summary of the Invention

[0005] The purpose of this invention is to provide a biomimetic simulation material for termite nests in earth-rock dams and its preparation method, so as to solve the problems of existing simulation materials having single aggregate, softening too quickly when exposed to water, poor crack resistance, and low matching degree with the characteristics of real nest walls.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] According to the first aspect of this disclosure, a biomimetic simulation material for termite nests in earth-rock dams is proposed, which is composed of mixed aggregates, basic binder, auxiliary binder and composite reinforcing fibers.

[0008] The mixed aggregate is a dry mixture of sand and clay, with a dry mass ratio of sand to clay of 1:2.

[0009] The basic gelling agent is composed of dry gelatin powder and pregelatinized starch in a dry mass ratio of 1:2;

[0010] The auxiliary gelling agent is a 1% (w / w) aqueous solution of polyvinyl alcohol (PVA).

[0011] The composite reinforcing fiber is composed of dried fine cellulose and coarse lignin, with the coarse lignin accounting for 50% of the total dry mass of the composite reinforcing fiber.

[0012] The dry basis total mass ratio of the mixed aggregate, basic binder and composite reinforcing fiber is (90-105):(2-5):(0.5-2), and the dosage of the auxiliary binder is such that the mass moisture content of the mixture after mixing is up to 18%.

[0013] Furthermore, the polyvinyl alcohol (PVA) is of type 17-88, which is incorporated in the form of a 1% (w / w) aqueous solution of polyvinyl alcohol (PVA).

[0014] Furthermore, the particle size of the mixed aggregate is no greater than 2 mm, of which the content of particles with a particle size greater than 0.075 mm is 80.7%, the non-uniformity coefficient is 18.3, the curvature coefficient is 1.1, and the gradation is good.

[0015] Furthermore, the dry basis total mass ratio of the mixed aggregate, basic binder and composite reinforcing fiber is 96:3:1.

[0016] Furthermore, the physical properties of the biomimetic simulation material are as follows: wet density 1.74 g / cm³. 3 Dry density 1.47 g / cm³ 3 It has a liquid limit of 31.3%, a plastic limit of 12.6%, and a plasticity index of 18.6, classifying it as a medium-plastic soil.

[0017] Furthermore, the mechanical properties of the biomimetic simulation material are as follows: unconfined compressive strength 11.1 MPa, splitting tensile strength 0.61 MPa, cohesion under saturated consolidation without drainage 19.56 kPa, and internal friction angle 5.4°.

[0018] Furthermore, the hydrophysical performance indicators of the biomimetic simulation material are as follows: the disintegration rate is 72.64% after immersion in still water for 60 minutes, and the impact resistance coefficient is 0.35 L / g after being washed by a constant flow of water at a flow rate of 16.62 L / h for 10 minutes.

[0019] According to the second aspect of this disclosure, a method for preparing a biomimetic simulation material for termite nests in earth-rock dams is proposed, used to prepare the biomimetic simulation material in the first aspect, comprising the following steps:

[0020] S1. Pass the sand and clay through a 2mm sieve to remove particles larger than 2mm. Weigh the sieved sand and clay at a dry mass ratio of 1:2 and mix them evenly to obtain the mixed aggregate.

[0021] S2. Weigh the mixed aggregate, basic binder and composite reinforcing fiber according to the dry basis total mass ratio of 96:3:1, add them to the mixing equipment and stir at a speed of 30-50 r / min for 3-5 min to obtain a uniform dry mixture;

[0022] S3. Prepare a 1% (w / w) polyvinyl alcohol (PVA) aqueous solution and slowly add it to the dry mixture. Stir continuously for 5-8 minutes until the mixture is uniform. Control the moisture content of the mixture after mixing to 18%.

[0023] S4. The mixed material is prepared according to a wet density of 1.74 g / cm³. 3 Pressed into specimens of specified dimensions;

[0024] S5. The molded specimen is cured for 7 days under standard conditions of temperature 20±2℃ and relative humidity ≥95%, and then transferred to a ventilated and shaded environment at 20℃ and placed until constant weight is obtained, thus obtaining the biomimetic simulation material.

[0025] Furthermore, in step S4, static pressure is used for pressing and molding, with a loading rate of 0.5-1 kN / s and a holding time of 2-3 min.

[0026] Furthermore, the criterion for determining whether the sample has been air-dried to constant weight in step S5 is that the mass difference between two consecutive weighings with a 24-hour interval does not exceed 0.1% of the total mass of the sample.

[0027] Compared with existing technologies, this invention provides a biomimetic simulation material for termite nests in earth-rock dams and its preparation method. It improves the material's density and crack resistance by forming a core-shell structure using a mixture of sand and clay aggregates; enhances the material's dry strength and initial structural stability upon contact with water by forming a continuous cementitious film using PVA-assisted binder; and optimizes the pore structure and enhances the material's crack resistance and toughness through composite reinforcement with coarse and fine fibers. The developed MCTM-SPF3 optimal formulation material highly matches the physical properties, mechanical properties, hydrological characteristics, and microstructure of natural termite nest walls. The overall preparation method is simple and controllable, with good molding performance, and can realistically simulate the mechanical behavior and hydrological response of termite nests in earth-rock dams. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0029] Figure 1 Particle size distribution curve of MCTM-SPF3 biomimetic simulation material in the embodiments of the present invention;

[0030] Figure 2 The deviatoric stress-axial strain curves of MCTM-SPF3 under different confining pressures in the embodiments of the present invention;

[0031] Figure 3 Mohr-Coulomb destruction envelope diagram of MCTM-SPF3 in this embodiment of the invention;

[0032] Figure 4 The unconfined compressive strength test results of MCTM-S in this embodiment of the invention, wherein, Figure 4 Figure a shows the variation of the unconfined compressive strength of MCTM-S under different sand-clay mix ratios. Figure 4 b is the unconfined compressive stress-strain curve of MCTM-S under different sand-clay mix ratios;

[0033] Figure 5 The unconfined compressive strength test results of MCTM-SP in this embodiment of the invention, wherein, Figure 5 Figure a shows the variation of unconfined compressive strength of MCTM-SP with different PVA doping levels. Figure 5 b is the unconfined compressive stress-strain curve of MCTM-SP with different PVA doping amounts;

[0034] Figure 6 The unconfined compression test results of MCTM-SPF in this embodiment of the invention, wherein, Figure 6Figure a shows the variation of unconfined compressive strength of MCTM-SPF under different wood fiber ratios. Figure 6 b is the unconfined compressive stress-strain curve of MCTM-SPF with different wood fiber ratios;

[0035] Figure 7 The splitting tensile test results of MCTM-S in the embodiments of the present invention, wherein, Figure 7 Figure a shows the variation of splitting tensile strength of MCTM-S under different sand-clay mix ratios. Figure 7 b is the splitting tensile stress-strain curve of MCTM-S under different sand-clay mix ratios;

[0036] Figure 8 The splitting tensile test results of MCTM-SP in the embodiments of the present invention, wherein, Figure 8 Figure a shows the variation of splitting tensile strength of MCTM-SP under different PVA doping levels. Figure 8 b is the tensile stress-strain curve of MCTM-SP splitting resistance under different PVA doping contents;

[0037] Figure 9 The splitting tensile test results of MCTM-SPF in the embodiments of the present invention, wherein, Figure 9 Figure a shows the variation of splitting tensile strength of MCTM-SPF under different wood fiber ratios. Figure 9 b is the splitting tensile stress-strain curve of MCTM-SPF under different wood fiber ratios;

[0038] Figure 10 The microstructure of MCTM-S4 in this embodiment of the invention, wherein, Figure 10 a is a magnified image of 300x. Figure 10 b is a magnified image of 1000x;

[0039] Figure 11 The microstructure of MCTM-SP1 in this embodiment of the invention, wherein, Figure 11 a is a magnified image of 300x. Figure 11 b is a magnified image of 1000x;

[0040] Figure 12 The microstructure of MCTM-SPF3 in this embodiment of the invention, wherein, Figure 12 a is a magnified image of 300x. Figure 12 b is a magnified image of 1000x;

[0041] Figure 13 Cumulative pore volume distribution curves of the improved simulation materials at each stage in the embodiments of the present invention;

[0042] Figure 14Fourier transform infrared (FTIR) spectra of the improved simulation materials at each stage in the embodiments of the present invention. Detailed Implementation

[0043] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0044] All embodiments of this invention use the same experimental materials, preparation and curing conditions, and testing methods:

[0045] Experimental materials: Cellulose-adhesive-pregelatinized cemented yellow clay material (MCTM) was used as the reference. This reference material was composed of yellow clay, cellulose, adhesive powder and pregelatinized starch in a mass ratio of 96:1:1:2. Water was added and mixed to a moisture content of 20% before molding and curing. The sand and clay used in the experiment were taken from the engineering site. The adhesive powder, pregelatinized starch, fine cellulose and coarse wood fiber were commercially available industrial-grade products. Polyvinyl alcohol PVA of type 17-88 was used.

[0046] Preparation and curing conditions: mixing moisture content 18%, wet density 1.74 g / cm³ 3 After 7 days of standard curing (temperature 20±2℃, relative humidity ≥95%), air dry at 20℃ in the shade until constant weight.

[0047] Test method:

[0048] ① Unconfined compressive strength test: A cylindrical specimen with a diameter of φ39.1mm × 80mm was used, with a loading rate of 1mm / min. The strength was calculated using the following formula:

[0049]

[0050] in, The unconfined compressive strength (MPa); The breaking pressure (kN); The cross-sectional area of ​​the sample (mm²) 2 ).

[0051] ② Splitting tensile strength test: A φ50mm×30mm cylindrical specimen was used, with a loading rate of 0.8mm / min. The tensile strength was calculated using the following formula:

[0052]

[0053] in, The splitting strength of the specimen is (MPa). The failure load (kN); The height of the sample is (m). The diameter of the sample is (m).

[0054] ③ Saturated consolidation undrained triaxial shear test: A cylindrical specimen with a diameter of φ39.1mm × 80mm was used. The specimen was first vacuum saturated, with the saturation degree controlled to be ≥95%. Confining pressures of 50, 100, 150, and 200 kPa were applied. After consolidation, undrained shear was performed at a shear rate of 0.4 mm / min. The peak value of the deviatoric stress and the corresponding deviatoric stress-axial strain curve were recorded. Then, the Mohr stress circle was plotted to determine the cohesion and internal friction angle of the simulated material.

[0055] ④ Hydrophysiological properties test: The disintegration test used 5cm×5cm×5cm cubic specimens, and the disintegration amount and experimental morphology changes were recorded at 1, 3, 10, 30 and 60 min.

[0056] The scouring test was conducted at a depth of 60cm. 3 The ring sample was subjected to a constant flow of water at a velocity of 16.62 L / h for 10 minutes, with the nozzle 15 cm above the sample surface. The dry weight loss before and after rinsing was measured, and the impact resistance coefficient was calculated. The impact resistance coefficient was calculated using the following formula:

[0057]

[0058] in, Impact resistance coefficient (L / g); The flushing flow rate is (L / min). The flushing time is in minutes. The mass of dried mud and sand (g).

[0059] ⑤ Microstructure characterization: Scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and Fourier transform infrared spectroscopy (FTIR) were used to characterize the microstructure, pore structure, and chemical composition, respectively.

[0060] Example 1: Aggregate gradation optimization test

[0061] This embodiment aims to address the issues of single aggregate composition and poor skeleton stability in the benchmark MCTM material. Single yellow clay aggregate is replaced with a sand-clay mixture. Five dry mass ratios of sand to clay are set: 3:1 (S1), 2:1 (S2), 1:1 (S3), 1:2 (S4), and 1:3 (S5), with the 1:2 ratio (S0) without curing agent serving as the baseline control group. The optimal aggregate ratio is determined through unconfined compressive strength and splitting tensile strength tests.

[0062] 1. Results of unconfined compressive strength test: such as Figure 4As shown in Figure a, with the increase of clay content, the unconfined compressive strength of each test group showed a trend of first increasing and then decreasing. When the sand:clay ratio was 1:2 (S4 group), the unconfined compressive strength of MCTM-S reached a peak of 7.52 MPa, which was about 1.79 times higher than the baseline control group S0's 4.21 MPa. When the sand:clay ratio was 1:3, the strength dropped to 5.43 MPa, a decrease of about 28% compared to the 1:2 group. When the sand content was too high (such as in the 3:1 and 2:1 groups), there was insufficient clay filling between sand particles, the number of contact points between particles decreased, the bonding force decreased, and the strength also decreased.

[0063] From the stress-strain curve ( Figure 4 (b) It can be seen that all the specimens exhibited brittle failure characteristics of first rising and then falling. Group S4 had the highest peak stress and relatively large peak strain, indicating that the introduction of an appropriate amount of sand not only improved the strength but also improved the deformation capacity of the material. Group 1:3 had the lowest peak stress and a steeper stress drop after the peak, exhibiting typical brittle failure characteristics.

[0064] 2. Splitting tensile strength test results: such as Figure 7 As shown, the splitting strength first decreases and then increases with increasing clay content. The splitting strength of group S0 is 0.20 MPa, exhibiting typical brittle failure; group S3 (sand:clay = 1:1) has a splitting strength of 0.60 MPa, group S4 (1:2) increases to 0.64 MPa, group S5 (1:3) reaches 0.86 MPa, and group S2 (2:1) has a splitting strength of 0.70 MPa.

[0065] However, although the splitting strength of the 1:3 S5 group was higher than that of the 1:2 S4 group, its unconfined compressive strength dropped sharply, resulting in an imbalance between compressive and tensile properties. The 2:1 S2 group had insufficient cohesion, resulting in a low overall stress level, and the post-peak curve showed significant fluctuations. Taking all factors into consideration, a sand:clay ratio of 1:2 was ultimately selected as the optimal aggregate ratio, and the material at this stage is denoted as MCTM-S.

[0066] Example 2: Optimization Test of Gelation System

[0067] This embodiment, based on the optimal aggregate ratio (S4) of Example 1, adds PVA as an auxiliary binder to solve the problem of the reference material softening too quickly upon contact with water. Three groups of PVA solution concentrations were set up: 1% (SP1), 2% (SP2), and 3% (SP3), with the S4 group (without PVA) serving as the control group. The optimal PVA content was determined through mechanical property tests.

[0068] 1. Results of unconfined compressive strength test: such as Figure 5As shown in Figure a, the strength decreases with increasing PVA content. When the PVA content is 1% (SP1 group), the strength reaches a peak of 10.42 MPa, approximately 1.39 times higher than the 7.52 MPa of the control group S4. This is because the hydroxyl groups on the PVA molecular chain form hydrogen bonds with the surface of clay minerals, forming a continuous cementitious film in the dry state, significantly improving the dry strength of the material. When the PVA content increases to 2% and 3%, the strength gradually decreases. This is because excessive PVA leads to an overly thick cementitious film, increasing shrinkage stress during drying, increasing internal microcracks, and weakening the structural strength.

[0069] From the stress-strain curve ( Figure 5 (b) As can be seen, the peak intensity of the curve in the SP1 group with 1% PVA increased significantly, while the peak strain was similar to that of the control group. The downward segment of the curve was also smoother, indicating that the hydrogen bond network effectively enhanced the plastic deformation capacity of the material and delayed crack propagation. The peak intensity of the curves in the SP2 group with 2% PVA and the SP3 group with 3% PVA was slightly lower than that in the SP1 group with 1% PVA, but still maintained a smooth downward trend and did not show obvious brittle characteristics.

[0070] 2. Splitting tensile strength test results: such as Figure 8 As shown, the splitting strength of the materials at the three PVA concentration gradients is close to that of the control group. The strength of the SP1 group with 1% PVA is 0.59 MPa, the SP2 group with 2% PVA rises to 0.65 MPa, and the SP3 group with 3% PVA falls back to 0.58 MPa. Although the splitting strength of the SP2 group is relatively high, combined with the unconfined compressive strength results, the compressive performance of the SP1 group is significantly superior, and its post-peak stress decrease is gradual, exhibiting the most significant plastic deformation characteristics, which is beneficial for simulating the progressive failure of anthill materials. Considering both compressive and tensile properties, the SP1 solution concentration was determined to be the optimal dosage, and the material at this stage is denoted as MCTM-SP.

[0071] Example 3: Coarse and fine fiber composite reinforcement test

[0072] This embodiment, based on the optimal ratio (SP1) of Example 2, adopts a coarse and fine fiber composite reinforcement strategy to solve the problem of poor crack resistance of the reference material. Keeping the total fiber content constant, coarse lignocellulose is gradually replaced with fine cellulose at 25% (SPF1), 37.5% (SPF2), 50% (SPF3), and 62.5% (SPF4) of the total fiber content. The optimal fiber ratio is determined through mechanical property tests.

[0073] 1. Results of unconfined compressive strength test: such as Figure 6As shown in Figure a, the strength first increases and then decreases with the increase of the proportion of wood fiber. When the proportion of wood fiber is 25%, the strength of SPF1 group is 7.5 MPa; when the proportion increases to 37.5%, the strength of SPF2 group rises to 8.63 MPa; when the proportion is 50%, the strength of SPF3 group reaches a peak of 11.1 MPa, which is 7% higher than that of the optimal PVA content group SP1; when the proportion is 62.5%, the strength of SPF4 group drops to 6.87 MPa.

[0074] An appropriate amount of wood fiber can play a reinforcing role through the composite of coarse and fine fibers: fine cellulose fills the micropores, while coarse fibers divide and connect the macropores and act as bridges, thereby significantly improving strength; excessive fiber, due to the agglomeration effect, leads to insufficient matrix encapsulation, weakened interfacial bonding, and decreased strength.

[0075] From the stress-strain curve ( Figure 6 b) It can be seen that the SPF3 group, with 50% wood fiber, has the highest peak strength, and the curve descends in a gentle manner, exhibiting ductile failure characteristics overall, indicating that fiber bridging effectively inhibits crack propagation.

[0076] 2. Splitting tensile strength test results: such as Figure 9 As shown, the splitting strength generally increases with the increase of the proportion of wood fiber. The splitting strength is 0.58 MPa in the 25% group, drops to the lowest value of 0.46 MPa in the 37.5% group (it is speculated that the spatial distribution of coarse and fine fibers is uneven at this proportion, forming weak cementation zones in some areas), rises to 0.61 MPa in the 50% group, and reaches 0.64 MPa in the 62.5% group.

[0077] Although the 62.5% SPF4 group exhibited the highest strength, its post-peak stress dropped sharply, indicating significant brittle fracture characteristics. In contrast, the 50% SPF3 group showed a relatively gentle decline in its post-peak curve, demonstrating better ductile fracture characteristics, which better met the toughness requirements of materials simulating termite nests. Considering both strength and ductility, the 50% wood fiber SPF3 group was selected as the optimal solution. This material is designated as MCTM-SPF3, which is the final biomimetic simulation material determined in this invention.

[0078] Example 4: Preparation method of MCTM-SPF3

[0079] 1. MCTM-SPF3 is composed of mixed aggregates, a base binder, an auxiliary binder, and composite reinforcing fibers. The mixed aggregates are a dry mixture of sand and clay, with a dry mass ratio of 1:2. The base binder consists of dry adhesive powder and pregelatinized starch in a dry mass ratio of 1:2. The auxiliary binder is a 1% (w / w) polyvinyl alcohol (PVA) aqueous solution. The composite reinforcing fibers consist of dry fine cellulose and coarse lignin, with a dry mass ratio of 1:1. The dry mass ratio is mixed aggregates: base binder: composite reinforcing fibers = 96:3:1. The moisture content of the mixture is 18%.

[0080] 2. Specific preparation steps of MCTM-SPF3:

[0081] Step 1: Pass the sand and clay through a 2mm sieve to remove particles larger than 2mm. Weigh the sieved sand and clay at a dry weight ratio of 1:2 and mix them evenly to obtain the mixed aggregate.

[0082] Step 2: Weigh the mixed aggregate, basic binder and composite reinforcing fiber according to the dry basis total mass ratio of 96:3:1, add them to the mixing equipment and stir at a speed of 30-50 r / min for 3-5 min to obtain a uniform dry mix;

[0083] Step 3: Prepare a 1% (w / w) aqueous solution of type 1788 polyvinyl alcohol (PVA), and slowly add it to the dry mixture. Continue stirring for 5-8 minutes until the mixture is uniform. Control the moisture content of the mixture after mixing to 18%.

[0084] Step 4: Mix the combined material according to a wet density of 1.74 g / cm³. 3 The specimens were prepared by static pressure method, with a loading rate of 0.5-1 kN / s and a holding time of 2-3 min.

[0085] Step 5: Curing the molded specimens under standard conditions of 20±2℃ and relative humidity ≥95% for 7 days, and then transferring them to a ventilated and shaded environment at 20℃ until the mass difference between two consecutive weighings with an interval of 24 hours does not exceed 0.1% of the total mass of the sample, thus obtaining the biomimetic simulation material MCTM-SPF3 for termite nests in earth-rock dams.

[0086] 3. Performance Verification

[0087] ① Basic physical properties: The physical properties of MCTM-SPF3 are shown in Table 1 below, and its particle size distribution curve is as follows. Figure 1 As shown:

[0088] Table 1. Basic physical properties of MCTM-SPF3 material

[0089]

[0090] From Table 1 and Figure 1 It can be seen that the physical properties of MCTM-SPF3 are stable, the particle size distribution curve shows a single peak, the content of particles larger than 0.075mm is 80.7%, and no particles larger than 2mm were detected, indicating that it is clay sand. The uniformity coefficient is 18.3, the curvature coefficient is 1.1, the gradation is good, and the coarse-grained skeleton and fine-grained filling can form an effective core-shell structure, which is beneficial to improving the overall stability and deformation resistance of the material.

[0091] ②Mechanical properties: Based on the results of saturated consolidated undrained triaxial shear tests, such as Figure 2 and Figure 3 As shown, the axial strain curves of MCTM-SPF3 under different confining pressures all exhibit strain-hardening characteristics with no obvious peak points. In the initial loading stage, the deviatoric stress increases rapidly with increasing axial strain, but the rate of increase slows down after the strain exceeds approximately 2%. The confining pressure significantly affects the deviatoric stress-strain relationship of the specimen. As the confining pressure increases, the overall deviatoric stress level shifts upward, indicating that the confining pressure enhances the lateral constraint ability of the material, suppresses the lateral displacement of particles, and thus improves the shear strength.

[0092] Based on the Mohr-Coulomb failure criterion, using the deviatoric stress corresponding to 15% axial strain as the failure value, the failure stress circle and strength envelope under different confining pressures are plotted. Figure 3 The cohesion of the material was found to be c = 19.56 kPa, and the internal friction angle was φ = 5.4°. The relatively small internal friction angle indicates that the interparticle frictional interlocking effect is limited, and the strength mainly depends on the cohesion. This is consistent with the cementation mechanism formed by the encapsulation and bridging of clay particles by PVA and fibers.

[0093] ③Water properties:

[0094] Disintegration test results: The disintegration test results of the optimal group at each stage are shown in Table 2 below:

[0095] Table 2 Disintegration test results

[0096]

[0097] As shown in Table 2, MCTM-SPF3 exhibits the most ideal disintegration behavior, characterized by a gradual process of initial water absorption, crack initiation, gradual peeling, and eventual stabilization. At 1 minute, the disintegration rate is -1.89%, exhibiting initial water absorption characteristics; at 3 minutes, the disintegration rate is 10.21%, at 10 minutes it is 43.40%, and at 60 minutes it is 72.64%. The disintegration rate is significantly slower than SP1, and the disintegration process is more stable. This is because the introduction of PVA allows the material to maintain a certain structural strength in the initial stage of water immersion, while the composite of coarse wood fibers inhibits rapid crack propagation through bridging.

[0098] Scouring test results: The scouring test results of the optimal group in each stage are shown in Table 3:

[0099] Table 3 Comparison of optimal simulated material scour test results at each stage

[0100]

[0101] As shown in Table 3, the erosion amount of MCTM-SPF3 is 8.02g, the erosion rate is 9.09%, and the impact resistance coefficient is 0.35L / g. Compared with SP1, the erosion amount is reduced by about 5.9%, and the impact resistance coefficient is improved. The bridging effect of the wood fibers enhances the overall integrity of the material surface, making particle peeling more uniform and controllable, and avoiding excessive local peeling.

[0102] ④ Microstructure

[0103] i. SEM test results

[0104] Microscopic morphology of materials at each stage, such as Figure 10 , Figure 11 , Figure 12 As shown.

[0105] MCTM-S4 ( Figure 10 The mixture of sand and clay aggregates formed a preliminary "core-shell" structure, but the cement on the particle surface was discontinuous and spotted, and no complete coating was formed. The interparticle bridging structure was sparse, and the main structure was physical accumulation and local clay connection.

[0106] MCTM-SP1 ( Figure 11 The particle surface is covered by a continuous PVA adhesive film with a relatively uniform thickness and wide coverage. A distinct membrane-like bridging structure is formed between the particles, and the original irregular pores are filled or divided by the adhesive film, thus enhancing the overall structure.

[0107] MCTM-SPF3 ( Figure 12 Coarse and fine fibers are randomly distributed in the matrix, with fine fibers filling the micropores and coarse fibers bridging the gaps between particles to form a spatial bridging network. Matrix particles adhere to the fiber surface, resulting in good interfacial bonding. The interweaving of the PVA adhesive film and fibers constructs a fiber-adhesive synergistic framework, exhibiting the densest and most uniform microstructure.

[0108] ii. MIP test results

[0109] The cumulative pore volume distribution curves of the improved simulated materials at each stage are shown below. Figure 13 As shown, the characteristic parameters of the pore structure are shown in Table 4:

[0110] Table 4. Pore structure characteristics of nest walls and modified materials

[0111]

[0112] Depend on Figure 13 As shown in Table 4, the median pore size of MCTM-SPF3 is significantly smaller than that of the first two stages, while the average pore size is close to that of MCTM-S4, exhibiting the highest tortuosity. Fiber bridging successfully corrected the large interconnected pores formed by the introduction of PVA, while simultaneously increasing the pore tortuosity, resulting in a more refined and complex pore structure.

[0113] iii. FTIR test results

[0114] Infrared spectral analysis results of the improved simulation materials at each stage are as follows: Figure 14 As shown. The main functional group characteristics of MCTM-SPF3 are obvious: 3620 cm⁻¹ -1 The hydroxyl stretching vibration peak at 2929 cm⁻¹ -1 Nearby CH stretching vibration peak, 1026 cm -1 The Si-O-Si asymmetric stretching vibration peaks at the sites were clearly visible. The PVA cemented film and fiber covering the clay surface weakened the signal intensity of hydroxyl and Si-O-Si, confirming the gradual enhancement of organic encapsulation, which is consistent with the SEM observation results.

[0115] in conclusion

[0116] 1) Through stepwise optimization of the aggregate-cementing system, the optimal formulation was determined, using sand:clay = 1:2 as aggregate, 1% PVA concentration, and 50% wood fiber as cementing components. The obtained MCTM-SPF3 exhibited an unconfined compressive strength of 11.1 MPa and a splitting tensile strength of 0.61 MPa, with a ductile failure mode, which meets the strength requirements for the ant nest and tunnel structure to withstand compaction without damage in physical model construction.

[0117] 2) MCTM-SPF3 exhibits a gradual softening and disintegration characteristic when exposed to water, with a disintegration rate of 72.64% in 60 minutes and an impact resistance coefficient of 0.35 L / g. This is close to the disintegration degree and impact resistance of real nest wall materials, and can reproduce the instability of ant tunnel structures and the process of soil and water loss under seepage conditions.

[0118] 3) Microscopic analysis confirms that the PVA cemented film and the wood fiber bridging network synergistically reconstruct a microscopic framework similar to the natural nest wall, making the modified material approach the real nest wall in key characteristics such as chemical composition, pore distribution, and tortuosity, thus providing a reliable material basis for the physical simulation of the disaster-causing process from a mechanistic perspective.

[0119] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A biomimetic simulation material for termite nests in earth-rock dams, characterized in that, It consists of mixed aggregates, basic binder, auxiliary binder and composite reinforcing fibers; The mixed aggregate is a dry mixture of sand and clay, with a dry mass ratio of sand to clay of 1:

2. The basic gelling agent is composed of dry gelatin powder and pregelatinized starch in a dry mass ratio of 1:2; The auxiliary gelling agent is a 1% (w / w) aqueous solution of polyvinyl alcohol (PVA). The composite reinforcing fiber is composed of dried fine cellulose and coarse lignin, with the coarse lignin accounting for 50% of the total dry mass of the composite reinforcing fiber. The dry basis total mass ratio of the mixed aggregate, basic binder and composite reinforcing fiber is (90-105):(2-5):(0.5-2), and the dosage of the auxiliary binder is such that the mass moisture content of the mixture after mixing is up to 18%.

2. The biomimetic simulation material for termite nests in earth-rock dams according to claim 1, characterized in that, The polyvinyl alcohol (PVA) is of type 17-88, and it is incorporated in the form of a 1% (w / w) aqueous solution of polyvinyl alcohol (PVA).

3. The biomimetic simulation material for termite nests in earth-rock dams according to claim 1, characterized in that, The mixed aggregate has a particle size of no more than 2 mm, of which the content of particles with a particle size greater than 0.075 mm is 80.7%, the uniformity coefficient is 18.3, the curvature coefficient is 1.1, and the gradation is good.

4. The biomimetic simulation material for termite nests in earth-rock dams according to claim 1, characterized in that, The dry basis total mass ratio of the mixed aggregate, basic binder and composite reinforcing fiber is 96:3:

1.

5. The biomimetic simulation material for termite nests in earth-rock dams according to claim 1, characterized in that, The physical properties of the biomimetic material are as follows: wet density 1.74 g / cm³. 3 Dry density 1.47 g / cm³ 3 It has a liquid limit of 31.3%, a plastic limit of 12.6%, and a plasticity index of 18.6, classifying it as a medium-plastic soil.

6. The biomimetic simulation material for termite nests in earth-rock dams according to claim 1, characterized in that, The mechanical properties of the biomimetic material are as follows: unconfined compressive strength 11.1 MPa, splitting tensile strength 0.61 MPa, cohesion under saturated consolidation without drainage 19.56 kPa, and internal friction angle 5.4°.

7. The biomimetic simulation material for termite nests in earth-rock dams according to claim 1, characterized in that, The hydrophysical performance indicators of the biomimetic simulation material are as follows: the disintegration rate is 72.64% after immersion in still water for 60 minutes, and the impact resistance coefficient is 0.35L / g after being washed by a constant flow of water at a flow rate of 16.62L / h for 10 minutes.

8. A method for preparing a biomimetic simulation material for termite nests in earth-rock dams, used to prepare the biomimetic simulation material as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Pass the sand and clay through a 2mm sieve to remove particles larger than 2mm. Weigh the sieved sand and clay at a dry mass ratio of 1:2 and mix them evenly to obtain the mixed aggregate. S2. Weigh the mixed aggregate, basic binder and composite reinforcing fiber according to the dry basis total mass ratio of 96:3:1, add them to the mixing equipment and stir at a speed of 30-50 r / min for 3-5 min to obtain a uniform dry mixture; S3. Prepare a 1% (w / w) polyvinyl alcohol (PVA) aqueous solution and slowly add it to the dry mixture. Stir continuously for 5-8 minutes until the mixture is uniform. Control the moisture content of the mixture after mixing to 18%. S4. The mixed material is prepared according to a wet density of 1.74 g / cm³. 3 Pressed into specimens of specified dimensions; S5. The molded specimen is cured for 7 days under standard conditions of temperature 20±2℃ and relative humidity ≥95%, and then transferred to a ventilated and shaded environment at 20℃ and placed until constant weight is obtained, thus obtaining the biomimetic simulation material.

9. The method for preparing a biomimetic simulation material for termite nests in an earth-rock dam according to claim 8, characterized in that, In step S4, static pressure is used for pressing and molding, with a loading rate of 0.5-1 kN / s and a holding time of 2-3 min.

10. The biomimetic simulation material for termite nests in earth-rock dams and its preparation method according to claim 8, characterized in that, In step S5, the criterion for determining whether the sample has been air-dried to constant weight is that the difference between two consecutive weighings with a 24-hour interval does not exceed 0.1% of the total mass of the sample.

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