Raw material ratio optimization method of earthen ruin ramming modification material

Abstract

The invention relates to the technical field of earthen archaeological site repair, and discloses an earthen archaeological site ramming modification material raw material ratio optimization method, which comprises: 1, selecting plain soil having the same or similar property with the earthen archaeological site rammed earth as a ramming main material; step 2, screening a pure soil modification material; 3, designing a three-element three-level test proportioning scheme for the three modified materials in the step 2; 4, determining the specification of the sample; 5, aiming at the determined sample specification, preparing a material test sample according to the proportioning scheme designed in the step 3; step 6, curing the prepared sample; step 7, performing indoor related tests on the cured sample; and step 8, analyzing test results in the step 7, and determining the optimal proportion of the earthen ruin ramming modification material. The invention provides a systematic and quantitative ramming reinforcement modified material proportion optimization method, so that material modification is more scientific, reasonable, economical and efficient, and it is also ensured that the modified rammed earth material is higher in strength and better in durability.

Description

Technical Field

[0001] The present invention relates to the technical field of earthen heritage restoration, and particularly to a method for optimizing the raw material ratio of a rammed and repaired modification material for earthen heritage. Background Art

[0002] Rammed earth buildings are one of the main forms of traditional residential buildings in China. Well-known examples such as the Great Wall, Hakka earth buildings, and military defensive city walls are all representatives of rammed earth buildings in China. However, rammed earth buildings also have material defects such as the inability of soil materials to resist water, poor resistance to weathering, and susceptibility to wind and rain erosion. There are numerous rammed earth sites distributed in some areas of northwest and north China, dating back to the Qin and Han dynasties and as recent as the Ming and Qing dynasties. Under the long-term action of different environmental factors, different types and degrees of diseases have occurred, such as cracks, collapses, gullies, and erosion.

[0003] Currently, for different diseases existing in rammed earth buildings, there are mainly treatment measures such as bolt reinforcement, crack grouting, patching, and ramming and repairing. Among them, ramming and repairing is the most common and effective measure for earthen heritage reinforcement. Currently, the main ramming and repairing material is plain soil. Due to its defects such as weak water resistance, poor durability in terms of dry-wet resistance and freeze-thaw resistance, it often needs to be modified. There are various plain soil modification materials, and their ratios often rely on experience, are relatively arbitrary, lack systematicness and quantification, and are not conducive to the development and popularization of rammed earth material modification technology.

[0004] In view of this, the present invention is specifically proposed. Through the present invention, the optimal ratio of rammed earth modification materials can be selected scientifically, reasonably, economically, efficiently, and systematically, ensuring that the modified rammed earth materials have higher strength and better durability, and providing a reliable method for selecting the technological parameters for the protection and reinforcement of geotechnical cultural relics, especially rammed earth sites. Summary of the Invention

[0005] Aiming at the deficiencies in the selection of the ratio of rammed earth modification materials, the present invention provides a method for optimizing the ratio of rammed and repaired modification materials for earthen heritage. This method makes up for the defects of relying on experience and arbitrary value taking in the past material ratio, making the selection of the material ratio more systematic and quantitative, and achieving scientific rationality, economy, and efficiency.

[0006] The present invention is implemented by the following technical solutions: A method for optimizing the raw material ratio of a rammed and repaired modification material for earthen heritage, comprising the following steps:

[0007] Step 1: Select plain soil with the same or similar properties as the rammed earth of the earthen heritage as the main ramming and repairing material, including but not limited to silty sand, silt, or silty clay;

[0008] Step 2: Screen plain soil modification materials, and the modification materials include but not limited to gravel, quicklime, or building cellulose;

[0009] Step 3: Design a three-factor and three-level experimental ratio plan for the three modified materials in Step 2 based on the principle of orthogonal experimental design;

[0010] Step 4: Determine the specimen specifications;

[0011] Step 5: For the specimen specifications determined in Step 4, according to the specimen ratio plan designed in Step 4, determine the mass of each raw material component in the test sample, and mix the plain soil and the three modified materials evenly according to the ratio mass, and then manually tamp to prepare the specimen;

[0012] Step 6: Cure the prepared specimens;

[0013] Step 7: Conduct unconfined compressive strength tests, wet-dry cycle tests, and freeze-thaw cycle tests on the cured specimens respectively;

[0014] Step 8: Analyze and summarize the obtained test results, and obtain the test ratio of the specimens with higher strength, less mass loss and strength loss, which is the optimal ratio of the raw materials of the rammed repair modified material for the earthen site.

[0015] Preferably, in Step 1, through particle analysis tests, soluble salt tests, X-ray diffraction analysis, and X-ray fluorescence spectroscopy analysis, select plain soil with the same or similar properties as the rammed earth of the earthen site.

[0016] Preferably, in Step 2, the gravel is natural gravel with a particle size not greater than 20 mm; the quicklime needs to pass through a 2 mm sieve; the building cellulose is selected as hydroxypropyl methylcellulose.

[0017] Preferably, in Step 3, the mass ratio of gravel is 10% - 20%, the mass ratio of quicklime is 5% - 15%, and the mass ratio of building cellulose is 1% - 5%.

[0018] Preferably, in Step 4, the specimen is a cube, and the size is preferably appropriate.

[0019] Preferably, in Step 5, the specimen needs to be prepared by layered compaction, and the compaction degree of the specimen needs to reach the compaction degree of the original rammed earth of the earthen site; where: compaction degree = dry density of rammed earth / maximum dry density × 100%, and the maximum dry density is determined by indoor compaction tests.

[0020] Preferably, during the process of preparing the specimen by layered compaction, the thickness of each layer is determined according to the specimen specifications.

[0021] Preferably, in Step 6, the curing is adjusted to normal temperature and humidity (20 ± 2°C, 65 ± 20% RH), and the curing time is 28 days.

[0022] Preferably, in Step 7, the number of wet-dry cycles is 25 times, and the number of freeze-thaw cycles is 25 times.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The present invention is particularly suitable for the ramming and reinforcement of earth ruins under arid and semi-arid environmental conditions in the northwest and north of China, which conforms to the concept and principle of cultural relics protection, has low cost, is easy to operate, and has good material modification effect, providing a practical and effective method for optimizing the proportion of ramming and reinforcement and modification materials for the existing earth ruins in China.

[0025] The present invention introduces the principle of orthogonal experiment, obtains the maximum experimental effect with the least number of experiments, has a simple process implementation, uses a mature experimental method, and the materials used are low-cost, safe and environmentally friendly.

[0026] The present invention provides a systematic and quantitative method for optimizing the proportion of ramming and reinforcement and modification materials for earth ruins, making the material modification more scientific, reasonable, economical and efficient, and at the same time ensuring that the modified rammed earth material has higher strength and better durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 FIG. is a flowchart of the implementation of a method for optimizing the proportion of ramming and modification materials for earth ruins provided by the present invention.

[0028] Figure 2 FIG. is a particle analysis curve of the rammed earth of the ruins in the embodiment of the present invention.

[0029] Figure 3 FIG. is a particle analysis curve of the raw earth material in the embodiment of the present invention.

[0030] Figure 4 FIG. is a graph showing the change of the compressive strength of the modified rammed earth with the mix ratio in the embodiment of the present invention.

[0031] Figure 5 FIG. is a graph showing the change of the strength loss of the modified rammed earth under dry-wet cycles in the embodiment of the present invention.

[0032] Figure 6 FIG. is a graph showing the change of the strength loss of the modified rammed earth under freeze-thaw cycles in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Hereinafter, in combination with the drawings and specific embodiments, the present invention will be further described. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined to form new embodiments.

[0034] Embodiment 1:

[0035] Referring to Figures 1-6 , a method for optimizing the proportion of ramming and modification materials for earth ruins proposed in this solution includes the following steps:

[0036] Step 1: Through the comparison of particle analysis tests, soluble salt tests, X-ray diffraction analysis (XRD) and X-ray fluorescence spectrometry analysis (XRF) tests, select plain soil with the same or similar properties as the rammed earth of the earthen site as the main rammed repair material, including silty sand, silt or silty clay.

[0037] Step 2: Screen the plain soil modification materials, including gravel, quicklime and building cellulose. It is required that the gravel is natural gravel with a particle size not greater than 20 mm; the quicklime is required to pass through a 2 mm sieve; the building cellulose is selected as hydroxypropyl methylcellulose (HPMC).

[0038] Step 3: Based on the principle of orthogonal experimental design, design a three-factor and three-level experimental ratio scheme for the three selected modification materials. Among them, the mass ratio of gravel is 10% - 20%, the mass ratio of quicklime is 5% - 15%, and the mass ratio of building cellulose is 1% - 5%, that is, gravel: quicklime: hydroxypropyl methylcellulose = (10% - 20%): (5% - 15%): (1% - 5%).

[0039] Step 4: To facilitate the comparison of test results, uniformly stipulate the test sample specifications. It is stipulated that the test specimen is a cube with a specification of 100 mm × 100 mm × 100 mm. When preparing the test specimen, large-sized samples can be made and then cut into test specimens of the specified size.

[0040] Step 5: For the specified test specimen specifications, according to the designed specimen ratio scheme, determine the mass of each component of the modified rammed repair material test sample. Mix the plain soil and the three modification materials evenly according to the ratio mass, and then prepare the specimen by manual ramming. It is required to prepare the specimen by ramming in layers, with a layer thickness of 50 mm and the ramming degree reaching the ramming degree of the original rammed earth of the earthen site. The ramming degree = dry density of rammed earth / maximum dry density × 100%, where the maximum dry density is determined by the indoor compaction test.

[0041] Step 6: Cure the prepared specimens under normal temperature and humidity (20 ± 2 °C, 65 ± 20% RH) conditions for 28 days.

[0042] Step 7: Conduct unconfined compressive strength tests, dry-wet cycle tests and freeze-thaw cycle tests on the cured specimens respectively. Among them, it is required that the number of dry-wet cycles is 25 times and the number of freeze-thaw cycles is 25 times.

[0043] Step 8: Analyze and summarize the test results, and obtain the test ratio with higher strength and the least strength loss as the optimal ratio of the modified rammed repair material for the earthen site. The strength loss refers to the value of the unconfined compressive strength loss of the specimen during 25 dry-wet cycles or freeze-thaw cycles, that is, strength loss (%) = [unconfined compressive strength value of the specimen before the test (MPa) - unconfined compressive strength value of the specimen after the test (MPa)] / unconfined compressive strength value of the specimen before the test (MPa) × 100%.

[0044] Example 2:

[0045] Taking the Ming Fort Site on the top of Yungang Grottoes as an example, this embodiment optimizes the proportion of the rammed earth repair and reinforcement modification materials for the Ming Fort Site. The specific implementation process is as follows:

[0046] In the first step, 3 groups of rammed earth samples of the earthen site were taken on-site. Then, based on the principle of "using local materials" and in combination with the analysis of relevant data of the earthen site, 3 groups of raw soil samples were taken from the site near the earthen site, and particle analysis tests, soluble salt tests, X-ray diffraction analysis (XRD), and X-ray fluorescence spectroscopy analysis (XRF) were carried out respectively.

[0047] According to the results of the particle analysis test of the rammed earth sample of the earthen site, the rammed earth of the earthen site is silty sand, and the calculated coefficient of uniformity is 26.63, and the coefficient of curvature is 0.52; according to the results of the particle analysis test of the raw soil sample, the raw soil is silty sand, and the calculated coefficient of uniformity is 16.78, and the coefficient of curvature is 0.57. By comparing the results of the particle size analysis test, the rammed earth and the raw soil have the same composition, the coefficient of uniformity is greater than 5, and the coefficient of curvature is less than 1, and the particle gradations of the two are the same.

[0048] Comparative analysis of the test results of soluble salts in the rammed earth and raw soil of the earthen site shows that the soluble salt contents of the two are similar, the soluble salt content is less than 0.5%, and the pH value shows a slightly alkaline nature. The comparison of the test results is shown in Table 1.

[0049] Table 1 Comparison of Test Results of Soluble Salts in Rammed Earth and Raw Soil

[0050]

[0051] Comparative analysis of the X-ray diffraction analysis results of the rammed earth and raw soil of the earthen site shows that the mineral compositions of the two are the same and the contents are similar. The comparison of the analysis results is shown in Table 2.

[0052] Table 2 Comparison of X-ray Diffraction Analysis Results of Rammed Earth and Raw Soil

[0053]

[0054] Comparing the X-ray fluorescence spectroscopy analysis results of the rammed earth and raw soil, the main chemical components of the two are Na2O, MgO, Al2O3, SiO2, P2O5, SO3, K2O, CaO, TiO2, Cr2O3, MnO, Fe2O3, NiO, CuO, ZnO, Rb2O, SrO, Tb4O7, Ru, and BaO, etc. Among them, the content of SiO2 is the highest, followed by Al2O3, CaO, and Fe2O3.

[0055] Comparative analysis of the test results shows that the properties of the raw soil are similar to those of the rammed earth of the earthen site, and the raw soil can be used as the main material for rammed earth repair and reinforcement of the earthen site.

[0056] Step 2: From the perspective of enhancing the strength of rammed earth, its crack resistance, resistance to dry-wet changes, freeze-thaw cycles and other durability aspects, select the plain soil modification materials, including gravel, quicklime and building cellulose. It is required that the gravel is natural gravel with a particle size not greater than 20 mm; the quicklime is required to pass through a 2 mm sieve; the building cellulose is selected as hydroxypropyl methylcellulose (HPMC).

[0057] Step 3: Based on the principle of orthogonal experimental design, design a three-factor and three-level experimental ratio scheme for the three selected modification materials. Among them, gravel: quicklime: hydroxypropyl methylcellulose = (10% - 20%): (5% - 15%): (1% - 5%) (mass percentage). The specific orthogonal experimental ratio scheme is shown in Table 3.

[0058] Table 3 Orthogonal experimental ratio scheme

[0059]

[0060] Step 4: For the convenience of comparing the test results, uniformly determine that the test sample is a cube with a specification of 100 mm × 100 mm × 100 mm.

[0061] Step 5: For the given specimen specifications, according to the designed specimen ratio scheme in Table 2, determine the mass of each component of the modified ramming and filling material test sample, as shown in Table 4. Mix the plain soil powder sand and the three modification materials evenly according to the ratio mass, and then prepare the specimen by manual ramming. Prepare the specimen by ramming in layers, with a layer thickness of 50 mm, and the ramming degree reaches the original ramming degree of the earth relics.

[0062] And the ramming degree = dry density of rammed earth / maximum dry density × 100% = 1.78 g / cm 3 / 1.91 g / cm 3 , taking the value of 94%. The dry density of rammed earth is calculated and determined from the indoor moisture content and density test results, taking the larger value; the maximum dry density is determined by the indoor compaction test to obtain the maximum dry density.

[0063] Table 4 Mass distribution of each component of the specimen under different ratios

[0064]

[0065] Step 6: Cure the prepared specimens under normal temperature and humidity (20 ± 2 °C, 65 ± 20% RH) conditions for 28 days.

[0066] Step 7: Conduct unconfined compressive strength tests, dry-wet cycle tests and freeze-thaw cycle tests on the cured specimens respectively. Among them, the number of dry-wet cycles is 25 times, and the number of freeze-thaw cycles is 25 times. The test results of the specimens are shown in Figures 4-6 .

[0067] Step 8: Through the test results Figures 4-6Analysis shows that under the same test conditions, when the mix ratio of the rammed earth sample is Mix Ratio 7, its unconfined compressive strength is the highest, and the strength loss values of the dry-wet cycle sample and the freeze-thaw cycle test are the lowest. Therefore, the optimal mix ratio of the rammed earth repair and modification material for this earthen site obtained by this method is Mix Ratio 7, that is, cellulose (HPMC): gravel: quicklime = 1%: 20%: 15%.

[0068] The above-mentioned implementation manners are only the preferred implementation manners of the present invention, and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A method for optimizing the raw material ratio of a rammed repair and modification material for earthen sites, characterized in that, It includes the following steps: Step 1: Select plain soil with the same or similar properties as the rammed earth of the earthen site as the main rammed repair material, including but not limited to silty sand, silt or silty clay; Step 2: Screen the plain soil modification materials, and the modification materials include but not limited to gravel, quicklime or building cellulose; Step 3: Design a three-factor and three-level test mixing ratio scheme for the three modification materials in Step 2 based on the principle of orthogonal test design; Step 4: Determine the specimen specifications; Step 5: For the specimen specifications determined in Step 4, according to the specimen mixing ratio scheme designed in Step 4, determine the mass of each raw material component in the test sample, and mix the plain soil and the three modification materials evenly according to the mixing ratio mass, and then manually ram to prepare the specimen; Step 6: Cure the prepared specimens; Step 7: Conduct unconfined compressive strength tests, wet-dry cycle tests and freeze-thaw cycle tests on the cured specimens respectively; Step 8: Analyze and summarize the obtained test results, and obtain the test mixing ratio of the specimens with higher strength, less mass loss and strength loss, which is the optimal mixing ratio of the raw materials of the rammed repair modification material for the earthen site.

2. The preferred method for the raw material ratio of a rammed repair and modification material for earthen heritage sites according to claim 1, wherein In Step 1, through particle analysis tests, soluble salt tests, X-ray diffraction analysis and X-ray fluorescence spectroscopy analysis, plain soil with the same or similar properties as the rammed earth of the earthen site is selected.

3. The preferred method for the raw material ratio of a rammed repair and modification material for earthen ruins according to claim 1, characterized in that, In Step 2, the gravel is natural gravel and the particle size is not more than 20 mm; the quicklime needs to pass through a 2 mm sieve; the building cellulose selected is hydroxypropyl methyl cellulose.

4. The preferred raw material ratio method of a rammed repair and modification material for earthen ruins according to claim 1, characterized in that In Step 3, the mass ratio of gravel is 10% - 20%, the mass ratio of quicklime is 5% - 15%, and the mass ratio of building cellulose is 1% - 5%.

5. The preferred method for the raw material ratio of a rammed repair and modification material for earth relics according to claim 1, characterized in that, In Step 4, the specimen is a cube.

6. The raw material ratio optimization method of a rammed repair and modification material for earthen ruins as described in claim 1, characterized in that, In Step 5, it is necessary to ram in layers to prepare the specimen, and the ramming degree of the specimen needs to reach the ramming degree of the original rammed earth of the earthen site; where: ramming degree = dry density of rammed earth / maximum dry density × 100%, and the maximum dry density is determined by indoor compaction tests.

7. The preferred method for the raw material ratio of a rammed repair and modification material for earth relics as described in claim 1, wherein During the process of ramming in layers to prepare the specimen, the thickness of each layer is determined according to the size of the specimen specifications.

8. The preferred method for the raw material ratio of a rammed and repaired modified material for earthen sites according to claim 1, wherein, In Step 6, the curing is adjusted to normal temperature and normal humidity, and the curing time is 28 days.

9. The preferred method for the raw material ratio of a rammed repair and modification material for earthen ruins as described in claim 1, characterized in that, In Step 7, the number of wet-dry cycles is 25 times, and the number of freeze-thaw cycles is 25 times.

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