A mixing ratio adjusting method for preparing controllable low-strength material based on mechanism sand

Abstract

The application discloses a mixing proportion adjusting method for preparing controllable low-strength material based on machine-made sand, which takes water-solid ratio, ash-water ratio and fine material content as basic parameters of the mixing proportion, simultaneously takes fluidity and 28d unconfined compressive strength as control indexes, adjusts the fine material content through the machine-made sand, and combines a fluidity empirical calculation model and a strength empirical calculation model to determine the value range of the water-solid ratio and the ash-water ratio. The technical scheme provided by the application can determine the specific usage of each raw material of the CLSM, reduces the total usage of sand and stone materials, and saves resources.

Description

Technical Field

[0001] The invention relates to the field of geotechnical testing, and in particular to a scheme for determining the mix ratio of controllable low-strength materials. Background Art

[0002] In backfill projects with narrow areas and limited construction space (such as trench backfill and three-way backfill), using excavated soil backfill can result in loose backfill in some areas. Furthermore, as the scale of underground projects increases, large amounts of waste soil become difficult to dispose of and dispose of. Against this backdrop, controlled low-strength material (CLSM), a self-leveling, low-strength road backfill material, has been developed using waste soil as raw material, supplemented with machine-made sand. This material, known as CLSM, can meet the needs of backfill projects while recycling waste soil, reducing project costs and protecting the natural environment. Due to its self-compacting and self-leveling properties, CLSM is particularly suitable for backfill projects with various irregular cross-sections. For example, in mountainous and hilly terrain along project routes with numerous bridges and culverts, the roller's compaction range is limited in some backfill sections, making compaction quality control difficult. This can easily lead to road surface subsidence and vehicle bouncing under subsequent vehicle loads, jeopardizing vehicle safety. CLSM backfill construction can fully fill every corner and void during the backfill process without the need for vibration compaction, effectively ensuring the density of the backfill material near the back of the platform. Therefore, excellent fluidity is the hallmark of CLSM and the key that distinguishes CLSM from other materials.

[0003] When designing the mix ratio of CLSM in engineering applications, it is often necessary to adjust the water-to-solid ratio of the material and the amount of sand added to control its fluidity so as to achieve good filling of the target area with CLSM while avoiding the fluid pressure generated on adjacent structures that affects the stability of adjacent structures.

[0004] However, the CLSM mix ratio given by the existing scheme is not accurate enough to determine the specific amount of each CLSM raw material in engineering applications, resulting in a waste of construction resources in actual application. Summary of the Invention

[0005] Technical name explanation:

[0006] The water-solid ratio is the mass ratio of water to solid materials in the mixture, where solid materials include sand aggregate, cement, fly ash, etc.

[0007] The cement-water ratio is the mass ratio of cement to water in the mixture.

[0008] In response to the problems existing in the CLSM mix ratio determined in the existing scheme, the purpose of the present invention is to provide a mix ratio preparation method for preparing controllable low-strength materials based on machine-made sand. This method can provide CLSM mix ratios and recommended mix ratios that meet engineering requirements on the basis of ensuring CLSM control indicators, and can accurately determine the specific dosage of each CLSM raw material in engineering applications, reduce the total usage of sand and gravel materials, and save construction resources.

[0009] In order to achieve the above-mentioned purpose, the present invention provides a mix ratio preparation method for preparing controllable low-strength materials based on machine-made sand, which takes water-solid ratio, ash-water ratio and fine material content as basic parameters of the mix ratio, and takes fluidity and 28d unconfined compressive strength as control indicators. The fine material content is adjusted by machine-made sand, and the value range of the water-solid ratio and the ash-water ratio is determined by combining the fluidity empirical calculation model and the strength empirical calculation model.

[0010] In some embodiments of the present invention, the mixing ratio preparation method includes:

[0011] (1) Determine the index values ​​of fluidity and 28d unconfined compressive strength;

[0012] (2) Determination of fine matter content in soil used for CLSM;

[0013] (3) Based on the determined fine material content, the fluidity empirical calculation model and the strength empirical calculation model are used to calculate and determine the range of water-solid ratio and ash-water ratio;

[0014] (4) Based on the determined fine material content and the range of values ​​of the water-solid ratio and the ash-water ratio calculated and determined in step (3), an initial mix ratio is determined to prepare a test piece, and a verification test is performed on the prepared test piece to determine whether its fluidity and 28d unconfined compressive strength meet the index values ​​determined in step (1); if the index requirements are not met, machine-made sand is added on the basis of the existing fine material content, and after changing its fine material content, steps (3) and (4) are repeated until the verification test results meet all index requirements;

[0015] (5) Determine the ash-water ratio, water-solid ratio, and fine material content based on the fine material content, water-solid ratio value range, and ash-water ratio value range corresponding to the test piece that meets all index requirements in step (4);

[0016] (6) Based on the ash-water ratio, water-solid ratio and fine material content determined in step (5), the material dosage calculation model is used to calculate the sand mass, cement mass and water mass to determine the mix ratio.

[0017] In some embodiments of the present invention, the fluidity (F) index value determined in step (1) is 20-30 cm, and the 28d unconfined compressive strength (q) index value is 0.35-8.4 MPa.

[0018] In some embodiments of the present invention, in step (2), the soil used for CLSM is excavated and subjected to the steps of drying, crushing, screening, and measuring, and then the fine material content (f) is determined.

[0019] In some embodiments of the present invention, the liquidity experience calculation model is constructed based on the following formula:

[0020]

[0021] Where: y—CLSM slump expansion value (cm);

[0022] a—fitting coefficient related to water-solid ratio;

[0023] W / S—water-to-solid ratio;

[0024] b—fitting coefficient related to fine material content;

[0025] f—fine particle content;

[0026] c—fitting parameter.

[0027] In some embodiments of the present invention, the strength empirical calculation model is constructed based on the following formula:

[0028]

[0029] Where: q o —fitting parameters;

[0030] C / W—ash-water ratio;

[0031] m—parameter related to the gray-water ratio;

[0032] f—fine matter content;

[0033] n—Parameter related to fine material content.

[0034] In some embodiments of the present invention, when machine-made sand is added in step (4), the order of adding materials is to first add soil, machine-made sand, fly ash and cement, and then add water after dry mixing.

[0035] In some embodiments of the present invention, step (4) verifies whether the test piece meets the performance requirements of segregation, shrinkage, and setting time.

[0036] In some embodiments of the present invention, in step (5), the fine material content (f) is calculated and determined based on the minimum value of the added machine-made sand aggregate, the ash-water ratio (C / W) is determined by the middle value of the ash-water ratio value range determined in step (4), and the water-solid ratio (W / S) is determined by the middle value of the water-solid ratio value range determined in step (4).

[0037] In some embodiments of the present invention, the material usage calculation model in step (6) is constructed based on the following formula:

[0038]

[0039] The present invention provides a mix proportioning method for preparing controllable low-strength materials based on machine-made sand. The method innovatively uses the water-solid ratio (W / S), the ash-water ratio (C / W), and the fine material content (f) as basic parameters (independent variables) for constructing the corresponding mix proportion. Meanwhile, corresponding fluidity empirical calculation models and strength empirical calculation models are constructed. Fluidity (F) and 28d unconfined compressive strength (q) are used as control indicators (dependent variables) for the mix proportioning. On the basis of ensuring the CLSM control indicators, a CLSM mix proportion range and a recommended mix proportion that meet engineering requirements are given. The method can accurately determine the specific amount of each CLSM raw material in engineering applications, reduce the total usage of sand and gravel materials, and save construction resources.

[0040] The invention provides a mix ratio preparation method for preparing controllable low-strength materials based on machine-made sand, which has a scientific and reasonable design and high feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0042] Figure 1 This is a schematic diagram of the process for preparing the mix ratio of controllable low-strength materials based on machine-made sand provided in an example of the present invention. DETAILED DESCRIPTION

[0043] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below with reference to specific illustrations.

[0044] Since the use of river sand with round particles and smooth surface has a more significant impact on the fluidity of CLSM than the machine-made sand with sharp edges and high needle-like content, the index response of CLSM material performance is more sensitive to the fine material content (f) caused by the addition of machine-made sand compared with other sand materials; at the same time, the fine material content (f) will simultaneously affect the water-solid and sand content of CLSM, further affecting its fluidity.

[0045] In contrast, there is no confirmed correlation between the material properties of CLSM configured with manufactured sand and the material properties of manufactured sand and CLSM.

[0046] On this basis, the application gives the mixing proportion adjusting method of the controllable low-strength material based on the mechanism sand, takes the water-solid ratio (W / S), the cement-water ratio (C / W) and the fine material content (f) as the basic parameters (independent variables) of the mixing proportion, takes the fluidity (F) and the 28d unconfined compressive strength (q) as the control indexes (dependent variables), determines the water-solid ratio and the cement-water ratio through the fine material content of the mechanism sand, and combines the fluidity empirical calculation model and the strength empirical calculation model to determine the value range of the water-solid ratio and the cement-water ratio, so that the mixing proportion scheme meeting the engineering requirements can be provided on the basis of guaranteeing the CLSM performance, the specific usage of each raw material of the CLSM can be accurately determined, the total usage of the sand and stone materials is reduced, and resources are saved

[0047] Specifically, the fluidity (F) and the 28d unconfined compressive strength are the most important performance indexes of the CLSM, and the experimental data proves that there is no significant correlation between the two, in addition, the control indexes should not be too many, and the most important indexes should be selected, and the indexes should be independent of each other.

[0048] Accordingly, the application takes the fluidity (F) and the 28d unconfined compressive strength (q) as the control indexes (dependent variables), so that the accuracy and feasibility of the final result of the scheme can be effectively guaranteed.

[0049] According to the characteristics of the controllable low-strength material mixing proportion and the fluidity (F) and the 28d unconfined compressive strength (q) as the control indexes (dependent variables), the application takes the water-solid ratio (W / S), the cement-water ratio (C / W) and the fine material content (f) as the basic parameters (independent variables) of the mixing proportion, all of the three have an influence on the CLSM performance that cannot be ignored (that is, the three parameters are the higher significant influence factors relative to the CLSM performance), and the three are independent of each other, so that the reasonable and accurate controllable low-strength material mixing proportion can be determined according to the control indexes (dependent variables).

[0050] Further, according to the soil classification method, the fine material content refers to the percentage of the particles below 0.075mm in the total mass of the soil sample, and the soil with the fine material content greater than 50% is called fine-grained soil. Therefore, the fine material content is a key parameter for distinguishing different soil samples, and is suitable to be the control parameter of the experimental mixing proportion.

[0051] The water-solid ratio and the cement-water ratio are the key parameters for controlling the CLSM performance. The water-solid ratio is the key parameter for affecting the fluidity of the CLSM, and the cement-water ratio is the key parameter for affecting the strength, and the fluidity and the strength are the important indexes for distinguishing the CLSM from other cement-based materials, so the water-solid ratio and the cement-water ratio are adopted as the control parameters in the application. The water-solid ratio is the mass ratio of water to solid materials in the mixture, and the solid materials include the sand aggregate, cement, fly ash and the like; the cement-water ratio is the mass ratio of cement to water in the mixture.

[0052] On this basis, the present invention provides a method for preparing a controllable low-strength material mix ratio based on machine-made sand, which is specifically achieved through the following steps: Figure 1 As shown:

[0053] (1) Determine the fluidity and strength requirements.

[0054] In this step, the index values ​​of the material fluidity (F) and the 28d unconfined compressive strength (q) are specifically determined, and the index value can be a value range.

[0055] (2) Determination of fine matter content (f) of soil using CLSM.

[0056] (3) Based on the determined fine material content (f), the fluidity empirical calculation model and the strength empirical calculation model are used to calculate and determine the range of values ​​of the water-solid ratio and the ash-water ratio.

[0057] (4) Based on the determined fine material content and the range of values ​​of the water-solid ratio and the ash-water ratio calculated and determined in step (3), a mix ratio is determined to prepare a test piece, and a verification test is performed on the prepared test piece to determine whether its fluidity and 28d unconfined compressive strength meet the index values ​​determined in step (1); if the index requirements are not met, machine-made sand is added on the basis of the existing fine material content, and after changing its fine material content, steps (3) and (4) are repeated until the verification test results meet all index requirements;

[0058] (5) Determine the ash-water ratio, water-solid ratio, and fine material content based on the fine material content, water-solid ratio value range, and ash-water ratio value range corresponding to the test piece that meets all index requirements in step (4);

[0059] (6) Based on the ash-water ratio, water-solid ratio and fine material content determined in step (5), the material dosage calculation model is used to calculate the sand mass, cement mass and water mass to determine the mix ratio.

[0060] In some embodiments of the present invention, for the index values ​​of material fluidity (F) and 28d unconfined compressive strength (q) determined in step (1), if there are no special requirements, the fluidity (F) can be 20-30cm, and the 28d unconfined compressive strength (q) can be 0.35-8.4MPa.

[0061] In some embodiments of the present invention, when determining the fine material content (f) of the soil used for CLSM in step (2), the soil used for CLSM is excavated and the fine material content (f) is determined after completing the drying, crushing, screening, and measurement processes in sequence, and the type of the soil is determined according to the current "Highway Geotechnical Test Procedures".

[0062] In some embodiments of the present invention, when calculating and determining the water-to-solid ratio range in step (3), a corresponding fluidity empirical calculation model is constructed, and the corresponding water-to-solid ratio range is calculated based on the determined fine material content.

[0063] The liquidity empirical calculation model here is constructed based on the following formula (1):

[0064]

[0065] Where: y—CLSM slump expansion value (cm);

[0066] a—fitting coefficient related to water-solid ratio;

[0067] W / S—water-to-solid ratio;

[0068] b—fitting coefficient related to fine material content;

[0069] f—fine particle content;

[0070] c—fitting parameter.

[0071] In some embodiments of the present invention, when calculating and determining the ash-water ratio value range in step (3), a corresponding strength empirical calculation model is constructed, and the corresponding ash-water ratio value range is calculated based on the determined fine material content.

[0072] The strength empirical calculation model here is constructed based on the following formula (2):

[0073]

[0074] Where: q o —fitting parameters;

[0075] C / W—ash-water ratio;

[0076] m—parameter related to the gray-water ratio;

[0077] f—fine matter content;

[0078] n—Parameter related to fine material content.

[0079] In some embodiments of the present invention, in step (4), the prepared test piece is specifically verified for segregation, shrinkage, and setting time performance indicators to determine whether its fluidity and 28d unconfined compressive strength meet the indicator values ​​determined in step (1).

[0080] Here, when preparing the molded specimens, use step (3) to calculate the water-solid ratio (W / S) and the ash-water ratio (C / W) ranges, select representative values, and prepare the specimens. As an example, here we can select 3 water-solid ratio values ​​and 3 ash-water ratio values ​​to prepare 9 groups of mix ratio specimens.

[0081] On this basis, each specimen is verified to see whether it meets the performance requirements of segregation, shrinkage and setting time. If so, it means that the water-solid ratio (W / S) and ash-water ratio (C / W) values ​​are acceptable. If not, it is necessary to add machine-made sand and change its fine material content (f). Based on step (3), the water-solid ratio (W / S) and ash-water ratio (C / W) are recalculated, and the specimens are tested to test their various properties until all performance index requirements are met.

[0082] Here, when adding machine-made sand, the order of adding materials is to add soil, machine-made sand, fly ash and cement first, and then add water after dry mixing.

[0083] In some embodiments of the present invention, the reasonable value ranges of the ash-water ratio (C / W), water-solid ratio (W / S), and fine material content (f) are determined based on the results determined by the experiment and dynamic calculation in step (4).

[0084] On this basis, when determining the appropriate range of values ​​for the ash-water ratio (C / W), water-solid ratio (W / S), and fine aggregate content (f), the value of the fine aggregate content (f) is preferably calculated based on the minimum value of the added machine-made sand aggregate to save material costs; on this basis, the ash-water ratio (C / W) and water-solid ratio (W / S) are preferably the middle value of the range.

[0085] In some embodiments of the present invention, in step (6), the sand mass, cement mass and water mass are calculated by constructing a corresponding material usage calculation model to determine the mix ratio.

[0086] The material consumption calculation model here is constructed based on the following formula (3):

[0087]

[0088] In some embodiments of the present invention, a corresponding mix proportioning calculation platform is constructed for the mix proportioning method of preparing controllable low-strength materials based on machine-made sand provided by the present invention to assist in implementing the solution of the present invention.

[0089] As an example, the mix proportion preparation calculation platform here is composed of a corresponding calculation server (such as calculation) and a mix proportion preparation software program running on the calculation server.

[0090] The mix proportioning software program here has an index value setting module, a fine material content input module, a water-solid ratio value calculation module, an ash-water ratio value calculation module, an experimental data input module, a parameter determination module, and a material consumption calculation module.

[0091] The index value setting module is used to determine the index values ​​of the fluidity (F) and the 28-day unconfined compressive strength (q) of the storage material. The fluidity (F) can be 20-30 cm, and the 28-day unconfined compressive strength (q) can be 0.35-8.4 MPa.

[0092] The fine material content input module is used to input the fine material content (f) value of the soil used for CLSM into the mix ratio calculation platform, and to adjust and modify the corresponding fine material content (f) according to the amount of machine-made sand added during the experiment.

[0093] The water-to-solid ratio calculation module interacts with the fine material content input module. Based on the fine material content (f) determined by the fine material content input module, the fluidity empirical calculation model is used to calculate the water-to-solid ratio range. This fluidity empirical calculation model is based on the aforementioned formula (1) and will not be elaborated on here.

[0094] The ash-water ratio calculation module interacts with the fine material content input module. Based on the fine material content (f) determined by the fine material content input module, the strength empirical calculation model is used to calculate the ash-water ratio range. This strength empirical calculation model is based on the aforementioned formula (2) and will not be elaborated on here.

[0095] The experimental data input module is used to collect the results of the test piece experimental verification in the aforementioned step (4), and compare the collected experimental verification results with the index value determined by the index value setting module to determine whether the index is met. If the index is met, the fine material content (f) input by the current fine material content input module, the water-solid ratio value range calculated by the water-solid ratio value calculation module, and the ash-water ratio value range calculated by the ash-water ratio value calculation module are synchronously recorded.

[0096] The parameter determination module extracts the optimal fine material content (f), ash-water ratio (C / W), and water-solid ratio (W / S) values ​​based on the fine material content (f), water-solid ratio value range, and ash-water ratio value range required by the indicators.

[0097] For example, the recommended value for the fine material content (f) is calculated based on the minimum value of the added machine-made sand aggregate to save material costs; on this basis, the middle value is extracted as the recommended value for the range of values ​​of the ash-water ratio (C / W) and the water-solid ratio (W / S).

[0098] The material consumption calculation module is used to call the material consumption calculation model to calculate the sand mass, cement mass and water mass according to the recommended values ​​of the three groups of fine material content (f), ash-water ratio (C / W) and water-solid ratio (W / S) determined by the parameter determination module to determine the mix ratio.

[0099] The material usage calculation model here is constructed based on the aforementioned formula (3).

[0100] The mix proportion calculation platform constructed based on this can well assist the implementation of the mix proportion preparation method of controllable low-strength materials based on machine-made sand, which can greatly improve the implementation efficiency.

[0101] The implementation process of the solution of the present invention is further illustrated below through specific application examples.

[0102] Here we take the mix proportioning of controlled low strength material (CLSM) on the back of a national highway as an example.

[0103] In this example, the excavated soil samples were dried and crushed at the construction site. The cement used in this example was 425 ordinary Portland cement (PO 42.5). The machine-made sand selected had flat, angular particles and a fineness modulus of 3.65, making it a coarse sand.

[0104] Based on this, the whole mix ratio preparation process is as follows, combined with Figure 1 As shown:

[0105] Step F1: Determine the fluidity and strength requirements; according to the engineering design standards, determine the index values ​​of material fluidity (F) and 28d unconfined compressive strength (q): fluidity is 26cm, and strength is 0.8MPa.

[0106] The fluidity test was conducted using the material fluidity evaluation method based on slump expansion proposed by Yuan Qiu. This method used a metal slump cylinder with a height of 200 mm and an inner diameter of 100 mm for the test, and used slump expansion as the evaluation index. The evaluation criteria are shown in Table 1.

[0107] Unconfined compressive strength is usually used to characterize the ability of a material to withstand loads. The low and controllable strength ensures the economic applicability of CLSM as a backfill material and the requirements for secondary excavation. Due to the low compressive strength of CLSM, the error of using the traditional concrete compressive strength test method is large, and the test method needs to be adjusted, referring to ASTM D4832. The specific experimental steps are: after the mixture is evenly stirred, it is placed in a Φ100×200mm cylindrical mold; the specimen is placed in a standard curing room (20℃±1℃, 100% RH) for curing; after 72 hours, the specimen is demoulded and continued to be cured; before testing, the surfaces of both ends of the specimen are leveled with a scraper; the strength is tested with an MTS testing machine or a universal press at a loading rate of 0.5mm / min, and the maximum pressure value that the specimen can withstand is read using the test equipment, and the failure pressure values ​​of the specimen at 7d and 14d are measured respectively;

[0108] The unconfined compressive strength of the specimen is calculated according to formula 4:

[0109] R e =P / A (4)

[0110] Where: Re —Unconfined compressive strength of the specimen (MPa);

[0111] P—maximum pressure when the specimen is destroyed (N);

[0112] A—cross-sectional area of ​​the specimen (mm 2 ), A=0.25πD 2 ;

[0113] D—diameter of the specimen (mm).

[0114] Table 1 Fluidity evaluation criteria

[0115] Step F2: Determine the fine material content (f) and calculate the range of the ash-water ratio (C / W) and water-solid ratio (W / S). Excavate the soil used for CLSM and complete the drying, crushing, screening, and measurement processes to determine the fine material content (f). Based on empirical formulas for fluidity and strength, calculate the range of the ash-water ratio (C / W) and water-solid ratio (W / S). The formula for predicting fluidity at 26 cm is as follows:

[0116]

[0117] The liquidity prediction formula is subject to the following restrictions:

[0118] The formula is more accurate when the collapse extension value of CLSM material is between 26 cm; the collapse extension value is measured by a Φ100mm×200mm cylindrical collapse cone.

[0119] The empirical formula of CLSM's 28d unconfined compressive strength is as follows:

[0120]

[0121] Step F3: Prepare molded specimens to verify segregation, shrinkage, and setting time performance indicators. Using the calculated water-to-solid ratio (W / S) and cement-to-water ratio (C / W) ranges, select representative values ​​and prepare specimens. In this example, three water-to-solid ratio (W / S) values, three cement-to-water ratio (C / W) values, and three fine sand values ​​were selected (Table 2), resulting in a total of 15 experimental mix ratios (Table 3).

[0122] Table 2 Mix ratio parameter values

[0123] Parameter name English abbreviation Value unit Fine material content f 54、45、38 ％ Water-solid ratio W / S 0.35、0.4、0.45 ％ Ash-water ratio C / W 0.1、0.2、0.3 ％

[0124] Table 3 Experimental mix ratio

[0125]

[0126]

[0127] Test pieces are molded in sequence for the mix ratios in Table 3 to verify whether they meet the performance requirements for segregation, shrinkage, and setting time. The specific test methods for segregation, shrinkage, and setting time are as follows:

[0128] Segregation testing was performed using a three-section cylindrical mold with inserts separating each section. After the specimens were formed, the density of the top, middle, and bottom layers was measured. The dispersion of the three density values ​​was used to evaluate the material's segregation performance. Specific segregation criteria are shown in Table 4.

[0129] Table 4 Segregation evaluation criteria

[0130] Separation performance Segregation value Insufficient liquidity <1cm Basically no segregation 1cm-3cm The segregation phenomenon is relatively mild 3cm-5cm Serious segregation >5cm

[0131] Setting time test method: Setting time refers to the time it takes for a CLSM material to transition from a fluid state after mixing to a solidified state and develop a certain bearing capacity. In this example, a mortar penetration resistance meter was used to test the setting time. This method considers initial setting of the material when the penetration resistance reaches 0.5 MPa. For detailed test procedures, see the "Standard for Test Methods for Basic Properties of Building Mortar."

[0132] Experimental method of shrinkage test: During the CLSM hardening process, water evaporates continuously, and cement hydration reaction occurs continuously inside the mixture, causing the material to shrink in volume. The experimental steps of the shrinkage test are as follows: wipe the 40mm×40mm×160mm mold clean, apply oil, and fix the shrinkage head in the holes at both ends of the mold, with the shrinkage head exposed to (8±1) mm from the end face of the specimen; install the CLSM into the mold and place it in a curing room (20℃±1℃, 100% RH) for curing; remove the mold after 7 days, use a micrometer to measure the initial length and initial mass of the specimen, and continue curing; measure the length and mass of the specimen on the 1st, 3rd, 7th, 14th, 28th, 56th, and 90th day after the initial measurement, and calculate the shrinkage strain of the specimen according to the following formula:

[0133]

[0134] Where: ε at —Accumulated drying shrinkage strain value on the corresponding day t;

[0135] L—specimen length (160mm);

[0136] L0—initial length of the specimen, that is, the length measured 7 days after the specimen is formed (mm);

[0137] L d —Measured length on day t (mm).

[0138] According to the above experimental method, if the segregation, shrinkage and setting time meet the requirements, it means that the water-solid ratio (W / S) and ash-water ratio (C / W) values ​​are acceptable; if not, it is necessary to add machine-made sand, change its fine material content (f), recalculate its water-solid ratio (W / S) and ash-water ratio (C / W), and try to prepare test pieces to continue testing whether the segregation, shrinkage and setting time meet the design requirements.

[0139] Step F4: until the specimen in step F3 meets all performance index requirements, determine the mix ratio and calculate the actual amount of materials used; the calculation formula for the amount of each raw material is:

[0140]

[0141] Based on the calculation results, the recommended mix ratio scheme is shown in the following table.

[0142] Table 5 Recommended mix ratio scheme

[0143] Cooperation plan Machine-made sand cement water earth Sand-soil ratio Ash-water ratio Water-solid ratio Fine aggregate content Mix design 19.2％ 5.3％ 21.9％ 47.5％ 0.6 0.2 0.4 0.38 Total dosage 120 27.8 139.1 200

[0144] From the above examples, it can be seen that the solution provided by the present invention can propose a CLSM mix design method and recommended mix ratio that meets engineering needs on the basis of ensuring the CLSM control indicators, accurately determine the specific amount of each CLSM raw material in engineering applications, reduce the total usage of sand and gravel materials, and save construction resources.

[0145] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a mix ratio of controllable low-strength materials based on machine-made sand, characterized in that: The water-solid ratio, ash-water ratio, and fine aggregate content are used as basic parameters for the mix ratio. Fluidity and 28d unconfined compressive strength are used as control indicators. The fine aggregate content is adjusted using machine-made sand. The ranges of the water-solid ratio and ash-water ratio are determined by combining an empirical fluidity calculation model with an empirical strength calculation model. The empirical fluidity calculation model is constructed based on the following formula: Where: y—CLSM slump expansion value, unit is centimeter; a—fitting coefficient related to water-solid ratio; W / S—water-to-solid ratio; b—fitting coefficient related to fine material content; f—fine matter content; c—fitting parameter; The strength empirical calculation model is constructed based on the following formula: Where: q o —fitting parameters; C / W—ash-water ratio; m—parameter related to the gray-water ratio; f—fine matter content; n—Parameter related to fine material content.

2. The method for preparing a controllable low-strength material based on machine-made sand according to claim 1, characterized in that: The mix ratio preparation method comprises: (1) Determine the index values ​​of fluidity and 28d unconfined compressive strength; (2) Determination of fine matter content of soil used in CLSM; (3) Based on the determined fine material content, the fluidity empirical calculation model and the strength empirical calculation model are used to calculate and determine the range of water-solid ratio and ash-water ratio; (4) Based on the determined fine material content and the range of values ​​of the water-solid ratio and the ash-water ratio calculated and determined in step (3), an initial mix ratio is determined to prepare a test piece, and a verification test is performed on the prepared test piece to determine whether its fluidity and 28d unconfined compressive strength meet the index values ​​determined in step (1); if the index requirements are not met, machine-made sand is added on the basis of the existing fine material content, and after changing its fine material content, steps (3) and (4) are repeated until the verification test results meet all index requirements; (5) Determine the ash-water ratio, water-solid ratio, and fine material content based on the fine material content, water-solid ratio value range, and ash-water ratio value range corresponding to the test piece that meets all index requirements in step (4); (6) Based on the ash-water ratio, water-solid ratio and fine material content determined in step (5), the material dosage calculation model is used to calculate the sand mass, cement mass and water mass to determine the mix ratio.

3. The method for preparing a controllable low-strength material based on machine-made sand according to claim 2, characterized in that: The fluidity F index value determined in step (1) is 20-30 cm, and the 28d unconfined compressive strength q index value is 0.35-8.4 MPa.

4. The method for preparing a controllable low-strength material based on machine-made sand according to claim 2, characterized in that: In step (2), the soil used for CLSM is excavated and subjected to the drying, crushing, screening, and measurement processes in sequence, and then the fine material content f is determined.

5. The method for preparing a controllable low-strength material based on machine-made sand according to claim 2, characterized in that: When adding machine-made sand in step (4), the order of adding materials is to first add soil, machine-made sand, fly ash and cement, and then add water after dry mixing.

6. The method for preparing a controllable low-strength material based on machine-made sand according to claim 2, characterized in that: Step (4) verifies whether the specimen meets the performance requirements of segregation, shrinkage, and setting time.

7. The method for preparing a controllable low-strength material based on machine-made sand according to claim 2, characterized in that: In step (5), the fine material content f is calculated based on the minimum amount of machine-made sand aggregate added, the ash-water ratio C / W is determined by the middle value of the ash-water ratio range determined in step (4), and the water-solid ratio W / S is determined by the middle value of the water-solid ratio range determined in step (4).

8. The method for preparing a controllable low-strength material based on machine-made sand according to claim 2, characterized in that: The material consumption calculation model in step (6) is constructed based on the following formula:

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