Method for manufacturing cement mixing pile of soft soil in coastal area

Abstract

The application provides a manufacturing method of cement mixing piles of soft soil in coastal areas, and belongs to the field of cement mixing piles. The method determines a plurality of sample parameter groups, creates a plurality of cement mixing pile samples corresponding to the plurality of sample parameter groups, respectively performs impermeability testing and compression testing on the plurality of cement mixing pile samples, and obtains an impermeability parameter group and a compression parameter group of each cement mixing pile sample, determines the impermeability parameter and the compression parameter of each cement mixing pile sample, obtains a comprehensive parameter of each cement mixing pile sample in the plurality of cement mixing pile samples, and the comprehensive parameter is the sum of the compression parameter and the impermeability parameter of the cement mixing pile sample; the sample parameter group corresponding to the cement mixing pile sample with the maximum comprehensive parameter is determined as a target parameter group, and the cement mixing pile is manufactured based on the target parameter group, so that the performance of the manufactured cement mixing pile is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cement mixing pile, in particular to a manufacturing method of cement mixing pile for soft soil in coastal areas. BACKGROUND

[0002] The cement mixing pile is an underground structure for reinforcing soft soil foundation.

[0003] In a manufacturing method of cement mixing pile, a plurality of cement mixing pile samples are manufactured based on different parameters, and after the manufacturing, strength test is performed on each sample to determine the sample with the highest strength, and then the cement mixing pile is manufactured according to the parameters corresponding to the sample with the highest strength.

[0004] However, in the above method, the process of determining the parameters for manufacturing the cement mixing pile is relatively single, resulting in poor performance of the manufactured cement mixing pile. SUMMARY

[0005] The embodiment of the present application provides a manufacturing method of cement mixing pile for soft soil in coastal areas, which can solve the problem of poor performance of the cement mixing pile in the related art. The technical solution is as follows:

[0006] According to a first aspect of the present application, a manufacturing method of cement mixing pile for soft soil in coastal areas is provided, which is used for manufacturing the cement mixing pile applied to the soft soil foundation in the coastal area, and the method comprises the following steps:

[0007] determining a plurality of sample parameter groups, each of the sample parameter groups comprising a cement mixing amount, a phosphogypsum mixing amount and a crystal nucleus early strength agent mixing amount in the cement mixing pile, and at least one of the cement mixing amount, the phosphogypsum mixing amount and the crystal nucleus early strength agent mixing amount in any two of the sample parameter groups is different;

[0008] manufacturing a plurality of cement mixing pile samples corresponding to the plurality of sample parameter groups;

[0009] performing impermeability test and compression test on the plurality of cement mixing pile samples respectively, and obtaining a permeability coefficient group and a compression coefficient group of each of the cement mixing pile samples, the permeability coefficient group comprising a permeability coefficient of the cement mixing pile sample on the n th day after manufacturing and a permeability coefficient on the 4n th day, the compression coefficient group comprising an unconfined compressive strength of the cement mixing pile sample on the n th day after manufacturing and an unconfined compressive strength on the 4n th day, and n≥7;

[0010] determining an impermeability parameter of each of the cement mixing pile samples based on the permeability coefficient group of the plurality of cement mixing pile samples, the impermeability parameter being negatively correlated with the permeability coefficient in the permeability coefficient group;

[0011] determine a compressive parameter of each cement mixing pile sample based on a compressive coefficient group of the plurality of cement mixing pile samples, the compressive parameter being positively correlated with an unconfined compressive strength in the compressive coefficient group;

[0012] obtain a comprehensive parameter of each cement mixing pile sample in the plurality of cement mixing pile samples, the comprehensive parameter being a sum of the compressive parameter and an impermeability parameter of the cement mixing pile sample;

[0013] determine a target parameter group as a sample parameter group of the cement mixing pile sample with the largest comprehensive parameter;

[0014] manufacture the cement mixing pile based on the target parameter group.

[0015] Optionally, each cement mixing pile sample includes at least one impermeability sample and at least one compressive sample.

[0016] the impermeability test and the compressive test on the plurality of cement mixing pile samples include:

[0017] perform the impermeability test on the impermeability sample, and obtain a permeability coefficient of the impermeability sample on the nth day after manufacturing and a permeability coefficient on the 4nth day based on a permeability coefficient calculation formula, the permeability coefficient calculation formula including:

[0018] ;

[0019] wherein k t is the permeability coefficient, Q is a total amount of seepage in time t, L is a distance between pressure measuring holes when the impermeability test is performed on the impermeability sample, A is a cross-sectional area of the impermeability sample, H is a water head difference, and T is time;

[0020] perform the compressive test on the compressive sample.

[0021] Optionally, the determination of the impermeability parameter of each cement mixing pile sample based on the permeability coefficient group of the plurality of cement mixing pile samples includes:

[0022] sort the impermeability samples in the plurality of cement mixing pile samples based on a permeability parameter sum of the impermeability samples to obtain an impermeability sample sequence, the permeability parameter sum being a sum of the permeability coefficient on the nth day after manufacturing and the permeability coefficient on the 4nth day of the impermeability sample in the cement mixing pile sample, and the size of the serial number of each impermeability sample in the impermeability sample sequence being negatively correlated with the permeability parameter sum of the cement mixing pile sample where the impermeability sample is located;

[0023] determine the serial number of each impermeability sample as the impermeability parameter of the cement mixing pile sample where the impermeability sample is located.

[0024] Optionally, the determining the compressive parameter of each cement mixing pile sample based on the compressive parameter group of the plurality of cement mixing pile samples comprises:

[0025] sequencing the compressive samples in the plurality of cement mixing pile samples based on the compressive parameter and of the compressive samples to obtain a compressive sample sequence, the compressive parameter and of a compressive sample in the cement mixing pile sample being a sum of the unconfined compressive strength of the compressive sample on the nth day after manufacturing and the unconfined compressive strength on the 4nth day, and the size of the serial number of each compressive sample in the compressive sample sequence being positively correlated with the compressive parameter and of the cement mixing pile sample in which the compressive sample is located;

[0026] determining the serial number of each compressive sample as the compressive parameter of the cement mixing pile sample in which the compressive sample is located.

[0027] Optionally, the determining the plurality of sample parameter groups comprises:

[0028] determining three cement contents, the three cement contents being 15%, 20% and 25% respectively, the cement content being a mass ratio of cement to clay in the cement mixing pile;

[0029] determining three phosphogypsum contents, the three phosphogypsum contents being 10%, 20% and 30% respectively, the phosphogypsum content being a mass ratio of phosphogypsum to clay in the cement mixing pile;

[0030] determining three crystal nucleus early strength agent contents, the three crystal nucleus early strength agent contents being 0.5%, 1% and 1.5% respectively, the crystal nucleus early strength agent content being a mass ratio of crystal nucleus early strength agent to clay in the cement mixing pile;

[0031] obtaining nine sample parameter groups based on the three cement contents, the three phosphogypsum contents and the three crystal nucleus early strength agent contents and the orthogonal test method.

[0032] Optionally, the manufacturing the plurality of cement mixing pile samples corresponding to the plurality of sample parameter groups comprises:

[0033] obtaining clay in the soft soil subgrade;

[0034] drying the clay and screening impurities in the clay through a sieve to obtain screened clay;

[0035] adding water to the screened clay to obtain target clay, the water content in the target clay being the same as that of the clay in the soft soil subgrade;

[0036] obtaining cement, phosphogypsum and crystal nucleus early strength agent based on cement content, phosphogypsum content and crystal nucleus early strength agent content in the first sample parameter set in the plurality of sample parameter sets;

[0037] dissolving the crystal nucleus early strength agent into water, and stirring and mixing the cement and the phosphogypsum according to a water-solid ratio of 0.5 to obtain a cement slurry;

[0038] loading the cement slurry into the mold of the cement mixing pile sample;

[0039] placing the mold containing the cement slurry into a standard curing chamber and keeping it still for 24 hours;

[0040] demolding the mold to obtain the cement mixing pile sample.

[0041] Optionally, the mass ratio of the components in the cement includes 27.19% of silicon dioxide, 11.32% of aluminum oxide, 3.76% of iron trioxide, 51.78% of calcium oxide, 1.98% of magnesium oxide and 3.97% of sulfur trioxide.

[0042] Optionally, the mass ratio of the components in the phosphogypsum includes 9.01% of silicon dioxide, 2.01% of aluminum oxide, 0.49% of iron trioxide, 35.41% of calcium oxide, 0.21% of magnesium oxide and 52.87% of sulfur trioxide.

[0043] Optionally, the loading of the cement slurry into the mold of the cement mixing pile sample includes:

[0044] injecting the cement slurry into an anti-permeability mold and an anti-compression mold, the anti-permeability mold and the anti-compression mold are both columnar, the diameter of the anti-permeability mold is 39.1 mm and the height is 80 mm, the diameter of the anti-compression mold is 50 mm and the height is 100 mm, the anti-permeability mold is used to manufacture the anti-permeability sample, and the anti-compression mold is used to manufacture the anti-compression sample.

[0045] Optionally, before determining the anti-compression parameter of each cement mixing pile sample based on the anti-compression parameter set of the plurality of cement mixing pile samples, the method further includes:

[0046] determining whether there is an anti-compression parameter set whose unconfined compressive strength on the 4nth day after manufacturing is less than the preset unconfined compressive strength in the anti-compression parameter set of the plurality of cement mixing pile samples;

[0047] when there is, removing the anti-compression parameter set whose unconfined compressive strength on the 4nth day after manufacturing is less than the preset unconfined compressive strength.

[0048] The technical scheme provided by the embodiments of the present application has at least the following beneficial effects:

[0049] By respectively performing impermeability test and compression test on the plurality of cement mixing pile samples, the permeability coefficient set and the compression coefficient set of each cement mixing pile sample are obtained, and the permeability coefficient set and the compression coefficient set both include data of the nth day and the 4nth day, then the impermeability parameter and the compression parameter of each cement mixing pile sample are determined based on the data, and further the comprehensive parameter of each cement mixing pile sample is obtained, then the cement mixing pile sample corresponding to the sample parameter set with the maximum comprehensive parameter can be used to manufacture the cement mixing pile. The method not only comprehensively considers the permeability parameter and the compression parameter of the cement mixing pile sample, but also respectively obtains these parameters at different times, and overall considers the overall performance of the cement mixing pile sample manufactured by different sample parameter sets, so that the performance of the manufactured cement mixing pile is improved. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0051] Figure 1 is a flow chart of a manufacturing method of a cement mixing pile of soft soil in a coastal area provided by an embodiment of the present application;

[0052] Figure 2 is a flow chart of another manufacturing method of a cement mixing pile of soft soil in a coastal area provided by an embodiment of the present application.

[0053] Through the above drawings, the specific embodiments of the present application have been shown, and more detailed description will be given in the following. These drawings and textual descriptions are not intended to limit the scope of the concept of the present application by any means, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the present application more clear, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0055] Figure 1 is a flow chart of a manufacturing method of a cement mixing pile of soft soil in a coastal area provided by an embodiment of the present application, and the method is used to manufacture a cement mixing pile applied to a soft soil roadbed in a coastal area, and the method comprises:

[0056] Step 101, determining a plurality of sample parameter groups, each sample parameter group comprising a cement content, a phosphogypsum content and a crystal nucleus early strength agent content in the cement mixing pile, and at least one content of the cement content, the phosphogypsum content and the crystal nucleus early strength agent content in any two sample parameter groups being different.

[0057] Step 102, manufacturing a plurality of cement mixing pile samples corresponding to the plurality of sample parameter groups.

[0058] Step 103, respectively performing impermeability tests and compression tests on the plurality of cement mixing pile samples, and obtaining a permeability coefficient group and a compression coefficient group of each cement mixing pile sample, the permeability coefficient group comprising a permeability coefficient of the cement mixing pile sample on the nth day after manufacturing and a permeability coefficient on the 4nth day, the compression coefficient group comprising an unconfined compressive strength of the cement mixing pile sample on the nth day after manufacturing and an unconfined compressive strength on the 4nth day, n≥7.

[0059] Step 104, determining an impermeability parameter of each cement mixing pile sample based on the permeability coefficient group of the plurality of cement mixing pile samples, the impermeability parameter being negatively correlated with the permeability coefficient in the permeability coefficient group.

[0060] Step 105, determining a compression parameter of each cement mixing pile sample based on the compression coefficient group of the plurality of cement mixing pile samples, the compression parameter being positively correlated with the unconfined compressive strength in the compression coefficient group.

[0061] Step 106, obtaining a comprehensive parameter of each cement mixing pile sample in the plurality of cement mixing pile samples, the comprehensive parameter being a sum of the compression parameter and the impermeability parameter of the cement mixing pile sample.

[0062] Step 107, determining a sample parameter group corresponding to the cement mixing pile sample with the maximum comprehensive parameter as a target parameter group.

[0063] Step 108, manufacturing a cement mixing pile based on the target parameter group.

[0064] To sum up, the method for manufacturing the cement mixing pile of soft soil in the coastal area provided in the embodiments of the present application obtains the permeation coefficient set and the compression resistance coefficient set of each cement mixing pile sample by respectively performing the impermeability test and the compression resistance test on the plurality of cement mixing pile samples, and the permeation coefficient set and the compression resistance coefficient set each include the data of the n th day and the 4n th day, then determines the impermeability parameter and the compression resistance parameter of each cement mixing pile sample based on the data, and further obtains the comprehensive parameter of each cement mixing pile sample, and then the cement mixing pile can be manufactured based on the sample parameter group corresponding to the cement mixing pile sample with the maximum comprehensive parameter. The method not only comprehensively considers the permeation parameter and the compression resistance parameter of the cement mixing pile sample, but also respectively obtains these parameters at different times, and comprehensively considers the overall performance of the cement mixing pile sample manufactured by different sample parameter groups, thereby achieving the effect of improving the performance of the manufactured cement mixing pile.

[0065] Figure 2 FIG. 2 is another flow chart of a method for manufacturing the cement mixing pile of soft soil in the coastal area provided in the embodiments of the present application. The method is used for manufacturing the cement mixing pile applied to the soft soil subgrade in the coastal area, and the method includes the following steps.

[0066] Step 201, determining a plurality of sample parameter groups.

[0067] The method provided in the embodiments of the present application is a method related to foundation treatment and reinforcement, excavation and filling.

[0068] Each sample parameter group includes the cement content, the phosphogypsum content and the crystal nucleus early strength agent content in the cement mixing pile, and at least one content of the cement content, the phosphogypsum content and the crystal nucleus early strength agent content in any two sample parameter groups is different. Three cement contents A1, A2 and A3 are respectively 15%, 20% and 25%, and the cement content is the mass ratio of cement to clay in the cement mixing pile;

[0069] Three phosphogypsum contents B1, B2 and B3 are respectively 10%, 20% and 30%, and the phosphogypsum content is the mass ratio of phosphogypsum to clay in the cement mixing pile;

[0070] Three crystal nucleus early strength agent contents C1, C2 and C3 are respectively 0.5%, 1% and 1.5%, and the crystal nucleus early strength agent content is the mass ratio of crystal nucleus early strength agent to clay in the cement mixing pile;

[0071] Nine sample parameter groups are obtained based on the three cement contents, the three phosphogypsum contents and the three crystal nucleus early strength agent contents and the orthogonal test method, and Table 1 is specific:

[0072] Table 1 Orthogonal test table

[0073]

[0074] Step 202, manufacturing a plurality of cement mixing pile samples corresponding to a plurality of sample parameter groups.

[0075] This step 202 includes:

[0076] 1. Obtain clay in soft soil subgrade.

[0077] 2. Dry the clay and screen out impurities in the clay through a sieve to obtain screened clay. The drying process can use air drying or other drying methods, which are not limited in the embodiments of the present application. After the clay is completely dried, a sieve with a mesh size of 2 mm is used to screen out impurities in the clay. The mesh size of the sieve can also be 1 mm, 3 mm or other values, which are not limited in the embodiments of the present application.

[0078] 3. Add water to the screened clay to obtain target clay, and the water content of the target clay is the same as that of the clay in the soft soil subgrade.

[0079] The soil particle density of the target clay is 19.1 kN / m 3 , the permeability coefficient is 9.1 x 10 -3 cm / s, the water content is 22.8%, the liquid limit is 28.6%, the plastic limit is 19.4%, and the plasticity index is 9.2. The soil particle density refers to the gravity of soil particles in a unit volume, the water content refers to the percentage of the mass of water in the soil to the mass of solid particles, the permeability coefficient is used to characterize the ability of the soil to be penetrated by water, the liquid limit refers to the critical water content at which the soil changes from a plastic state to a flowing state, the plastic limit refers to the critical water content at which the soil changes from a plastic state to a semi-solid state, and the plasticity index indicates the range of water content when the soil is in a plastic state.

[0080] 4. Obtain cement, phosphogypsum and crystal nucleus early strength agent based on the cement content, phosphogypsum content and crystal nucleus early strength agent content in the first sample parameter group in the plurality of sample parameter groups.

[0081] The cement is ordinary portland cement with a strength grade of 42.5 MPa, and the mass ratio of the components in the cement includes 27.19% of silicon dioxide, 11.32% of aluminum oxide, 3.76% of iron trioxide, 51.78% of calcium oxide, 1.98% of magnesium oxide and 3.97% of sulfur trioxide.

[0082] The phosphogypsum is a byproduct left after extracting phosphoric acid from phosphorite using sulfuric acid, and the mass ratio of the components in the phosphogypsum includes 9.01% of silicon dioxide, 2.01% of aluminum oxide, 0.49% of iron trioxide, 35.41% of calcium oxide, 0.21% of magnesium oxide and 52.87% of sulfur trioxide.

[0083] The crystal nucleus early strength agent is selected as a white powder with an effective content of 50% (the crystal nucleus substance accounts for 50% of the mass of the entire crystal nucleus early strength agent powder) and a density of 1.15 g / cm3, and the crystal nucleus early strength agent promotes cement hydration and improves the early strength of concrete.

[0084] 5. The crystal nucleus early strength agent is dissolved into water, and the cement and the phosphogypsum are stirred and mixed at a water-solid ratio of 0.5 to obtain a cement slurry.

[0085] 6. The cement slurry is loaded into a mold of the cement mixing pile sample.

[0086] The cement slurry is injected into a permeability mold and a compression mold, and the permeability mold and the compression mold are both columnar, the diameter of the permeability mold is 39.1 mm, the height is 80 mm, the diameter of the compression mold is 50 mm, and the height is 100 mm, the permeability mold is used to manufacture a permeability sample, the compression mold is used to manufacture a compression sample, and the permeability mold and the compression mold can also have other shapes, which are not limited in the embodiment of the application.

[0087] 7. The mold loaded with the cement slurry is placed in a standard curing room for 24 hours.

[0088] 8. The mold is demolded to obtain the cement mixing pile sample.

[0089] Step 203, the permeability test and the compression test are performed on the plurality of cement mixing pile samples respectively, and the permeability coefficient group and the compression coefficient group of each cement mixing pile sample are obtained.

[0090] The permeability coefficient group includes the permeability coefficient of the cement mixing pile sample on the nth day after manufacturing and the permeability coefficient on the 4nth day, the compression coefficient group includes the unconfined compression strength of the cement mixing pile sample on the nth day after manufacturing and the unconfined compression strength on the 4nth day, and n≥7; each cement mixing pile sample includes at least one permeability sample and at least one compression sample.

[0091] The step 203 includes:

[0092] 1. The permeability test is performed on the permeability sample, and the permeability coefficient of the permeability sample on the nth day after manufacturing and the permeability coefficient on the 4nth day are obtained based on the permeability coefficient calculation formula, and the permeability coefficient calculation formula includes:

[0093] ;

[0094] wherein, k t is the permeability coefficient, Q is the total amount of seepage in time t, L is the distance of the pressure measuring hole when the permeability test is performed on the permeability sample, A is the cross-sectional area of the permeability sample, H is the water head difference, and T is the time.

[0095] In one embodiment provided by the application, when n is 7 and 4n is 28, the permeability coefficients of the anti-permeation samples on the 7th day after manufacturing and on the 28th day are obtained based on the 9 sample parameter groups obtained from Table 1 by using the permeability coefficient calculation formula, and the specific values are shown in Table 2 below:

[0096] Table 2

[0097]

[0098] As shown in the above table, the permeability coefficient of the A2B2C3 group on the 7th day is the smallest, which is 2.05x10 -7 cm / s, and on the 28th day, the permeability coefficient of the A3B1C2 group is the smallest, which is 1.89x10 -7 cm / s. In addition, it is found by comparison that when the gypsum content is 30% of the cement mass, the permeability coefficient of the cement soil increases significantly, which indicates that the excessive gypsum content increases the amount of ettringite in the cement soil slurry, the volume expansion increases the voids of the slurry, and the permeability coefficient of the cement soil increases. Therefore, the permeability coefficients of the anti-permeation samples on the 7th day and the 28th day are further analyzed by range and variance. Table 3 is a range analysis table of the permeability coefficients of the anti-permeation samples:

[0099] Table 3

[0100]

[0101] In the above Table 3, R is the range, and k represents the average value of all test results under the nth level of a certain factor (for example, cement content A). For example, k1 represents the average value of all test results under the 1st level of cement content A. As shown in the above table, the three factors cause different changes in the permeability coefficients of the anti-permeation samples on the 7th day and the 28th day. For the 7th day permeability coefficient, the influencing factors are B>A>C, i.e. phosphogypsum content > cement content > early strength agent content, and the change of phosphogypsum content has the most obvious effect on the 7th day permeability. Similarly, on the 28th day, the influencing factors of the permeability coefficient are B>A>C, i.e. phosphogypsum content > cement content > early strength agent content, which is consistent with the performance results on the 7th day. When the amount of gypsum used is small, the amount of ettringite generated is small, which mainly plays a filling role in the cement soil, increases its compactness, and reduces the overall porosity, so that the permeability coefficient of the cement soil decreases. Early strength agent mainly promotes cement hydration, improves the overall compactness, and reduces the permeability of the cement soil, and similarly, the effect is weakened on the 28th day, which is similar to the change of strength. On the 28th day, the gypsum content has the greatest impact on the permeability of the cement soil, a small amount of compact structure, and excessive ettringite generated by the gypsum content, which causes volume expansion, plays a role in destroying the slurry, increases the overall microcracks, and thus the impact is greater than that of cement and early strength agent.

[0102] In this embodiment of the application, an analysis of variance was also performed on the permeability coefficient of the anti-permeability sample. By performing statistical analysis on the permeability coefficient of the sample, the significance of the influence between each variable and the response value was studied. The analysis of variance of the permeability coefficient is shown in Table 4 below:

[0103] Table 4

[0104]

[0105] In Table 4 above, "-" in the significance indicator indicates no significance. "" indicates general significance, SS is the sum of squares, df is the degrees of freedom, F-value is the ratio of the mean square between groups to the mean square within groups, and P-value is the direct reflection of the significance level. From the variance results in Table 4, it can be seen that on days 7 and 28, the cement dosage and the early-strength agent dosage had no significant effect on the permeability coefficient of the samples, while the effect of phosphogypsum was significant. The main reason is that excessive phosphogypsum may cause micro-expansion of the slurry, which weakens the density and strength, thus increasing the permeability coefficient. A small amount has a promoting effect, reducing the permeability coefficient of the samples, exhibiting two opposite effects. Therefore, the effect of ettringite on the permeability coefficient of cement-soil is more significant.

[0106] 2. Conduct a compression resistance test on the compression-resistant sample.

[0107] Permeability and compressive strength tests can be conducted according to the methods and procedures specified in the Chinese transportation industry standard "Specifications for Geotechnical Testing of Highways" (JTG 3430-2020).

[0108] In one embodiment provided in this application, when n is 7 and 4n is 28, the 9 sample parameter groups obtained in Table 1 are used as compression samples for compression testing. The unconfined compressive strength of the 9 compressive strength coefficient groups on the 7th day after manufacturing and the unconfined compressive strength on the 28th day are obtained, as shown in Table 5 below:

[0109] Table 5

[0110]

[0111] As can be seen from Table 5 above, the cement-soil of group A3B2C1 had the highest compressive strength on day 7, at 2.25 MPa. However, by day 28, the group with the highest compressive strength was group A3B1C2 at 3.95 MPa, which was 0.46 MPa higher than that of group A3B2C1.

[0112] Range analysis was performed on the unconfined compressive strength of the above-mentioned compressive samples on day 7 and day 28, as shown in Table 6 below:

[0113] Table 6

[0114]

[0115] In the above Table 6, R is the range, and k represents the average of all test results of a certain factor (for example, cement content A) at the nth level. The three factors have different effects on the strength of the compression samples at the 7th day and the 28th day. For the 7th day strength, the factors are A > C > B, i.e. cement content > early strength agent content > phosphogypsum content, and the change of cement content has the most obvious effect on the 7th day strength. The best combination of the ratio at this time is A3B2C3, i.e. cement: phosphogypsum: early strength agent = 25%:20%:1.5%. The reason for the change is that the higher the cement content, the more the amount of hydration reaction and the hydration product, which promotes the compactness of the cement soil and improves the unconfined compressive strength. At the same time, a small amount of gypsum forms ettringite in the process of cement hydration reaction. However, with the increase of the phosphogypsum content, the amount of ettringite increases too much, which may damage the compactness of the cementing body. The addition of early strength agent can provide more nucleation sites, promote cement hydration, form more C-S-H gel, compact the paste, and to some extent, inhibit the damage of excessive ettringite. At the 28th day, the factors affecting the strength of the compression samples are slightly different from those at the 7th day, and the factors are A > B > C, i.e. cement content > phosphogypsum content > early strength agent content, and the change of cement content still has the most obvious effect on the 28th day strength, and the change of early strength agent is the weakest. The best combination of the ratio at this time is A3B1C2, i.e. cement: phosphogypsum: early strength agent = 25%:10%:1%. At the 28th day, cement still provides the main strength, the effect of early strength agent is gradually weakened, and the appropriate amount of phosphogypsum is 10%, which can ensure a sufficient amount of ettringite and not too much ettringite to affect the strength change.

[0116] In the embodiments of the present application, the variance analysis of the strength of the compression samples is also performed. The significance of the influence between the variables and the response value is studied by statistical analysis of the strength of the samples. The variance analysis of the strength is shown in Table 7:

[0117] Table 7

[0118]

[0119] In the above Table 7, "-" in significance indicates no significance, " indicates general significance, ​" indicates very significant, SS is sum of squares, df is degrees of freedom, F value is the ratio of inter-group mean square deviation and intra-group mean square deviation, and P value is a value reflecting the significance level. As can be seen from the variance results in Table 7, at day 7, the influence of cement on the strength of the compression sample is significant, while the influence of early strength agent and phosphorus gypsum is not significant. However, at day 28, the influence of all three on the strength is significant, and the contribution of cement to the strength of the compression sample is the largest, followed by gypsum, and early strength agent is relatively the weakest. The main reason is that the early strength agent can play its nucleation effect before the seventh day, so that the cement can be rapidly hydrated, and the early strength of the compression sample is improved. At day 28, the effect of the early strength agent is weakened, and the excessive production of ettringite by the phosphorus gypsum may cause the slurry to swell slightly, thereby weakening the strength and causing a negative impact, which also causes the results to change significantly.

[0120] Step 204, determine whether there is a compression series group with a unconfined compressive strength less than a preset unconfined compressive strength at the 4nth day after manufacturing in the plurality of cement mixing pile samples; when there is, execute step 205, and when there is not, execute step 206.

[0121] In an embodiment provided by the present application, the preset unconfined compressive strength is greater than or equal to 3.5 MPa. It is confirmed whether the unconfined compressive strength of the 9 compression series groups in Table 5 above at day 28 is less than 3.5 MPa, and the preset unconfined compressive strength can also be other values, which are not limited in the embodiment of the present application.

[0122] Step 205, remove the compression series group with a unconfined compressive strength less than a preset unconfined compressive strength at the 4nth day after manufacturing. Execute step 206.

[0123] In an embodiment provided by the present application, as shown in Table 5, of the 9 compression series groups, only the compression series group A3B1C2 has a unconfined compressive strength of 3.95 MPa at day 28, which is greater than or equal to 3.5 MPa. That is, the unconfined compressive strength of the remaining compression series groups except the compression series group A3B1C2 at the 4nth day after manufacturing is less than the preset unconfined compressive strength. The remaining compression series groups except the compression series group A3B1C2 can be removed. Of course, the above is only an example of the present application, and the preset unconfined compressive strength can be any strength value, which is not limited in the embodiment of the present application.

[0124] Step 206, sort the anti-permeation samples in the plurality of cement mixing pile samples based on the permeation parameters and of the plurality of cement mixing pile samples, to obtain an anti-permeation sample sequence.

[0125] The permeation parameter and of each impermeable sample is the sum of the permeation coefficient of the impermeable sample in the cement mixing pile sample after the n th day of manufacture and the permeation coefficient of the impermeable sample after the 4n th day of manufacture, and the sequence number of each impermeable sample is negatively correlated with the permeation parameter and of the cement mixing pile sample in which the impermeable sample is located.

[0126] For example, as shown in Table 2 above, the permeation parameter and of the impermeable sample A1B1C3 is the sum of the permeation coefficient 12.98x10 -7 cm / s of the impermeable sample in the cement mixing pile sample after the 7th day of manufacture and the permeation coefficient 2.89x10 -7 cm / s after the 28th day of manufacture, which is 15.87x10 -7 cm / s. After calculating the permeation parameter and of all impermeable samples, the 9 impermeable samples in Table 2 above are sorted according to the sequence number of each impermeable sample, which is negatively correlated with the permeation parameter and of the cement mixing pile sample in which the impermeable sample is located, to obtain the following sequence numbers 1 to 9:

[0127] The impermeable sample A2B3C2 of the 1st sequence number has a permeation parameter and of 67.8x10 -7 cm / s; the impermeable sample A3B3C3 of the 2nd sequence number has a permeation parameter and of 52x10 -7 cm / s; the impermeable sample A1B3C1 of the 3rd sequence number has a permeation parameter and of 48.6x10 -7 cm / s; the impermeable sample A3B2C1 of the 4th sequence number has a permeation parameter and of 21.54x10 -7 cm / s; the impermeable sample A2B2C3 of the 5th sequence number has a permeation parameter and of 19.02x10 - 7 cm / s; the impermeable sample A1B1C3 of the 6th sequence number has a permeation parameter and of 15.87x10 -7 cm / s; the impermeable sample A1B2C2 of the 7th sequence number has a permeation parameter and of 15.09x10 -7 cm / s; the impermeable sample A2B1C1 of the 8th sequence number has a permeation parameter and of 13.95x10 -7 cm / s; and the impermeable sample A3B1C2 of the 9th sequence number has a permeation parameter and of 8.07x10 -7 cm / s.

[0128] Step 207, determining the sequence number of each impermeable sample as the impermeability parameter of the cement mixing pile sample in which the impermeable sample is located.

[0129] In this step, the sequence number of any impermeable sample can be determined as the impermeability parameter of the cement mixing pile sample in which the impermeable sample is located. For example, if the sequence number of an impermeable sample is 1, the impermeability parameter of the impermeable sample is 1, and if the sequence number of another impermeable sample is 2, the impermeability parameter of the impermeable sample is 2.

[0130] Step 208, based on the compressive parameters and of the plurality of cement mixing pile samples, the compressive samples in the plurality of cement mixing pile samples are sorted to obtain a compressive sample sequence.

[0131] The compressive parameter and is the sum of the unconfined compressive strength of the compressive sample in the cement mixing pile sample on the n th day after manufacturing and the unconfined compressive strength on the 4n th day. In the compressive sample sequence, the size of the serial number of each compressive sample is positively correlated with the compressive parameter and of the cement mixing pile sample in which the compressive sample is located. For example, as shown in Table 5 above, the compressive parameter and of the compressive sample A1B1C3 is the sum of the unconfined compressive strength of the compressive sample in the cement mixing pile sample on the 7th day after manufacturing, which is 1.55 MPa, and the unconfined compressive strength on the 28th day, which is 2.63 MPa, and is 4.18 MPa. After calculating the compressive parameter and of all the compressive samples, the 9 compressive samples in the above Table 5 are sorted according to the positive correlation between the size of the serial number of each compressive sample and the compressive parameter and of the cement mixing pile sample in which the compressive sample is located, to obtain the following serial numbers 1 to 9:

[0132] The compressive parameter and of the compressive sample A1B3C1 is 3.18 MPa; the compressive parameter and of the compressive sample A1B2C2 is 3.95 MPa; the compressive parameter and of the compressive sample A1B1C3 is 4.18 MPa; the compressive parameter and of the compressive sample A2B3C2 is 4.41 MPa; the compressive parameter and of the compressive sample A2B2C3 is 4.83 MPa; the compressive parameter and of the compressive sample A2B1C1 is 5.04 MPa; the compressive parameter and of the compressive sample A3B3C3 is 5.38 MPa; the compressive parameter and of the compressive sample A3B2C1 is 5.74 MPa; and the compressive parameter and of the compressive sample A3B1C2 is 5.80 MPa.

[0133] Step 209, determining the serial number of each compressive sample as the compressive parameter of the cement mixing pile sample in which each compressive sample is located.

[0134] In this step, the serial number of any one compressive sample can be determined as the compressive parameter of the cement mixing pile sample in which each compressive sample is located. For example, the serial number of one compressive sample is 1, and the compressive parameter of the compressive sample is 1. The serial number of another compressive sample is 2, and the compressive parameter of the compressive sample is 2.

[0135] Step 210, obtaining the comprehensive parameter of each cement mixing pile sample in the plurality of cement mixing pile samples, the comprehensive parameter being the sum of the compressive parameter and the impermeability parameter of the cement mixing pile sample.

[0136] The cement mixing pile sample A2B3C2 has a compression parameter of No. 4 and an anti-permeation parameter of No. 1, and thus the comprehensive parameter of the compression sample A2B3C2 is 5; the cement mixing pile sample A3B3C3 has a compression parameter of No. 7 and an anti-permeation parameter of No. 2, and thus the comprehensive parameter of the compression sample A3B3C3 is 9; the cement mixing pile sample A1B3C1 has a compression parameter of No. 1 and an anti-permeation parameter of No. 3, and thus the comprehensive parameter of the compression sample A1B3C1 is 4; the cement mixing pile sample A3B2C1 has a compression parameter of No. 8 and an anti-permeation parameter of No. 4, and thus the comprehensive parameter of the compression sample A3B2C1 is 12; the cement mixing pile sample A2B2C3 has a compression parameter of No. 5 and an anti-permeation parameter of No. 5, and thus the comprehensive parameter of the compression sample A2B2C3 is 10; the cement mixing pile sample A1B1C3 has a compression parameter of No. 3 and an anti-permeation parameter of No. 6, and thus the comprehensive parameter of the compression sample A1B1C3 is 9; the cement mixing pile sample A1B2C2 has a compression parameter of No. 2 and an anti-permeation parameter of No. 7, and thus the comprehensive parameter of the compression sample A1B2C2 is 9; the cement mixing pile sample A2B1C1 has a compression parameter of No. 6 and an anti-permeation parameter of No. 8, and thus the comprehensive parameter of the compression sample A2B1C1 is 14; the cement mixing pile sample A3B1C2 has a compression parameter of No. 9 and an anti-permeation parameter of No. 9, and thus the comprehensive parameter of the compression sample A3B1C2 is 18.

[0137] Step 211, determining the sample parameter group corresponding to the cement mixing pile sample with the maximum comprehensive parameter as the target parameter group.

[0138] The cement mixing pile sample with the maximum comprehensive parameter is the cement mixing pile sample A3B1C2, and the sample parameter group corresponding to the cement mixing pile sample A3B1C2 is that the cement content is 25%, the phosphogypsum content is 10%, and the early strength agent content is 1%. The sample parameter group is determined as the target parameter group.

[0139] Step 212, manufacturing the cement mixing pile based on the target parameter group.

[0140] According to the orthogonal test, it can be found that the cement has the most significant influence on the strength of the cement mixing pile on the 7th day and the 28th day, the early strength agent has a greater influence than the phosphogypsum in the early stage, and the phosphogypsum is harder than the early strength agent on the 28th day; the permeability of the cement mixing pile shows different changes, the change in the influence on the 7th day is phosphogypsum>early strength agent>cement, and the change on the 28th day is phosphogypsum>cement>early strength agent, a small amount of phosphogypsum is beneficial to the strength and permeability of the cement mixing pile, and excessive phosphogypsum content will reduce the strength of the cement mixing pile and increase the permeability; it is also found that the early strength agent is beneficial to the strength and permeability of the cement mixing pile, and the early effect is better.

[0141] The cement mixing pile based on the target parameter group can obtain the highest compressive strength and the lowest permeability coefficient on the 28th day, and meanwhile, other damages caused by excessive phosphogypsum are avoided, the purpose of fast pile forming is achieved, and the requirements of engineering design are met.

[0142] In summary, the method for manufacturing the cement mixing pile in soft soil in coastal areas provided by the embodiments of the present application obtains the permeability coefficient group and the compressive strength coefficient group of each cement mixing pile sample by respectively performing the impermeability test and the compressive test on the plurality of cement mixing pile samples, and the permeability coefficient group and the compressive strength coefficient group both include the data on the nth day and the 4nth day, then determines the impermeability parameter and the compressive parameter of each cement mixing pile sample based on the data, and further obtains the comprehensive parameter of each cement mixing pile sample, and then the cement mixing pile can be manufactured based on the sample parameter group corresponding to the cement mixing pile sample with the maximum comprehensive parameter. The method not only comprehensively considers the permeability parameter and the compressive parameter of the cement mixing pile sample, but also respectively obtains these parameters at different times, and comprehensively considers the overall performance of the cement mixing pile sample manufactured based on different sample parameter groups, and the effect of improving the performance of the manufactured cement mixing pile is achieved.

[0143] In the present application, the terms "first", "second", etc. are only used for description purposes, and cannot be understood as indicating or implying relative importance. The term "plurality" refers to two or more, unless otherwise explicitly limited.

[0144] The above only describes optional embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for manufacturing cement-mixing piles in soft soil in coastal areas, characterized in that, The method for manufacturing cement-mixed piles for use in soft soil subgrades in coastal areas includes: Three cement dosages are determined, namely 15%, 20% and 25%, where the cement dosage is the mass ratio of cement to clay in the cement mixing pile. Three phosphogypsum dosages were determined, namely 10%, 20%, and 30%, respectively, wherein the phosphogypsum dosage was the mass ratio of phosphogypsum to clay in the cement mixing pile; The dosages of three early-strength nucleating agents were determined to be 0.5%, 1%, and 1.5%, respectively. The dosage of the early-strength nucleating agent was the mass ratio of the early-strength nucleating agent to the clay in the cement mixing pile. Based on the three cement dosages, three phosphogypsum dosages, and three nucleation accelerator dosages, and using orthogonal experimental methods, multiple sample parameter groups are obtained. The number of sample parameter groups is nine. Each sample parameter group includes the cement dosage, phosphogypsum dosage, and nucleation accelerator dosage in the cement mixing pile. At least one of the cement dosage, phosphogypsum dosage, and nucleation accelerator dosage in any two sample parameter groups is different. Obtain the clay from the soft soil subgrade; The clay is dried and impurities are removed by sieving through a sieve to obtain sieved clay with a mesh size of 2 mm. Water is added to the sieved clay to obtain the target clay, the moisture content of which is the same as that of the clay in the soft soil subgrade, and the unit weight of the target clay particles is 19.1 kN / m³. 3 Permeability coefficient 9.1×10 -3 The viscosity is 1000 cm / s, the moisture content is 22.8%, the liquid limit is 28.6%, the plastic limit is 19.4%, and the plasticity index is 9.

2. Based on the cement content, phosphogypsum content, and nucleation accelerator content in the first sample parameter group of the multiple sample parameter groups, cement, phosphogypsum, and nucleation accelerator were obtained. The cement was a silicate cement with a strength grade of 42.5 MPa. The mass proportions of the cement components included: 27.19% silicon dioxide, 11.32% aluminum oxide, 3.76% ferric oxide, 51.78% calcium oxide, 1.98% magnesium oxide, and 3.97% sulfur trioxide. The mass proportions of the phosphogypsum components included: 9.01% silicon dioxide, 2.01% aluminum oxide, 0.49% ferric oxide, 35.41% calcium oxide, 0.21% magnesium oxide, and 52.87% sulfur trioxide. The nucleation accelerator had an effective content of 50% and a density of 1.15 g / cm³. 3 It is a white powder. The nucleation early strength agent is dissolved in water, and the cement and phosphogypsum are mixed at a water-to-solid ratio of 0.5 to obtain cement slurry. The cement slurry is injected into an anti-permeability mold and a pressure-resistant mold. Both the anti-permeability mold and the pressure-resistant mold are columnar. The diameter of the anti-permeability mold is 39.1 mm and the height is 80 mm. The diameter of the pressure-resistant mold is 50 mm and the height is 100 mm. The anti-permeability mold is used to manufacture anti-permeability samples, and the pressure-resistant mold is used to manufacture pressure-resistant samples. The mold containing the cement slurry was placed in a standard curing room and left to stand for 24 hours. Demolding the mold yields a cement mixing pile sample; Multiple cement mixing pile samples were subjected to permeability and compressive strength tests, and permeability coefficient groups and compressive strength coefficient groups were obtained for each cement mixing pile sample. The permeability coefficient group includes the permeability coefficient of the cement mixing pile sample on the nth day after manufacturing and the permeability coefficient on the 4nth day after manufacturing. The compressive strength coefficient group includes the unconfined compressive strength of the cement mixing pile sample on the nth day after manufacturing and the unconfined compressive strength on the 4nth day after manufacturing, where n is 7 and 4n is 28. Based on the permeability parameters of the multiple cement mixing pile samples, the anti-permeability samples in the multiple cement mixing pile samples are sorted to obtain an anti-permeability sample sequence. The permeability parameters are the sum of the permeability coefficients of the anti-permeability samples in the cement mixing pile samples on the nth day after manufacturing and the permeability coefficients on the 4nth day. In the anti-permeability sample sequence, the number of each anti-permeability sample is negatively correlated with the permeability parameters of the cement mixing pile sample in which it belongs. The serial number of each anti-seepage sample is determined as the anti-seepage parameter of the cement mixing pile sample to which each anti-seepage sample belongs, and the anti-seepage parameter is negatively correlated with the permeability coefficient in the permeability coefficient group; Determine whether there exists a group of compressive coefficients among the multiple cement mixing pile samples whose unconfined compressive strength on the 4nth day after manufacturing is less than a preset unconfined compressive strength, wherein the preset unconfined compressive strength is greater than or equal to 3.5 MPa. When present, remove the group of compressive strength coefficients whose unconfined compressive strength on the 4nth day after manufacturing is less than the preset unconfined compressive strength. Based on the compressive strength coefficient group of the multiple cement mixing pile samples, the compressive strength parameter of each cement mixing pile sample is determined, and the compressive strength parameter is positively correlated with the unconfined compressive strength in the compressive strength coefficient group; Obtain the comprehensive parameters of each cement mixing pile sample from the plurality of cement mixing pile samples. The comprehensive parameters are the sum of the compressive strength parameters and the impermeability parameters of the cement mixing pile sample. The sample parameter group corresponding to the cement mixing pile sample with the largest comprehensive parameters is determined as the target parameter group. The target parameter group has a cement content of 25%, a phosphogypsum content of 10%, and an early strength agent content of 1%. The cement mixing pile is manufactured based on the target parameter set.

2. The method according to claim 1, characterized in that, Each of the cement mixing pile samples includes at least one impermeable sample and at least one compressive strength sample; The process of performing impermeability tests and compressive strength tests on the multiple cement mixing pile samples includes: The impermeability sample was subjected to an impermeability test, and the permeability coefficient of the impermeable sample on the nth day after manufacturing and on the 4nth day were obtained based on the permeability coefficient calculation formula, wherein the permeability coefficient calculation formula includes: ； Where, k t Where A is the permeability coefficient, Q is the total seepage within time t, L is the spacing of the pressure measuring holes when performing a permeability test on the permeability sample, A is the cross-sectional area of ​​the permeability sample, H is the hydraulic head difference, and T is time. The compression test was performed on the compression-resistant sample.

3. The method according to claim 2, characterized in that, The determination of the compressive strength parameters for each cement mixing pile sample based on the compressive strength coefficient group of the multiple cement mixing pile samples includes: Based on the compressive strength parameters of the multiple cement mixing pile samples, the compressive strength samples in the multiple cement mixing pile samples are sorted to obtain a compressive strength sample sequence. The compressive strength parameters are the sum of the unconfined compressive strength of the compressive strength samples in the cement mixing pile samples on the nth day after manufacturing and the unconfined compressive strength on the 4nth day. In the compressive strength sample sequence, the number of each compressive strength sample is positively correlated with the compressive strength parameters of the cement mixing pile sample in which it belongs. The serial number of each compressive strength sample is determined as the compressive strength parameter of the cement mixing pile sample to which each compressive strength sample belongs.

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