Method for evaluating effect of solid waste in soft soil treatment of silt and optimizing proportioning

Abstract

The application discloses a kind of utility evaluation and proportioning optimization method of solid waste in silt soft soil treatment in the technical field of inorganic composite material.The method comprises the following steps: S1: carry out pH value test and x fluorescence test to the industrial solid waste to be used, the industrial solid waste to be used is divided into two categories: I is silicon aluminum base waste residue or alkaline waste residue, II is gypsum base waste residue;S2: construct the strength prediction model of pure cement silt solidified soil, and carry out coefficient calibration;S3: based on the strength prediction model of pure cement silt solidified soil, construct the strength prediction model of waste residue base silt solidified soil, and carry out coefficient calibration;S4: according to waste residue base silt solidified soil strength prediction model, the proportioning of each type of waste residue is optimized and adjusted.The utility evaluation and proportioning optimization method based on the strength prediction model of waste residue base silt solidified soil can not only realize the rapid and effective evaluation of silt solidified soil strength under different waste residue proportioning, but also optimize the waste residue proportioning in solidified silt soil.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic composite materials, and particularly relates to a method for evaluating the effectiveness of solid waste and optimizing the proportioning in soft soil treatment. BACKGROUND

[0002] A large amount of dredged mud with high water content and low strength is generated in river and lake dredging and marine dredging projects. Due to poor engineering properties, a large amount of dredged mud is abandoned. Inland dredged mud is usually used to build cofferdams for storage, and marine dredged mud is discarded in the sea. The disposal of dredged mud causes waste of resources and threatens the environment. Chemical solidification treatment is an effective method for the recycling of dredged mud. Through chemical improvement, dredged mud can be converted into good quality soil and used for engineering filling construction. The solidification treatment method has the advantages of high treatment efficiency and short construction period, but usually uses high energy consumption resources such as cement, which has high economic cost and greatly increases carbon emissions.

[0003] With the rapid development of urban construction, a large amount of industrial waste slag is long-term stockpiled due to ineffective utilization, which not only occupies land resources but also has a serious impact on the environment. Large solid waste is wide in quantity, outstanding in environmental impact, and broad in utilization prospect, which is the core field of resource comprehensive utilization. Industrial solid waste has potential chemical activity, which often plays a beneficial role under the activation of the cement chemical environment. If industrial solid waste is combined and utilized in cement solidified mud, the cement consumption can be reduced, and the stock of industrial solid waste can be absorbed, which has great economic and environmental benefits.

[0004] However, due to the large number of types of industrial solid waste, standardization is difficult, which is mainly due to the different roles of industrial waste slag in cement-based materials, and the lack of classification and general methods. The evaluation of the role of solid waste needs to be carried out through specific indoor tests, and the selection of the test proportion is also relatively blind, so the utilization efficiency of industrial solid waste in soft soil treatment is very low. When the amount of waste slag is too high, it often has a negative effect, and even causes engineering accidents. For example, when too much phosphogypsum is mixed in the roadbed, swelling and cracking often occur. SUMMARY

[0005] In order to solve or partially solve the above problems, the present application provides a method for evaluating the effectiveness of solid waste and optimizing the proportioning in soft soil treatment, which is used to evaluate the effectiveness of solid waste in soft soil treatment, and to optimize the proportioning between different waste slags through methods such as seeking the maximum strength.

[0006] The present application provides a method for evaluating the effectiveness of solid waste and optimizing the proportioning in soft soil treatment, which includes the following steps:

[0007] S1: pH value test and x fluorescence test are carried out on the industrial solid waste to be used, so as to obtain the acid-base degree and chemical composition characteristics of the industrial solid waste; according to the acid-base degree and chemical composition characteristics, the industrial solid waste to be used is divided into two categories: I-class waste residue and II-class waste residue, the I-class waste residue is a silicon-aluminum-based waste residue or an alkaline waste residue, and the II-class waste residue is a gypsum-based waste residue;

[0008] S2: a strength prediction model of pure cement silt solidified soil is constructed, and a coefficient is calibrated, and a specific expression of the strength prediction model of the pure cement silt solidified soil is as follows:

[0009] (1);

[0010] wherein: q u is the uniaxial compressive strength; w is the initial water content of silt soil; w / c is the water-cement ratio of solidified silt, that is, the ratio of the initial water content of silt soil to the cement content; A and n are fitting coefficients based on Abrams' law; and λ is the influence coefficient of the composition of solidified soil;

[0011] S3: based on the strength prediction model of the pure cement silt solidified soil, a strength prediction model of waste residue-based silt solidified soil is constructed, and a coefficient is calibrated, and a specific expression of the strength prediction model of the waste residue-based silt solidified soil is as follows:

[0012] (2);

[0013] wherein, q and r are respectively the dosages of I-class waste residue and II-class waste residue, k1 is the pozzolanic enhancement coefficient of I-class waste residue, m1 is the ettringite filling enhancement coefficient of II-class waste residue, and d1 is the cementation damage coefficient of II-class waste residue;

[0014] S4: according to the strength prediction model of the waste residue-based silt solidified soil, the ratio of various types of waste residue in the industrial solid waste is optimized and adjusted.

[0015] The beneficial effects of the above embodiments are that the utility evaluation and proportion optimization method divides the industrial waste to be used into two categories: I-silicon aluminum base-alkaline waste and II-gypsum base waste by pH test and x fluorescence test. The I-class waste mainly promotes the pozzolanic reaction in the solidified silt soil, and the II-class waste mainly promotes the ettringite formation. Based on the definition of the effect of the waste, the pozzolanic enhancement effect k, the ettringite filling enhancement effect m, and the cementation damage effect d in the silt solidified soil are defined, which can be quantified by the unconfined compressive strength test, so as to adjust the proportion of the waste content by the strength prediction formula. The utility evaluation and proportion optimization method based on the strength prediction model of the waste base silt solidified soil can not only realize the rapid and effective evaluation of the strength of the silt solidified soil under different waste proportions, but also realize the reasonable regulation of the cementation and filling effects in the solidified silt soil and the optimization of the waste proportion.

[0016] On the basis of the above embodiments, the application can be further improved, specifically as follows:

[0017] In one of the embodiments of the application, in the step S1, the discrimination standard of the alkaline waste is that the pH is greater than 10; the discrimination standard of the silicon aluminum base waste is that the sum of the contents of Al2O3 and S i O2 is greater than 50%; and the discrimination standard of the gypsum base waste is that the content of SO3 is greater than 40% and the content of CaO is greater than 20%.

[0018] In one of the embodiments of the application, in the step S1, the pH test and x fluorescence test can not be carried out for the industrial solid waste with significant chemical composition characteristics. For example, the fly ash and the blast furnace slag can be directly classified as the I-class silicon aluminum base waste, the red mud can be directly classified as the I-class alkaline waste, and the phosphogypsum and the desulfurization gypsum can be directly classified as the II-class waste.

[0019] In one of the embodiments of the application, in the step S2, based on the strength prediction model of the pure cement silt solidified soil, a plurality of unconfined compressive strength tests of the pure cement silt solidified soil are carried out, so as to determine A, n and λ in formula (1).

[0020] In one of the embodiments of the application, in the step S2, when carrying out the plurality of unconfined compressive strength tests of the pure cement silt solidified soil, the plurality of pure cement silt solidified soils at least contain two different initial water contents and at least two different water-cement ratios.

[0021] In one of the embodiments of the application, in the step S3, according to the strength prediction model of the waste base silt solidified soil, a plurality of unconfined compressive strength tests of different waste content combinations are carried out, so as to determine k1, m1 and d1 in formula (2).

[0022] In one embodiment of this application, the same curing age is selected when conducting the unconfined compressive strength test in steps S2 and S3. Neither formula (1) nor formula (2) considers the influence of the curing age; therefore, the same curing age should be selected when calibrating the coefficients through the unconfined compressive strength test.

[0023] In one embodiment of this application, in step S3, k1 mainly represents the promoting effect of active ions directly provided by ion-based waste residue and active ions in alkaline-enhanced dissolved silt clay minerals on the volcanic ash reaction. Due to the generation of more cementing substances such as hydrated calcium silicate, the bonding strength between particles and aggregates is increased; m1 mainly represents the promoting effect of hydrated calcium sulfate provided by gypsum-based waste residue on the formation reaction of ettringite. Due to the increase in the amount of ettringite, the filling and compaction effect of ettringite is enhanced, the contact between particles is increased, and the micro-density is improved, which is equivalent to reducing the water content and porosity; d1 mainly represents the damaging effect of the expansion effect of ettringite on the generated cementing substances and cemented structure. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0025] Figure 1 This is a flowchart illustrating the steps of a method for evaluating the effectiveness and optimizing the proportion of solid waste in the treatment of silt and soft soil, as described in an embodiment of this application.

[0026] Figure 2 This is a trend graph showing the unconfined compressive strength of the silt-stabilized soil as a function of the solid waste ratio in the embodiments of this application. Detailed Implementation

[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0028] Example:

[0029] like Figure 1 As shown, a method for evaluating the effectiveness and optimizing the proportion of solid waste in the treatment of silt and soft soil includes the following steps:

[0030] S1: Perform pH value test and x fluorescence test on the industrial solid waste to be used to obtain the pH value and chemical composition characteristics of the industrial solid waste; according to the pH value and chemical composition characteristics, the industrial solid waste to be used is divided into two categories: I type waste residue and II type waste residue, the I type waste residue is a silicon aluminum based waste residue or an alkaline waste residue, and the II type waste residue is a gypsum based waste residue;

[0031] Among them, the discrimination standard of alkaline waste residue is pH greater than 10; the discrimination standard of silicon aluminum based waste residue is the sum of the contents of Al2O3 and S i O2 is greater than 50%; the discrimination standard of gypsum based waste residue is that the content of SO3 is greater than 40% and the content of CaO is greater than 20%.

[0032] For industrial solid waste with significant chemical composition characteristics, pH value test and x fluorescence test can not be performed. For example, fly ash and blast furnace slag can be directly classified as I type silicon aluminum based waste residue, and red mud can be directly classified as I type waste residue; phosphogypsum and desulfurization gypsum can be directly classified as II type waste residue.

[0033] S2: Construct a strength prediction model of pure cement silt solidified soil, and calibrate the coefficients, the specific expression of the strength prediction model of pure cement silt solidified soil is:

[0034] (1);

[0035] Among them: q u is the uniaxial compressive strength; w is the initial water content of silt soil; w / c is the water-cement ratio of solidified silt, that is, the ratio of the initial water content of silt soil to the cement content; A, n are fitting coefficients based on Abrams' law; λ is the influence coefficient of the composition of solidified soil;

[0036] Based on the strength prediction model of pure cement silt solidified soil, a plurality of unconfined compressive strength tests of pure cement silt solidified soil are carried out, so as to determine A, n and λ in formula (1). Among them, when a plurality of unconfined compressive strength tests of pure cement silt solidified soil are carried out, at least two different initial water contents and at least two different water-cement ratios are contained in the plurality of pure cement silt solidified soil.

[0037] S3: Based on the strength prediction model of pure cement silt solidified soil, a strength prediction model of waste residue based silt solidified soil is constructed, and the coefficients are calibrated, and the specific expression of the strength prediction model of waste residue based silt solidified soil is as follows:

[0038] (2);

[0039] Among them, q, r are the contents of I type waste residue and II type waste residue respectively, k1 is the pozzolanic enhancement coefficient of I type waste residue, m1 is the ettringite filling enhancement coefficient of II type waste residue, and d1 is the cementation damage coefficient of II type waste residue.

[0040] According to the strength prediction model of the waste residue-based sludge solidified soil, a plurality of different waste residue content combination ratio unconfined compressive strength tests are carried out, so as to determine k1, m1 and d1 in formula (2).

[0041] Wherein, k1 mainly represents the promotion effect of active ions directly provided by ion-based waste residue and active ions in alkaline enhanced dissolved sludge clay minerals on the pozzolanic reaction, because more hydrated calcium silicate and other cementitious materials are generated, the cementation strength between particles and aggregates is increased;m1 mainly represents the promotion effect of hydrated calcium sulfate provided by gypsum-based waste residue on the ettringite formation reaction, because the amount of ettringite is increased, the filling and compaction effect of ettringite is enhanced, the contact between particles is increased, the micro-compactness is improved, which is equivalent to reducing the water content and the porosity ratio;d1 mainly represents the damage effect of the expansion of ettringite on the generated cementitious materials and cementation structure.

[0042] S4: According to the strength prediction model of the waste residue-based sludge solidified soil, the ratio of each type of waste residue is optimized and adjusted.

[0043] Further, the influence of curing age is not considered in formula (1) and formula (2), therefore the same curing age should be selected in the coefficient calibration in steps S2 and S3 through the unconfined compressive strength test.

[0044] The solid waste utility evaluation and ratio optimization method for sludge soft soil treatment proposed in the application considers the strength essential characteristics of the solidified soil, the strength of the solidified sludge is determined by the cementation strength and the fabric characteristics, wherein the cementation strength is determined by the water-cement ratio (w / c), and the water-cement ratio reflects the amount of cement per unit volume;Because the water content in the sludge is high, it is generally considered that the hydration reaction and the pozzolanic reaction are sufficient, so the water-cement ratio can reflect the density of the cementation product. And the fabric characteristics are mainly determined by the pore characteristics, and the initial water content is a decisive index for determining the pore characteristics of the sludge solidified soil, therefore the traditional Abrams' law is modified to obtain the strength expression of the pure cement solidified sludge. The solid waste used in the sludge soft soil treatment mainly has two effects on the strength of the solidified sludge, one is that it provides an alkaline environment to promote the dissolution of active silicon and aluminum ions in the sludge minerals or directly provides active silicon and aluminum ions, thereby promoting the pozzolanic reaction and increasing the cementation strength, so this part of the effect is equivalent to increasing the cement content;The second is to provide sulfate ions, thereby promoting the generation of ettringite, which is an expansive mineral, and its generation and growth process can play a role in filling pores and promoting compaction, so it is equivalent to reducing the water content;And the expansion of ettringite also has a damaging effect on the existing cementation, thereby causing the deterioration of the microstructure and the reduction of the cementation strength, which is equivalent to reducing the cement content.

[0045] The application innovatively proposes an evaluation method considering the effects of solid wastes from the aspects of cementation and composition. Based on the strength evaluation and prediction method, the contents of I-silicon aluminum-based-alkaline waste slag and II-gypsum-based waste slag can be optimized by finding the maximum value.

[0046] The following will introduce the utility evaluation and ratio optimization method of the cement solidified silt industrial solid waste in detail with an actual case. The case is to use industrial solid waste red mud and phosphogypsum to cement Lianyungang marine silt, and the purpose is to optimize the ratio of red mud and phosphogypsum. The basic physical property indexes of Lianyungang marine silt are shown in Table 1, and the cement used is standard Portland cement with a label of 42.5.

[0047]

[0048] The specific implementation steps are as follows:

[0049] 1) Perform pH value test and x fluorescence test on the industrial solid waste to be used to obtain the acidity and alkalinity and chemical composition characteristics of the industrial solid waste. The pH values of red mud and phosphogypsum are 10.3 and 3.2 respectively, and the chemical compositions of red mud and phosphogypsum are shown in Table 2. According to the test results of acidity and alkalinity and chemical composition, the red mud is classified as I type waste, and the phosphogypsum is classified as II type waste.

[0050]

[0051] 2) Determine the coefficients in the strength prediction model of pure cement silt solidified soil, i.e. the coefficients A, λ and n in formula (1). Perform three groups of tests, select three groups of different water contents and water-cement ratios for testing as shown in Table 3, and select standard curing conditions to perform unconfined compressive strength test (20±2℃, 95% humidity).

[0052]

[0053] According to the test results, the minimum value of the square sum of the difference between the predicted value and the measured value is solved by using the planning solving function of excel, and finally the undetermined coefficients are A=168783, λ=3, n=1. Then formula (1) is:

[0054] (3).

[0055] 3) Perform unconfined compressive strength test of five groups of different red mud and phosphogypsum ratios for two different water contents and cement contents, and the results are shown in Table 4.

[0056]

[0057] According to the test results, the solving is performed by using the planning solving function of Excel, the minimum value of the square sum of the difference between the strength prediction value (i.e. formula (2), wherein A=168783, λ=3, n=1) and the measured value (test value) is determined, so as to determine the coefficients k1, m1 and d1 in formula (2).

[0058] When the initial water content is 80% and the cement content is 8%, formula (2) is:

[0059] (4),

[0060] That is, k1=0.133, m1=0.05, d1=0.045;

[0061] When the initial water content is 120% and the cement content is 12%, formula (2) is:

[0062] (5),

[0063] That is, k1=0.047, m1=0.193, d1=0.046.

[0064] 4) According to formula (2), the change of strength with the change of waste residue content can be obtained, as shown in Figure 2 . Figure 2 The change of the strength of the sludge solidified soil with the change of the red mud content under two water contents and cement contents (the total amount of red mud and phosphogypsum is 10% of the dry soil mass) is shown in Figure 2 . According to Figure 2 , the best ratio of red mud to phosphogypsum here is approximately 9:1, which can guide the engineering practice and ensure the strength.

[0065] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method for evaluating the utility of solid waste in the treatment of soft soil sludge and optimizing the proportioning, characterized in that, The method comprises the following steps: S1: pH value test and x fluorescence test are carried out on the industrial solid waste to be used, and the industrial solid waste to be used is divided into two categories: I type waste residue and II type waste residue, the I type waste residue is a silicon aluminum based waste residue or an alkaline waste residue, and the II type waste residue is a gypsum based waste residue; S2: a strength prediction model of pure cement sludge solidified soil is constructed, and coefficient calibration is carried out, and the specific steps are as follows: The specific expression of the strength prediction model of the pure cement sludge solidified soil is: (1)； wherein: q u is the uniaxial compressive strength; w is the initial water content of the silt soil; w / c is the water-cement ratio of the cured silt, i.e. the ratio of the initial water content of the silt soil to the cement content; A, n are fitting coefficients based on the Eberm's law; λ is the influence coefficient of the cured soil fabric; Based on the strength prediction model of the pure cement sludge solidified soil, a plurality of unconfined compressive strength tests of the pure cement sludge solidified soil are carried out, so as to determine A, n and λ in formula (1); S3: based on the strength prediction model of the pure cement sludge solidified soil, a strength prediction model of waste residue based sludge solidified soil is constructed, and coefficient calibration is carried out, and the specific steps are as follows: The specific expression of the strength prediction model of the waste residue based sludge solidified soil is as follows: (2)； Wherein, q and r are the mixing amounts of I type waste residue and II type waste residue respectively, k1 is the pozzolanic enhancement coefficient of I type waste residue, m1 is the ettringite filling enhancement coefficient of II type waste residue, and d1 is the cementation damage coefficient of II type waste residue; According to the strength prediction model of the waste residue based sludge solidified soil, a plurality of unconfined compressive strength tests of the waste residue based sludge solidified soil with different waste residue mixing amount combinations are carried out, so as to determine k1, m1 and d1 in formula (2); S4: according to the strength prediction model of the waste residue based sludge solidified soil, the ratio of each type of waste residue is optimized and adjusted.

2. The method of claim 1, wherein: The step S1, wherein the alkali waste residue is determined by pH greater than 10; the silicon-aluminum-based waste residue is determined by the sum of Al2O3 and SiO2 content greater than 50%; and the gypsum-based waste residue is determined by SO3 content greater than 40% and CaO content greater than 20%. i The step S1, wherein the alkali waste residue is determined by pH greater than 10; the silicon-aluminum-based waste residue is determined by the sum of Al2O3 and SiO2 content greater than 50%; and the gypsum-based waste residue is determined by SO3 content greater than 40% and CaO content greater than 20%.

3. The method of claim 1, wherein: In the step S1, the industrial solid waste with significant chemical composition characteristics can be directly classified.

4. The method of claim 1, wherein: In the step S2, when a plurality of unconfined compressive strength tests of the pure cement sludge solidified soil are carried out, the plurality of pure cement sludge solidified soils contain at least two different initial water contents and at least two different water cement ratios.

5. The method of claim 1, wherein: In the steps S2 and S3, the same curing age is selected when the unconfined compressive strength test is carried out.

6. The method of claim 1, wherein: In step S3, k1 represents the promotion effect of active ions directly provided by ion-based waste residue and active ions in alkaline enhanced dissolved sludge clay minerals on pozzolanic reaction; m1 represents the promotion effect of hydrated calcium sulfate provided by gypsum-based waste residue on ettringite formation reaction; d1 represents the damage effect of ettringite expansion on the generated cementitious material and cementation structure.

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