Method for determining appropriate mix proportion of high-clay-content foam light soil for reorganization and expansion of embankment on soft soil road section

Abstract

The invention relates to the technical field of road reconstruction and extension projects, in particular to a method for determining the appropriate mix proportion of high-clay-content foam light soil of a soft soil road section reconstruction and extension embankment, which comprises the following steps: step 1, determining the improvement critical density (rho cr) of the foam light soil; 2, determining the sequence of the influence of the mixing amount factors on the strength and density of the foam light soil; step 3, determining a suitable mix proportion of the foam light soil; step 4, according to the determined suitable mix proportion of the foam light soil, performing a soil test of the density and unconfined compressive strength of the large-size foam light soil cube test block to verify that the foam light soil has feasibility in actual engineering; the method has the advantages that it is guaranteed that the foam light soil can meet relevant roadbed standard requirements in roadbed construction, and meanwhile the effects of cost saving and environmental protection can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of road reconstruction and expansion engineering, and in particular to a method for determining a suitable mix ratio of high-clay-content foamed lightweight soil for reconstruction and expansion of embankments on soft soil sections. Background Art

[0002] Road reconstruction and expansion project is an engineering project of building a new and widened highway based on the original highway foundation. Since the original highway foundation has basically completed settlement and consolidation, the foundation of the newly built and widened highway will experience a large consolidation settlement during the construction period after the embankment load is applied, especially in soft soil sections. Due to the large compression coefficient and significant rheological properties of soft soil, during the construction period of the new embankment, the soft soil foundation will produce a large consolidation settlement under the action of the self-weight of the new embankment. When the construction speed is too fast, in addition to causing excessive differential settlement damage, it is even easy to cause serious embankment sliding deformation damage.

[0003] In order to solve the problem of differential settlement and sliding damage of new and old embankments in highway reconstruction and expansion projects in soft soil sections, a new type of embankment filling material, foam lightweight soil, which is cast-in-place and solidified, has been developed by using part of the embankment filling to replace cement in foam concrete. The foam lightweight soil has the characteristics of light weight, adjustable strength and density, good uprightness, fast molding, and convenient construction. The problem with making foam lightweight soil is that replacing part of the embankment filling with cement will not only increase the consistency of the foam lightweight soil slurry, reduce the foaming efficiency, and increase the density of the foam lightweight soil, but also reduce the strength of the foam lightweight soil due to the addition of soil materials. Therefore, the difficulty in making foam lightweight soil is that when the filling amount is small, it is difficult to overcome the high cost and environmental protection of the foam concrete roadbed. The defect of poor insulation performance; however, when the fill volume is large, it is difficult to ensure that the foam lightweight soil has a sufficiently high strength and a sufficiently low density to meet the requirements of the roadbed specifications. However, at present, it is impossible to determine the mix ratio of foam lightweight soil filler through theoretical calculation, and the strength of the foam lightweight soil formed after the fill material is added will be greatly reduced, while the density will be greatly increased, which makes the application scope of foam lightweight soil in widening embankments in soft soil foundation sections limited to a certain extent. Therefore, the appropriate mix ratio of foam lightweight soil is closely related to the strength and compressibility of the soft soil foundation, and is also significantly affected by factors such as the engineering characteristics of the embankment fill soil and the embankment filling height. Therefore, how to determine the appropriate mixing amount of various materials in the foam lightweight soil construction process has become a difficult problem in the production of foam lightweight soil. Summary of the invention

[0004] The main problem to be solved by the present invention is how to determine the appropriate mix ratio of foam lightweight soil filling material suitable for widening embankments on soft soil foundation sections, so as to ensure that the foam lightweight soil can meet the requirements of relevant roadbed specifications during roadbed construction while achieving the purposes of cost savings and environmental protection. The present application provides a method for determining the appropriate mix ratio of foam lightweight soil with high clay content for the reconstruction and expansion of embankments on soft soil sections. The initial value of each admixture is calculated based on the geotechnical parameters of each soil layer of the soft soil foundation obtained from the geotechnical engineering survey data of the soft soil section site, and then the orthogonal test method is used to analyze the importance of different admixture factors to the density index and strength index of the foam lightweight soil, and a systematic evaluation is performed. Finally, based on the experimental results of the mix ratio, the intersection analysis method of the density and strength dual index slopes is used to obtain the appropriate mix ratio of the foam lightweight soil.

[0005] The above invention objectives of the present application are achieved through the following technical solutions:

[0006] A method for determining an appropriate mix ratio of foamed lightweight soil with high clay content for reconstruction and expansion of embankments on soft soil sections comprises the following steps:

[0007] Step 1: Improved critical density of foamed lightweight soil (ρ cr ) is determined by: according to the geotechnical parameters of each soil layer of the soft soil foundation obtained from the geotechnical engineering investigation data of the soft soil section, and assuming that the load on the foundation surface (f0) = the design value of the soft soil foundation bearing capacity (f), the initial calculation critical density (ρ'3) of the foam lightweight soil is calculated. According to the initial calculation critical density (ρ'3) of the foam lightweight soil and the design height of the embankment (h), the first verification foundation settlement (S1) is calculated. If the first verification foundation settlement (S1) is greater than the design required foundation settlement (S0), the initial calculation critical density (ρ'3) of the foam lightweight soil is taken as the critical density (ρ cr ) and reduce the initial calculated critical density (ρ'3) of the foam lightweight soil to obtain the second calculated critical density ρ″3. Then, according to the second calculated critical density ρ″3 and the embankment design height (h), calculate the second verification foundation settlement (S2). If the second verification foundation settlement (S2) is greater than the design required foundation settlement (S0), repeat the above steps to calculate the i-th verification foundation settlement (S i ) and compared with the foundation settlement required by the design (S0); if the foundation settlement calculated for the i-th time (S i ) is less than or equal to the foundation settlement required by the design (S0), then the first calculated critical density that meets the requirements (S i ) as the critical density (ρ cr ) to determine the improved critical density (ρ cr ).

[0008] Step 2: Determine the order of influence of dosage factors on strength and density of foamed lightweight soil: Consult the relevant information of improved soil, and obtain the median values ​​of the commonly used dosage ranges of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer in improved soil in turn as the medium dosage levels of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer, which are a 正2 、b 正2 、c 正2 and 正2 , cement, hydrogen peroxide, water-to-material ratio and foam stabilizer are graded downward and upward to take a low dosage level (a 正1、 b 正1 、c 正1 and 正1 ) and a high doping level (a 正3、 b 正3 、c 正3 and 正3 );

[0009] Then, according to the above four dosage factors and the data of low, medium and high dosage levels, an orthogonal test table (Table 1) was prepared. Table 1 is as follows:

[0010] Table 1 Orthogonal test table of 4 factors and 3 levels

[0011]

[0012] According to Table 1, 9 groups of foam lightweight soil cube test blocks were tested for density and unconfined compressive strength. The density of 3 foam lightweight soil cube parallel test blocks from test group 1 to test group 9 was measured respectively, and the average value was calculated to obtain the density value of each group of orthogonal tests: ρ 正1 , 正2 , 正3 …ρ 正9 ; The three foam lightweight soil cube parallel test blocks of test group 1 to test group 9 after density measurement were tested for unconfined compressive strength, and the average value was taken as the unconfined compressive strength test value σ of the orthogonal test of this group 正1 , σ 正2 , σ 正3 …σ 正9 ;

[0013] According to the density measurement results, the density of foam lightweight soil (ρ 正 ) to conduct range analysis and obtain the density range of each dosage factor: cement density range R' A , hydrogen peroxide density range R' B , water-to-material density extreme value R' C , foam stabilizer density extreme value R' D According to the strength test results, the compressive strength of foam lightweight soil (σ 正) to conduct range analysis and obtain the range value of compressive strength of each dosage factor: Cement compressive strength range value R″ A , hydrogen peroxide compressive strength extreme value R″ B , water-to-material ratio compressive strength extreme value R″ C , the extreme difference value of compressive strength of foam stabilizer R″ D ;

[0014] According to the density range and compressive strength range of each dosage factor, the weighted coefficient w′ of each dosage factor on the density of foam lightweight soil is calculated respectively. j The weighted coefficient w of the influence of and on the compressive strength of foam lightweight soil j ", that is, the density weight coefficients of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer are w' A 、w' B 、w' C 、w' D , and the compressive strength weight coefficient w″ of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer A , w″ B , w″ C , w″ D ; Then, the equal weighted coefficient method was used to calculate the effect of each dosage factor on the density of foam lightweight soil (ρ 正 ) and compressive strength (σ 正 )’s comprehensive influence coefficient w j , that is, the comprehensive influence coefficients of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer are w A 、w B 、w C 、w D According to the comprehensive influence coefficient, the order of influence of cement content, hydrogen peroxide content, water-to-material ratio and foam stabilizer on the compressive strength and density of foam lightweight soil is determined;

[0015] Step 3: Determine the appropriate mix ratio of foamed lightweight soil: Consult the relevant information of improved soil and obtain the usual cement dosage range a1-a in improved soil in sequence. n The median value of a n / 2 is taken as the medium cement content level, denoted as x a5 , that is, x a5 = an / 2, and use the gradient to select 4 low cement content levels x downward and upward respectively a1 、x a2 、x a3 、x a4 and 4 high cement content x a6 、x a7 、x a8 、x a9 ; Obtain the medium dosage level x of hydrogen peroxide, water-to-material ratio and foam stabilizer in foamed lightweight soilb5 、x c3 and x d4 , and the four low dosage levels of hydrogen peroxide were obtained by differential b1 、x b2 、x b3 、x b4 and 4 high doping levels x b6 、x b7 、x b8 、x b9 ; Water-to-material ratio 2 low dosage levels x c1 、x c2 and 3 high doping levels x c4 、x c5 、x c6 ; 4 low dosage levels of foam stabilizer x d1 、x d2 、x d3 、x d4 and 3 high doping levels x d6 、x d7 、x d8 ;

[0016] Step 4: According to the order of the comprehensive influence of the dosage factors obtained in step 2 from large to small: factor (K1), factor (K2), factor (K3), factor (K4), single factor tests are carried out from K1 to K4 in turn; factor (K1) is adjusted according to the dosage value a1-a n The control variable method is used to make the dosage values ​​of the other three factors take the median value b n / 2 、c n / 2 d n / 2 , design a number of geotechnical tests on the density and unconfined compressive strength of foam lightweight soil cube specimens, and find the critical density (ρ) closest to the foam lightweight soil based on the test results. cr ) of foam lightweight soil test density (ρ a ), and determine the unconfined compressive strength σ of the foam lightweight soil at this density according to the roadbed specification requirements a Whether it meets the requirements: If the unconfined compressive strength of the foam lightweight soil meets the requirements, the dosage value under this density is selected as the appropriate dosage value (a) of factor (K1); if the unconfined compressive strength does not meet the requirements of the roadbed specification, the dosage value of factor (K1) needs to be appropriately increased;

[0017] Step 5: Factor (K2) according to the dosage value b1-b n The dosage of factor (K1) is set to the appropriate dosage value (a) and the dosage values ​​of the other two factors are set to the median value c. n / 2 d n / 2, design a number of geotechnical tests on the density and unconfined compressive strength of foam lightweight soil cube specimens, and according to the test results, the density values ​​of each group of single factor tests of factor (K2) are recorded as ρ in sequence. b1 , b2 , b3 …ρ b9 , corresponding to the unconfined compressive strength test value of each group of tests, denoted as σ b1 , σ b2 , σ b3 …σ b9 The density value and the unconfined compressive strength test value are plotted into a point-line graph, and the density slope of each dosage value interval is calculated according to formula (1) as follows: The slopes of the unconfined compressive strength are Formula (1) is as follows: Where n is the test group number; if the experimental density index ρ in the interval bn >ρ cr +0.2(g / cm 3 ), then exclude this interval; sort the density slope and the unconfined compressive strength slope from large to small, and mark the intervals with the top three slopes; if the two slope intervals intersect, the dosage value is taken at the midpoint of the interval as the appropriate dosage value (b); if the two slope intervals are tangent, the dosage value is taken at the tangent point as the appropriate dosage value (b); if the two slope intervals are separated, select the test density (ρ b ) The dosage value at the minimum density value in the maximum interval of the slope of the curve is the appropriate dosage value (b), so as to obtain the appropriate dosage value (b) of the factor (K2);

[0018] Step 6: According to step 5, geotechnical tests and data analysis of the density and unconfined compressive strength of foam lightweight soil cube specimens are carried out on factors (K3) and (K4) in turn to obtain the appropriate dosage value of factor K3 (c) and the appropriate dosage value of factor K4 (d).

[0019] Step 7: Based on the appropriate mix ratio of foam lightweight soil determined in steps 5 and 6, geotechnical tests on the density and unconfined compressive strength of large-sized foam lightweight soil cube specimens are carried out to verify the feasibility of foam lightweight soil in actual engineering.

[0020] Preferably, in step 1, the specific calculation formula (2) of the load (f0) on the foundation surface is: f0=ρ1·h1+ρ2·h2+ρ3·h3+P; the specific calculation formula (3) of the designed filling height (h3) of the foamed lightweight soil is: h3=h-h1-h2; the specific calculation formula (4) of the initial calculated critical density (ρ'3) of the foamed lightweight soil is: ρ'3=(f-ρ1·h1-ρ2·h2-P) / h3;

[0021] In formula (2), formula (3) and formula (4), ρ1 is the density of the pavement structure material (kg / m 3 );ρ2 is the density of the upper embankment filler (kg / m 3 );ρ3 is the initial value of the critical density of foam lightweight soil (kg / m 3 ); h1 is the height of the pavement structure layer (m); h2 is the height of the upper embankment (m); h3 is the designed filling height of the foam lightweight soil (m); P is the pavement load of the road.

[0022] Preferably, in step 1, the foundation settlement (S i The specific calculation formula (5) is: In formula (5): S i is the i-th verification of foundation settlement (m), i = 1, 2, 3, 4; Δσ is the load applied by the roadbed (MPa), Δσ = ρ1·h1+ρ2·h2+ρ'3·h3+P; E is the elastic modulus of the foundation soil (MPa); h is the height of the embankment (m); C c is the compression index of foundation soil; e0 is the initial porosity of foundation soil; e is the final porosity of foundation soil.

[0023] Preferably, in step 1, each time the foundation settlement (S i ) is greater than the foundation settlement (S0) required by the design, the initial calculated critical density of the foam lightweight soil is reduced by 0.2 (g / cm 3 ).

[0024] Preferably, in step 2, the density of the foam lightweight soil cube test block and the geotechnical test of the unconfined compressive strength are measured, and the specific steps are as follows:

[0025] Step (1): For each group of tests, three foam lightweight soil cubes with a size of 100 mm × 100 mm × 100 mm are prepared according to the dosage level in Table 1 for parallel test. The density of the three parallel test blocks of test group 1 is measured, and the relative error of the density is calculated. If the relative error of the density of the three parallel test blocks is not greater than ±2%, the average value of the density of the three test blocks is taken as the density value of the group of tests; if the relative error of the density of the three parallel test blocks is greater than ±2%, it is necessary to re-prepare the sample for density test until the relative error of the three parallel test blocks is not greater than ±2%, and the average value of the density of the three test blocks is taken as the density value of the group of orthogonal tests;

[0026] Step (2): According to step (1), the density of three cubic parallel test blocks of foam lightweight soil in test groups 2 to 9 is measured, and the average value is calculated to obtain the density value of each group of orthogonal tests: ρ 正1 , 正2 ,正3 …ρ 正9 ;

[0027] Step (3): Perform unconfined compressive strength tests on the three cube parallel test blocks after the orthogonal test density determination in each group, and take the average value as the unconfined compressive strength test value of the orthogonal test group, which is denoted as σ 正1 , σ 正2 , σ 正3 …σ 正9 .

[0028] Preferably, in step 2, the weighted coefficient w′ of each dosage factor on the density of the foam lightweight soil is j The specific calculation formula (6) is: Weighted coefficient w of each dosage factor on the compressive strength of foam lightweight soil j The specific calculation formula (7) is: The comprehensive influence coefficient of each dosage factor on the density and compressive strength of foam lightweight soil w j The specific calculation formula (8) is: j =0.5*w′ j +0.5*w j ”; in formulas (6), (7), (8): w′ j is the density weight coefficient; R' j is the density range of each dosage factor; w j ” is the weighted coefficient of compressive strength; R j " is the extreme difference of compressive strength of each dosage factor; w j is the comprehensive influence coefficient; j is the dosage factors A, B, C, D; w′ j is the density weight coefficient of each dosage factor j; w j ” is the compressive strength weight coefficient of each dosage factor j.

[0029] Preferably, in step 2, the cement is added at a low level (a 正1 ) and a high doping level (a 正3 ) is 10%, hydrogen peroxide, water-to-material ratio and foam stabilizer are 0.1%, 0.05% and 0.2% respectively, and the low dosage level of hydrogen peroxide, water-to-material ratio and foam stabilizer is obtained (b 正1 、c 正1 and 正1 ) and high dosage levels (b 正3 、c 正3 and 正3 ).

[0030] Preferably, in step 3, the cement is taken at 4 low cement content levels x respectively downward and upward. a1、x a2 、x a3 、x a4 and 4 high cement content x a6 、x a7 、x a8 、x a9 , the difference used is 5%, that is, x a4 =x a5 -5%, x a3 =x a4 -5%, x a2 =x a3 -5%, x a1 =x a2 -5% and x a6 =x a5 +5%, x a7 =x a6 +5%, x a8 =x a7 +5%, x a9 =x a8 +5%; hydrogen peroxide, water-to-material ratio and foam stabilizer dosage level x b5 、x c3 and x d4 Using 0.05%, 0.05%, and 0.2% steps in sequence, we can obtain four low dosage levels of hydrogen peroxide x b1 、x b2 、x b3 、x b4 and 4 high doping levels x b6 、x b7 、x b8 、x b9 ; Water-to-material ratio 2 low dosage levels x c1 、x c2 and 3 high doping levels x c4 、x c5 、x c6 ; 4 low dosage levels of foam stabilizer x d1 、x d2 、x d3 、x d4 and 3 high doping levels x d6 、x d7 、x d8 .

[0031] Preferably, in step 7, the geotechnical test of density and unconfined compressive strength of large-sized foam lightweight soil cube test blocks is carried out in the following specific steps:

[0032] Step (1): According to the appropriate dosage values ​​of each factor determined in step 5 and step 6, three foam lightweight soil cubes with specifications of 500mm×500mm×500mm are respectively prepared for parallel test, and the density of the three parallel test blocks is measured, and the relative error of the density is calculated. If the relative error of the density of the three parallel test blocks is not greater than ±2%, the average value of the density of the three test blocks is taken as the density value of the group test; if the relative error of the density of the three parallel test blocks is greater than ±2%, it is necessary to re-prepare the sample for density test until the relative error of the three parallel test blocks is not greater than ±2%, and the average value of the density of the three test blocks is taken as the density value of the group test (ρ 模 );

[0033] Step (2): Perform unconfined compressive strength tests on the three parallel test blocks of each group of test density measurements, and take the average value as the unconfined compressive strength test value of the group of tests (σ 模 );

[0034] Step (3): Compare and analyze the density values ​​(ρ) obtained in step (1) and step (2) 模 ) and unconfined compressive strength test value (σ 模 ), if the density of foam lightweight soil (ρ 模 ) is not equal to the initial density of foam lightweight soil (ρ cr ), it is necessary to adjust the dosage factor (K1) that has the greatest impact on the physical properties of foam lightweight soil so that the large-scale simulation test results meet the requirements; if the compressive strength of the foam lightweight soil cube (σ 模 ) does not meet the requirements of the roadbed specification, the cement content needs to be appropriately increased; if the foam lightweight soil density (ρ 模 ) is equal to the initial density of foam lightweight soil (ρ cr ), and the cube compressive strength (σ 模 ) meets the requirements of roadbed specifications, it proves that this mix ratio is feasible in actual embankment engineering.

[0035] Compared with the prior art, the beneficial effects of the present invention are: a method for determining the appropriate mix ratio of foamed lightweight soil with a high clay content for the reconstruction and expansion of embankments in soft soil sections, which can solve the problem that the mix ratio of foamed lightweight soil fillers cannot be determined by theoretical calculation at present, and a comprehensive method is used to determine the appropriate mix ratio of foamed lightweight soil, ensuring that the foamed lightweight soil can meet the requirements of relevant roadbed specifications during roadbed construction while achieving the goals of cost savings and environmental protection.

[0036] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a dot-line graph of the density value and the unconfined compressive strength test value when the density slope interval of the factor (k2) in step 5 of the present invention intersects with the unconfined compressive strength slope interval;

[0038] Figure 2 It is a dot-line graph of density value and unconfined compressive strength test value when the density slope interval of factor (k2) in step 5 of the present invention is tangent to the unconfined compressive strength slope interval;

[0039] Figure 3 It is a dot-line graph of density value and unconfined compressive strength test value when the density slope interval of factor (k2) in step 5 of the present invention is separated from the unconfined compressive strength slope interval;

[0040] Figure 4 It is a dot-line graph of the density value of the water-to-material ratio factor and the unconfined compressive strength test value in the embodiment of the present invention;

[0041] Figure 5 It is a dot-line graph of cement factor density value and unconfined compressive strength test value in an embodiment of the present invention;

[0042] Figure 6 It is a dotted line graph of the density value of the foam stabilizer factor and the unconfined compressive strength test value in the embodiment of the present invention. DETAILED DESCRIPTION

[0043] The following is a description of exemplary embodiments of the present application in conjunction with the accompanying drawings, including various details of the embodiments of the present application to facilitate understanding, which should be considered as merely exemplary. Therefore, it should be recognized by those of ordinary skill in the art that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. Similarly, for the sake of clarity and conciseness, the description of well-known functions and structures is omitted in the following description.

[0044] It should be noted that the terms "first", "second", etc. in the present invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure.

[0045] In addition, the term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article, unless otherwise specified, generally means that the associated objects before and after are in an "or" relationship.

[0046] The following describes, with reference to the accompanying drawings, a method for determining a suitable mix ratio of foamed lightweight soil with a high clay content for reconstruction and expansion of embankments on soft soil sections of the present application.

[0047] The method for determining the appropriate mix ratio of foamed lightweight soil with high clay content for the reconstruction and expansion of embankments on soft soil sections includes the following steps:

[0048] Step 1: Improved critical density of foamed lightweight soil (ρ cr ) is determined by: according to the geotechnical parameters of each soil layer of the soft soil foundation obtained from the geotechnical engineering investigation data of the soft soil section, and assuming that the load on the foundation surface (f0) = the design value of the soft soil foundation bearing capacity (f), the initial calculation critical density (ρ'3) of the foam lightweight soil is calculated. According to the initial calculation critical density (ρ'3) of the foam lightweight soil and the design height of the embankment (h), the first verification foundation settlement (S1) is calculated. If the first verification foundation settlement (S1) is greater than the design required foundation settlement (S0), the initial calculation critical density (ρ'3) of the foam lightweight soil is taken as the critical density (ρ cr ) and reduce the initial calculated critical density (ρ'3) of the foam lightweight soil to obtain the second calculated critical density ρ″3. Then, according to the second calculated critical density ρ″3 and the embankment design height (h), calculate the second verification foundation settlement (S2). If the second verification foundation settlement (S2) is greater than the design required foundation settlement (S0), repeat the above steps to calculate the i-th verification foundation settlement (S i ) and compared with the foundation settlement required by the design (S0); if the foundation settlement calculated for the i-th time (S i ) is less than or equal to the foundation settlement required by the design (S0), then the first calculated critical density that meets the requirements (S i ) as the critical density (ρ cr ) to determine the improved critical density (ρ cr ).

[0049] Among them, in step 1, the specific calculation formula (2) of the load (f0) on the ground surface is: f0 = ρ1·h1+ρ2·h2+ρ3·h3+P; the specific calculation formula (3) of the design filling height (h3) of the foam lightweight soil is: h3 = h-h1-h2; the specific calculation formula (4) of the initial calculation critical density (ρ'3) of the foam lightweight soil is: ρ'3 = (f-ρ1·h1-ρ2·h2-P) / h3; in formula (2), formula (3) and formula (4): ρ1 is the density of the pavement structure layer material (kg / m 3 );ρ2 is the density of the upper embankment filler (kg / m 3 );ρ3 is the initial value of the critical density of foam lightweight soil (kg / m 3); h1 is the height of the pavement structure layer (m); h2 is the height of the upper embankment (m); h3 is the designed filling height of the foam lightweight soil (m); P is the pavement load of the road.

[0050] In step 1, the foundation settlement (S i The specific calculation formula (5) is: In formula (5): S i is the i-th verification of foundation settlement (m), i = 1, 2, 3, 4; Δσ is the load applied by the roadbed (MPa), Δσ = ρ1·h1+ρ2·h2+ρ'3·h3+P; E is the elastic modulus of the foundation soil (MPa); h is the height of the embankment (m); C c is the compression index of foundation soil; e0 is the initial porosity of foundation soil; e is the final porosity of foundation soil.

[0051] In step 1, each time the foundation settlement (S i ) is greater than the foundation settlement (S0) required by the design, the initial calculated critical density of the foam lightweight soil is reduced by 0.2 (g / cm 3 ).

[0052] It should be noted that if the fourth calculated foundation settlement (S4) is still greater than the design required foundation settlement (S0), according to existing experience, the foam improved critical density ρ obtained after the fifth calculated foundation settlement (S4) is cr It is likely to be lower than 0.8g / cm 3 , and because the critical density is lower than 0.8g / cm 3 It is difficult to fully ensure that the construction strength of foam lightweight soil meets the requirements of roadbed strength. Therefore, in this case, for the sake of engineering safety, it is not recommended to use foam lightweight soil as roadbed filling for the embankment of this soft soil foundation section.

[0053] Step 2: Determine the order of influence of dosage factors on strength and density of foamed lightweight soil: Consult the relevant information of improved soil, and obtain the median values ​​of the commonly used dosage ranges of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer in improved soil in turn as the medium dosage levels of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer, which are a 正2 、b 正2 、c 正2 and 正2 , cement, hydrogen peroxide, water-to-material ratio and foam stabilizer are graded downward and upward to take a low dosage level (a 正1、 b 正1 、c 正1 and 正1 ) and a high doping level (a 正3、 b 正3 、c 正3and 正3 );

[0054] Then, according to the above four dosage factors and the data of low, medium and high dosage levels, an orthogonal test table (Table 1) was prepared. Table 1 is as follows:

[0055] Table 14 Orthogonal test table of factor 3 level

[0056]

[0057]

[0058] According to Table 1, 9 groups of foam lightweight soil cube test blocks were tested for density and unconfined compressive strength. The density of 3 foam lightweight soil cube parallel test blocks from test group 1 to test group 9 was measured respectively, and the average value was calculated to obtain the density value of each group of orthogonal tests: ρ 正1 , 正2 , 正3 …ρ 正9 ; The three foam lightweight soil cube parallel test blocks of test group 1 to test group 9 after density measurement were tested for unconfined compressive strength, and the average value was taken as the unconfined compressive strength test value σ of the orthogonal test of this group 正1 , σ 正2 , σ 正3 …σ 正9 ;

[0059] According to the density measurement results, the density of foam lightweight soil (ρ 正 ) to conduct range analysis and obtain the density range of each dosage factor: cement density range R' A , hydrogen peroxide density range R' B , water-to-material density extreme value R' C , foam stabilizer density extreme value R' D According to the strength test results, the compressive strength of foam lightweight soil (σ 正 ) to conduct range analysis and obtain the range value of compressive strength of each dosage factor: Cement compressive strength range value R″ A , hydrogen peroxide compressive strength extreme value R″ B , water-to-material ratio compressive strength extreme value R″ C , the extreme difference value of compressive strength of foam stabilizer R″ D ;

[0060] According to the density range and compressive strength range of each dosage factor, the weighted coefficient w′ of each dosage factor on the density of foam lightweight soil is calculated respectively. j The weighted coefficient w of the influence of and on the compressive strength of foam lightweight soil j ", that is, the density weight coefficients of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer are w'A 、w' B 、w' C 、w' D , and the compressive strength weight coefficient w″ of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer A , w″ B , w″ C , w″ D ; Then, the equal weighted coefficient method was used to calculate the effect of each dosage factor on the density of foam lightweight soil (ρ 正 ) and compressive strength (σ 正 )’s comprehensive influence coefficient w j , that is, the comprehensive influence coefficients of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer are w A 、w B 、w C 、w D According to the comprehensive influence coefficient, the order of influence of the four dosage factors of cement dosage, hydrogen peroxide dosage, water-to-material ratio and foam stabilizer on the compressive strength and density of foam lightweight soil is determined.

[0061] Specifically, in step 2, the density of the foam lightweight soil cube specimen is measured and the geotechnical test of the unconfined compressive strength is performed. The specific steps are as follows:

[0062] Step (1): For each group of tests, three foam lightweight soil cubes with a size of 100 mm × 100 mm × 100 mm are prepared according to the dosage level in Table 1 for parallel test. The density of the three parallel test blocks of test group 1 is measured, and the relative error of the density is calculated. If the relative error of the density of the three parallel test blocks is not greater than ±2%, the average value of the density of the three test blocks is taken as the density value of the group of tests; if the relative error of the density of the three parallel test blocks is greater than ±2%, it is necessary to re-prepare the sample for density test until the relative error of the three parallel test blocks is not greater than ±2%, and the average value of the density of the three test blocks is taken as the density value of the group of orthogonal tests;

[0063] Step (2): According to step (1), the density of three cubic parallel test blocks of foam lightweight soil in test groups 2 to 9 is measured, and the average value is calculated to obtain the density value of each group of orthogonal tests: ρ 正1 , 正2 , 正3 …ρ 正9 ;

[0064] Step (3): Perform unconfined compressive strength tests on the three cube parallel test blocks after the orthogonal test density determination in each group, and take the average value as the unconfined compressive strength test value of the orthogonal test group, which is denoted as σ 正1 , σ 正2 , σ 正3 …σ正9 .

[0065] Among them, in step 2, the weighted coefficient w′ of each dosage factor on the density of foam lightweight soil is j The specific calculation formula (6) is: Weighted coefficient w of each dosage factor on the compressive strength of foam lightweight soil j The specific calculation formula (7) is: The comprehensive influence coefficient of each dosage factor on the density and compressive strength of foam lightweight soil w j The specific calculation formula (8) is: j =0.5*w′ j +0.5*w j ”; in formulas (6), (7), (8): w′ j is the density weight coefficient; R' j is the density range of each dosage factor; w j ” is the weighted coefficient of compressive strength; R j " is the extreme difference of compressive strength of each dosage factor; w j is the comprehensive influence coefficient; j is the dosage factors A, B, C, D; w′ j is the density weight coefficient of each dosage factor j; w j ” is the compressive strength weight coefficient of each dosage factor j.

[0066] And in step 2, cement is taken to a low content level (a 正1 ) and a high doping level (a 正3 ) is 10%, hydrogen peroxide, water-to-material ratio and foam stabilizer are 0.1%, 0.05% and 0.2% respectively, and the low dosage level of hydrogen peroxide, water-to-material ratio and foam stabilizer is obtained (b 正1 、c 正1 and 正1 ) and high dosage levels (b 正3 、c 正3 and 正3 ).

[0067] Step 3: Determine the appropriate mix ratio of foamed lightweight soil: Consult the relevant information of improved soil and obtain the usual cement dosage range a1-a in improved soil in sequence. n The median value of a n / 2 is taken as the medium cement content level, denoted as x a5 , that is, x a5 = an / 2, and take 4 low cement content levels x downward and upward respectively by using the gradient a1 、x a2 、x a3 、x a4and 4 high cement content x a6 、x a7 、x a8 、x a9 ; Obtain the medium dosage level x of hydrogen peroxide, water-to-material ratio and foam stabilizer in foamed lightweight soil b5 、x c3 and x d4 , and the four low dosage levels of hydrogen peroxide were obtained by differential b1 、x b2 、x b3 、x b4 and 4 high doping levels x b6 、x b7 、x b8 、x b9 ; Water-to-material ratio 2 low dosage levels x c1 、x c2 and 3 high doping levels x c4 、x c5 、x c6 ; 4 low dosage levels of foam stabilizer x d1 、x d2 、x d3 、x d4 and 3 high doping levels x d6 、x d7 、x d8 ;

[0068] Specifically, in step 3, cement is taken at 4 low cement content levels x downward and upward respectively. a1 、x a2 、x a3 、x a4 and 4 high cement content x a6 、x a7 、x a8 、x a9 , the difference used is 5%, that is, x a4 =x a5 -5%, x a3 =x a4 -5%, x a2 =x a3 -5%, x a1 =x a2 -5% and x a6 =x a5 +5%, x a7 =x a6 +5%, x a8 =x a7 +5%, x a9 =x a8 +5%; hydrogen peroxide, water-to-material ratio and foam stabilizer dosage level x b5 、x c3and x d4 Using 0.05%, 0.05%, and 0.2% steps in sequence, we can obtain four low dosage levels of hydrogen peroxide x b1 、x b2 、x b3 、x b4 and 4 high doping levels x b6 、x b7 、x b8 、x b9 ; Water-to-material ratio 2 low dosage levels x c1 、x c2 and 3 high doping levels x c4 、x c5 、x c6 ; 4 low dosage levels of foam stabilizer x d1 、x d2 、x d3 、x d4 and 3 high doping levels x d6 、x d7 、x d8 .

[0069] Step 4: According to the order of the comprehensive influence of the dosage factors obtained in step 2 from large to small: factor (K1), factor (K2), factor (K3), factor (K4), single factor tests are carried out from K1 to K4 in turn; factor (K1) is adjusted according to the dosage value a1-a n The control variable method is used to make the dosage values ​​of the other three factors take the median value b n / 2 、c n / 2 d n / 2 , design a number of geotechnical tests on the density and unconfined compressive strength of foam lightweight soil cube specimens, and find the critical density (ρ) closest to the foam lightweight soil based on the test results. cr ) of foam lightweight soil test density (ρ a ), and determine the unconfined compressive strength σ of the foam lightweight soil at this density according to the roadbed specification requirements a Whether it meets the requirements: If the unconfined compressive strength of the foam lightweight soil meets the requirements, the dosage value under this density is selected as the appropriate dosage value (a) of factor (K1); if the unconfined compressive strength does not meet the requirements of the roadbed specification, the dosage value of factor (K1) needs to be appropriately increased;

[0070] Step 5: Factor (K2) according to the dosage value b1-b n The dosage of factor (K1) is set to the appropriate dosage value (a) and the dosage values ​​of the other two factors are set to the median value c. n / 2 d n / 2 , design a number of geotechnical tests on the density and unconfined compressive strength of foam lightweight soil cube specimens, and according to the test results, the density values ​​of each group of single factor tests of factor (K2) are recorded as ρ in sequence.b1 , b2 , b3 …ρ b9 , corresponding to the unconfined compressive strength test value of each group of tests, denoted as σ b1 , σ b2 , σ b3 …σ b9 , and plot the density value and the unconfined compressive strength test value into a point-line graph, such as Figure 1 , Figure 2 and Figure 3 As shown, according to formula (1), the density slope of each dosage value interval is calculated in sequence as follows: The slopes of the unconfined compressive strength are Formula (1) is as follows: Where n is the test group number; if the experimental density index ρ in the interval bn >ρ cr +0.2(g / cm 3 ), then exclude this interval; sort the density slope and the unconfined compressive strength slope from large to small, and mark the intervals with the slope ranked in the top three; Figure 1 As shown in , if the two slope intervals intersect, the dosage value is taken at the midpoint of the interval as the appropriate dosage value (b); Figure 2 As shown in , if the two slope intervals are tangent, the dosage value is taken at the tangent point as the appropriate dosage value (b); Figure 3 As shown, if the two slope intervals are separated, the test density (ρ b ) The dosage value at the minimum density value in the maximum interval of the slope of the curve is the appropriate dosage value (b), so as to obtain the appropriate dosage value (b) of the factor (K2);

[0071] Step 6: According to step 5, geotechnical tests and data analysis of the density and unconfined compressive strength of foam lightweight soil cube specimens are carried out on factors (K3) and (K4) in turn to obtain the appropriate dosage value of factor K3 (c) and the appropriate dosage value of factor K4 (d).

[0072] Step 7: Based on the appropriate mix ratio of foam lightweight soil determined in steps 5 and 6, geotechnical tests on the density and unconfined compressive strength of large-sized foam lightweight soil cube specimens are carried out to verify the feasibility of foam lightweight soil in actual engineering.

[0073] Specifically, in step 7, the geotechnical test of density and unconfined compressive strength of large-sized foam lightweight soil cube specimens is carried out in the following steps:

[0074] Step (1): According to the appropriate dosage values ​​of each factor determined in step 5 and step 6, three foam lightweight soil cubes with specifications of 500mm×500mm×500mm are respectively prepared for parallel test, and the density of the three parallel test blocks is measured, and the relative error of the density is calculated. If the relative error of the density of the three parallel test blocks is not greater than ±2%, the average value of the density of the three test blocks is taken as the density value of the group test; if the relative error of the density of the three parallel test blocks is greater than ±2%, it is necessary to re-prepare the sample for density test until the relative error of the three parallel test blocks is not greater than ±2%, and the average value of the density of the three test blocks is taken as the density value of the group test (ρ 模 );

[0075] Step (2): Perform unconfined compressive strength tests on the three parallel test blocks of each group of test density measurements, and take the average value as the unconfined compressive strength test value of the group of tests (σ 模 );

[0076] Step (3): Compare and analyze the density values ​​(ρ) obtained in step (1) and step (2) 模 ) and unconfined compressive strength test value (σ 模 ), if the density of foam lightweight soil (ρ 模 ) is not equal to the initial density of foam lightweight soil (ρ cr ), it is necessary to adjust the dosage factor (K1) that has the greatest impact on the physical properties of foam lightweight soil so that the large-scale simulation test results meet the requirements; if the compressive strength of the foam lightweight soil cube (σ 模 ) does not meet the requirements of the roadbed specification, the cement content needs to be appropriately increased; if the foam lightweight soil density (ρ 模 ) is equal to the initial density of foam lightweight soil (ρ cr ), and the cube compressive strength (σ 模 ) meets the requirements of roadbed specifications, it proves that this mix ratio is feasible in actual embankment engineering.

[0077] Example:

[0078] This embodiment is to determine the appropriate mix ratio of foamed lightweight soil for the reconstruction and expansion of the embankment at a certain soft soil section.

[0079] 1. Determination of preliminary experimental indicators:

[0080] In this embodiment, the following parameters can be obtained from the geotechnical engineering investigation and design data of a soft soil section, as shown in Table 2:

[0081] Table 2

[0082]

[0083] According to the actual load on the soft soil foundation, the bearing capacity of the soft soil foundation (f0) can be calculated according to formula (2):

[0084] f0=ρ1·h1+ρ2·h2+ρ3·h3+P; (2)

[0085] In formula (2), f0 is the load on the foundation surface, f0≤f; ρ1 is the density of the pavement structure material (kg / m 3 ), taken as 2200kg / m 3 ; ρ2 is the density of the upper embankment filler (kg / m 3 ), taken as 2200kg / m 3 ; ρ3 is the initial value of the critical density of foam lightweight soil (kg / m 3 ); h1 is the height of the pavement structure layer (m), measured as 0.3m; h2 is the height of the upper embankment (m), measured as 1.5m; h3 is the designed filling height of the foam lightweight soil (m); P is the pavement load of the road, and the pavement load of ordinary roads is 15kN.

[0086] 2. The design height of the embankment in the soft soil section to be treated is measured as h = 5m. According to formula (3), the design filling height of the foam lightweight soil can be calculated as h3 = 3.2m;

[0087] h3=h-h1-h2 (3)

[0088] 3. Assuming that the load on the foundation surface (f0) = the design value of the soft soil foundation bearing capacity (f), and the filling height of the foam lightweight soil is 3.2m, calculate using formula (4):

[0089] ρ'3=(f-ρ1·h1-ρ2·h2-P) / h3 (4)

[0090] The maximum density (ρ'3) of foamed lightweight soil is ρ'3=1406kg / m 3 .

[0091] 4. It is necessary to verify whether the foundation settlement meets the requirements of the specification and substitute it into formula (5) to calculate:

[0092]

[0093] In formula (5), S is the foundation settlement (m); Δσ is the load applied by the roadbed (MPh), Δσ = ρ1·h1+ρ2·h2+ρ3·h3+P; E is the elastic modulus of the foundation soil (MPh); h is the height of the embankment (m); C c is the compression index of foundation soil; e0 is the initial porosity of foundation soil; e is the final porosity of foundation soil.

[0094] 5. Substituting into formula (5), the first calculated foundation settlement S1=5.8cm is obtained. The foundation settlement S0=5.5cm does not meet the design requirements. It is necessary to reduce the initial calculated critical density of the foam lightweight soil;

[0095] 6. Let the second calculation of critical density ρ″3=ρ'3-0.2=1.2(g / cm 3 ), the second critical density is calculated as ρ″3=1.2g / cm 3 Substituting into formula (5), the foundation settlement of the second verification (S2) is calculated, and S2 = 5.6 cm is obtained. The foundation settlement that does not meet the design requirements is S0 = 5.5 cm;

[0096] 7. Continue to calculate the critical density for the third time ρ″′3=ρ″′3-0.2=1.0(g / cm 3 ), the third critical density is calculated as ρ″′3=1.0g / cm 3 Substituting into formula (5), the foundation settlement of the third verification (S3) is calculated, and the settlement S = 5.4 cm is obtained. The foundation settlement that meets the design requirements is S0 = 5.5 cm;

[0097] 8. Take the three calculated critical density of foamed lightweight soil ρ″′3=1.0g / cm 3 is the critical density ρ cr .

[0098] 2. Determination of the order of influence of dosage factors on the strength and density of foam lightweight soil

[0099] The factors affecting the density and compressive strength of foam lightweight soil are cement dosage (A), hydrogen peroxide dosage (B), water-to-cement ratio (C) and foam stabilizer dosage (D). In order to effectively reduce the experimental amount and quickly obtain the order of influence of each dosage factor on the strength and density of foam lightweight soil, the orthogonal test with four factors and three levels and the weighted coefficient method of density and compressive strength were used for analysis.

[0100] 1. Select the cement dosage level: Consult the relevant information of improved soil to obtain the general cement dosage value in improved soil, and use it as the intermediate dosage, recorded as a 正2 = 30%, and take a low dosage (a 正1 ) and high dosage (a 正3 ), let a 正1 =a 正2 -10% = 20% and a 正3 =a 正2 +10% = 40%;

[0101] 2. Select the level of hydrogen peroxide dosage: Consult the relevant information of foam concrete and, based on existing experience, obtain the high dosage value of hydrogen peroxide in foamed lightweight soil.正3 =0.3%, let the content value b 正2 =b 正3 -0.1% = 0.2%, low dosage value b 正1 =b 正3 -0.2% = 0.1%;

[0102] 3. Select the water-to-material ratio level: Consult the relevant information on foam concrete and improved soil, and take the middle value of the water-to-material ratio as c 正2 and take a low doping amount (c 正1 ) and high dosage (c 正3 ), let c 正1 =c 正2 -0.05 and c 正3 =c 正2 +0.05;

[0103] 4. Select the dosage level of the foam stabilizer: Consult the relevant information of foam concrete to obtain the general dosage value of the foam stabilizer in the improved soil, and use it as the intermediate dosage (d 正2 ), and d 正2 =1%, and take a low dosage (d 正1 ) and high dosage (d 正3 ), let d 正1 =d 正2 -0.2% = 0.8% and d 正3 =d 正2 +0.2%=1.2%;

[0104] 5. Develop an orthogonal test table (Table 3);

[0105] Table 3 Orthogonal test table

[0106]

[0107]

[0108] 6. Carry out 9 groups of tests according to the orthogonal test table. For each group of tests, a 100mm×100mm×100mm cubic test block is made. The density ρ of the foam lightweight soil cubic test block of tests 1 to 9 is measured respectively. 正1 =1.415g / cm 3 , 正2 =1.051g / cm 3 , 正3 =0.76g / cm 3 , 正4 =1.122g / cm 3 , 正5 =1.053g / cm 3 , 正6 =0.912g / cm3 , 正7 =1.031g / cm 3 , 正8 =0.986g / cm 3 , 正9 =0.884g / cm 3 , and the unconfined compressive strength σ 正1 =805.15kPa,σ 正2 =327.25kPa, σ 正3 =114.15kPa,σ 正4 =689.15kPa,σ 正5 =517.25kPa,σ 正6 =713.42kPa, σ 正7 =803.02kPa,σ 正8 =805.25kPa,σ 正9 =500.16kPa,

[0109] 7. Orthogonal test to obtain the density of foam lightweight soil (ρ 正 ) to conduct range analysis and obtain the range value of each dosage factor: Cement dosage (A) range value R' A =0.062, hydrogen peroxide dosage (B) extreme value R' B =0.335, water-to-material ratio (C) extreme value R' C =0.154, the extreme value of the foam stabilizer dosage (D) R' D =0.159;

[0110] 8. The compressive strength of foam lightweight soil (σ 正 ) to conduct range analysis and obtain the range value of each dosage factor: Cement dosage (A) range value R″ A =296.46, hydrogen peroxide dosage (B) extreme value R″ B =323.20, water-to-material ratio (C) extreme value R″ C , = 287.29, the extreme value of the foam stabilizer dosage (D) R″ D =78.38;

[0111] 9. Using the weighted coefficient method, the density of foam lightweight soil (ρ 正 ) and compressive strength (σ 正 ) The order of influence. The extreme value R' calculated for the density of foam lightweight soil by the four dosage factors A , R' B , R' C , R' D Calculate the weight coefficient and get the weight coefficient w' according to formula (6): A=0.087, w' B =0.472, w' C =0.217, w' D =0.224;

[0112]

[0113] In formula (6): w′ j is the weighting coefficient, j is the dosage factors A, B, C, D; R' is the extreme value of the dosage of each factor.

[0114] 10. The range value R″ calculated for the compressive strength of foam lightweight soil using four dosage factors A , R″ B , R″ C , R″ D Calculate the weight coefficient and get the weight coefficient w″ according to formula (7) A =0.302, w″ BB =0.328, w″ C =0.291, w″ D =0.079, the specific calculation is as follows:

[0115]

[0116] In formula (7): w j ” is the weighting coefficient, j is the dosage factors A, B, C, D; R is the extreme value of the dosage of each factor.

[0117] 11. The weight coefficient w of cement content (A) can be obtained A =w' A +w″ A =0.389, weight coefficient w of hydrogen peroxide dosage (B) B =w' B +w″ B =0.8, weight coefficient w of water-to-material ratio (C) C =w' C +w″ C =0.508, weight coefficient w of foam stabilizer dosage (D) D =w' D +w″ D =0.303;

[0118] 12. Compare the size of each weight coefficient and get w B >w C >w A >w DThe order of the influence of dosage factors on the physical properties of foam lightweight soil is: hydrogen peroxide dosage (B) > water-to-material ratio (C) > cement dosage (A) > foam stabilizer dosage (D). Single factor experiments are carried out according to this order to gradually determine the appropriate dosage values ​​of the dosage factors.

[0119] 3. Determination of the appropriate mix ratio of foam lightweight soil

[0120] 1. In the above steps, the critical density of foamed lightweight soil (ρ cr ) and hydrogen peroxide dosage (B) have the greatest influence on the physical properties of foam lightweight soil. It is necessary to first conduct a single factor test on the hydrogen peroxide dosage (B) to determine the appropriate dosage value (a).

[0121] According to the existing experience, 9 dosage values ​​of hydrogen peroxide (B) are designed: a1 = 0.1%, a2 = 0.15%, a3 = 0.2% ... a9 = 0.5%. The other three dosage factors are taken as the median of the design range. The cement dosage is 30%, the water-to-material ratio is 0.55, and the foam stabilizer dosage is 0.8%. A 100mm×100mm×100mm cubic test block is made and its density ρ is tested. a1 =1.036,ρ a2 =0.982,

[0122] ρ a3 =0.957, ρ a4 =0.924, ρ a5 =0.872, ρ a6 =0.788,ρ a7 =0.724, ρ a8 =0.685,

[0123] ρ a9 =0.648(g / cm 3 ), and the unconfined compressive strength of the cube σ a1 =529.482,σ

[0124] a2 =402.256,σ a3 =298.435,σ a4 =253.452,σ a5 =224.254,σ a6 =182.245,

[0125] σ a7 =168.227,σ a8 =157.245,σ a9 =142.683 (kPa), according to the experimental results, the test density of foam lightweight soil ρ is found a1 =1.036 is close to the critical density of foam lightweight soil (ρcr ), and the unconfined compressive strength of foam lightweight soil at this density is a1 =529.482 kPa, which meets the requirements of the roadbed design specifications. Therefore, the appropriate amount of hydrogen peroxide (B) is selected as 0.1%.

[0126] 2. Select the water-to-material ratio (C) that ranks second in the weight coefficient order for single factor experiment to determine the appropriate dosage value (b).

[0127] According to the existing experience, 6 groups of single factor tests were conducted on the water-to-material ratio (C), with test numbers 1 to 6. The water-to-material ratio (C) values ​​were b1=0.45, b2=0.5, b3=0.55...b6=0.7. Among them, the appropriate dosage value a of hydrogen peroxide (B) was 0.1%, and the other two dosage factors were taken from the median of the design range. The cement dosage (A) was 30%, and the foam stabilizer dosage (D) was 0.8%. A 100mm×100mm×100mm cubic test block was made to test its density ρ b1 =1.278,ρ b2 =1.058,ρ b3 =0.907,ρ b4 =0.878,ρ b5 =0.854, ρ b6 =0.813(g / cm 3 ), and the unconfined compressive strength σ b1 =762.514,σ b2 =632.145,σ b3 =482.354,σ b4 =395.214,σ b5 =375.245,σ b6 =342.325 (kPa), and draw a point-line graph, and use the double index slope intersection method to analyze the appropriate dosage value (b).

[0128] The slope of density and compressive strength in each dosage value interval is calculated by formula (1), and the interval with the larger slope of density and compressive strength is marked. If the test density index ρ in the interval is b >ρ cr +0.2(g / cm 3 ), exclude this interval, and then select the appropriate dosage value;

[0129]

[0130] In formula (1): n is the test number;

[0131] For the cube compressive strength slope kσ b1 =2607.38, kσ b2=2995.82, kσ b3 =1742.8, kσ b4 =399.38, kσ b5 =658.4, for the density slope kρ b1 =4.4, kρ b2 =3.02, kρ b3 =0.58, kρ b4 =0.48, kρ b5 =0.82, mark the interval with larger slope between density and compressive strength, e.g. Figure 4 As shown, due to ρ b1 =1.278(g / bm 3 ) is greater than the critical density ρ of foam lightweight soil cr +0.2(g / cm 3 ), after excluding this point, it can be seen that the two intervals intersect between the water-to-material ratio of 0.5 and 0.55. The midpoint of this interval is selected, and the unconfined compressive strength σ of the midpoint of this interval is b中 =557.249kPa meets the requirements of roadbed specifications, so the appropriate value b of the water-to-material ratio (C) is 0.525.

[0132] 3. Select the cement content (A) with the third highest weight coefficient to conduct a single factor experiment to determine the appropriate content value (c).

[0133] According to the existing experience, 9 groups of single factor tests were conducted on the cement content (A), with test numbers 1 to 9. The cement content (A) was c1 = 10%, c2 = 15%, c3 = 20%...c9 = 50%. Among them, the appropriate value a of the hydrogen peroxide content (B) was 0.1%, the appropriate value b of the water-to-material ratio (C) was 0.525, and the remaining foam stabilizer content (D) was 0.8%. A 100mm×100mm×100mm cubic test block was made to test its density ρ c1 =1.524, ρ c2 =1.398,ρ c3 =1.294,ρ c4 =1.204,ρ c5 =1.056, ρ c6 =1.092,ρ c7 =1.097,ρ c8 =1.125,ρ c9 =1.142(g / cm 3 ), and the unconfined compressive strength σ c1 =324.158,σ c2 =376.215,σ c3 =444.339,σ c4 =495.215,σ c5=529.428,σ c6 =634.254,σ c7 =728.480,σ c8 =998.415,σ c9 =1277.674 (kPa), and draw a point-line graph, and use the double index slope intersection method to analyze the appropriate dosage value (c).

[0134] The slope of density and compressive strength in each dosage value interval is calculated by formula (9), and the interval with a larger slope of density and compressive strength is marked. If the test density index ρ in the interval is c >ρ cr +0.2(g / cm 3 ), exclude this interval, and then select the appropriate dosage value;

[0135]

[0136] Where: n---test number;

[0137] For the cube compressive strength slope kσ c1 =1041.14, kσ c2 =1362.48, kσ c3 =1017.52, kσ c4 =684.26, kσ c5 =2096.52, kσ c6 =1884.52, kσ c7 =5398.7, kσ c8 =5585.18, for the density slope we have kρ c1 =2.52, kρ c2 =2.08, kρ c3 =1.80, kρ c4 =2.96, kρ c5 =0.72, kρ c6 =0.1, kρ c7 =0.56, kρ c8 =0.34, mark the interval with larger slope between density and compressive strength, e.g. Figure 5 As shown, due to ρ c1 =1.524, ρ c2 =1.398,ρ c3 =1.294(g / cm 3 ) are greater than the critical density ρ of foam lightweight soil cr +0.2(g / cm 3 ), after excluding this interval, it can be seen that the two intervals intersect at the cement content of 30%, and the unconfined compressive strength σ c5=529.428kPa meets the requirements of roadbed specifications, so the appropriate cement content (A) value c is 30%.

[0138] 4. Select the foam stabilizer dosage (D) with the smallest weight coefficient, and conduct 8 groups of single factor experiments on the foam stabilizer dosage (D), with the test numbers 1 to 8. According to existing experience, the foam stabilizer dosage (D) takes values ​​of d1 = 0%, d2 = 0.2%, d3 = 0.4%...d8 = 1.4%, among which the appropriate value a of hydrogen peroxide dosage (B) is 0.1%, the appropriate value b of water-to-material ratio (C) is 0.525, and the appropriate value c of cement dosage (A) is 30%. Make a 100mm×100mm×100mm cubic test block and test its density ρ d1 =1.524, ρ d2 =1.501,ρ d3 =1.425, ρ d4 =1.324,ρ d5 =1.128,ρ d6 =1.016,ρ d7 =0.894,ρ d8 =0.882(g / cm 3 ), and the unconfined compressive strength σ d1 =923.742,σ d2 =878.548,σ d3 =702.245,σ d4 =600.145,σ d5 =568.214,σ d6 =548.274,σ d7 =350.142,σ d8 =212.247 (kPa), and draw a point-line graph, and use the double index slope intersection method to analyze the appropriate dosage value (d).

[0139] The slope of density and compressive strength in each dosage value interval is calculated by formula (10), and the interval with a larger slope of density and compressive strength is marked. If the test density index ρ in the interval is d >ρ cr +0.2(g / cm 3 ), exclude this interval, and then select the appropriate dosage value;

[0140]

[0141] In formula (10): n is the test number;

[0142] For the cube compressive strength slope kσ d1 =225.97, kσ d2 =881.51, kσd3 =510.5, kσ d4 =159.65, kσ d5 =99.7, kσ d6 =990.66, kσ d7 =689.47, for the density slope kρ d1 =0.12, kρ d2 =0.38, kρ d3 =0.51, kρ d4 =0.98, kρ d5 =0.56, kρ d6 =0.61, kρ d7 = 0.06, mark the interval with larger slope between density and compressive strength, such as Figure 6 As shown, due to ρ d2 =1.501,ρ d3 =1.425,ρ d4 =1.324(g / cm 3 ) are greater than the critical density ρ of foam lightweight soil cr +0.2(g / cm 3 ), after excluding this interval, it can be seen that the two intervals intersect between 1.0% and 1.2% of the foam stabilizer dosage. The midpoint of this interval is selected, and the unconfined compressive strength σ d中 =449.208kPa meets the requirements of roadbed specifications, so the appropriate value d of the foam stabilizer dosage (D) is 1.1%.

[0143] 5. After comprehensive analysis, it can be concluded that the appropriate value c of cement content (A) in the foam lightweight soil mix is ​​30%, the appropriate value a of hydrogen peroxide content (B) is 0.1%, the appropriate value b of water-to-material ratio (C) is 0.525, and the appropriate value d of foam stabilizer content (D) is 1.1%.

[0144] 4. After finding the appropriate mix ratio of foam lightweight soil according to the above method, a large-scale simulation test is required for this mix ratio. According to the mix ratio, the appropriate value c of cement content (A) is 30%, the appropriate value a of hydrogen peroxide content (B) is 0.1%, the appropriate value b of water-to-material ratio (C) is 0.525, and the appropriate value d of foam stabilizer content (D) is 1.1%. A 100cm×100cm×100cm cubic model is made. After curing according to the specifications, its density ρ is tested. 模 =1.056g / cm 3 , unconfined cube compressive strength σ 模 =559.428 kPa, which meets the test density of large-scale foam lightweight soil model (ρ 模 ) is close to the initial density of foam lightweight soil (ρ cr), and the unconfined cube compressive strength meets the requirements of the roadbed specification, which proves that this mix ratio is feasible in actual embankment engineering and also provides a certain reference value for on-site process tests.

[0145] The above specific implementations do not constitute a limitation on the protection scope of this application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of this application should be included in the protection scope of this application.

Claims

1. A method for determining the appropriate mix ratio of high clay content foamed lightweight soil for embankment reconstruction and expansion on soft soil sections, characterized in that: The steps include: Step 1: Improved critical density of foamed lightweight soil (ρ cr ) is determined by: according to the geotechnical parameters of each soil layer of the soft soil foundation obtained from the geotechnical engineering investigation data of the soft soil section, and assuming that the load on the foundation surface (f0) = the design value of the soft soil foundation bearing capacity (f), the initial calculation critical density (ρ'3) of the foam lightweight soil is calculated. According to the initial calculation critical density (ρ'3) of the foam lightweight soil and the design height of the embankment (h), the first verification foundation settlement (S1) is calculated. If the first verification foundation settlement (S1) is greater than the design required foundation settlement (S0), the initial calculation critical density (ρ'3) of the foam lightweight soil is taken as the critical density (ρ cr ) and reduce the initial calculated critical density (ρ'3) of the foam lightweight soil to obtain the second calculated critical density ρ'3', and then calculate the second verification foundation settlement (S2) based on the second calculated critical density ρ'3' and the embankment design height (h). If the second verification foundation settlement (S2) is greater than the design required foundation settlement (S0), repeat the above steps to calculate the i-th verification foundation settlement (S i ) and compared with the foundation settlement (S0) required by the design; If the foundation settlement (S i ) is less than or equal to the foundation settlement required by the design (S0), then the first calculated critical density that meets the requirements (S i ) as the critical density (ρ cr ) to determine the improved critical density (ρ cr ). Step 2: Determine the order of influence of dosage factors on strength and density of foamed lightweight soil: Consult the relevant information of improved soil, and obtain the median values ​​of the commonly used dosage ranges of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer in improved soil in turn as the medium dosage levels of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer, which are a 正2 、b 正2 、c 正2 and 正2 , cement, hydrogen peroxide, water-to-material ratio and foam stabilizer are graded downward and upward to take a low dosage level (a 正1 、b 正1 、c 正1 and 正1 ) and a high doping level (a 正3 、b 正3 、c 正3 and 正3 ); Then, according to the above four dosage factors and the data of low, medium and high dosage levels, an orthogonal test table (Table 1) was prepared. Table 1 is as follows: Table 14 Orthogonal test table of factor 3 level According to Table 1, 9 groups of foam lightweight soil cube test blocks were tested for density and unconfined compressive strength. The density of 3 foam lightweight soil cube parallel test blocks from test group 1 to test group 9 was measured respectively, and the average value was calculated to obtain the density value of each group of orthogonal tests: ρ 正1 , 正2 , 正3 …ρ 正9 ; The three foam lightweight soil cube parallel test blocks of test group 1 to test group 9 after density measurement were tested for unconfined compressive strength, and the average value was taken as the unconfined compressive strength test value σ of the orthogonal test of this group 正1 , σ 正2 , σ 正3 …σ 正9 ; According to the density measurement results, the density of foam lightweight soil (ρ 正 ) to conduct range analysis and obtain the density range of each dosage factor: cement density range R' A , hydrogen peroxide density range R' B , water-to-material density extreme value R' C , foam stabilizer density extreme value R' D According to the strength test results, the compressive strength of foam lightweight soil (σ 正 ) to conduct range analysis and obtain the range value of compressive strength of each dosage factor: Cement compressive strength range value R' A ' A , hydrogen peroxide compressive strength extreme value R' B ', Extreme value of compressive strength of water-to-material ratio R' C ', Extreme value of compressive strength of foam stabilizer R' D ' D ; According to the density range and compressive strength range of each dosage factor, the weighted coefficient w of each dosage factor on the density of foam lightweight soil is calculated respectively. j ' and the weighted coefficient w of the influence on the compressive strength of foam lightweight soil j ", that is, the density weight coefficients of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer are w' A 、w' B 、w' C 、w' D , and the compressive strength weight coefficient w' of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer A ', w' B ', w' C ', w' D ' D ; Then, the equal weighted coefficient method was used to calculate the effect of each dosage factor on the density of foam lightweight soil (ρ 正 ) and compressive strength (σ 正 )’s comprehensive influence coefficient w j , that is, the comprehensive influence coefficients of cement, hydrogen peroxide, water-to-material ratio and foam stabilizer are w A 、w B 、w C 、w D According to the comprehensive influence coefficient, the order of influence of cement content, hydrogen peroxide content, water-to-material ratio and foam stabilizer on the compressive strength and density of foam lightweight soil is determined; Step 3: Determine the appropriate mix ratio of foamed lightweight soil: Consult the relevant information of improved soil and obtain the usual cement dosage range a1-a in improved soil in sequence. n The median value of a n / 2 is taken as the medium cement content level, denoted as x a5 , that is, x a5 = an / 2, and take 4 low cement content levels x downward and upward respectively by using the gradient a1 、x a2 、x a3 、x a4 and 4 high cement content x a6 、x a7 、x a8 、x a9 ; Obtain the medium dosage level x of hydrogen peroxide, water-to-material ratio and foam stabilizer in foamed lightweight soil b5 、x c3 and x d4 , and the four low dosage levels of hydrogen peroxide were obtained by differential b1 、x b2 、x b3 、x b4 and 4 high doping levels x b6 、x b7 、x b8 、x b9 ; Water-to-material ratio 2 low dosage levels x c1 、x c2 and 3 high doping levels x c4 、x c5 、x c6 ; 4 low dosage levels of foam stabilizer x d1 、x d2 、x d3 、x d4 and 3 high doping levels x d6 、x d7 、x d8 ; Step 4: According to the order of the comprehensive influence of the dosage factors obtained in step 2 from large to small: factor (K1), factor (K2), factor (K3), factor (K4), single factor tests are carried out from K1 to K4 in turn; factor (K1) is adjusted according to the dosage value a1-a n The control variable method is used to make the dosage values ​​of the other three factors take the median value b n / 2 、c n / 2 d n / 2 , design a number of geotechnical tests on the density and unconfined compressive strength of foam lightweight soil cube specimens, and find the critical density (ρ) closest to the foam lightweight soil based on the test results. cr ) of foam lightweight soil test density (ρ a ), and determine the unconfined compressive strength σ of the foam lightweight soil at this density according to the roadbed specification requirements a Whether it meets the requirements: If the unconfined compressive strength of the foam lightweight soil meets the requirements, the dosage value under this density is selected as the appropriate dosage value (a) of factor (K1); if the unconfined compressive strength does not meet the requirements of the roadbed specification, the dosage value of factor (K1) needs to be appropriately increased; Step 5: Factor (K2) according to the dosage value b1-b n The dosage of factor (K1) is set to the appropriate dosage value (a) and the dosage values ​​of the other two factors are set to the median value c. n / 2 d n / 2 , design a number of geotechnical tests on the density and unconfined compressive strength of foam lightweight soil cube specimens, and according to the test results, the density values ​​of each group of single factor tests of factor (K2) are recorded as ρ in sequence. b1 , b2 , b3 …ρ b9 , corresponding to the unconfined compressive strength test value of each group of tests, denoted as σ b1 , σ b2 , σ b3 …σ b9 The density value and the unconfined compressive strength test value are plotted into a point-line graph, and the density slope of each dosage value interval is calculated according to formula (1) as k ρ1 , k ρ2 , k ρ3 …k ρ8 The slope of the unconfined compressive strength is k σ1 , k σ2 , k σ3 …k σ8 , formula (1) is as follows: Where n is the test group number; if the experimental density index ρ in the interval bn >ρ cr +0.2(g / cm 3 ), then exclude this interval; sort the density slope and the unconfined compressive strength slope from large to small, and mark the intervals with the top three slopes; if the two slope intervals intersect, the dosage value is taken at the midpoint of the interval as the appropriate dosage value (b); if the two slope intervals are tangent, the dosage value is taken at the tangent point as the appropriate dosage value (b); if the two slope intervals are separated, select the test density (ρ b ) The dosage value at the minimum density value in the maximum interval of the slope of the curve is the appropriate dosage value (b), so as to obtain the appropriate dosage value (b) of the factor (K2); Step 6: According to step 5, geotechnical tests and data analysis of the density and unconfined compressive strength of foam lightweight soil cube specimens are carried out on factors (K3) and (K4) in turn to obtain the appropriate dosage value of factor K3 (c) and the appropriate dosage value of factor K4 (d). Step 7: Based on the appropriate mix ratio of foam lightweight soil determined in steps 5 and 6, geotechnical tests on the density and unconfined compressive strength of large-sized foam lightweight soil cube specimens are carried out to verify the feasibility of foam lightweight soil in actual engineering.

2. A method for determining an appropriate mix ratio of high clay content foamed lightweight soil for embankment reconstruction and expansion of soft soil sections as claimed in claim 1, characterized in that: In step 1, the specific calculation formula (2) of the load (f0) on the foundation surface is: f0 = ρ1·h1+ρ2·h2+ρ3·h3+P; the specific calculation formula (3) of the design filling height (h3) of the foam lightweight soil is: h3 = h-h1-h2; the specific calculation formula (4) of the initial calculation critical density (ρ'3) of the foam lightweight soil is: ρ'3 = (f-ρ1·h1-ρ2·h2-P) / h3; In formula (2), formula (3) and formula (4), ρ1 is the density of the pavement structure material (kg / m 3 );ρ2 is the density of the upper embankment filler (kg / m 3 );ρ3 is the initial value of the critical density of foam lightweight soil (kg / m 3 ); h1 is the height of the pavement structure layer (m); h2 is the height of the upper embankment (m); h3 is the designed filling height of the foam lightweight soil (m); P is the pavement load of the road.

3. The method for determining the suitable mix ratio of high clay content foamed lightweight soil for embankment reconstruction and expansion of soft soil section as claimed in claim 1, characterized in that: In step 1, the foundation settlement (S i The specific calculation formula (5) is: In formula (5): S i is the i-th verification of foundation settlement (m), i = 1, 2, 3, 4; Δσ is the load applied by the roadbed (MPa), Δσ = ρ1·h1+ρ2·h2+ρ'3·h3+P; E is the elastic modulus of the foundation soil (MPa); h is the height of the embankment (m); C c is the compression index of foundation soil; e0 is the initial porosity of foundation soil; e is the final porosity of foundation soil.

4. The method for determining the suitable mix ratio of high clay content foamed lightweight soil for embankment reconstruction and expansion of soft soil section as claimed in claim 1, characterized in that: In step 1, each time the foundation settlement (S i ) is greater than the foundation settlement (S0) required by the design, the initial calculated critical density of the foam lightweight soil is reduced by 0.2 (g / cm 3 ).

5. The method for determining the suitable mix ratio of high clay content foamed lightweight soil for embankment reconstruction and expansion of soft soil section as claimed in claim 1, characterized in that: In step 2, the density of the foam lightweight soil cube specimen is determined and the geotechnical test of the unconfined compressive strength is carried out. The specific steps are as follows: Step (1): For each group of tests, three foam lightweight soil cubes with a size of 100 mm × 100 mm × 100 mm are prepared according to the dosage level in Table 1 for parallel test. The density of the three parallel test blocks of test group 1 is measured, and the relative error of the density is calculated. If the relative error of the density of the three parallel test blocks is not greater than ±2%, the average value of the density of the three test blocks is taken as the density value of the group of tests; if the relative error of the density of the three parallel test blocks is greater than ±2%, it is necessary to re-prepare the sample for density test until the relative error of the three parallel test blocks is not greater than ±2%, and the average value of the density of the three test blocks is taken as the density value of the group of orthogonal tests; Step (2): According to step (1), the density of three cubic parallel test blocks of foam lightweight soil in test groups 2 to 9 is measured, and the average value is calculated to obtain the density value of each group of orthogonal tests: ρ 正1 , 正2 , 正3 …ρ 正9 ; Step (3): Perform unconfined compressive strength tests on the three cube parallel test blocks after the orthogonal test density determination in each group, and take the average value as the unconfined compressive strength test value of the orthogonal test group, which is denoted as σ 正1 , σ 正2 , σ 正3 …σ 正9 .

6. The method for determining the appropriate mix ratio of high clay content foamed lightweight soil for embankment reconstruction and expansion of soft soil sections as claimed in claim 1, characterized in that: In step 2, the weighted coefficient w of each dosage factor on the density of foam lightweight soil is j The specific calculation formula (6) is: Weighted coefficient w of each dosage factor on the compressive strength of foam lightweight soil j The specific calculation formula (7) is: The comprehensive influence coefficient w of each dosage factor on the density and compressive strength of foam lightweight soil j The specific calculation formula (8) is: j =0.5*w j '+0.5*w j "; in formulas (6), (7), (8): w j ' is the density weight coefficient; R' j is the density range of each dosage factor; w j ” is the weighted coefficient of compressive strength; R j " is the extreme difference of compressive strength of each dosage factor; w j is the comprehensive influence coefficient; j is the dosage factors A, B, C, D; w j ' is the density weight coefficient of each dosage factor j; w j ” is the compressive strength weight coefficient of each dosage factor j.

7. The method for determining the suitable mix ratio of high clay content foamed lightweight soil for embankment reconstruction and expansion of soft soil section as claimed in claim 1, characterized in that: In step 2, cement is taken to a low level (a 正1 ) and a high doping level (a 正3 ) is 10%, hydrogen peroxide, water-to-material ratio and foam stabilizer are 0.1%, 0.05% and 0.2% respectively, and the low dosage level of hydrogen peroxide, water-to-material ratio and foam stabilizer is obtained (b 正1 、c 正1 and 正1 ) and high dosage levels (b 正3 、c 正3 and 正3 ).

8. The method for determining the appropriate mix ratio of high clay content foamed lightweight soil for embankment reconstruction and expansion of soft soil sections as claimed in claim 1, characterized in that: In step 3, cement is taken to four low cement content levels x downward and upward respectively. a1 、x a2 、x a3 、x a4 and 4 high cement content x a6 、x a7 、x a8 、x a9 , the difference used is 5%, that is, x a4 =x a5 -5%, x a3 =x a4 -5%, x a2 =x a3 -5%, x a1 =x a2 -5% and x a6 =x a5 +5%, x a7 =x a6 +5%, x a8 =x a7 +5%, x a9 =x a8 +5%; the medium dosage level of hydrogen peroxide, water-to-material ratio and foam stabilizer x b5 、x c3 and x d4 Using 0.05%, 0.05%, and 0.2% steps in sequence, we can obtain four low dosage levels of hydrogen peroxide x b1 、x b2 、x b3 、x b4 and 4 high doping levels x b6 、x b7 、x b8 、x b9 ; Water-to-material ratio 2 low dosage levels x c1 、x c2 and 3 high doping levels x c4 、x c5 、x c6 ; 4 low dosage levels of foam stabilizer x d1 、x d2 、x d3 、x d4 and 3 high doping levels x d6 、x d7 、x d8 .

9. The method for determining the appropriate mix ratio of high clay content foamed lightweight soil for embankment reconstruction and expansion of soft soil section as claimed in claim 1, characterized in that: In step 7, the geotechnical test of density and unconfined compressive strength of large-sized foam lightweight soil cube specimens is carried out as follows: Step (1): According to the appropriate dosage values ​​of each factor determined in step 5 and step 6, three foam lightweight soil cubes with specifications of 500mm×500mm×500mm are respectively prepared for parallel test, and the density of the three parallel test blocks is measured, and the relative error of the density is calculated. If the relative error of the density of the three parallel test blocks is not greater than ±2%, the average value of the density of the three test blocks is taken as the density value of the group test; if the relative error of the density of the three parallel test blocks is greater than ±2%, it is necessary to re-prepare the sample for density test until the relative error of the three parallel test blocks is not greater than ±2%, and the average value of the density of the three test blocks is taken as the density value of the group test (ρ 模 ); Step (2): Perform unconfined compressive strength tests on the three parallel test blocks of each group of test density measurements, and take the average value as the unconfined compressive strength test value of the group of tests (σ 模 ); Step (3): Compare and analyze the density values ​​(ρ) obtained in step (1) and step (2) 模 ) and unconfined compressive strength test value (σ 模 ), if the density of foam lightweight soil (ρ 模 ) is not equal to the initial density of foam lightweight soil (ρ cr ), it is necessary to adjust the dosage factor (K1) that has the greatest impact on the physical properties of foam lightweight soil so that the large-scale simulation test results meet the requirements; if the compressive strength of the foam lightweight soil cube (σ 模 ) does not meet the requirements of the roadbed specification, the cement content needs to be appropriately increased; if the foam lightweight soil density (ρ 模 ) is equal to the initial density of foam lightweight soil (ρ cr ), and the cube compressive strength (σ 模 ) meets the requirements of roadbed specifications, it proves that this mix ratio is feasible in actual embankment engineering.

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