Optimization design method and system of low-carbon cementitious material water-rich soil layer smw method pile

Abstract

The application discloses a low-carbon cementitious material water-rich powder soil layer SMW method pile optimization design method and system, and belongs to the technical field of geotechnical engineering and green building materials. The method comprises the following steps: establishing a supporting numerical model; determining the time-varying law of soil parameters and low-carbon material strength; initially selecting the arrangement and spacing of profiled steel; performing excavation simulation of the time-varying characteristics of the coupling material; establishing a database through parameterized analysis; quantifying the parameter influence weight by sensitivity analysis; determining the optimal supporting parameters through multi-objective optimization based on the weight; and according to the optimization results, the construction window is inverted, and the material ratio is iteratively adjusted until the material, structure and process are completely matched. The system comprises corresponding function modules. The application realizes the deep cooperation of material, design and construction, solves the contradiction between early slow setting and late high strength of the SMW method pile in the water-rich powder soil layer, ensures safety, and significantly reduces carbon emission and cost.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering support and green building materials, and in particular to an optimized design method and system for SMW piles in water-rich silty soil strata using low-carbon cementitious materials. This method achieves simultaneous optimization of support structure design and material performance through deep collaboration between numerical simulation and material research and development, in order to solve the safety, economic and environmental challenges faced during construction in water-rich soft strata. Background Technology

[0002] SMW (Soil Mixing Method) piles, a deep foundation pit support system integrating soil retention and water stopping functions, are widely used in silty soil strata rich in groundwater, such as those along coastlines and rivers. This method uses a triaxial mixing pile machine to forcibly mix the soil with a cement-based curing agent on-site, forming a continuous cement-soil mixing wall. H-beams and other reinforcing materials are then inserted into the wall as the main load-bearing components, forming a composite support structure.

[0003] However, there are two prominent technical bottlenecks in applying the SMW method piles in water-rich silty soil strata: 1. The contradiction between material properties and construction technology: Water-rich environments easily dilute traditional cement grout, leading to slow early strength development of the cement-soil mixture. This results in insufficient and timely bonding force for the steel sections, easily causing problems such as steel section misalignment and difficulty in insertion. To ensure sufficient time for steel section insertion, a longer setting time (retarded setting) of the grout is usually required. However, traditional retarded setting techniques often sacrifice the later strength of the material, making it difficult to meet the long-term load-bearing capacity requirements of the support structure. This contradiction between "retarded setting during construction" and "early and high strength during service" severely restricts the reliability and safety of the SMW method.

[0004] 2. Limitations of Structural Design Methods: Traditional designs often rely on engineering experience to determine the arrangement (e.g., "alternate insertion") and spacing of steel sections, lacking detailed analysis. Conservative designs result in excessive steel usage and poor economic efficiency; overly aggressive designs may lead to excessive deformation of the foundation pit or even instability. Furthermore, numerical simulation analysis typically treats the strength of cement-soil as a fixed value, failing to accurately reflect its strength growth process from a fluid to a solid state. This leads to significant deviations between deformation predictions and actual conditions, resulting in inaccurate design safety margins.

[0005] Meanwhile, with the advancement of "dual carbon" (carbon reduction and upgrading), the high carbon emissions of traditional silicate cement have become increasingly prominent, and the development and application of low-carbon cementitious materials has become an industry trend. However, a systematic approach has yet to be developed to combine the safety and efficiency characteristics of these new materials with the complex design of foundation pit support.

[0006] Therefore, there is an urgent need for a systematic design method that can deeply integrate the characteristics of low-carbon materials, construction technology and structural design to achieve a safe, economical and environmentally friendly support solution. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an optimized design method and system for SMW (Self-Mounted Weft) piles in water-rich silty soil strata using low-carbon cementitious materials. This method aims to establish a refined numerical model considering the time-varying characteristics of material strength, construct a closed-loop design process of "material performance control—structural parameter optimization—construction window inversion," thereby accurately matching material setting time with construction technology, scientifically determining the optimal steel section layout scheme, and systematically solving the aforementioned technical problems.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: On the one hand, this invention provides an optimized design method for SMW (Self-Mounted Welded Wheat) piles in water-rich silty soil strata using low-carbon cementitious materials, comprising the following steps: S1. Establish a numerical model for the excavation of foundation pits in water-rich silty soil using the SMW method with pile support. The support structure in the numerical model is characterized by equivalent beam elements, and its equivalent stiffness is determined by the contributions of cement soil formed by low-carbon cementitious materials and interpolated steel. S2. Determine the physical and mechanical parameters of the water-rich silty soil layer; S3. Preliminarily determine the mix proportion of low-carbon cementitious materials, and obtain the strength-age development law under the mix proportion of the material through experiments; S4. Preliminary determination of the support structure parameters for SMW method piles, including the arrangement and spacing of steel sections; S5. Input the parameters determined in steps S2, S3, and S4 into the numerical model in step S1 to simulate excavation. Here, time-varying strength parameters corresponding to the construction stage and based on the strength-age development law are dynamically assigned to the cement-soil material to obtain the foundation pit deformation and structural internal force response. S6. Based on the material ratio in step S3, change the support structure parameters and repeat step S5 to establish a response database under different support schemes. S7. Perform sensitivity analysis on the data in the response database from step S6, and quantify the influence weight of the support structure parameters on the foundation pit deformation. S8. Based on the influence weights obtained in step S7, a multi-objective optimization algorithm is used to determine the optimal support structure parameters under the current material mix, with the goal of controlling the deformation of the foundation pit. S9. Based on the optimal support structure parameters determined in step S8, simulate the actual construction process and back-calculate the time window required to complete the steel section insertion; determine whether the time window meets the setting time requirements of the current material ratio. If satisfied, the current material mix ratio and optimal support structure parameters will be output as the final design scheme. If the conditions are not met, the material ratio is adjusted based on the time window obtained by back calculation to form a new material ratio, and the process returns to step S3 to restart the iterative optimization with the new material ratio.

[0009] In addition to any of the possible implementations described above, another implementation is provided in which, in step S1, the equivalent bending stiffness (EI) of the equivalent beam element... eq and axial stiffness (EA) eq Calculated using the following formula: (EI) eq =E c I c + E s I s ; (EA) eq =E c A c + E s A s ; Among them, E c A c I c These are the elastic modulus, cross-sectional area, and moment of inertia of cement-soil, respectively; E s A s I s These are the elastic modulus, cross-sectional area, and moment of inertia of the steel section, respectively.

[0010] In addition to any of the possible implementations described above, a further implementation is provided in which, in step S3, the low-carbon cementitious material comprises the following components by weight percentage: 45%-55% sulfoaluminate cement, 20%-30% granulated blast furnace slag powder, 4%-7% silica fume, 8%-12% composite activator, 0.4%-1.0% retarding polycarboxylate superplasticizer, 0.2%-0.4% water retention agent, and the balance being water.

[0011] In addition to any of the possible implementations described above, a further implementation is provided in which, in step S3, the strength-age development law is obtained by testing the unconfined compressive strength of the low-carbon cementitious material at 0.1 days, 3 days, 7 days, and 28 days, and the strength reduction factor η(t) = F at each age relative to the 28-day age is calculated accordingly. c (t) / F c (28), where F c (t) represents the measured intensity at age t, F c (28) is the 28-day reference strength; in step S5, the time-varying simulation of material strength is achieved by assigning the strength reduction coefficient η(t) to the cement soil.

[0012] In addition to any of the possible implementations described above, another implementation is provided in which the arrangement of the steel profiles in step S4 is either an "alternate one, insert one" arrangement or an "insert two, skip one" arrangement.

[0013] In addition to any of the possible implementations described above, another implementation is provided in which, in step S7, the Morris sensitivity analysis method is used to quantify the influence weights of the support structure parameters, wherein the support structure parameters include at least the steel arrangement and the steel spacing.

[0014] In addition to any of the possible implementations described above, another implementation is provided in which the multi-objective optimization algorithm in step S8 is the NSGA-II algorithm, the optimization objective is to minimize the maximum lateral displacement of the foundation pit and the maximum settlement of the ground surface, the design variables are the steel arrangement form and the steel spacing, and the preset deformation control constraints and construction parameter boundary constraints are satisfied.

[0015] In addition to any of the possible implementations described above, another implementation is provided in which the condition for determining whether the condensation time requirement is met in step S9 is: T req ≤ T ini / k; Where T req T is the time window required for the back-calculated steel section insertion. ini is the measured initial setting time for the current material mix, and k is the safety factor.

[0016] In addition to any of the possible implementations described above, another implementation is provided in which the safety factor k ranges from 1.1 to 1.3.

[0017] On the other hand, the present invention also provides an optimized design system for SMW method piles in water-rich silty soil strata using low-carbon cementitious materials. The system is used to implement the above-mentioned method and includes: The numerical modeling module is used to build and run a numerical model of SMW method pile support excavation that takes into account the time-varying properties of materials. The materials database module is used to store the strength-age development data of low-carbon cementitious materials with different proportions; The parameterized analysis module is used to call the numerical modeling module to perform simulation calculations on different combinations of support structure parameters and establish a response database. The sensitivity analysis module is used to analyze the response database and quantify the influence weights of the support structure parameters; The multi-objective optimization module is used to perform optimization calculations based on the influence weights, with the goal of controlling the deformation of the foundation pit, and output the optimal support structure parameters. The process inversion and material adjustment module is used to inversely calculate the construction time window based on the optimal support structure parameters, and to determine and adjust the material ratio to meet the setting time requirements, driving the system to perform iterative optimization until the final solution is output.

[0018] The beneficial effects of this invention are as follows: 1. Achieved deep synergy between materials, structure, and process: It breaks down the barriers between materials, structure, and construction that are independent in traditional design. Through the bridge of "numerical simulation", it takes the time-varying properties of materials as the core design variable, forming a closed-loop design paradigm of "determining materials based on process requirements and optimizing structures based on material properties", which fundamentally solves the core contradiction of the SMW method in water-rich strata.

[0019] 2. Improved scientific design and prediction accuracy: By introducing the strength reduction factor η(t) to dynamically simulate the strength growth of cement-soil, the numerical model can more realistically reflect the mechanical behavior of the support structure from construction to service, greatly improving the accuracy of foundation pit deformation and structural internal force prediction, and providing a reliable basis for safe design.

[0020] 3. Ensures the overall optimality of the solution: By employing parametric analysis and multi-objective optimization techniques, the system can automatically find the support scheme with the lowest steel consumption and material cost under strict deformation control conditions. Simultaneously, the optimization process ensures the feasibility of the construction technology, avoiding a disconnect between design and construction.

[0021] 4. Adherence to green building principles: The use of a sulfoaluminate cement-slag powder-silica fume composite cementitious system significantly reduces the carbon emissions of cementitious materials. Optimized design reduces the amount of steel used, further lowering resource consumption and the project's carbon footprint, resulting in outstanding economic and environmental benefits.

[0022] 5. A standardized and scalable complete solution has been formed: providing a complete process method and supporting system from parameter acquisition, material testing, simulation optimization to solution output, which greatly improves the design efficiency and reliability of SMW pile construction under complex hydrogeological conditions and has broad engineering application value. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the overall process of the optimization design method described in this embodiment of the invention.

[0024] Figure 2 This is a flowchart illustrating the method for determining the physical and mechanical parameters of soil using a GDS testing device in an embodiment of the present invention.

[0025] Figure 3 This is a flowchart illustrating the sensitivity analysis performed using the Morris method in an embodiment of the present invention.

[0026] Figure 4 This is a flowchart of multi-objective parameter optimization based on the NSGA-II algorithm in an embodiment of the present invention.

[0027] Figure 5 The following is a schematic diagram of a three-dimensional numerical model of the foundation pit excavation in a water-rich stratum in an embodiment of the present invention: (a) Layout of the support structure; (b) SMW method pile retaining structure; (c) Layout of deformation monitoring points of the retaining structure. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0029] The accompanying drawings illustrate a layer structure according to an embodiment of the present invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0030] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] This invention provides an optimized design method for SMW (Surface Mount Welded Wheat Wool) piles in water-rich silty soil strata using low-carbon cementitious materials. The overall process is as follows: Figure 1 As shown, it includes the following steps: S1. Establish a refined numerical model: Obtain or establish a finite element (or finite difference) three-dimensional numerical model of the target water-rich silty soil foundation pit. In the model, the SMW method pile support structure is characterized by equivalent beam elements. Its equivalent stiffness comprehensively considers the combined contribution of the cement-soil formed by low-carbon cementitious materials and the interpolated steel, and the calculation formula is as follows: (EI) eq =E c I c + E s I s ; (EA) eq =E c A c + E s A s ; Among them, E c A c I c These are the elastic modulus, cross-sectional area, and moment of inertia of cement-soil, respectively; E s A s I s These are the elastic modulus, cross-sectional area, and moment of inertia of the steel section, respectively.

[0034] S2. Determine soil parameters: Through on-site investigation and laboratory tests, determine the physical and mechanical parameters of the water-rich silt layer to be excavated. Key parameters include: The effective internal friction angle ϕ, dilatation angle ψ, cohesion c, and reference secant modulus E were obtained through triaxial compression and shear tests. 50 ref Reference reloading modulus E ur ref Reference consolidation modulus E oed ref Stiffness stress level index m, reference initial shear modulus G o ref ; The initial permeability coefficient k0 and the seepage-strain coupling coefficient α were obtained through variable head permeability tests and consolidation-permeability combined tests.

[0035] S3. Preliminary determination of material proportions and acquisition of time-varying patterns: Based on the project scale and construction efficiency, estimate the time window T required for the initial steel section insertion. req (0), with this as the goal, develop a solution that satisfies T ini (0)>kT req (0) Low-carbon cementitious material ratio M i (where T) ini (0) represents the initial setting time of the material, and k is a safety factor of 1.1~1.3). Indoor tests were conducted on this material mix to measure its unconfined compressive strength F at critical ages of 0.1 days, 3 days, 7 days, and 28 days. c Plot the intensity-age development curves and calculate the reduction factor η(t) = F for intensity at each age relative to the 28-day intensity. c (t) / F c (28).

[0036] S4. Determine the preliminary support structure parameters: Based on mature construction methods and design experience in the industry, the support structure parameters of SMW method piles are initially selected, mainly including the steel arrangement form (such as "one every other insertion" or "two insertions and one skipping insertion") and the steel spacing L0.

[0037] S5. Excavation Simulation with Coupled Time-Varying Characteristics: Input the parameters determined in steps S2, S3, and S4 into the numerical model established in step S1. Throughout the simulation of the entire process of layered excavation and support application of the foundation pit, dynamically assign a strength reduction factor η(t) to the cement-soil material that matches the current construction stage (corresponding to the material age), thereby accurately simulating the material strength growth process. Calculate and output the maximum lateral displacement U of the foundation pit. x Maximum surface subsidence U y And key responses such as the maximum bending moment M on the steel section.

[0038] S6. Parametric Analysis and Database Construction: Fixing the Current Material Proportion M i Systematically change the arrangement and spacing L of the steel profiles. i Repeat steps S4 and S5 to perform multiple numerical simulations. Store all simulation results (input parameters and output responses) to build a support scheme database covering multiple design options.

[0039] S7. Sensitivity Analysis and Contribution Weight Quantification: Based on the database constructed in step S6, the Morris global sensitivity analysis method is used (process as follows). Figure 3 As shown), the response of different support structure parameters (steel arrangement and spacing) to the foundation pit deformation (U) is quantified. x U y The contribution weight W i This clarifies the order of importance of each parameter's impact on the results, providing direction for subsequent optimization.

[0040] S8. Determining the optimal support parameters through multi-objective optimization: Using the contribution weights obtained in step S7 as a reference, the NSGA-II multi-objective optimization algorithm is adopted (the process is as follows). Figure 4 As shown), to minimize the maximum lateral displacement U of the foundation pit. x and the maximum surface subsidence U y To optimize the target, the steel section arrangement A and spacing L are used as design variables, while meeting deformation control standards (such as δ). h Under constraints of ≤0.2%H (where H is the excavation depth) and construction boundary conditions, the algorithm performs automatic optimization. It outputs a Pareto optimal solution set, from which designers can select the current material mix M based on project safety and economic requirements. i The optimal combination of support parameters (A) i L i ).

[0041] S9. Construction process inversion and material ratio verification / iteration: a) Process inversion: Based on the optimal support parameters (A) obtained in step S8 i L i The numerical model more accurately simulates the construction process of SMW method piles (mixing, curing, and steel section insertion), and recalculates the actual time window T required to complete all steel section insertion operations. req (i+1).

[0042] b) Verification and iteration: Determine whether T is satisfied. req (i+1) ≤ T ini (i) / k.

[0043] If the following conditions are met: This indicates that the current material ratio M is... i Its setting properties are sufficient to support the optimized construction process, and the support structure is safe and economical. Current scheme (M) i A i L i If feasible, proceed to step S10.

[0044] If this condition is not met, it indicates that the material's setting time is too short to meet the requirements of optimized construction techniques. In this case, based on the new time requirement T... req (i+1), return to step S3, and develop a new material ratio M by adjusting the dosage of the retarding component (such as the retarding water-reducing agent). i+1 and ensure that it meets T req (i+1) ≤ T ini (i) / k. Then, with the new ratio M... i+1 Re-run the structural optimization iteration starting from S5.

[0045] S10. Output the final optimized solution: When the iterative process satisfies the feasibility condition of step S9, output the final converged global optimal solution, including: the final low-carbon cementitious material ratio M. final Optimal steel section arrangement form A opt Optimal steel section spacing L opt And the corresponding steel section insertion time window T ini (final).

[0046] An embodiment of the present invention provides an optimization design system for implementing the above method, the system comprising: Soil parameter input module: used to input and manage various soil physical and mechanical parameters described in step S2.

[0047] Low-carbon material performance database module: used to store and manage strength-age development curves and corresponding strength reduction coefficients η(t) under different material ratios.

[0048] Support structure parameter determination module: used to set and adjust preliminary support parameters such as steel section arrangement and spacing.

[0049] Time-varying excavation simulation module: This is the core calculation engine, with a built-in constitutive model interface that considers the time-varying characteristics of material strength. It can call the kernel of commercial or self-developed numerical analysis software to perform fluid-structure interaction excavation calculations.

[0050] Excavation Pit Deformation and Structural Response Database: Used to store all parametric simulation results generated in step S6.

[0051] Weight determination module: Integrates sensitivity analysis methods such as Morris to execute step S7 and automatically calculate the contribution weight of each design parameter.

[0052] Multi-objective parameter optimization module: Integrates optimization algorithms such as NSGA-II, used to execute step S8 and automatically search for the optimal support parameters.

[0053] Material proportioning inversion and iterative control module: used to execute step S9, calculate the construction window based on the optimization results, determine the feasibility of materials, and control the iterative loop of the entire optimization process until the final solution is output.

[0054] Example This embodiment uses a deep foundation pit project of a subway transfer station in a city in East China as an example, and applies the method of this invention to optimize the support design. The excavation depth of the foundation pit is H=16.0 m, the perimeter is about 480 m, and the safety level is Level 1. The site strata are mainly interlayered saturated silt and silty clay, with a groundwater level of only 1.5 m, belonging to typical water-rich soft strata. The original design proposed a support scheme using Φ850@600 triaxial mixing piles with H700×300×13×24 steel sections inserted (arranged in an alternating pattern, with a spacing of 1200 mm) combined with three layers of concrete internal bracing.

[0055] Step S1: Establish a refined numerical model A three-dimensional fluid-structure interaction model was established using the finite element software PLAXIS 3D. The model dimensions fully considered boundary effects: in the horizontal direction, the outer edge of the foundation pit was approximately four times the excavation width, and in the depth direction, it was twice the excavation depth. The soil was modeled using the HSS (Hardening Soil Small) constitutive model, which accurately simulates small strain characteristics. The SMW method piles were simulated using equivalent continuous wall (slab) elements, and their equivalent stiffness was calculated according to the formula provided in this invention. The elastic modulus E of the steel section is... s =2.1×10^5 MPa; Elastic modulus E of cement-soil c Based on its unconfined compressive strength F c (t) according to the empirical formula E c =1000*Fc (t) Dynamic calculation. The support is simulated using elastic rod elements. The model mesh is finely divided to ensure calculation accuracy. A simplified model diagram is shown below. Figure 5 As shown.

[0056] Step S2: Determine the physical and mechanical parameters of the soil by drilling undisturbed soil samples at representative locations around the foundation pit. For example... Figure 2 As shown in the flowchart, key soil parameters were determined by comprehensively utilizing conventional indoor tests, the GDS advanced triaxial testing system, and permeability tests. The main parameter values ​​are shown in Table 1. Step S3: Preliminary determination of the proportion and time variation of low-carbon cementitious materials According to the construction organization design, it is estimated that after the mixing of a single pile (three piles) is completed, the initial time window T for inserting all the steel sections within that pile section will be determined. req (0) = 130 min. Taking a safety factor k = 1.2, the required initial setting time T of the material is... ini ≥156min.

[0057] Based on this, the initial low-carbon cementitious material mix M1 was developed, with the following weight percentage composition: 50% sulfoaluminate cement, 25% granulated blast furnace slag powder, 6% silica fume, 10% composite activator (a mixture of Na2SO4 and Ca(OH)2 in a specific ratio), 0.6% retarding polycarboxylate superplasticizer, 0.3% water-retaining agent (hydroxypropyl methylcellulose), and 8.1% water. Specimens were prepared according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671), and their key age strength was tested: F c (0.1d) = 0.15 MPa, F c (3d) = 1.8 MPa, F c (28d) = 3.2 MPa. The initial setting time T was determined according to the "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement" (GB / T 1346). ini (1) = 165 min (meets the requirements).

[0058] The strength reduction factors are calculated as follows: η(0.1d) = 0.15 / 3.2 ≈ 0.047; η(3d) = 1.8 / 3.2 ≈ 0.56; η(28d) = 1.0. For intermediate ages, linear interpolation is used to determine the strength reduction factors.

[0059] Step S4: Determine the preliminary support parameters. The preliminary support parameters are designed based on the original experience: the steel arrangement pattern A = "one every other one", and the steel spacing L = 1200mm.

[0060] Steps S5 and S6: Parametric Simulation and Database Construction The fixed material ratio M1 and its time-varying strength law are established. Two steel section arrangement patterns A are set: "alternate one, insert one" and "two inserts, skip one". The steel section spacing L is taken at 200 mm intervals between 1000 mm and 1800 mm. A total of 2 (arrangement patterns) × 5 (spacing) = 10 combinations of support parameters are formed.

[0061] For each combination, the following construction sequence is fully simulated in PLAXIS 3D: initial ground stress equilibrium (considering pore pressure) → activation of SMW method pile elements (imparting initial low strength) → excavation to -3.0m (bottom of the first support) → activation of the first support and application of pre-stressed axial force → excavation to -8.0m → activation of the second support → excavation to -13.0m → activation of the third support → excavation to the bottom of the pit at -16.0m. At each excavation and support activation step, the strength reduction factor η(t) and elastic modulus E of the cement-soil are updated based on the time elapsed since mixing. c (t). After the simulation is completed, the maximum lateral U of the foundation pit under each scheme is extracted. x Maximum surface subsidence U y and the maximum bending moment M on the steel section. Connect the 10 inputs (A, L) and outputs (U) x U y , M) are stored in the database.

[0062] Step S7: Sensitivity Analysis The Morris method was used to analyze the database (see flowchart). Figure 3 Generate 40 sampling paths and calculate the output response (U) of each parameter (A, L). x U y The basic effect value (EE) of the , and then its absolute mean μ and contribution weight W are calculated.

[0063] The analysis results are shown in the following example: For lateral displacement U x The contribution weight W of the steel section spacing L L The contribution weight W of arrangement form A is approximately 0.75. A ≈0.25. This indicates that in this case, the spacing is the main factor affecting the deformation, and optimization should first focus on adjusting the spacing.

[0064] Step S8: Multi-objective optimization Based on the sensitivity analysis results, the NSGA-II algorithm was used for optimization (see flowchart). Figure 4 ).

[0065] Design variables: steel section arrangement form A (discrete variable: 1 represents "alternate one, insert one", 2 represents "two inserts, skip one"), steel section spacing L (continuous variable: 1000 mm ~ 1800 mm).

[0066] Objective function: Minimize f1=U x (Maximum lateral displacement) Minimize f2=U y (Maximum surface subsidence).

[0067] Constraints: Performance constraints: U x ≤0.2%H=32mm; U y ≤0.15%H=24mm; ; Stress ratio of steel section ≤ 0.9.

[0068] Boundary constraints: 1000mm≤L≤1800mm.

[0069] Algorithm parameters: population size 80, number of generations 50, crossover probability 0.9, mutation probability 0.1.

[0070] After the algorithm runs, the Pareto optimal frontier is obtained. An equilibrium scheme is selected from this scheme: the steel section arrangement is "two inserts, one jump," with an optimal spacing L1 = 1500 mm. Under this scheme, the predicted U... x =28.5mm, U y =20.1mm, all meeting the control standards, and saving about 20% of the steel compared to the original scheme ("alternate insertion", L=1200mm).

[0071] Step S9: Construction process inversion and material verification Process inversion: The construction sequence under the "two-insertion-one-skip" arrangement is precisely simulated in the model. The actual time window T required to complete the steel section insertion for one construction segment (approximately 20 piles) is calculated. req (2) =145min (due to the change in layout and the change in the amount of pile driving work, the time has increased slightly).

[0072] Verification: Check if T is satisfied. req (2)(145 min) ≤ T req (1) / k ( 165 / 1.2 ≈137.5 min ) ? 145>137.5, the condition is not met.

[0073] Iteration: The setting time of the current material M1 cannot support the optimized "two-insertion, one-skip" construction scheme. Material adjustments are needed. Return to step S3, based on the new time requirement T. req (2) = 145 min, requiring the initial setting time T of the new material. ini ≥1.2×145=174min.

[0074] The proportions were adjusted, with the dosage of the retarding water-reducing agent slightly increased from 0.6% to 0.8%, resulting in a new proportion M2. Testing showed that T... ini (2) = 180 min, 28-day intensity F c (28) = 3.0 MPa, the strength development law still meets the requirements.

[0075] The structural optimization iteration starting from step S5 is repeated with the new material ratio M2 (in this example, because the material strength changes very little, the optimization result (A2, L2) is basically the same as the previous one).

[0076] Step S10: Output the final solution After re-verification, the new scheme meets the requirements of T. req (2)(145 min) ≤ T ini (2) / k (180 / 1.2 =150 min).

[0077] The final optimized solution is as follows: Optimal low-carbon cementitious material ratio M final The composition is as follows: 50% sulfoaluminate cement, 25% slag powder, 6% silica fume, 10% composite activator, 0.8% retarded polycarboxylate superplasticizer, 0.3% water-retaining agent, and 7.9% water.

[0078] Optimal support structure parameters: The steel section arrangement is "two inserted and one skipped", and the optimal spacing is 1500 mm.

[0079] Construction guidance: The insertion time window for the steel profiles should be controlled within 145 minutes.

[0080] Application Results: After construction according to this optimized plan, on-site monitoring data showed that the maximum lateral displacement of the foundation pit was 29.8 mm, and the maximum surface settlement was 21.5 mm, which highly matched the predicted values ​​and were far below the control standards. Compared with the original experience-based design plan, the amount of steel used was reduced by approximately 22%, lowering material costs and carbon emissions, and achieving significant safety, economic, and environmental benefits.

[0081] The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​this application; at the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this application. Therefore, the content of this specification should not be construed as a limitation of this application.

[0082] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0083] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0084] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0085] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. An optimized design method for SMW (Self-Mounted Weave) piles in water-rich silty soil strata using low-carbon cementitious materials, characterized in that... Includes the following steps: S1. Establish a numerical model for the excavation of foundation pits in water-rich silty soil using the SMW method with pile support. The support structure in the numerical model is characterized by equivalent beam elements, and its equivalent stiffness is determined by the contributions of cement soil formed by low-carbon cementitious materials and interpolated steel. S2. Determine the physical and mechanical parameters of the water-rich silty soil layer; S3. Preliminarily determine the mix proportion of low-carbon cementitious materials, and obtain the strength-age development law under the mix proportion of the material through experiments; S4. Preliminary determination of the support structure parameters for SMW method piles, including the arrangement and spacing of steel sections; S5. Input the parameters determined in steps S2, S3, and S4 into the numerical model in step S1 to simulate excavation. Here, time-varying strength parameters corresponding to the construction stage and based on the strength-age development law are dynamically assigned to the cement-soil material to obtain the foundation pit deformation and structural internal force response. S6. Based on the material ratio in step S3, change the support structure parameters and repeat step S5 to establish a response database under different support schemes. S7. Perform sensitivity analysis on the data in the response database from step S6, and quantify the influence weight of the support structure parameters on the foundation pit deformation. S8. Based on the influence weights obtained in step S7, a multi-objective optimization algorithm is used to determine the optimal support structure parameters under the current material mix, with the goal of controlling the foundation pit deformation. S9. Based on the optimal support structure parameters determined in step S8, simulate the actual construction process and back-calculate the time window required to complete the steel section insertion; determine whether the time window meets the setting time requirements of the current material ratio. If satisfied, the current material mix ratio and optimal support structure parameters will be output as the final design scheme. If the conditions are not met, the material ratio is adjusted based on the time window obtained by back calculation to form a new material ratio, and the process returns to step S3 to restart the iterative optimization with the new material ratio.

2. The SMW method for optimizing pile design in water-rich silty soil strata using low-carbon cementitious materials as described in claim 1, characterized in that... In step S1, the equivalent bending stiffness (EI) of the equivalent beam element is... eq and axial stiffness (EA) eq Calculated using the following formula: (BE) eq =E c ESSENTIAL c + E s ESSENTIAL s ; (EA) eq =Yes c A c + Yes s A s ; Among them, E c A c I c These are the elastic modulus, cross-sectional area, and moment of inertia of cement-soil, respectively; E s A s I s These are the elastic modulus, cross-sectional area, and moment of inertia of the steel section, respectively.

3. The SMW method for optimizing pile design in water-rich silty soil strata using low-carbon cementitious materials as described in claim 1, characterized in that... In step S3, the low-carbon cementitious material comprises the following components by weight percentage: 45%-55% sulfoaluminate cement, 20%-30% granulated blast furnace slag powder, 4%-7% silica fume, 8%-12% composite activator, 0.4%-1.0% retarding polycarboxylate superplasticizer, 0.2%-0.4% water retention agent, and the balance being water.

4. The SMW method for optimizing pile design in water-rich silty soil strata using low-carbon cementitious materials as described in claim 3, characterized in that... In step S3, the strength-age development law is obtained by testing the unconfined compressive strength of the low-carbon cementitious material at 0.1 days, 3 days, 7 days, and 28 days, and the strength reduction factor η(t) = F at each age relative to the 28-day age is calculated accordingly. c (t) / F c (28), where F c (t) represents the measured intensity at age t, F c (28) is the 28-day reference strength; in step S5, the time-varying simulation of material strength is achieved by assigning the strength reduction coefficient η(t) to the cement soil.

5. The SMW method for optimizing pile design in water-rich silty soil strata using low-carbon cementitious materials as described in claim 1, characterized in that... In step S4, the arrangement of the steel profiles is either "one-alternate-one-insertion" or "two-insertion-one-skip".

6. The optimized design method for SMW pile construction in water-rich silty soil strata using low-carbon cementitious materials as described in claim 1, characterized in that... In step S7, the Morris sensitivity analysis method is used to quantify the influence weight of the support structure parameters, which include at least the steel arrangement and steel spacing.

7. The SMW method for optimizing pile design in water-rich silty soil strata using low-carbon cementitious materials as described in claim 1, characterized in that... In step S8, the multi-objective optimization algorithm is the NSGA-II algorithm. The optimization objective is to minimize the maximum lateral displacement of the foundation pit and the maximum settlement of the ground surface. The design variables are the steel arrangement and the steel spacing, and the preset deformation control constraints and construction parameter boundary constraints are satisfied.

8. The SMW method for optimizing pile design in water-rich silty soil strata using low-carbon cementitious materials as described in claim 1, characterized in that... In step S9, the condition for determining whether the setting time requirement is met is as follows: T req ≤ T ini / k ; Where T req T is the time window required for the back-calculated steel section insertion. ini is the measured initial setting time for the current material mix, and k is the safety factor.

9. The optimized design method for SMW pile construction in water-rich silty soil strata using low-carbon cementitious materials as described in claim 8, characterized in that... The safety factor k ranges from 1.1 to 1.

3.

10. A SMW method pile optimization design system for water-rich silty soil strata using low-carbon cementitious materials, characterized in that, The system is used to implement the method as described in any one of claims 1-9, the system comprising: The numerical modeling module is used to build and run a numerical model of SMW method pile support excavation that takes into account the time-varying properties of materials. The materials database module is used to store the strength-age development data of low-carbon cementitious materials with different proportions; The parametric analysis module is used to call the numerical modeling module to perform simulation calculations on different combinations of support structure parameters and establish a response database. The sensitivity analysis module is used to analyze the response database and quantify the influence weights of the support structure parameters; The multi-objective optimization module is used to perform optimization calculations based on the influence weights, with the goal of controlling the deformation of the foundation pit, and output the optimal support structure parameters. The process inversion and material adjustment module is used to inversely calculate the construction time window based on the optimal support structure parameters, and to determine and adjust the material ratio to meet the setting time requirements, driving the system to perform iterative optimization until the final solution is output.

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