Keyword

1 Introduction

The shield tunnel of a metro system is characterized by its considerable length and significant variations in geological conditions along the alignment. Influenced by the scale of the project and intricate geological conditions, the conventional depth of engineering geological exploration proves inadequate. Moreover, the information gathered from sporadically distributed exploration points does not align seamlessly with shield construction conducted on the basis of segment rings. Consequently, this mismatch introduces certain risks into the control of shield construction [1].

BIM model plays an important role in engineering construction because of its 3D visualization, coordination and simulation [2]. Finite element simulation serves as a vital tool for analyzing the interaction between shield tunnel segments and the surrounding rock and soil. It is instrumental in addressing issues related to shield construction parameters and construction control [3, 4].

The accuracy of finite element simulation in shield tunnel construction is significantly influenced by the completeness and depth of engineering geological information. Establishing a three-dimensional geological model based on the simulation requirements of shield tunnel construction and addressing the information transfer challenge between the geological model and the finite element simulation model constitute key aspects in resolving simulation issues under diverse engineering geological conditions.

The relevant problems was studied by many scholars. In 3D geological BIM modeling and information integration, using the original function of Civil 3D software, combined with the engineering example and the modeling idea, Li Wanhong [5] has created the 3D geological stratigraphic curved surface with the measured and inferred data and the characteristic line, and has established the complete 3D geological model; Using Revit software, combining with Civil3D and Dynamo, the parameterized tunnel engineering model and 3D geological model were established by Yangzhu [6]; Huang di [7] has carried on the 3D geology BIM model extension based on the IFC standard, has established the 3D geology modeling application system and the application frame based on the BIM. While these studies have approached the creation of 3D geological BIM models from various perspectives, their focus has primarily been on modeling methodologies and the integration of geological information. Notably, there has been a lack of further exploration into how BIM models can effectively guide construction processes, leading to a deficiency in the completeness of model information.

In the combination of BIM model and construction simulation, Liu Bei [8] studied the conversion method between BIM model and structural analysis model, and developed the interface program between Revit and ANSYS Using C# language to realize the automatic conversion from BIM model to finite element model; Xie Jisheng [9] established a connection channel between Revit and the finite element software ABAQUS by the file of “*. Sat”, and loaded the 3D model in the finite element software successfully; Liu Yujia [10] used BIM technology to build a parameterized 3D geological model, cut the model by Rhino and initially built the grid, which was imported into Kubrix for grid division, the information exchange between BIM model and numerical simulation software was realized, and the accuracy of calculation results was improved. While these studies successfully achieved the transfer of geometric information between BIM and finite element models, they fell short in transferring non-geometric information [11, 12], such as construction details. Consequently, the model depth does not fully meet the requirements of construction simulation.

Against the backdrop of the shield tunnel project from Wanqingsha Station to Hengli Station on Guangzhou Metro Line 18, this paper presents a modeling method and information transmission approach for a 3D geological information model based on BIM. The aim is to address challenges related to safety simulation and the rational selection of construction parameters under varying geological conditions.

2 Project Profile

2.1 Project Profile

The shield tunnel for the Guangzhou Metro Line 18, stretching from Wanjingsha Station to Hengli Station, is situated in Nansha District, Guangzhou City. The design parameters for the main line indicate a starting mileage of ZDK0 + 740.313 and a concluding mileage of ZDK5 + 775.094. This section includes one intermediate ventilation shaft and one shield shaft. The cover soil thickness ranges from 8.3 m to 24.9 m. The excavation diameter is 8850mm, the tunnel’s outer diameter is 8500 mm, the inner diameter is 7700 mm, and the segment wedge measures 46 mm. The assembly method employs a staggered seam assembly.

2.2 Engineering Geological Conditions

The project site is situated in the Pearl River Delta Plain, characterized by a sea-land interaction alluvial plain. The geological conditions at the site are stable, with no unfavorable features such as faults identified. The topography of the site is flat, exhibiting a small relative elevation difference, and the ground elevation along the line generally ranges from 3.11 to 8.90 m.

The overlying strata primarily consist of Quaternary marine-terrestrial sedimentary layers and continental alluvial and alluvial facies strata, while the underlying bedrock comprises Sinian migmatite and mixed granite. The site presents a complex geological profile, featuring diverse strata such as miscellaneous fill, plain fill, cultivated soil, silt, muddy soil, fine sand, medium-coarse sand, gravel sand, gravel, plastic silty clay, hard plastic silty clay, residual soil layers, total weathered rock, strong weathered rock, medium weathered rock, micro weathered rock, among others. Alluvial-alluvial soil layers are often interspersed and layered. The majority of the shield tunnel traverses through the muddy soil stratum, characterized by high compressibility and low strength.

3 BIM Modeling Software

The characteristics of metro shield tunnel modeling encompass the following aspects: 1) Involves multiple specialties, requiring collaborative efforts across various disciplines; 2) Encompasses multiple software applications, necessitating seamless information transfer; 3) Involves a vast amount of data, requiring modeling efficiency; 4) Offers convenience in model modification; 5) Exhibits extensibility.

Table 1 [13] makes a comparative analysis of the advantages and disadvantages of the commonly used 3D geological BIM modeling software and its applicability. Table 2 makes a comparative analysis of the applicability of the commonly used BIM modeling software.

Table 1. Comparison of 3D geological BIM modeling software.
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Table 2. Comparison of applicability of 3D geological BIM modeling software.
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In summary, Revit emerges as the most suitable software for metro shield tunnel modeling, given its robust versatility, information integration capabilities, and extensibility. However, it exhibits a slight weakness in handling massive data, necessitating the use of complementary software to enhance efficiency.

4 Three-Dimensional Geological BIM Modeling Method Based on Shield Tunneling Simulation

4.1 Three-Dimensional Geological BIM Modeling Method

Dynamo is an auxiliary tool for parametric design based on Revit, assisting users in customizing algorithms to process data and generate geometric shapes, significantly enhancing modeling efficiency. The project adopts the Revit + Dynamo method to establish a 3D geological BIM model, as illustrated in Fig. 1 [14]. The main steps are as follows:

  1. 1)

    Organize survey data from each borehole and input the geological boundary point data into an Excel file, including 3D coordinates of the point, rock and soil properties, depth, thickness information of different soil layers, etc.

  2. 2)

    Utilize Dynamo to read the survey data from the Excel file and extract point data from each borehole.

  3. 3)

    Group point data in Dynamo based on geotechnical properties.

  4. 4)

    Generate triangulation surfaces for each soil layer using the point data.

  5. 5)

    Connect upper and lower triangular mesh surfaces to form mesh entities.

  6. 6)

    Import the mesh entity into Revit software to generate a 3D geological BIM model entity.

The resulting 3D geological BIM model is depicted in Fig. 2.

Fig. 1.
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Creation process on 3D geological BIM model.

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Fig. 2.
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3D geological BIM model.

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4.2 Information Attribute of 3D Geological BIM Model

In BIM model, the information attributes of shield tunnel engineering are added in the form of family parameters as the carrier of information communication.

Engineering Geological Information

Engineering geological information is divided into five categories: general information, test parameters, in-situ test, hydrogeology and bad geology [15], with a total of 27 sub-items of information, as shown in Table 3. The parameter interface of Revit family for information input is shown in Fig. 3.

Table 3. Information of engineering geological.
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Fig. 3.
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Revit family parameter

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Design Information

The design information of excavated soil includes 8 sub-items of information as shown in Table 4.

Table 4. Design information of excavation soil.
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Construction Information

Construction information can be divided into three categories: time norm, construction measures and excavation parameters, with a total of 16 sub-items of information, as shown in Table 5.

Table 5. Construction information.
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Monitoring Information

According to different monitoring means, monitoring information includes 4 sub-items as shown in Table 6. The monitoring information is linked with the BIM model, which is a warning for shield construction.

Table 6. Monitoring information.
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After integrating the four types of information into the 3D geological BIM model, units such as investigation, design, construction, monitoring, and operation and maintenance can modify and utilize BIM model information within their respective authority. The communication flowchart of model information is illustrated in Fig. 4.

4.3 Information Inquiry and Transfer Between BIM Model and Finite Element Model

The 3D geological BIM model and finite element model are created using different software with distinct formats, making direct connection of data information unfeasible. To address this issue, the IFC standard or secondary development technology is often employed for solving information transmission problems [16, 17]. However, these methods are limited to transferring only the geometric information of the model, leaving non-geometric information untouched. Extracting information from the 3D geological BIM model and achieving intelligent transmission of finite element model data represents a critical challenge in the integration of BIM models with shield construction simulation.

Building upon the foundation of establishing a comprehensive 3D geological BIM model, this paper presents a method for rapidly extracting BIM model information from any shield tunnel section, addressing information query and transfer challenges. The steps are illustrated in Fig. 5 [18]:

1) Collect and sort out engineering geological investigation data; 2) Use Revit + Dynamo to create 3D geological BIM model based on survey data, and integrate engineering geology, design, construction, monitoring and other information on the model; 3) Use Revit to establish BIM model of all shield segments, and mark the basic information such as segment ring number; 4) Merge the shield segment BIM model into the 3D geological BIM model according to the coordinates, and set the transparency of the 3D geological BIM model to 60%; 5) Find the segment with the specified ring number, identify the color quickly, and create a profile on the BIM model of the segment; 6) Directly query the geometric and non-geometric information of the 3D geological BIM model on the BIM model displayed in the section, and transfer the information to the finite element model.

Fig. 4.
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Flow chart of model information communication.

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Fig. 5.
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Information transfer flow chart between BIM module and finite element model.

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The BIM model section corresponding to a shield ring number is shown in Fig. 6. The geological body where the shield segment is located can be directly identified on the section, and the spatial relationship between the shield segment and the geological body can be measured by measuring tools. Upon selecting the geological body, viewing family parameters allows for simultaneous querying of the comprehensive information integrated within that geological body, thus achieving information transfer within the BIM model.

Fig. 6.
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Profile information of 3D geological BIM model.

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Fig. 7.
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Finite element model.

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The project utilized MIDAS/GTS finite element analysis software to model and partition the grid, and input boundary conditions, as depicted in Fig. 7. Subsidence deformation of the ground under different shield parameters is calculated to predict the distribution of ground subsidence in time and space, optimizing shield parameters. By establishing a 3D geological model for shield construction simulation, the project combines different geological models with finite element simulation to address safety simulation during shield construction and the selection of rational construction parameters under varying geological conditions. This integration enables the automation of information updates and the informatization of construction objects.

5 Conclusion

  1. 1)

    This paper adopts the modeling approach of Revit + Dynamo, integrating survey, design, construction, and monitoring information through a three-dimensional geological BIM model. The generated information model meets the integrity and depth requirements of shield tunnel construction.

  2. 2)

    Building upon the 3D geological BIM model, a comparison with the segment BIM model is conducted. Using a sectional approach facilitates information exchange between BIM and finite element methods, resolving the issue of incompatible data interfaces across different software.

  3. 3)

    Simulation and analysis of shield parameters are performed under varying geological conditions, offering a method for selecting construction schemes. The predicted spatial and temporal distribution of deformations during construction provides theoretical support for monitoring plans.

  4. 4)

    The integration of the 3D geological modeling method with shield construction simulation addresses the automation of informationization and updates for shield construction projects, thereby enhancing the level of informationization in shield tunnel construction.