Earth Pressure Balance Shield Tunneling Research Articles

Experimental study on granule trajectory tracking for the EPB shield tunneling in sandy cobble stratum

An investigation into the movement characteristics of granules during Earth Pressure Balance (EPB) shield tunneling contributes significantly to understanding the interaction between the shield machine and the soil. This understanding also enables researchers to gain deeper insights into the cutting and guiding effects of the shield cutterhead on the soil, thus providing a scientific basis for optimizing shield tunneling parameters and cutterhead designs. To achieve this, indoor model shield tunneling experiments were conducted using independently developed shield tunneling equipment and spatial positioning devices developed by our research group. The research investigated the spatial movement trajectories, radial diffusion, and axial movement characteristics of granules at the face subjected to the action of a spoke-type cutterhead. Furthermore, the study proposes the use of average diffusion degree and movement rates of granules as metrics for evaluating the cutting and steering performance of the cutterhead. The influence of cutterhead rotational speed and advance rate on the movement characteristics of granules was further explored based on these two indicators. The study’s findings reveal the following: (1) Granules at the face predominantly exhibit a spiral movement trajectory when the EPB shield tunneling machine operates in a dynamic equilibrium state. (2) The cutting and steering performance of the cutterhead’s various areas is enhanced progressively from the center to the outer edge, as evidenced by a gradual decrease in the average diffusion degree of granules and an increase in the average axial movement rate (AMR). (3) The AMR and average diffusion degree of granules are influenced by both the rotational speed of the cutterhead and the advance rate of the shield machine. Optimal matching of the rotational speed and advance rate maximizes the average AMR of granules, minimizes the average diffusion degree, reduces the torque on the cutterhead to its lowest point, and consequently, optimizes the efficiency of shield tunneling. This research presents a novel perspective and methodology for understanding the movement characteristics of granules during shield tunneling operations. The outcomes of this study provide valuable insights for the structural design of shield machine cutterheads and the optimization of tunneling parameters.

Experimental study on the workability of sands conditioned with bentonite-silty clay modified slurry

With the widespread application of Earth Pressure Balance (EPB) shield technology, the generation of shield muck has been increasing yearly. This paper aims to investigate the effectiveness of bentonite-silty clay modified slurry (BSC) as a soil conditioner for enhancing the workability of sands during EPB shield tunneling, thus enabling the recycling and reuse of the discarded muck (waste silty clay). Standard slump tests were conducted on three typical sand specimens from Shenyang Metro Line 6. The influence of the types of conditioners and slurry injection ratio (SIR) on slump values were examined to determine an optimal conditioning scheme tailored to the specific formation conditions. Furthermore, the study explored the combined use of BSC and foam to improve workability, employing a three-factor four-level orthogonal experiment. Finally, the rheological parameters (yield stress) derived from the slump tests provide valuable insights for assessing material flow within the tunneling system. The results show that comparative analyses with pure bentonite slurries reveal that BSC is a suitable, economical, and effective alternative for soil conditioning. The particle size distribution of sand specimens significantly influences the conditioning process, necessitating adjustments to SIR and slurry viscosity for optimal results. When the slump value of slurry-conditioned soil falls within the range of 150–250 mm, the slump test can be effectively used to estimate its yield stress under atmospheric conditions. This study contributes to the development of sustainable and economical solutions for soil conditioning in urban tunnel projects, particularly by utilizing excavated materials effectively.

Real-time unsupervised monitoring of earth pressure balance shield-induced sinkholes in mixed-face ground conditions via convolutional variational autoencoders

This study introduces a real-time unsupervised monitoring framework for monitoring sinkhole formation events during earth pressure balance (EPB) shield tunneling operations. A feature extractor (FE) is constructed by coupling variational Autoencoders structure with convolutional neural network layers (VAE-CNN) to manage the complexity of EPB operational data, including non-linearity and temporal dependencies. The monitoring framework consists of two main phases: offline modeling and online monitoring. In the offline modeling phase, an FE model is trained using data-intensive techniques to define a subspace characterizing the behavior of multivariate data without sinkhole formations. The squared prediction error (SPE) statistics and the control limits are computed for detection. During the online monitoring phase, unseen EPB data is propagated to generate SPE values and determine sinkhole events based on whether these values surpass the control limit. Sensor validity index violation counts were used to isolate the most influential variables, while the results demonstrated the superiority of the proposed VAE-CNN method, achieving a 100% detection rate and a 0.9% false alarm rate. The influential variables identified include cutter resolutions per minute, jack speed, screw pressure, torque, and cutter seal components. The monitoring system shows great potential for early warnings during EPB operations to mitigate sinkhole formation risks.

Effects of residual foaming agent and defoamer on defoaming-flocculation-filterpress characteristics of earth pressure balance shield muck.

Foaming agents as a combination of several components are usually used as soil conditioning during earth pressure balance shield (EPBS) tunnelling. These residues in waste EPBS muck lead to a series of new challenges for in-situ recycling, i.e., foams overflow flocculation tank. This study investigates the effects of residual foaming agent components and defoamers on defoaming-flocculation-filterpress characteristics of EPBS muck using an improved flocculation and filterpress system. Residual foam height (Hf), defoaming ratio (DFR), antifoaming ratio (AFR), total suspended substance (TSS), turbidity, moisture content (MC), and zeta potential (ZP) were selected as characterization indices. The microstructure of filterpress cakes was analyzed using a scanning electron microscope. Results demonstrate that an enhancement within 0.0-1.0wt.% for sodium fatty alcohol polyoxyethylene ether sulfate (AES) and alpha olefin sulfonate (AOS) significantly reduces DFR and AFR. The MC and ZP decline, while the Hf and turbidity enhance. The combinations of nonionic surfactants alkyl polyglycoside (APG) and fatty alcohol-polyoxyethylene ether (AEO) in a concentration range of 0.0-1.0wt.% with 0.2wt.% AES causes the Hf, DFR, AFR, turbidity, and ZP to exhibit absolutely different variations. The MC with the growth in both APG and AEO presents a trend of first decreasing and then increasing. By increasing foam stabilizers sodium carboxymethyl cellulose (CMC) and guar gum (GG) within 0.02-0.10wt.%, the AFR, TSS, and ZP enhance in varying degrees, while the Hf, DFR, and MC gradually reduce. With the increase of defoamers hydroxyl silicone oil-glycerol polyoxypropylene ether (H-G) and dimethyl silicone oil-glycerol polyoxypropylene ether (D-G) within 0.002-0.010wt.%, the DFR and AFR are significantly improved, while the TSS, turbidity, MC, and ZP display varying degrees of reduction. Moreover, defoaming-flocculation-filterpress mechanisms of EPBS muck are explored to provide a useful reference for actual in-situ recycling projects.

Prediction of ground surface settlements by analytical and finite element methods

The soil surrounding the excavation of shallow tunnels may experience destructive deformation near the tunnels. Particularly in densely populated areas where land resources are scarce, ground subsidence caused by tunnel excavation, which in turn affects surrounding structures, deserves more attention. Over the past few decades, various research methods for predicting the maximum vertical ground surface settlement have been proposed. In this study, an empirical estimation method, an analytical technique for evaluating ground movements, and a numerical simulation method using Plaxis 2D, a finite element model software, were selected as prediction approaches for ground surface settlements. Subsidence measurements were obtained from a metro tunnel excavated using an earth pressure balance shield tunnel boring machine and constructed in a dense sandy gravel layer. Comparison of the monitored deformations with the estimation results calculated by different prediction approaches showed that the maximum vertical settlement of the ground surface evaluated by the analytical technique and finite element model agreed well with the actual measured values. This suggests that these two prediction methods have the potential for conserving nearby structures during the construction of underground infrastructures.

Development and evaluation of a process-oriented 3D finite element model for earth pressure balance shield tunneling

Thrust system performs the task of driving the shield machine forward and adjusting its posture, ensuring that the shield advances along a designed tunnel alignment. However, there is still no unanimously agreed approach for incorporating the thrust system in shield tunneling simulation. For this purpose, an attempt is made to embed the parallel mechanism properties of thrust system in simulation, i.e., modeling the thrust system as a 4-spherical-prismatic-spherical (4-SPS) branched chain. Meanwhile, a mesh-to-mesh solution mapping technique is introduced to ensure mesh compatibility across the cutterhead-soil interface without losing the stress history information generated during soil excavation. Thereby, a process-oriented 3D finite element model is developed for earth pressure balance (EPB) shield tunneling. The proposed model is quantitatively evaluated by reproducing a comprehensive field dataset collected from Changsha Metro Line 6 project. It is demonstrated that the proposed model can accurately reproduce the measured data for total thrust, grouped cylinder pressure, and total torque with mean relative errors of 5.8 %, 9.6 %, and 7.8 %, respectively. Moreover, the model can well reproduce the highly varied spatial distribution of the grouped cylinder pressure, highlighting its potential in capturing the mechanics for the posture variation of EPB shield.

Coupled DEM-FDM numerical model for EPB shield tunnelling simulation with foam conditioning

It is widely recognized that an appropriate application of soil conditioning significantly improves the tunnelling performance of earth pressure balance (EPB) shield tunnel boring machines (TBMs). This study presents a numerical approach that simulates an EPB shield tunnelling, considering the injection of foam into the soil. To enhance computational efficiency and reduce the number of particles simulated in the ground formation, the numerical study coupled the discrete element method (DEM) and the finite difference method (FDM). The properties of in-situ soil and foam-conditioned soil were incorporated into the DEM domain by determining the contact parameters of particles using two calibration models: the triaxial compression test and the pressurized vane shear test models. With the established model, tunnelling analyses were conducted under specific TBM operation conditions, such as the penetration rate, and rotational speed of the cutter head and the screw conveyor. The effect of foam injection on EPB shield TBM operation was evaluated by adjusting the contact parameters of DEM elements. The numerical simulations revealed that foam conditioning reduced the torque, thrust force, and forces on cutting tools. These simulations provided valuable insights into the applicability of the numerical approach in assessing foam conditioning for EPB shield TBMs.

Rheological characterization of the conditioned sandy soil under gas-loading pressure for earth pressure balance shield tunnelling

Soil conditioning technology is usually required to modify the excavated soil to a fluid plastic state during the construction with earth pressure balance (EPB) shield. The steady pressure distribution in the excavation face is linked to soil fluidity. Compared with the slump test, the rheological behavior of the conditioned soil can better reflect the dynamic flow characteristics. A gas-loading rotational rheometer is developed to test the rheological properties of the conditioning agents and the conditioned sandy soil, which can overcome the disadvantage of uneven mechanical loading and create gas-loading conditions. The rheological properties of sandy soil conditioned by different agents under atmospheric and gas-loading pressure conditions were studied, and the influences of foam injection ratio (FIR), bentonite slurry injection ratio (SIR), and polymer injection ratio (PIR) on soil viscosity were analyzed. The test results show that the ambient air pressure only greatly influences the experimental group with foam. Under the same gas-loading pressure, the foam’s apparent viscosity decreases with the foam expansion ratio (FER) increasing. The rheological behavior of the conditioned sandy soil conforms to the Bingham model under atmospheric pressure and conforms to the Power Law model when PIR ≤ 5 % under gas-loading pressure of 3 bar. The Weissenberg effect accounts for the differences. When PIR > 10 %, the rheological curve of three agents conditioned sand conforms to the Herschel Bulkley model. The higher content polymer reacts with bentonite to increase the soil viscosity, and blocks the foam seepage channel, making it difficult for the foam to re-enter the soil under gas-loading pressure. Investigating the rheological behavior of different conditioned sandy soil provides optimization strategies for EPB performance.

Machine learning–informed soil conditioning for mechanized shield tunneling

AbstractEffective soil conditioning is critical for mechanized shield tunneling, yet the selection of conditioning parameters remains experience‐oriented. This study presents a machine learning–informed soil conditioning strategy, aiming at enabling automatic decision‐making for soil conditioning during tunneling. The proposed procedure includes feature engineering to process raw data, the selection of an optimal model, and a committee‐based uncertainty quantification strategy to evaluate the reliability of models. High‐dimensional data visualization techniques are leveraged to examine the influence of data distribution on the model's performance. Results demonstrate that feature engineering and the selection of models lay a foundation for machine learning–enabled automatic soil conditioning, while historical soil conditioning parameters should be incorporated in models to account for time‐dependent features during tunneling. The committee‐based uncertainty quantification strategy can effectively identify the reliability of both interpolated and extrapolated predictions. The proposed data‐driven soil conditioning framework can promote the application of machine learning toward automating earth pressure balance (EPB) shield tunneling.

Analysis of the Drive Torque for the Spiral Pipe Section of an Earth Pressure Balanced Shield Tunnel Screw Conveyor

The driving torque of the shield machine is intricately linked to the soil silo muck load and the mechanical properties of both the muck and the spiral structure. Considering the shield screw conveyor’s mechanical structure and operational conditions, based on the momentum moment balance conditions, the separate calculation method was used to derive the spiral driving torque in the helical casing, the friction torque in the bearing and the friction torque of the sealing ring through mechanical analysis, and finally a torque calculation expression for the spiral pipe section was established. The research results provide technical guidance for the design and manufacture of shield screw conveyors and safe tunneling during construction.

Effect of water pressure on permeability of foam-conditioned sands for EPB shield tunneling

Foam conditioning is a widely adopted technique in earth pressure balance (EPB) shield tunneling for the purpose of reducing sand permeability and preventing water spewing. The permeability of foam-conditioned sands differs from that of natural sands due to the presence of foam bubbles. This study investigated the effect of water pressure on the permeability of foam-conditioned sands using novel laboratory permeability tests. The water pressure, for the first time, is decoupled with the hydraulic gradient, owing to a newly developed permeameter with the controllable downstream hydraulic pressure in the laboratory. The results show that the permeability is significantly affected by the water pressure, and the effect is also predominantly dependent upon the foam injection ratio. The initial hydraulic conductivity increases with the increasing water pressure, while the initial stable period duration decreases. The water-plugging structure formed by foam bubbles and sand particles is prone to be damaged under high water pressure due to the shrinkage of foam bubbles. This means that the existing permeability tests with low water pressure underestimate the permeability of foam-conditioned sands. The underlying mechanism of water pressure in modifying the permeability of foam-conditioned sands is also examined from a particle-scale perspective.

Real-time laser scanning for conditioned coarse-grained soil monitoring on conveyor belt in earth pressure balance shield

To address the hysteresis in assessing the workability of conditioned soils and the inefficiency in estimating the soil volume flow rate in tunnelling practice, a novel real-time assessment and monitoring approach was proposed. Based on laser scanning technology and point cloud data analysis, the approach can monitor the workability and the volume flow rate of conditioned soils on the horizontal conveyor belt of an earth pressure balance (EPB) shield in real-time. Firstly, the accuracy of laser scanning measurements was verified by comparing manually measured slump and spread values with laser scanning results. Then, a series of model tests for scanning the coarse-grained soils with different conditioning parameters and belt speeds on the horizontal conveyor belt were performed. The appropriate ranges of secant angle and unevenness of soil cross-sectional profile were obtained for assessing the workability of conditioned soils. The volume flow rate was calculated by integrating the cross-sectional areas of conditioned soils. Finally, the proposed approach was successfully applied in identifying the workability of conditioned soil and its discharge rate in the EPB shield tunnelling project. This study contributes to the real-time monitoring of conditioned soils on the horizontal conveyor belt and provides practical insights for the optimal management of EPB shield tunnelling.

Soil disturbance induced by shield tunnelling in sensitive clay: In situ test and analyses

Shield tunnelling in sensitive soil causes disturbance to the surrounding soil, damages the soil structure, and results in soil strength reduction. It has a significant impact on the strength and deformation of the soil during shield tunnelling, and further affects the long-term post-construction settlement of the tunnel structure. This paper firstly obtained the soil disturbance and its distribution especially under the tunnel by the in-situ measurement, and the effect of tunneling advancing speed on soil disturbance degree was analyzed. In this paper, in situ tests were performed on an earth pressure balanced (EPB) shield tunnelling site of a subway in deep soft soil layers in Ningbo. Before and after the shield tunnelling, the cone penetration tests (CPTs) were carried out along the axis and profile of the tunnel, and the cross-hole shear wave velocity tests were conducted. Displacement of the surrounding soil and excess pore water pressure (EPWP) were also monitored during shield tunnelling. The results showed that after shield tunnelling the cone penetration resistance (CPR) and shear wave velocity of the surrounding soil decreased remarkably, further confirming that shield tunnelling caused disturbance to the sensitive soft soil. The soil disturbance degree (SDD) is defined based on the CPR, and the soil disturbance boundary caused by shield tunnelling is determined based on distributions of SDD and EPWP. Horizontally, the disturbance boundary of the surrounding soil is located about 0.8D (D represents the tunnel diameter) outside the tunnel, and vertically, the bottom and top of the disturbance boundary are located about 1.29D below and 0.58D above the tunnel. The maximum SDD at the bottom and top of the tunnel reached 80% and 90% respectively, and the average SDD of the disturbance range below the tunnel is about 60%. The testing results indicated that a higher advancing speed causes a greater disturbance to the surrounding soil, and all the analysis results provide helpful guidance for optimizing the EPB shield tunnelling and reducing soil disturbance.

Experimental study on workability and permeability of sandy soils conditioned with thickened foam

Water spewing and muck plugging often occur during earth pressure balance (EPB) shield machines tunnelling in water-rich sandy strata, even though the conventional foam has been employed to condition sandy soils. In this study, a novel thickened foaming agent suitable for EPB shield tunnelling in water-rich sandy strata is developed. In contrast to conventional foam-conditioned sands, the thickened foam-conditioned sand has a low permeability due to the consistent filling of soil pores with the thickened foam, and the initial permeability coefficient decreases by approximately two orders of magnitude. It also exhibits a suitable workability, which is attributed to the enhanced capability of the thickened foam to condition sandy soils. In addition, the effect of concentration on the stability of the foam is explained by the Gibbs-Marangoni effect, and conditioning mechanisms for the thickened foam on sands are discussed from the evolution of foam bubbles.

Recycling the discharged soil from EPBS tunnels as a soil conditioner and its rheological behaviors

Earth pressure balance shield (EPBS) has become the mainstream construction method for metro tunnels in China, which inevitably generates a large amount of discharged soil, putting enormous pressure on the environment and the cost. In order to realize the resource utilization of shield dregs, this paper explored the feasibility of recycling the waste silty clay as a soil conditioner in EPBS tunnel construction. Mixtures of bentonite, wasted silty clay, carboxymethyl cellulose (CMC), and tap water in different ratios were prepared. Defining the substituted ratio as the mass ratio of silty clay to (bentonite + silty clay), the effect of the substituted ratio on the apparent viscosity, flow curve, rheological model and physical stability of bentonite-silty clay composite slurry were investigated. Furthermore, the relationship between slurry microstructures and macroscopic rheological properties was revealed by scanning electron microscopy (SEM). The results show that the constitutive relationship of bentonite slurry (0% substituted ratio) can be well described by Herschel-Bulkley model. The silty clay has a deteriorating effect on the rheological behavior and physical stability, and changes the flow pattern of the composite slurry. Microscopically, CMC makes the clay particles in slurries form agglomerates with larger particle sizes, and can absorb excess free water from the slurry, thus significantly increasing the yield stress and apparent viscosity. The recycling scheme proposed in this study can not only greatly reduce the procurement cost of raw materials, but also eliminate the transportation and disposal costs of discharged soil, which has significant environmental benefits and promising application prospects.

Investigation of disc cutter wear during shield tunnelling in weathered granite: A case study

Wear characteristics of disc cutter can vary significantly during shield tunnelling in different geological formations. This paper presents a case study on disc-cutter wear experienced during earth pressure balance shield tunnelling of the Guang-Fo intercity railway in Guangzhou, China. During excavation of the 2.8 km tunnel, 149 cutter inspections were conducted and 1163 cutters were consumed. Cutter wear morphology and cutter consumption was investigated. Cost-effectiveness of cutter replacement under different ground conditions was evaluated regarding time consumption. Field data revealed that cutter consumption varied with ground conditions, cutter mounting radii, and boring parameters. During mixed ground tunneling, it was noticed that the tips of cutter rings had been sharpened. An approximate estimation of when to inspect cutters during tunnelling can be determined using the field penetration index. Cutter replacement in hard rock ground was more cost-effective than in other ground conditions. The wear data provided here can serve as a reference for future operations in similar geological conditions.

Effect of conditioning schemes on mechanical properties of EPB shield soil

Shearing conditioned sands under different pressure conditions requires understanding their mechanical properties with various conditioning schemes to ensure feasible conditioning during earth pressure balance (EPB) shield tunnelling in sandy strata. This paper investigates the effect of bentonite slurry and foam, conditioned with sodium carboxymethyl cellulose (Na-CMC), on the workability of sand with varying water content, to obtain preliminary conditioning schemes. The conditioned sands with suitable workability are tested using a pressurized vane shear apparatus to obtain their mechanical properties, including compressibility, resilience, and shear strength before and after resiling. Results indicate that Na-CMC can reduce filtration loss of bentonite slurry and foam expansion ratio (FER) of foam, whereas enhance the stability of them. The foam injection ratio (FIR) of foam-conditioned sands and the maximum slurry addition of slurry-foam-conditioned sands decrease linearly with increasing the initial water content of sand, provided the conditioned sands have suitable workability. Increasing the FIR can remarkably increase the void ratio of conditioned sands, which maintains high compressibility and resilience, and low shear strength before and after resiling. The addition of bentonite improves the workability of sand. The conditioning schemes are feasible when the total stress is lower than a specific critical value. The critical total stress can be increased by increasing FIR and reducing the water content of sand or slurry-conditioned sands. This paper provides critical guidance for the design of conditioning schemes.

Upper bound analysis of longitudinally inclined EPB shield tunnel face stability in dense sand strata

Earth pressure balance (EPB) shield machine frequently drives along a route with a longitudinal inclination angle (δ) during tunnel construction. The tunnel face stability is a crucial issue for controlling the safety of tunneling. In this paper, the finite difference method (FDM) is used to investigate the face stability of longitudinally inclined shield tunnel in dense sand strata. Based on the numerical results of soil failure pattern in front of tunnel face, a novel two-dimensional (2D) failure mechanism is conceived following the upper bound theorem. It is assumed that the failure zone consists of an upper loosen zone, an arc-shaped shear band, and a triangular rigid body, which can calculate the active limit face support pressure pu. A scale factor for pu is introduced to quantify the three-dimensional (3D) behavior from the 2D calculation, with respect to different analysis approaches, e.g., numerical simulation, limit analysis, and limit equilibrium method. By incorporating the measure of scale factor, the calculation accuracy of the proposed 2D failure mechanism can be improved to provide reasonable prediction for longitudinally inclined tunnel.

Experimental study of foam infiltration from foam-sand mixture into saturated sand for EPB shield tunnelling: A mechanism study

This paper investigates the foam infiltration behavior from foam-sand mixture, resulting from foam conditioning of excavated sand inside of the excavation chamber of an Earth Pressure Balance (EPB) shield, into saturated sand at the tunnel face. The laboratory investigation was conducted using one dimensional element tests that simulate foam infiltration from the mixture into the saturated sand in front of the tunnel face. Pore pressures at different locations are measured near the sand surface, representing the tunnel face, while the sand column could provide a comparable hydraulic gradient to field conditions. Influences from foam injection ratio (FIR), remaining water content and sand type are examined. In the case of fine sand, it is found that there is little foam infiltration from the foam-sand mixture into the sand surface. Sedimentation of the foam-sand mixture on top of the saturated sand column is the dominating process that results in a dense mixture containing less liquid content with a smaller permeability. While for coarse-grained sand, foam infiltration will result in a foam infiltration zone with a lower permeability than the sedimented foam-sand mixture. Plastering effect at the tunnel face will increase with an increase in FIR and a decrease in remaining water content. Further analysis indicates that the sand matrix plays an important role in determining the permeability of a foam-sand mixture, as a higher density of sand results in a more tortuous seepage path for water. Mechanisms are discussed and implications for field applications are described.

Research on optimizing performance of new slurries for EPBS soil conditioning based on response surface method

Earth pressure balance shield (EPBS) construction process produces a large amount of untreatable shield dregs. Transporting these dregs directly to the landfill not only increases the costs, but also causes severe environmental problems. In order to improve the utilization rate of fine-grained shield dregs, a method of using waste silty clay to partially replace bentonite as a conditioner is proposed. Bentonite, wasted silty clay, additives, and tap water are selected to prepare the bentonite- silty clay modified slurry (BSC) and its various properties are tested. The whole tests are completed by the phased test method. Firstly, four additives are added into silty clay slurry for modification, and sodium carbonate is determined as the optimal additive and its dosage scheme. On this basis, the quantitative function relationship between the content of materials and the performance of BSC is established according to response surface method (RSM), and the performance optimization of BSC is completed. Finally, the microstructure of slurry is studied by scanning electron microscope (SEM) to explain the modification mechanism of BSC by sodium carbonate. The results show that the slurry-making capacity of silty clay can be modified effectively when the mixing ratio of sodium carbonate is 1%–3%. The regression model established by RSM is in good agreement with the experimental results, which can effectively predict the BSC properties under different material contents. When the mass ratio of water: bentonite: silty clay: sodium carbonate is 1000:58.91:297.97:3.14, the performance of BSC is close to that of bentonite slurry with soil–water ratio of 1:10. This study provides a feasible way for the recycling discharged soil from EPBS tunnel construction.