Dynamic Response of Foundations during Startup of High-Frequency Tunnel Equipment

The specialized equipment utilized in long-line tunnel engineering is evolving towards large-scale,multifunctional,and complex orientations.The vibration caused by the high-frequency units during regular operation is supported by the foundation of the units,and the magnitude of vibration and the operating frequency fluctuate in different engineering contexts,leading to variations in the dynamic response of the foundation.The high-frequency units yield significantly diverse outcomes under different startup conditions and times,resulting in failure to meet operational requirements,influencing the normal function of the tunnel,and causing harm to the foundation structure,personnel,and property in severe cases.This article formulates a finite element numerical computation model for solid elements using three-dimensional elastic body theory and integrates field measurements to substantiate and ascertain the crucial parameter configurations of the finite element model.By proposing a comprehensive startup timing function for high-frequency dynamic machines under different startup conditions,simulating the frequency andmagnitude variations during the startup process,and suggesting functions for changes in frequency and magnitude,a simulated startup schedule function for high-frequency machines is created through coupling.Taking into account the selection of the transient dynamic analysis step length,the dynamic response results for the lower dynamic foundation during its fundamental frequency crossing process are obtained.The validation checks if the structural magnitude surpasses the safety threshold during the critical phase of unit startup traversing the structural resonance region.The design recommendations for high-frequency units’dynamic foundations are provided,taking into account the startup process of the machine and ensuring the safe operation of the tunnel.

Evaluation and prediction of earth pressure balance shield performance in complex rock strata:A case study in Dalian,China

This research explores the potential for the evaluation and prediction of earth pressure balance shield performance based on a gray system model.The research focuses on a shield tunnel excavated for Metro Line 2 in Dalian,China.Due to the large error between the initial geological exploration data and real strata,the project construction is extremely difficult.In view of the current situation regarding the project,a quantitative method for evaluating the tunneling efficiency was proposed using cutterhead rotation(R),advance speed(S),total thrust(F)and torque(T).A total of 80 datasets with three input parameters and one output variable(F or T)were collected from this project,and a prediction framework based gray system model was established.Based on the prediction model,five prediction schemes were set up.Through error analysis,the optimal prediction scheme was obtained from the five schemes.The parametric investigation performed indicates that the relationships between F and the three input variables in the gray system model harmonize with the theoretical explanation.The case shows that the shield tunneling performance and efficiency are improved by the tunneling parameter prediction model based on the gray system model.

An integrated framework for automatic green building evaluation:A case study of China

With the burgeoning emphasis on sustainable construction practices in China,the demand for green building assessment has significantly escalated.The overall evaluation process comprises two key components:The acquisition of evaluation data and the evaluation of green scores,both of which entail considerable time and effort.Previous research predominantly concentrated on automating the latter process,often neglecting the exploration of automating the former in accordance with the Chinese green building assessment system.Furthermore,there is a pressing requirement for more streamlined management of structured standard knowledge to facilitate broader dissemination.In response to these challenges,this paper presents a conceptual framework that integrates building information modeling,ontology,and web map services to augment the efficiency of the overall evaluation process and the management of standard knowledge.More specifically,in accordance with the Assessment Standard for Green Building(GB/T 50378-2019)in China,this study innovatively employs visual programming software,Dynamo in Autodesk Revit,and the application programming interface of web map services to expedite the acquisition of essential architectural data and geographic information for green building assessment.Subsequently,ontology technology is harnessed to visualize the management of standard knowledge related to green building assessment and to enable the derivation of green scores through logical reasoning.Ultimately,a residential building is employed as a case study to validate the theoretical and technical feasibility of the developed automated evaluation conceptual framework for green buildings.The research findings hold valuable utility in providing a self-assessment method for applicants in the field.

Experimental and numerical investigation of the flexural performance of channel steel-bolt joint for prefabricated subway stations

Flexural performance of joints is critical for prefabricated structures.This study presents a novel channel steel-bolt(CB)joint for prefabricated subway stations.Full-scale tests are carried out to investigate the flexural behavior of the CB joint under the design loads of the test-case station.In addition,a three dimensional(3D)finite element(FE)model of the CB joint is established,incorporating viscous contact to simulate the bonding and detachment behaviors of the interface between channel steel and concrete.Based on the 3D FE model,the study examines the flexural bearing mechanism and influencing factors for the flexural performance of the CB joint.The results indicate that the flexural behavior of the CB joint exhibits significant nonlinear characteristics,which can be divided into four stages.To illustrate the piecewise linearity of the bending moment-rotational angle curve,a four-stage simplified model is proposed,which is easily applicable in engineering practice.The study reveals that axial force can enhance the flexural capacity of the CB joint,while the preload of the bolt has a negligible effect.The flexural capacity of the CB joint is approximate twice the value of the designed bending moment,demonstrating that the joint is suitable for the test-case station.

Uncovering the relationship among spatial vitality,perception,and environment of urban underground space in the metro zone

With the rapid development of rail transit,effectively developing urban underground space(UUS)in the metro zone has become an important approach to expanding urban space.However,UUS is currently facing problems,such as an uneven distribution or even loss of vitality,which restricts the utilization efficiency of the space.Thus,we established a UUS environmental assessment system based on the‘‘comfort-aesthetic-function-traffic-structure”using space syntax,instrumental measurement,and questionnaire surveys.By constructing a partial-least-square structural equation model,the internal relationships between the UUS environment and corresponding space vitality and space perception under different study areas,namely the underground transportation-oriented space(transportation space for short)and the underground commercial-oriented space(commercial space for short),were studied in detail throughout the working day.Results indicate the following:(1)the UUS in the metro zone environment influences spatial vitality.The vitality distribution of transportation space is significantly affected by the spatial traffic and structure.The vitality distribution of commercial space is significantly affected by the spatial function and traffic.(2)The environment of UUSs in the metro zone influences users’s perception.The perception of transportation space is significantly affected by aesthetics and comfort.The perception of commercial space is significantly affected by aesthetic,comfort,and spatial functions.(3)The user’s perception affects vitality,and the effect is more significant in commercial space.This study provides an in-depth understanding of the relationship between the complex environment and its spatial vitality as well as the spatial perception of the UUS in metro zones.Our research results provide a novel approach and theoretical basis for the development and application of UUS vitality in various cities.

DEM analysis of passive arching in a shallow trapdoor under eccentric loading

This study analyzed the passive arching effect under eccentric loading by developing a series of trapdoor discrete numerical models.The numerical models were validated by comparison with laboratory test results.The deformation pattern,soil arching ratio,force chain distribution,and coordination number under various surcharge magnitudes and deviation distances were analyzed.The numerical results showed that the deformation diagram of soil particles can be divided into three zones:principal displacement zone,transition zone,and static zone.With an increase in the surcharge magnitude,the range of the principal displacement zone decreased,but the range of the transition region increased.The curve of the soil arching ratio on the trapdoor can be divided into three phases,which can be well characterized by the tangent modulus.The passive arching effect is degraded by a surcharge.The ulti-mate soil arching ratio could be approximated as a W-shaped distribution along the+x-direction.With an increase in the trapdoor displacement,the force chain on the trapdoor gradually expanded outward to form an inverted funnel shape.The most powerful force on the trapdoor was mainly distributed on its edge.The average coordination number decreased gradually as the trapdoor moved upward.

Numerical study on transverse deformation characteristics of shield tunnel subject to local soil loosening

In this study,a refined numerical model for segmental lining of a shield tunnel,which contains detailed models of reinforcement and connecting bolts,is established using finite element software.The model is first validated by the results from a full-scale model test.Then,based on the load-structure method,this numerical model is adopted to investigate the internal force distribution and the transverse deformation characteristics of the shield tunnel when it is subject to local soil loosening.The influence of loosening position,loosening range,and loosening extent on the mechanical response is extensively studied through comprehensive numerical analyses.The results show that the main influence of local soil loosening on the ring is to disturb the force balance and change the constraint conditions,thus changing the deformation pattern and force state.After the loosening occurs,the bending moment of the ring in the loosening range increases and the axial force decreases.The vertical convergence of the ring is the largest and the equivalent stiffness of the ring is the smallest when the local soil loosened at the haunch and the loosening range a is 90°.The vertical convergence of the ring increases with increasing of the loosening extent,and the equivalent stiffness decreases linearly with increasing of the loosening extent.The results can enhance our understanding of mechanical behaviors of segmental lining associated soil loosening,and will show a possible way for detecting soil loosening based on the measured deformation and internal forces.

Data-driven real-time prediction for attitude and position of super-large diameter shield using a hybrid deep learning approach

The presented research introduces a novel hybrid deep learning approach for the dynamic prediction of the attitude and position of super-large diameter shields-a critical consideration for construction safety and tunnel lining quality.This study proposes a hybrid deep learning approach for predicting dynamic attitude and position prediction of super-large diameter shield.The approach consists of principal component analysis(PCA)and temporal convolutional network(TCN).The former is used for employing feature level fusion based on features of the shield data to reduce uncertainty,improve accuracy and the data effect,and 9 sets of required principal component characteristic data are obtained.The latter is adopted to process sequence data in predicting the dynamic attitude and position for the advantages and potential of convolution network.The approach’s effectiveness is exemplified using data from a tunnel construction project in China.The obtained results show remarkable accuracy in predicting the global attitude and position,with an average error ratio of less than 2 mm on four shield outputs in 97.30%of cases.Moreover,the approach displays strong performance in accurately predicting sudden fluctuations in shield attitude and position,with an average prediction accuracy of 89.68%.The proposed hybrid model demonstrates superiority over TCN,long short-term memory(LSTM),and recurrent neural network(RNN)in multiple indexes.Shapley additive exPlanations(SHAP)analysis is also performed to investigate the significance of different data features in the prediction process.This study provides a real-time warning for the shield driver to adjust the attitude and position of super-large diameter shields.