Assessing cutter-rock interaction during TBM tunnelling in granite:Large-scale standing rotary cutting tests and 3D DEM simulations

The widespread utilisation of tunnel boring machines(TBMs)in underground construction engineering requires a detailed investigation of the cutter-rock interaction.In this paper,we conduct a series of largescale standing rotary cutting tests on granite in conjunction with high-fidelity numerical simulations based on a particle-type discrete element method(DEM)to explore the effects of key cutting parameters on the TBM cutter performance and the distribution of cutter-rock contact stresses.The assessment results of cutter performance obtained from the cutting tests and numerical simulations reveal similar dependencies on the key cutting parameters.More specifically,the normal and rolling forces exhibit a positive correlation with penetration but are slightly influenced by the cutting radius.In contrast,the side force decreases as the cutting radius increases.Additionally,the side force shows a positive relationship with the penetration for smaller cutting radii but tends to become negative as the cutting radius increases.The cutter's relative effectiveness in rock breaking is significantly impacted by the penetration but shows little dependency on the cutting radius.Consequently,an optimal penetration is identified,leading to a low boreability index and specific energy.A combined Hertz-Weibull function is developed to fit the cutter-rock contact stress distribution obtained in DEM simulations,whereby an improved CSM(Colorado School of Mines)model is proposed by replacing the original monotonic cutting force distribution with this combined Hertz-Weibull model.The proposed model outperforms the original CSM model as demonstrated by a comparison of the estimated cutting forces with those from the tests/simulations.The findings from this work that advance our understanding of TBM cutter performance have important implications for improving the efficiency and reliability of TBM tunnelling in granite.

Machine learning-based automatic control of tunneling posture of shield machine

For a tunnel driven by a shield machine,the posture of the driving machine is essential to the construction quality and environmental impact.However,the machine posture is controlled by the experienced driver of shield machine by setting hundreds of tunneling parameters empirically.Machine learning(ML)algorithm is an alternative method that can let the computer to learn from the driver’s operation and try to model the relationship between parameters automatically.Thus,in this paper,three ML algorithms,i.e.multi-layer perception(MLP),support vector machine(SVM)and gradient boosting regression(GBR),are improved by genetic algorithm(GA)and principal component analysis(PCA)to predict the tunneling posture of the shield machine.A set of the parameters for shield tunneling is extracted from the construction site of a Shanghai metro.In total,53,785 pairwise data points are collected for about 373 d and the ratio between training set,validation set and test set is 3:1:1.Each pairwise data point includes 83 types of parameters covering the shield posture,construction parameters,and soil stratum properties at the same time.The test results show that the averaged R2 of MLP,SVM and GBR based models are 0.942,0.935 and 0.6,respectively.Then the automatic control for the posture of shield tunnel is illustrated with an application example of the proposed models.The proposed method is proved to be helpful in controlling the construction quality with optimized construction parameters.

Extra-large Undersea Shield Tunnel in Composite Ground:Maliuzhou Traffic Tunnel in Zhuhai

1Project objective Extra-large shield tunnels have become the best choice for urban transportation tunnels due to the advantage of taking the best use of underground space.Hengqin Island in Zhuhai is a demonstration area to explore a new cooperation mode among Guangzhou,Hong Kong and Macao,which is also an important pivot of the 21st Century Maritime Silk Road.Thus,it takes an important role in serving Hong Kong and Macao and driving the economic development of the Pearl River Delta.However,as typhoons are frequent in Zhuhai,Hengqin Island will be isolated to the mainland when bridges are obstructed in typhoon seasons.Therefore,the bridges cannot satisfy the traffic demand to the island.The inconvenient transportation has a neglect influence on production and live of people on the island,which also affects the long term development of Hengqin Island.Apart from the two existed bridges,Maliuzhou Traffic Tunnel in Zhuhai is the third major link of Hengqin Island to the mainland,which will put an end to the"losing connectionM problem due to obstructing the bridges in typhoon seasons.This linkage is able to promote Zhuhai tourism exploitation and the long term development of the city,and also increase the security of peopled lives.Meanwhile,the construction of the Maliuzhou Traffic Tunnel has conquered the challenges in designing and building of the extra-large shield tunnel in composite ground and undersea circumstances.The designing methods and constructing approaches used in this project will provide theoretical supports and technical guarantees to similar projects.

Smoke movement in a tunnel of a running metro train on fire

Research on the distribution of smoke in tunnels is significant for the fire emergency rescue after an operating metro train catches fire. A dynamic grid technique was adopted to research the law of smoke flow diffusion inside the tunnel when the bottom of a metro train was on fire and to compare the effect of longitudinal ventilation modes on the smoke motion when the burning train stopped. Research results show that the slipstream curves around the train obtained by numerical simulation are consistent with experimental data. When the train decelerates, the smoke flow first extends to the tail of the train. With the decrease of the train's speed, the smoke flow diffuses to the head of the train. After the train stops, the slipstream around the train formed in the process of train operation plays a leading role in the smoke diffusion in the tunnel. The smoke flow quickly diffuses to the domain in front of the train. After forward mechanical ventilation is provided, the smoke flow inside the tunnel continues to diffuse downstream. When reverse mechanical ventilation operates, the smoke in front of the train flows back rapidly and diffuses to the rear of the train.

Two-layer autonomous intelligence dynamic trajectory planning method based on shield-tunnel ring-geology interactions

To solve the problem that current attitude planning methods do not fully consider the interaction and constraints among the shield,segmental tunnel ring,and geology,and cannot adapt to the changes in the actual engineering environment,or provide feasible long-term and short-term attitude planning,this paper proposes autonomous intelligent dynamic trajectory planning(AI-DTP)to provide tunnel ring and centimeter-layer planning targets for a self-driving shield to meet long-term accuracy and short-term rapidity.AI-DTP introduces the Frenet coordinate system to solve the problem of inconsistent spatial representation of tunnel data,segmental tunnel ring location,and surrounding geological conditions,designs the long short-term memory attitude prediction model to accurately predict shield attitude change trend based on shield,tunnel,and geology,and uses a heuristic algorithm for trajectory optimization.AI-DTP provides ring-layer and centimeter-layer planning objectives that meet the needs of long-term accuracy and short-term correction of shield attitude control.In the Hangzhou-Shaoxing Intercity Railroad Tunnel Project in China,the‘‘Zhiyu”shield equipped with the AI-DTP system was faster and more accurate than the manually controlled shield,with a smoother process and better quality of the completed tunnel.

The Theoretically Studies and Field Testing of Self-Insulation Exterior Wall in the Hot Summer and Cold Winter Zone

The energy efficiency design of the exterior wall in the buildings of the hot summer and cold winter zone of China should consider the heat prevention in summer and the heat insulation in winter. The self-insulation of the exterior?wall is a more feasible design to satisfy the energy efficiency of buildings in the?zone. However, the systematic research is urgently needed for the self-insulation of the exterior wall in the hot summer and cold winter zone of China. The paper tested the thermal performance of the common non-clay materials such as shale sintered hollow brick, sand autoclaved aerated concrete block, etc. by means of indoor experiments. The energy efficiency effect of the common materials was verified using dynamic calculation soft PKPM and several constitutions of exterior wall with different main bricks and insulation materials on the heat bridge were simulated, too. Besides, the tests of the thermal performance of exterior wall in real constructions were carried out to testify the practical effect of the recommended constitutions of exterior wall with different main bricks and insulation materials on the heat bridge. The conclusions are: the physical and thermal properties of the six non-clay wall material are better than the clay porous brick;the thermal performance of the non-clay brick can be improved obviously through the rational arrangement of the holes;shale sintered hollow brick after increasing the holes and rationalizing the hole arrangement and sand autoclaved aerated concrete block are recommended for buildings in the hot summer and cold winter area of China. The dynamic calculation results show that the thermal performances?of the non-clay materials are all satisfied with the energy efficiency;The heat transfer coefficient of the exterior wall with composition?③,?in which?the main wall was sand autoclaved aerated concrete block and the material on the heat bridge was sand autoclaved aerated concrete plate, is the smallest among the three recommended compositions.

Impact of regional human capital and urban sprawl on forest——based on a forest conservation model

Metropolitan cities in China have become a major economic hubs with an unprecedented increase of land use and decline of environmental resources. Based on a simple and abstract forest conservation model, this paper attempts to explain changes of forest resources caused by urban sprawl. Through the research, it is found that high level of regional human capital is beneficial to curb urban sprawl. In this vein the model presents the urban forest conservation cost strategy at the Nash equilibrium of varied discount factor and parameter control.

A 3D sliced-soil-beam model for settlement prediction of tunnelling using the pipe roofing method in soft ground

The pipe roofing method is widely used in tunnel construction because it can realize a flexible section shape and a large section area of the tunnel,especially under good ground conditions.However,the pipe roofing method has rarely been applied in soft ground,where the prediction and control of the ground settlement play important roles.This study proposes a sliced-soil-beam(SSB)model to predict the settlement of ground due to tunnelling using the pipe roofing method in soft ground.The model comprises a sliced-soil module based on the virtual work principle and a beam module based on structural mechanics.As part of this work,the Peck formula was modified for a square-section tunnel and adopted to construct a deformation mechanism of soft ground.The pipe roofing system was simplified to a threedimensional Winkler beam to consider the interaction between the soil and pipe roofing.The model was verified in a case study conducted in Shanghai,China,in which it provided the efficient and accurate prediction of settlement.Finally,the parameters affecting the ground settlement were analyzed.It was clarified that the stiffness of the excavated soil and the steel support are the key factors in reducing ground settlement.

Investigation of the first quasi-rectangular metro tunnel constructed by the 0-θ method

Quasi-rectangular shield tunneling is a cutting-edge trenchless method for constructing metro tunnels with double tubes,owing to its advantages in saving underground space and reducing ground disturbance.However,the conventional quasi-rectangular shield tunneling method is not applicable when constructing a tunnel without a center pillar,such as a scissor crossover section of a metro line.Therefore,the O-0 tunneling method,which combines the quasirectangular shield and pipe jacking methods,was investigated in this study to solve the aforementioned construction challenges.This study presents a case study of the Sijiqing Station of the Hangzhou Metro Line 9 in China,in which the O-0 method was first proposed and applied.Key techniques such as switching between two types of tunneling modes and the tunneling process control in complex construction environments were investigated.The results demonstrated that the O-0 method can address the technical challenges presented by the post-transition line with a high curvature and a scissors crossover line.In addition,the adoption of the 0-0 method ensured that the transformation between shield tunneling and pipe jacking was safe and efficient.The ground settlement monitoring results demonstrated that the disturbance to the surrounding environment can be limited to a safe level.This case study contributes to the construction technology for a metro tunnel containing both post-transition lines with a small turning radius and a scissors crossover line.A practical construction experience and theoretical guidance were provided in this study,which are of significance for both the industry and academia.

Synchronous shield tunnelling technology combining advancement and segment fabrication:Principle,verification and application

Through the active control of shield thrust system oil pressures,a synchronous shield tunnelling technology combining advancement and segment fabrication was proposed.The key to this technology was to completely exploit the additional stroke of the hydraulic jacks generated by the axial insertion of a key block to assemble the segments.Taking the tunnelling project of the Shanghai Airport Railway Link Line as a demonstration project,this paper uses a large model test platform for this synchronous technology.A single-ring construction process along a straight line was simulated,in which the theoretical external loads were implemented on the shield machine.The feasibility and reliability of this synchronous technology were evaluated considering the accuracy of total thrust force control,maintenance of tunnelling speed and shield postures and segment compression.The effectiveness of the redistribution principle for the missing thrust force due to the withdrawal of cylinders located in the segment fabrication region was discussed.Furthermore,some other interesting phenomena were observed in the practical application in addition to the model test.This technology primarily realizes synchronous assembly by improving the control of the propulsion system of conventional shield machines without any transformation of the shield machine’s primary structure,segment patterns or excavation method.The proposed method has good adaptability and a low construction cost,which will be beneficial for future long-distance tunnelling projects.

为盾构机(TBM)有效始发而对隧道工作井进行改造的经验分享（英文）

通过分享临时工程设计和施工前景,讨论并强调承包商如何从工程角度调整原设计,并在不利地质条件下,综合考虑有效的隧道始发井。共享经验涵盖如何运用不同的工作井施工方法,在2个隧道掘进机(TBM)始发井中避免支撑横跨工作井而造成不便。

新加坡路陆交通管理局T206项目运用系统模板的经验（英文）

通过分享临时工程设计和施工,讨论并强调承包商如何在其施工过程和挡土墙支护系统(ERSS)中进行模板支护设计;将新加坡建筑行业目前采用不同分包模式作对比,阐述良好模板支护系统设计具有减少人力、时间,节约成本并改善安全性。选择和购买系统模板运用于建设施工看似简单,但在地下车站和隧道施工中,挡土墙支护系统中有支撑体系,使系统模板的采用变得困难。

Evaluation on cutting performance of novel PDC cutter for pipe jacking machine

It is inevitable to cut reinforced concrete(RC)appeared in cross passage of city metro by cutting tools when constructing in densely populated area.The previous cutters employed to cut RC are insufficient and easily damaged,so a new polycrystalline diamond compact(PDC)cutter is used to solve this question.Based on the theoretical analysis of cutting mechanism,both circular and tapered PDC cutters with cutting edge angle of 90and negative front rack angle of 10are used to cut RC.The peeling and breaking patterns of cutting concrete are proposed,the nodular and grainy chips are the preferred modes in cutting steel bars.The LS-DYNA is employed to investigate the cutting performance in advance.The simulation results show that the average and peak cutting forces increase with the growth of penetration depth,cutting speed,and roundness,and subsequently the recommended penetration depth less than 1.2 mm is obtained to cut RC due to the existence of steel bars.Moreover,the linear cutting platform is adopted to investigate the force ability and damage state of PDC cutters.It is concluded that the cutting force increases abruptly and fluctuates heavily when cutting the coarse aggregates.The patterns occurred in both numerical and experimental results are generally similar.Notably,the steel bar is pulled out and the PDC cutter is damaged at the penetration depth of 0.8 mm,while a good cut occurs at the penetration depth of 0.3 mm.The tapered PDC cutter with a relatively low cutting force is prone to be broken compared with circular PDC cutter.It is suggested that the circular PDC cutter at the penetration depth of 0.3 mm should be used to cut RC in practical engineering.

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.

Characterization of geological uncertainties from limited boreholes using copula-based coupled Markov chains for underground construction

This paper proposes an efficient method for quantifying the stratigraphic uncertainties and modeling the geological formations based on boreholes.Two Markov chains are used to describe the soil transitions along different directions,and the transition probability matrices(TPMs)of the Markov chains are analytically expressed by copulas.This copula expression is efficient since it can represent a large TPM by a few unknown parameters.Due to the analytical expression of the TPMs,the likelihood function of the Markov chain model is given in an explicit form.The estimation of the TPMs is then re-casted as a multi-objective constrained optimization problem that aims to maximize the likelihoods of two independent Markov chains subject to a set of parameter constraints.Unlike the method which determines the TPMs by counting the number of transitions between soil types,the proposed method is more statistically sound.Moreover,a random path sampling method is presented to avoid the directional effect problem in simulations.The soil type at a location is inferred from its nearest known neighbors along the cardinal directions.A general form of the conditional probability,based on Pickard’s theorem and Bayes rule,is presented for the soil type generation.The proposed stratigraphic characterization and simulation method is applied to real borehole data collected from a construction site in Wuhan,China.It is illustrated that the proposed method is accurate in prediction and does not show an inclination during simulation.

Novel wreck salvaging method using curved rectangular pipe basing method:A case study of"Yangtze River EstuaryⅡ"ancient shipwreck salvage project

Shipwreck salvage is a risky,time-consuming,and expensive process.Although there are many sunken ships along coastlines and in the open seas,the salvage process of a sunken ship has rarely been reported.The integrated salvage of the"Yangtze River EstuaryⅡ"shipwreck used a novel method with 22 closely locked curved rectangular pipes to form a watertight base that wrapped the shipwreck inside.The basing was lifted out of the water using a powerful crane situated on an engineering ship.For the first time,the tunneling method was used in a shipwreck salvage project,significantly reducing the disturbance to the shipwreck and its stowage,thereby preserving the original state and integrity of the shipwreck to the greatest extent.In this study,the basic concepts of the salvage method and process are explained.Solutions to critical issues in the new salvage method are provided,including jacking force prediction and major considerations for the structural design of the salvage system.The design of the salvage system and salvage process of the"Yangtze River EstuaryⅡ"shipwreck are introduced.The monitored jacking force,pipe deformation,and observed water-tightness verified that the proposed method was effective and efficient.Other possible application scenarios for the proposed method are presented at the end.

Response of operating metro tunnels to compensation grouting of an underlying large-diameter shield tunnel:A case study in Hangzhou

Due to the shield tunneling underneath,long-term settlements may develop in the existing metro tunnels.The compensation grouting is applied worldwide to stabilize the settlement of ground and existing structures.Few field studies concerning large-diameter shield pass-ing tunnel from below have analyzed the interaction between the compensation grouting and the existing tunnel.This paper presents a case study on the response of the operating metro tunnels to the compensation grouting of an underlying large-diameter tunnel in muddy clay stratum.The tunnel deformations before,during,and after the compensation grouting were monitored and analyzed.The long-term tunnel settlements were mitigated and stabilized by the timely compensation grouting.Smaller settlement rates were observed during the grouting treatment,and the settlement was gradually stabilized three months after the grouting.The grouting holes at the tunnel invert were used initially for better grouting efficiency.The horizontal displacement and convergence developed during the grouting construc-tion and remained stable after the grouting process.Moreover,some limitations of the grouting treatment were discussed.The tunnel settlement in the section close to the center-line of the south-line tunnel cannot be prevented effectively.The differential displacement cannot be reduced by this grouting program.

Advanced finite element analysis of a complex deep excavation case history in Shanghai

The construction of the North Square Shopping Center of the Shanghai South Railway Station is a large scale complex top-down deep excavation project. The excavation is adjacent to several current and newly planned Metro lines, and influenced by a neighboring Exchange Station excavation. The highly irregular geometry of this excavation greatly increases the complexity in 3D Finite Element modeling. The advanced numerical modeling described in this paper includes detailed structural and geotechnical behavior. Important features are considered in the analysis, e.g., 1） the small-strain stiffness of the soil, 2） the construction joints in the diaphragm wall, 3） the shrinkage in the concrete floor slabs and beams, 4） the complex construction sequences, and 5） the shape effect of the deep excavation. The numerical results agree well with the field data, and some valuable conclusions are generated.

Prototype Loading Tests on Full-Ring Segmental Lining of Rectangular Shield Tunnel

A series of full-scale loading tests are performed for a prospective subway tunnel with a rectangular shape including two reliability tests: one stagger-jointed three-ring reliability test, and one ultimate failure test on a single ring. Comprehensive measuring programs are designed to record the deformation of both lining structure and joints and the stresses of concrete, bolts and reinforcements. Experimental results show that in both the single-ring and three-ring loading cases, the long sides of tunnel cross section bend inwards while the short sides of tunnel cross section bend outwards. The inner part of joints opens while the outer part of joints closes at places experiencing positive moment and vice versa. Joint's rotational stiffness varies at different locations. Concrete cracking and crushing are the chief damage modes, and they are closely related to the distribution of bending moment. Stagger-jointed fabrication significantly increases the overall rigidity of lining system, which thereby greatly reduces the deformation of both concrete lining and joints in comparison with the single-ring case. It is shown that the routinely-used uniform rigidity model is conservative and the preliminary design can be optimized by applying an effective rigidity ratio(ERR) of 0.5.

A simplified method for investigating the bending behavior of piles supporting embankments on soft ground

In recent years,concrete and reinforced concrete piles have been widely used to stabilize soft ground under embankments.Previous research has shown that bending failure,particularly during rapid filling on soft ground,is the critical failure mode for pile-supported embankments.Here,we propose an efficient two-stage method that combines a test-verified soil deformation mechanism and Poulos’solution for pile–soil interaction to investigate the bending behavior of piles supporting embankments on soft ground.The results reveal that there are three possible bending failure scenarios for such piles:at the interface between the soft and firm ground layers,at mid-depths of the fan zone,and at the boundary of the soil deformation mechanism.The location of the bending failure depends on the position and relative stiffness of the given pile.Furthermore,the effect of embedding a pile into a firm ground layer on the bending behavior was investigated.When the embedded length of a pile exceeded a critical value,the bending moment at the interface between the soft and firm ground layers reached a limiting value.In addition,floating piles that are not embedded exhibit an overturning pattern of movement in the soft ground layer,and a potential failure is located in the upper part of these piles.