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Effectiveness of predicting tunneling-induced ground settlements using machine learning methods with small datasets

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第4期14卷 1028-1041页

作者： Linan Liu Wendy Zhou marte gutierrez Department of Geology and Geological Engineering Colorado School of MinesGoldenCO80401USA Department of Civil and Environmental Engineering Colorado School of MinesGoldenCO80401USA

Prediction of tunneling-induced ground settlements is an essential task,particularly for tunneling in urban settings.Ground settlements should be limited within a tolerable threshold to avoid damages to aboveground structures.Machine learning(ML)methods are becoming popular in many fields,including tunneling and underground excavations,as a powerful learning and predicting technique.However,the available datasets collected from a tunneling project are usually small from the perspective of applying ML methods.Can ML algorithms effectively predict tunneling-induced ground settlements when the available datasets are small?In this study,seven ML methods are utilized to predict tunneling-induced ground settlement using 14 contributing factors measured before or during tunnel excavation.These methods include multiple linear regression(MLR),decision tree(DT),random forest(RF),gradient boosting(GB),support vector regression(SVR),back-propagation neural network(BPNN),and permutation importancebased BPNN(PI-BPNN)models.All methods except BPNN and PI-BPNN are shallow-structure ML methods.The effectiveness of these seven ML approaches on small datasets is evaluated using model accuracy and stability.The model accuracy is measured by the coefficient of determination(R2)of training and testing datasets,and the stability of a learning algorithm indicates robust predictive performance.Also,the quantile error(QE)criterion is introduced to assess model predictive performance considering underpredictions and overpredictions.Our study reveals that the RF algorithm outperforms all the other models with the highest model prediction accuracy(0.9)and stability(3.0210^(-27)).Deep-structure ML models do not perform well for small datasets with relatively low model accuracy(0.59)and stability(5.76).The PI-BPNN architecture is proposed and designed for small datasets,showing better performance than typical BPNN.Six important contributing factors of ground settlements are identified,including tunnel depth,the distance between tunnel face an

关键词： Ground settlements Tunneling Machine learning Small dataset Model accuracy Model stability Feature importance

Physical model simulation of rock-support interaction for the tunnel in squeezing ground

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第1期14卷 82-92页

作者： Ketan Arora marte gutierrez Ahmadreza Hedayat Civil and Environmental Engineering Colorado School of MinesGoldenCO80401USA

The existence of squeezing ground conditions can lead to significant challenges in designing an adequate support system for tunnels.Numerous empirical,observational and analytical methods have been suggested over the years to design support systems in squeezing ground conditions,but all of them have some limitations.In this study,a novel experimental setup having physical model for simulating the tunnel boring machine(TBM)excavation and support installation process in squeezing clay-rich rocks is developed.The observations are made to understand better the interaction between the support and the squeezing ground.The physical model included a large true-triaxial cell,a miniature TBM,laboratoryprepared synthetic test specimen with properties similar to natural mudstone,and an instrumented cylindrical aluminum support system.Experiments were conducted at realistic in situ stress levels to study the time-dependent three-dimensional tunnel support convergence.The tunnel was excavated using the miniature TBM in the cubical rock specimen loaded in the true-triaxial cell,after which the support was installed.The confining stress was then increased in stages to values greater than the rock’s unconfined compressive strength.A model for the time-dependent longitudinal displacement profile(LDP)for the supported tunnel was proposed using the tunnel convergence measurements at different times and stress levels.The LDP formulation was then compared with the unsupported model to calculate the squeezing amount carried by the support.The increase in thrust in the support was backcalculated from an analytical solution with the assumption of linear elastic support.Based on the test results and case studies,a recommendation to optimize the support requirement for tunnels in squeezing ground is proposed.

关键词： Squeezing ground Tunnel support system Longitudinal displacement profile Rock-support interaction

Empirical approach for reliability evaluation of tunnel excavation stability using the Q rock mass classification system

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Underground Space 2022年第5期7卷 862-881页

作者： Hui Lu marte gutierrez Eunhye Kim McMillen Jacobs Associates Walnut CreekCAUSA Department of Civil and Environmental Engineering Colorado School of MinesGoldenCOUSA Federal Energy Regulatory Commission San FranciscoCAUSA

The critical strain concept has been widely used in analytical or numerical approaches to evaluate the stability of underground excavations.Analytical,empirical,and numerical procedures are usually used to determine the critical strain values.This paper presents a reliability assessment procedure for evaluating excavation stability using the empirical approach based on the rock mass classification Q and the first order reliability method(FORM).In contrast to deterministic critical strain values,a probabilistic critical strain,which considers uncertainties in rock mass parameters,was incorporated in a limit state function for reliability analysis.Using the rock mass classification Q,the empirically estimated tunnel stain was included in the limit state function.The critical strain and estimated tunnel strain were probabilistically characterized based on the rock mass classification Q-derived rock mass properties.Monte Carlo simulations were also conducted for comparing the reliability analysis results with those derived from the FORM algorithm.A highway tunnel case study was used to demonstrate the reliability assessment procedure.The effects of the input ground parameter correlations,probability distributions,and coefficients of variation on tunnel reliability were investigated.Results show that uncorrelated and normally distributed input parameters(intact rock strength and elastic modulus)have generated more conservative reliability.The reliability analysis results also show that the tunnel had relatively high reliability(reliability index of 2.78 and probability of failure of 0.27%),indicating the tunnel is not expected to experience instability after excavation.The tunnel excavation stability was assessed using analytical and numerical approaches for comparison.The results were consistent with the reliability analysis using the FORM algorithm’s Q-based empirical method.

关键词： Reliability analysis Tunnel Critical strain Rock mass classification Q First order reliability method

Coupled hydro-thermo-mechanical modeling of hydraulic fracturing in quasi-brittle rocks using BPM-DEM

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第1期9卷 92-104页

作者： Ingrid Tomac marte gutierrez Department of Structural Engineering University of California San Diego Department of Civil and Environmental Engineering Colorado School of Mines Department of Geosciences University of Oslo

This paper presents an improved understanding of coupled hydro-thermo-mechanical(HTM) hydraulic fracturing of quasi-brittle rock using the bonded particle model(BPM) within the discrete element method(DEM). BPM has been recently extended by the authors to account for coupled convective econductive heat flow and transport, and to enable full hydro-thermal fluidesolid coupled modeling.The application of the work is on enhanced geothermal systems(EGSs), and hydraulic fracturing of hot dry rock(HDR) is studied in terms of the impact of temperature difference between rock and a flowing fracturing fluid. Micro-mechanical investigation of temperature and fracturing fluid effects on hydraulic fracturing damage in rocks is presented. It was found that fracture is shorter with pronounced secondary microcracking along the main fracture for the case when the convectiveeconductive thermal heat exchange is considered. First, the convection heat exchange during low-viscosity fluid infiltration in permeable rock around the wellbore causes significant rock cooling, where a finger-like fluid infiltration was observed. Second, fluid infiltration inhibits pressure rise during pumping and delays fracture initiation and propagation. Additionally, thermal damage occurs in the whole area around the wellbore due to rock cooling and cold fluid infiltration. The size of a damaged area around the wellbore increases with decreasing fluid dynamic viscosity. Fluid and rock compressibility ratio was found to have significant effect on the fracture propagation velocity.

关键词： Hydro-thermo-mechanical(HTM) modeling Enhanced geothermal systems(EGSs) Discrete element method(DEM) Bonded particle model(BPM) Conductive-convective heat flow and transport Hydraulic fracturing Rock permeability enhancement

Axisymmetric alternating direction explicit scheme for efficient coupled simulation of hydro-mechanical interaction in geotechnical engineering-Application to circular footing and deep tunnel in saturated ground

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第2期10卷 259-279页

作者： Simon Heru Prassetyo marte gutierrez Department of Civil and Environmental Engineering Colorado School of MinesGoldenUSA Mining Engineering Program Institut Teknologi BandungBandungIndonesia

Explicit solution techniques have been widely used in geotechnical engineering for simulating the coupled hydro-mechanical(H-M) interaction of fluid flow and deformation induced by structures built above and under saturated ground, i.e. circular footing and deep tunnel. However, the technique is only conditionally stable and requires small time steps, portending its inefficiency for simulating large-scale H-M problems. To improve its efficiency, the unconditionally stable alternating direction explicit(ADE)scheme could be used to solve the flow problem. The standard ADE scheme, however, is only moderately accurate and is restricted to uniform grids and plane strain flow conditions. This paper aims to remove these drawbacks by developing a novel high-order ADE scheme capable of solving flow problems in nonuniform grids and under axisymmetric conditions. The new scheme is derived by performing a fourthorder finite difference(FD) approximation to the spatial derivatives of the axisymmetric fluid-diffusion equation in a non-uniform grid configuration. The implicit Crank-Nicolson technique is then applied to the resulting approximation, and the subsequent equation is split into two alternating direction sweeps,giving rise to a new axisymmetric ADE scheme. The pore pressure solutions from the new scheme are then sequentially coupled with an existing geomechanical simulator in the computer code fast Lagrangian analysis of continua(FLAC). This coupling procedure is called the sequentially-explicit coupling technique based on the fourth-order axisymmetric ADE scheme or SEA-4-AXI. Application of SEA-4-AXI for solving axisymmetric consolidation of a circular footing and of advancing tunnel in deep saturated ground shows that SEA-4-AXI reduces computer runtime up to 42%-50% that of FLAC’s basic scheme without numerical instability. In addition, it produces high numerical accuracy of the H-M solutions with average percentage difference of only 0.5%-1.8%.

关键词： Hydro-mechanical(H-M) interaction Explicit coupling technique Alternating direction explicit(ADE) scheme High-order finite difference(FD) Non-uniform grid Axisymmetric consolidation Circular footing Deep tunnel in saturated ground

Effect of surface loading on the hydro-mechanical response of a tunnel in saturated ground

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Underground Space 2016年第1期1卷 1-19页

作者： Simon Heru Prassetyo marte gutierrez Department of Civil and Environmental Engineering Colorado School of MinesGoldenCO 80401USA

The design of underground spaces in urban areas must account not only for the current overburden load but also for future surface loads,such as from construction of high-rise buildings above underground structures.In saturated ground,the surface load will generate an additional mechanical response through stress changes and ground displacement,as well as a hydraulic response through pore pressure changes.These hydro-mechanical(H-M)changes can severely influence tunnel stability.This paper examines the effect of surface loading on the H-M response of a typical horseshoe-shaped tunnel in saturated ground.Two tunnel models were created in the computer code Fast Lagrangian Analysis of Continua(FLAC).One model represented weak and low permeability ground(stiff clay),and the other represented strong and high permeability ground(weathered granite).Each of the models was run under two liner permeabilities:permeable and impermeable.Two main cases were compared.In Case 1,the surface load was applied 10 years after tunnel construction.In Case 2,the surface load was applied after the steady state pore pressure condition was achieved.The simulation results show that tunnels with impermeable liners experienced the most severe influence from the surface loading,with high pore pressures,large inward displacement around the tunnels,and high bending moments in the liner.In addition,the severity of the response increased toward steady state.This induced H-M response was worse for tunnels in clay than for those in granite.Furthermore,the long-term liner stabilities in Case 1 and Case 2 were similar,indicating that the influence of the length of time between when the tunnel was completed and when the surface load was applied was negligible.These findings suggest that under surface loading,in addition to the ground strength,tunnel stability in saturated ground is largely influenced by liner permeability and the long-term H-M response of the ground.

关键词： Surface loading Hydro-mechanical response Urban tunnels Saturated ground

Stress-dependent shear wave splitting and permeability in fractured porous rock

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第1期11卷 1-11页

作者： Daisuke Katsuki marte gutierrez Abdulhadi Almrabat Petroleum Engineering Department Colorado School of Mines Department of Civil and Environmental Engineering Colorado School of Mines

It is well known that shear wave propagates slower across than parallel to a fracture, and as a result, a travelling shear wave splits into two directions when it encounters a fracture. Shear wave splitting and permeability of porous rock core samples having single fracture were experimentally investigated using a high-pressure triaxial cell, which can measure seismic shear wave velocities in two directions mutually perpendicular to the sample axis in addition to the longitudinal compressive wave velocity. A single fracture was created in the samples using a modified Brazilian split test device, where the cylindrical sample edges were loaded on two diametrically opposite lines by sharp guillotines along the sample length. Based on tilt tests and fracture surface profilometry, the method of artificially induced tensile fracture in the sample was found to create repeatable fracture surfaces and morphologies. Seismic velocities of the fractured samples were determined under different levels of stress confinement and fracture shear displacement or mismatch. The effective confining stress was varied from 0.5 MPa to55 MPa, while the fractures were mismatched by 0 mm, 0.45 mm and 1 mm. The degree of matching of the fracture surfaces in the core samples was evaluated using the joint matching coefficient(JMC). Shear wave splitting, as measured by the difference in the magnitudes of shear wave velocities parallel(V_(S1))and perpendicular(V_(S2)) to the fracture, is found to be insensitive to the degree of mismatching of the fracture joint surfaces at 2 MPa, and decreased and approached zero as the effective stress was increased.Simple models for the stress-and JMC-dependent shear wave splitting and fractured rock permeability were developed based on the experimental observations. The effects of the joint wall compressive strength(JCS), JMC and stress on the stress dependency of joint aperture were discussed in terms of hydro-mechanical response. Finally, a useful relationship between fractured rock permeability and shear w

关键词： Fractured rock Sandstone Stress dependency Shear wave splitting Wave velocity Permeability Fracture stiffness Elastic modulus

Nonlinear shear behavior of rock joints using a linearized implementation of the Barton-Bandis model

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第4期9卷 671-682页

作者： Simon Heru Prassetyo marte gutierrez Nick Barton Department of Civil and Environmental Engineering Colorado School of Mines Golden CO 80401 USA Nick Barton and Associates Oslo Norway

Experiments on rock joint behaviors have shown that joint surface roughness is mobilized under shearing,inducing dilation and resulting in nonlinear joint shear strength and shear stress vs.shear displacement behaviors.The Barton-Bandis(B-B) joint model provides the most realistic prediction for the nonlinear shear behavior of rock joints.The B-B model accounts for asperity roughness and strength through the joint roughness coefficient(JRC) and joint wall compressive strength(JCS) parameters.Nevertheless,many computer codes for rock engineering analysis still use the constant shear strength parameters from the linear Mohr-Coulomb(M-C) model,which is only appropriate for smooth and non-dilatant joints.This limitation prevents fractured rock models from capturing the nonlinearity of joint shear behavior.To bridge the B-B and the M C models,this paper aims to provide a linearized implementation of the B-B model using a tangential technique to obtain the equivalent M-C parameters that can satisfy the nonlinear shear behavior of rock joints.These equivalent parameters,namely the equivalent peak cohesion,friction angle,and dilation angle,are then converted into their mobilized forms to account for the mobilization and degradation of JRC under shearing.The conversion is done by expressing JRC in the equivalent peak parameters as functions of joint shear displacement using proposed hyperbolic and logarithmic functions at the pre-and post-peak regions of shear displacement,respectively.Likewise,the pre-and post-peak joint shear stiffnesses are derived so that a complete shear stress-shear displacement relationship can be established.Verifications of the linearized implementation of the B-B model show that the shear stress-shear displacement curves,the dilation behavior,and the shear strength envelopes of rock joints are consistent with available experimental and numerical results.

关键词： Rock joints Joint shear behavior Friction and dilation Barton-Bandis(B-B) model Equivalent Mohr-Coulomb(M-C) parameters

Effects of fracture distribution and length scale on the equivalent continuum elastic compliance of fractured rock masses

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第6期7卷 626-637页

作者： marte gutierrez Dong-Joon Youn Department of Civil and Environmental Engineering Colorado School of Mines Department of Civil Infrastructure and Environmental Engineering Khalifa University

Fracture systems have strong influence on the overall mechanical behavior of fractured rock masses dueto their relatively lower stiffness and shear strength than those of the rock matrix. Understanding theeffects of fracture geometrical distribution, such as length, spacing, persistence and orientation, isimportant for quantifying the mechanical behavior of fractured rock masses. The relation betweenfracture geometry and the mechanical characteristics of the fractured rock mass is complicated due tothe fact that the fracture geometry and mechanical behaviors of fractured rock mass are stronglydependent on the length scale. In this paper, a comprehensive study was conducted to determine theeffects of fracture distribution on the equivalent continuum elastic compliance of fractured rock massesover a wide range of fracture lengths. To account for the stochastic nature of fracture distributions, threedifferent simulation techniques involving Oda＇s elastic compliance tensor, Monte Carlo simulation （MCS）,and suitable probability density functions （PDFs） were employed to represent the elastic compliance offractured rock masses. To yield geologically realistic results, parameters for defining fracture distributionswere obtained from different geological fields. The influence of the key fracture parameters andtheir relations to the overall elastic behavior of the fractured rock mass were studied and discussed. Adetailed study was also carried out to investigate the validity of the use of a representative elementvolume （REV） in the equivalent continuum representation of fractured rock masses. A criterion was alsoproposed to determine the appropriate REV given the fracture distribution of the rock mass.

关键词： Fractured rock mass Equivalent continuum elastic compliance Monte Carlo simulation(MCS) Representative element volume(REV) Scale effects