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Numerical computation of anti-liquefaction effect of lattice-type cement-mixed soil countermeasure

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Journal of Central South University 2008年第S2期15卷 155-160页

作者：高玉峰杨雪玲沈扬周源 Key Laboratory of Ministry of Education for Geomechanics and Embankment engineering Hohai University geotechnical Research institute Hohai University East China Electric Power Design geotechnical engineering Company

Continuous soil-cement wall confinement method to resist liquefaction is a new kind of process. However, whether it also has a good effect on anti-liquefaction or not needs to be urgently answered for earthquake engineering. Quiet boundary is adopted on the lateral face while free field boundary is employed at the bottom. Byrne model on dynamic pore water pressure generation is accepted and natural seismic wave EI Centro whose peak acceleration is adjusted to 0.2 g in proportion is used for input. A double-layer foundation with sandy soil in the upper portion while clay soil in the lower part is chosen as the calculation model, which is 30 m in length and 20 m in width. The groundwater level is on the ground surface. Excess pore water pressure rate is considered as a liquefaction index in the three-dimensional non-linear earthquake response computation. The anti-liquefaction effectiveness and its influencing factors, such as confinement element area are studied. For the natural double-layer foundation, it is liquefied when the excess pore water pressure rate reaches 1.0 under the seismic load. Under the same earthquake load, the peak excess pore water pressure reduces to 0.56 after adopting reinforcement of the continuous soil-cement wall, which is 46% lower than before. It indicates that continuous soil-cement wall confinement method can attain the purpose of anti-liquefaction. Accordingly, it can be a sort of engineering measure to carry on the anti-liquefaction foundation treatment.

关键词： lattice-type cement-mixed soil countermeasure anti-liquefaction excess pore pressure ratio the smallest lattice area

Equivalent elastic compliance tensor for rock mass with multiple persistent joint sets:Exact derivation via modified crack tensor

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Journal of Central South University 2016年第6期23卷 1486-1507页

作者：崔洁江权冯夏庭李邵军高红李帅军 State Key Laboratory of Geomechanics and geotechnical engineering Institute of Rock and Soil MechanicsChinese Academy of Sciences

Discontinuities constitute an integral part of rock mass and inherently affect its anisotropic deformation *** work focuses on the equivalent elastic deformation of rock mass with multiple persistent joint sets.A new method based on the space geometric and mechanical properties of the modified crack tensor is proposed,providing an analytical solution for the equivalent elastic compliance tensor of rock mass.A series of experiments validate the capability of the compliance tensor to accurately represent the deformation of rock mass with multiple persistent joint sets,based on conditions set by the basic *** spatially varying rules of the equivalent elastic parameters of rock mass with a single joint set are analyzed to reveal the universal law of the stratified rock mass.

关键词： equivalent elastic compliance tensor crack tensor multiple joint sets rock mass

A practical ANN model for predicting the excavation-induced tunnel horizontal displacement in soft soils

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Underground Space 2022年第2期7卷 278-293页

作者： Zhong-Kai Huang Dong-Mei Zhang Xiao-Chuang Xie Key Laboratory of geotechnical and Underground engineering of Ministry of Education Department of Geotechnical EngineeringTongji UniversityShanghaiChina

The objective of this study is to propose an artificial neural network(ANN)model to predict the excavation-induced tunnel horizontal displacement in soft *** this purpose,a series of finite element data sets from rigorously verified numerical models were collected to be utilized for the development of the ANN *** excavation width,the excavation depth,the retaining wall thickness,the ratio of the average shear strength to the vertical effective stress,the ratio of the average unloading/reloading Young’s modulus to the vertical effective stress,the horizontal distance between the tunnel and retaining wall,and the ratio of the buried depth of the tunnel crown to the excavation depth were chosen as the input variables,while the excavation-induced tunnel horizontal displacement was considered as an output *** results demonstrated the feasibility of the developed ANN model to predict the excavation-induced tunnel horizontal *** proposed ANN model in this study can be applied to predict the excavation-induced tunnel horizontal displacement in soft soils for practical risk assessment and mitigation decision.

关键词： Artificial neural network Excavation Tunnel horizontal displacement Soft soils

ROCK INITIATION AND PROPAGATION SIMULATION UNDER COMPRESSION-SHEAR LOADING USING CONTINUOUS-DISCONTINUOUS CELLULAR AUTOMATON METHOD

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Acta Mechanica Solida Sinica 2015年第4期28卷 384-399页

作者： Fei Yan Xiating Feng Pengzhi Pan Shao jun Li State Key Laboratory of Geomechanics and geotechnical engineering Institute of Rock and Soil MechanicsChinese Academy of Sciences

A continuous-discontinuous cellular automaton method is developed for rock initiation and propagation simulations, in which the level set method, discontinuous enrichment shape functions and discontinuous cellular automaton are combined. No renmshing is needed for crack growth analysis, and all calculations are restricted to cells without an assembled global stiffness matrix. The frictional contact theory is employed to construct the contact model of normal pressure and tangential shear on crack surfaces. A discontinuous cellular automaton updating rule suitable for frictional contact of rock is proposed simultaneously with Newton＇s iteration method for nonlinear iteration. Besides, a comprehensive fracturing criterion for brittle rock under compression-shear loading is developed. The accuracy and effectivenesss of the proposed method is proved by numerical simulation.

关键词： continuous-discontinuous cellular automaton method rock fracturing process compressionshear loading frictional contact comprehensive fracturing criterion

Modelling three dimensional dynamic problems using the fournode tetrahedral element with continuous nodal stress

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Science China(Technological Sciences) 2018年第12期61卷 1889-1900页

作者： ZHANG GuoHua YANG YongTao State Key Laboratory of Geomechanics and geotechnical engineering Institute of Rock and Soil MechanicsChinese Academy of Sciences

A partition of unity(PU) based four-node tetrahedral element with continuous nodal stress(Tetr4-CNS) was recently proposed for static analysis of three-dimensional solids. By simply using the same mesh as the classical four-node tetrahedral(Tetr4)element, high order global approximation function in the Tetr4-CNS element can be easily constructed without extra nodes or nodal DOFs. In this paper, the Tetr4-CNS element is further applied in the analysis of three dimensional dynamic problems. A series of free vibration and forced vibration problems are solved using the Tetr4-CNS element. The numerical results show that,for regular meshes, accuracy obtained using the Tetr4-CNS element is superior to that obtained using the Tetr4 and eight-node hexahedral(Hexa8) elements. For distorted meshes, the Tetr4-CNS element has better mesh-distortion tolerance than both the Tetr4 and Hexa8 elements.

关键词： partition of unity tetrahedral element Tetr4-CNS mesh distortion dynamic problems

Compressibility of fine-grained soils subjected to closed-system freezing and thaw consolidation

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Mining Science and Technology 2009年第5期19卷 631-635页

作者： BOLEY Conrad institute for Soil Mechanics and geotechnical engineering University of the Bundeswehr Munich

In order to investigate the effects of freezing and thawing on the compressibility of fine-grained soils, freezing and thawing tests and subsequent compression tests with fine-grained soils in an oedometer were carried out. During the freezing, a part of the soils is loosened and another part is over-consolidated under the freezing pressure σE. The compression curves after the freezing and thaw consolidation are neither different from the normal consolidation curve nor from the rebound curve of an unfrozen soil, until the consolidation pressure σz = σE is arrived. Based on the experimental results, a theoretical model has been devel- oped to predict the frost heaves, the thaw-settlements and the compressive deformations of fine-grained soils after the thaw consolidation. The theoretical results are very close to the experimental results.

关键词： ice lens frost heave thaw settlement compressibility

Three-Stage Transfer Learning with AlexNet50 for MRI Image Multi-Class Classification with Optimal Learning Rate

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Computer Modeling in engineering & Sciences 2025年第1期142卷 155-183页

作者： Suganya Athisayamani A.Robert Singh Gyanendra Prasad Joshi Woong Cho School of Computing Sastra Deemed to be UniversityThanjavur613401India Department of Computational Intelligence SRM Institute of Science and TechnologyKattankulathur603203India Department of AI and Software engineering Kangwon National UniversitySamcheok25913Republic of Korea Department of Electronics Information and Communication EngineeringKangwon National UniversitySamcheok25913Republic of Korea

In radiology,magnetic resonance imaging(MRI)is an essential diagnostic tool that provides detailed images of a patient’s anatomical and physiological *** is particularly effective for detecting soft tissue ***,radiologists manually interpret these images,which can be labor-intensive and time-consuming due to the vast amount of *** address this challenge,machine learning,and deep learning approaches can be utilized to improve the accuracy and efficiency of anomaly detection in MRI *** manuscript presents the use of the Deep AlexNet50 model for MRI classification with discriminative learning *** are three stages for learning;in the first stage,the whole dataset is used to learn the *** the second stage,some layers of AlexNet50 are frozen with an augmented dataset,and in the third stage,AlexNet50 with an augmented dataset with the augmented *** method used three publicly available MRI classification datasets:Harvard whole brain atlas(HWBA-dataset),the School of Biomedical engineering of Southern Medical University(SMU-dataset),and The National institute of Neuroscience and Hospitals brain MRI dataset(NINS-dataset)for *** hyperparameter optimizers like Adam,stochastic gradient descent(SGD),Root mean square propagation(RMS prop),Adamax,and AdamW have been used to compare the performance of the learning ***-dataset registers maximum classification *** evaluated the performance of the proposed classification model using several quantitative metrics,achieving an average accuracy of 98%.

关键词： MRI tumors classification AlexNet50 transfer learning hyperparameter tuning optimizer

Mesomechanical simulation of direct shear test on outwash deposits with granular discrete element method

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Journal of Central South University 2013年第4期20卷 1094-1102页

作者：石崇王盛年刘琳孟庆祥张强 Key Laboratory of Ministry of Education for Geomechanics and Embankment engineering (Hohai University) institute of geotechnical engineering Hohai University

The mechanical properties of outwash deposits which are taken as unconsolidated geo-materials with the characteristics of non-uniformity, heterogeneity and multiphase have attracted much attention in engineering. According to the results of laboratory direct shear test on the remolded samples, the soil particle parameters of numerical model based on in-situ particle size cumulative curves and 3D granular discrete element method were determined. Then, numerical experiments on different lithology, stone content and gradation composition were conducted. The results show that it is not a flat surface but a shear band that yields in the sample. The curve of particle velocity vs distance from the designed shear surface of test model that is taken as a datum plane in the vertical section of sample shows in "S" shape. The shear disturbance area is about twice the maximum diameter of stone blocks. The greater the stiffness of stone is, the rougher the shear surface is. The shear strength of outwash deposits is largely controlled by lithology and stone content, and the bite force between stone blocks is the root reason of larger friction angle. It is also shown that strain hardening and low shear dilatancy occur under high confining pressure as well as possibility of shear shrinkage. But it is easy to behave shear dilatation and strain softening under low confining pressure. The relationship between particle frictional coefficient and stone content presents an approximately quadratic parabola increase. The strain energy first increases and then drops with the increase of frictional energy. The cohesion increases with soil stiffness increasing but decreases with stone stiffness increasing. Numerical results are consistent with the laboratory test results of remolded samples, which indicate that this method can be a beneficial supplement to determine the parameters of engineering deposit bodies.

关键词： outwash deposit direct shear test granular discrete element mesomechanics

Theoretical analysis of a row of piles as passive barriers and an equivalent in-filled trench model

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Journal of Central South University 2015年第5期22卷 1919-1928页

作者：高广运宋健杨峻 Department of geotechnical engineering Tongji University Key Laboratory of geotechnical and Underground engineering of Ministry of Education(Tongji University) Department of Civil engineering The University of Hong Kong

A theoretical study on the ground vibration isolation efficiency by a row of piles as passive barrier in a three-dimensional context was presented. The analysis was accomplished with the aid of integral equations governing Rayleigh wave scattering, used to predict the complicated Rayleigh wave field generated by a number of irregular scatters embedded in an elastic half-space. Then, the passive isolation effectiveness of a row of piles for screening Rayleigh wave was studied in detail. The effects of relevant parameters on the screening effectiveness were investigated and analyzed from the perspective of equivalence with in-filled trench. The results show that using a row of rigid piles as wave barrier is more effective than that of flexible ones, and an optimum reduction of vibration can be achieved either by increasing the size of piles or by decreasing the net spacing between the piles. Finally, based on the derived integral equation for Rayleigh wave scattering, the principle of equivalent modeling of the barrier of piles by an in-filled trench is put forward, which simplifies the analysis of vibration isolation by a row of piles.

关键词： Rayleigh wave scattering integral equation piles in-filled trench ground vibration passive isolation equivalence principle