Deformation Analysis Method Research Articles

A continuous-discontinuous coupling computational method for multi-material mixtures

Considering the important role of particle-reinforced composites (PRCs), and to accurately assess the mechanical properties of PRC with arbitrarily complex internal structures, this paper proposes a new continuous-discontinuous coupled computational method, i.e., the multi-material integrated analysis (MIA) method, by combining the advantages of the discontinuous deformation analysis (DDA) method, the numerical manifold method (NMM), and the meshless method, for the continuous-discontinuous dual state of this kind of materials when they are subjected to forces. The core idea of this method is by establishing a single physical cover (PC) on each particle and defining a unified and piecewise approximation function over it to achieve displacement coordination between the particles and the matrix. In this model, the particles can maintain the contact and separation characteristics like the blocks, while the matrix is able to achieve the bonding function by overlapping different covers. Two numerical integration schemes, namely single-point Gaussian integration and Monte Carlo integration, are proposed to address the integration issues in stiffness matrix calculations. Meanwhile by considering the similarity between NMM and meshless method interpolation function construction, this paper combines circular coverage and 0th-order moving least squares to construct the interpolation function to form the displacement approximation function for the whole solution space. Moreover, the method of lattice retrieval (also Nearest Neighbor Search, NNS) is invoked for particle contact determination to improve the efficiency of contact and coverage relationship determination. The validity of the model is verified by taking asphalt mixture, a typical PRC, as a demonstrative case study. The results show that the MIA method solves the one-sided problem that the existing algorithms usually only consider the continuous or discontinuous properties of PRC, and provides a new method for comprehensively analyzing the micromechanical response of PRC and solving its large deformation problem.

Investigations of sequential excavation and reinforcement in tunnels based on the extended three-dimensional discontinuous deformation analysis method

The unloading effect of excavation is the key factor leading to rock mass instability, and bolt support is the key means of controlling the stability. However, the original three-dimensional discontinuous deformation analysis method (3D DDA) can only simulate rock mass instability and bolt support after the tunnel is excavated, which makes it difficult to study the effect of tunnel excavation and bolt support on rock mass stability. Therefore, an algorithm to confirm the excavated blocks and reinforced blocks based on the volume judgment method (VJM) was proposed in this paper. Sequential excavation and reinforcement in tunnels can be simulated by introducing the time variables of block excavation and bolt deployment into the 3D DDA method. By embedding these two algorithms in the 3D DDA method, an extended 3D DDA method for sequential excavation and reinforcement in tunnels was developed, named the 3D DDA_ES method. Based on the 3D DDA_ES method, the collapse that occurred during the construction of the Huangjiazhuang Tunnel was simulated, and the displacement of key blocks and the axial force of the bolts were analyzed. According to the simulation results, the axial force on the bolts is strongly related to the position of the key blocks, and the axial force on the bolts at the tunnel roof is much greater than that at the tunnel arch shoulder. In this regard, these bolts with axial forces less than 1 kN are removed during the simulation, and the key blocks remain stable with a maximum displacement of 12 cm. The research results can provide a theoretical basis for tunnel construction and reinforcement parameter optimization for similar projects.

Methods and research for deformation monitoring of earth and rock dams based on close-range photogrammetry

Abstract Traditional means of monitoring deformation in earth and rock dams encounter challenges such as low monitoring efficiency and limited coverage. Despite the potential of emerging technologies such as GPS and three-dimensional laser scanning, their adoption is expensive and hard to promote. This paper presents a deformation monitoring method for earth and rock dams based on the close-range photogrammetry technique. The proposed approach focuses on analytical algorithm the design and deployment of monitoring points, photographic schemes, camera checking and calibration, as well as deformation analysis methods. Initially, based on the analysis of the parsing algorithms’ applicability, they are fused to address the shortcomings of common image parsing methods in meeting the requirements of high precision and multi-image processing for deformation monitoring of earth and rock dams. Subsequently, the fused algorithm is introduced to analyze the acquired image data for 3D reconstruction, and the deformation in earth and rock dams is assessed based on the generated dense point cloud model. The proposed deformation monitoring method is applied to Pine Bridge Reservoir Dam, and the results demonstrated its capacity to comprehensively analyze the deformation. Furthermore, the required equipment is simple and easy to operate, aligning with the requirements for deformation monitoring accuracy of earth and rock dams.

3D deformation analysis for earth dam monitoring based on terrestrial laser scanning (TLS) and the iterative closest point (ICP) algorithm

Introduction: The conventional 3-D point cloud-based deformation analysis methods, such as the shortest distance (SD), cloud-to-cloud (C2C), and multiscale model-to-model cloud comparison (M3C2), essentially regard the closest distance between two periods of point cloud data as the deformation, rather than the true position of the same point in 3-D space before and after deformation.Methods: This paper proposes a method based on the ICP algorithm to calculate the differences between the chunked multi-period point clouds to recognizes the 3-D deformations.Results and discussion: The results show that the obtained results are very close to the GNSS data but with a much larger spatial monitoring range. The accuracy is higher than that of the SD method. Moreover, we analyze the statistical relationship between the point cloud block size and the deformation vector error and determine the optimal block size. The aim of this article is to optimize the deformation analysis method and improve its accuracy to provide techniques and ideas for the wider surface deformation monitoring research field. For instance, combining this method with data from contact methods constructs a 3D overall deformation model of the mountain, enabling real-time monitoring and early warning of debris flows.

Evolution of Shear Rupture Along a Prescribed Interface Using the Discontinuous Deformation Analysis Method

Evolution of Shear Rupture Along a Prescribed Interface Using the Discontinuous Deformation Analysis Method

A Deformation Analysis Method for Sluice Structure Based on Panel Data

Deformation, as the most intuitive index, can reflect the operation status of hydraulic structures comprehensively, and reasonable analysis of deformation behavior has important guiding significance for structural long-term service. Currently, the health evaluation of dam deformation behavior has attracted widespread attention and extensive research from scholars due to its great importance. However, given that the sluice is a low-head hydraulic structure, the consequences of its failure are easily overlooked without sufficient attention. While the influencing factors of the sluice’s deformation are almost identical to those of a concrete dam, nonuniform deformation is the key issue in the sluice’s case because of the uneven property of the external load and soil foundation, and referencing the traditional deformation statistical model of a concrete dam cannot directly represent the nonuniform deformation behavior of a sluice. In this paper, we assume that the deformation at various positions of the sluice consist of both overall and individual effects, where overall effect values describe the deformation response trend of the sluice structure under external loads, and individual effect values represent the degree to which the deformation of a single point deviates from the overall deformation. Then, the random coefficient model of panel data is introduced into the analysis of sluice deformation to handle the unobservable overall and individual effects. Furthermore, the maximum entropy principle is applied, both to approximate the probability distribution function of individual effect extreme values and to determine the early warning indicators, completing the assessment and analysis of the nonuniform deformation state. Finally, taking a project as an example, we show that the method proposed can effectively identify the overall deformation trend of the sluice and the deviation degree of each measuring point from the overall deformation, which provides a novel approach for sluice deformation behavior research.

A hybridized DDA-DDM for modeling jointed rock masses

The complexity of geo-materials’ behaviors surpass the capabilities of conventional numerical methods alone, particularly when realistically modeling rock structures. Coupling methods can enhance the realism of numerical modeling. Discontinuous deformation analysis (DDA) and displacement discontinuity method (DDM) are combined to model block displacement and crack propagation mechanisms in a blocky rock mass. DDA calculates stresses, strains, rotations, and displacements of the blocks, while DDM predicts crack propagation paths based on specified boundary conditions. The displacements result from DDA are transformed into stresses, followed by investigating crack propagation mechanisms within each block using Kelvin's solution. Boundary stresses are adjusted as cracks propagate, updating stress boundary conditions in DDA. This iterative process continues until crack propagation halts or a new block emerges. In this paper, the complete failure process of a rock slab with one pre-existing non-persistent joint located on the crest of a rock slope and compression test on the rock-like specimen with a single random crack with a 45° slope angle is simulated using the proposed numerical approach. The proposed numerical solution is compared with existing numerical results. This comparison confirms the accuracy and effectiveness of the proposed procedure, as the predicted crack propagation paths from the coupled numerical method align well with the corresponding numerical results from the rock-like samples.

Modeling the failure process of rock masses using a 3D nodal-based continuous-discontinuous deformation analysis method

A three-dimensional nodal-based continuous-discontinuous deformation analysis method (3D-NCDDAM) is developed in this study for modeling the failure process of rock masses. In the 3D-NCDDAM, four-node tetrahedral elements which can be automatally generated are used to discretize the problem domain. To reduce computational cost, and effectively model the failure process of rock masses at concerned regions, the problem domain is devided into two types of regions, namely, the “non-destructive region” and “possible destructive region”. The non-destructive region is mainly used to reduce the boundary effects on the numerical results, and is regarded transitional zone in which the failure of rock masses is not considered. For the possible destructive region, artificial joint elements are inserted, and the failure of these joint elements is used to represent fracture initiation and propagation in rock masses. Additionally, the contact potential which is initially proposed in finite-discrete element method (FDEM) is incorporated into the 3D-NCDDAM to simuate the opening and slipping of discontinuous structural planes involved in rock masses’ failure process. Note that the difficultly in determing contact types in the traditional 3D discontinuous deformation analysis (3D-DDA) method is avoided in the 3D-NCDDAM. The proposed 3D-NCDDAM can be treated as a hybrid method, which inherite both the advantage of DDA method and FDEM. To validate the 3D-NCDDAM, seven numerical examples are conducted. The numerical results indicte that the 3D-NCDDAM can effectively model the failure process of rock masses in both experimental scale and engineering scale.

A modified discontinuous deformation analysis method considering the bonding effect for the simulation of structural loess

A modified discontinuous deformation analysis method considering the bonding effect for the simulation of structural loess

An extended 3D discontinuous deformation analysis method considering bolt supports and its application in tunnels

Implementing bolt supports is the main means of controlling block instability. However, the original three-dimensional discontinuous deformation analysis method (3D ODDA) is still unable to simulate bolt supports, making it difficult to study the control effect of bolt supports on block instabilities. Therefore, an extended three-dimensional discontinuous deformation analysis method (3D EDDA) that can simulate the effect of bolt supports is proposed in this article. Based on the 3D ODDA method, we proposed a simulation algorithm for bolt supports, which improves the constitutive model of the bolt in the original DDA method. Then, we analysed the failure process of a bolt between two blocks and compared the numerical simulation results with the theoretical analysis results to verify the accuracy of the bolt support algorithm in the 3D EDDA method. With the 3D EDDA method, we simulated the failure process of the surrounding rock in a jointed rock mass tunnel at the engineering scale under conditions with bolt supports and without bolt supports. By comparing the results of these two conditions, we deduced the evolution law of the block displacement and bolt axial force around the tunnel and determined the anisotropic characteristics of these items. Specifically, the axial force of the local bolts is relatively small and has a small control effect on the stability of the block in the area. During actual construction, the length or strength of these bolts can be reduced, which can provide a theoretical basis for the design of tunnel bolt support parameters.

Implementation of Viscoelastic Artificial Boundary and Seismic Motion Input Method in Three-Dimensional Discontinuous Deformation Analysis Method

Implementation of Viscoelastic Artificial Boundary and Seismic Motion Input Method in Three-Dimensional Discontinuous Deformation Analysis Method

A continuous-discontinuous deformation analysis method for research on the mechanical properties of coarse granular materials

The mechanical properties of coarse granular materials play a crucial role in the safety of rockfill dams. From a mesoscopic viewpoint, the macroscopic mechanical properties of these materials are a result of the interactions between particles and the progression of particle breakage. Traditional continuum-based numerical methods struggle to accurately analyze the mechanical properties of coarse granular materials. Discontinuous deformation analysis (DDA) is a more suitable algorithm for studying these properties due to its significant benefits in block displacement mode and open-close iteration for contact handling. In this paper, a continuous-discontinuous deformation analysis method (CDDA) based on the conventional DDA is developed for the numerical investigation of coarse granular materials' mechanical properties. This method incorporates critical kinetic damping, multi-stageloading, stricter displacement convergence criteria and particle breakage simulation. It can provide a comprehensive representation of deformation, particle breakage, force chain, shear zone, and stress–strain curve evolutions. The CDDA results are found to be consistent with indoor test results and can more effectively disclose the deformation and failure mechanism of coarse granular materials. Furthermore, CDDA is employed to examine the impacts of particle size and end friction, leading to valuable insights regarding these effects.

Feature-constrained automatic geometric deformation analysis method of bridge models toward digital twin

ABSTRACT It is very important to construct digital twin scenes, which can accurately describe the dynamically changing geographical environment and improve the level of refined management in bridge construction. This article proposes a feature constrained automatic diagnostic analysis method for geometric deformation of bridge digital twins. The geometric deformation feature library of bridge twins was first created to accurately describe structural relationships and behavior characteristics. Secondly, line surface feature constraints were used to extract geometric deformation information from bridge digital twins. Then, a geometric deformation diagnosis algorithm was designed based on an improved Hausdorff method. Finally, a case study was conducted to implement experimental analysis. The experimental results show that the method proposed in this paper can automatically extract the geometric morphology and rapidly calculate line and surface deformations for point cloud bridge digital twins. It achieves an efficiency improvement above 90% and with millimeter-level accuracy, which effectively enhances the diagnostic analysis capabilities for geographical digital twin models.

Study on rock block seismic sliding using three‐dimensional discontinuous deformation analysis

AbstractThe seismic sliding of rock masses is an important phenomenon that is widely involved in earthquake geological hazards. Practical seismic sliding is a three‐dimensional problem, namely, the seismic loads may act in any direction and the rock masses may move in an arbitrary direction relative to the sliding plane. In the present work, the functions of two different seismic loading methods, that is, loading as body force time histories to the sliders or as displacement time histories to the base, are added to the program of the three‐dimensional discontinuous deformation analysis (3D‐DDA) method that is based on the contact theory to study the seismic sliding of rock blocks. The theoretical solutions of single‐block sliding on an incline under the two seismic loading methods are derived. By comparing the 3D‐DDA results of single‐block seismic sliding with the corresponding theoretical results, and comparing the 3D‐DDA results of seismic sliding of three‐stacked‐blocks under the two seismic loading methods, the correctness of 3D‐DDA for seismic sliding simulations is validated. Thereafter, the influence of three‐dimensional seismic components on single‐block sliding, and the movement of block groups under different seismic load conditions are investigated by 3D‐DDA simulations, which indicate the importance to consider rock mass seismic sliding as a three‐dimensional problem and the capability of 3D‐DDA for its analysis. This work builds a meaningful basis for the further numerical simulation study on the earthquake‐induced rock mass movements by 3D‐DDA.

Slope Stability Analysis Based on the Explicit Smoothed Particle Finite Element Method

A landslide is a common natural disaster that causes environmental damage, casualties and economic losses, which seriously affects the sustainable development of society. In geomechanics, it is one of the largest deformation problems. Herein, the GPU-accelerated explicit smoothed particle finite element method (eSPFEM) for large deformation analysis in geomechanics was developed on the CUDA platform based on high-performance computing using a self-designed eSPFEM program code. The eSPFEM combines the strain smoothing nodal integration techniques found in the particle finite element method (PFEM) framework, which allows for the use of low-order triangular elements without volume locking and avoids frequent information transfer and mapping errors between Gaussian points and particles in PFEM. A numerical simulation of slope instability using the eSPFEM and based on a strength reduction technique was conducted using various examples, including a cohesive homogeneous slope, a non-cohesive homogeneous slope, a non-homogeneous slope and a slope with a thin soft band. The calculation results show that the eSPFEM can be applied to slope stability analysis under different working conditions, simulating the entire process of slope instability initiation, sliding and reaccumulation, and obtaining reliable FOS values. A numerical simulation was conducted to analyse a landslide that occurred in the Zhangjiazhuang tunnel on the Lanzhou–Xinjiang high-speed railway line on 18 January 2016. A natural unsaturated soil slope, a soil slope with a high moisture content and a soil slope with a high moisture content subjected to an earthquake were analysed. The findings of this study are in good agreement with the actual slope failure conditions. The primary triggers identified for the landslide were heavy rainfall and earthquakes. The verification results indicate that the eSPFEM can effectively simulate an actual landslide case, showcasing high accuracy and applicability in simulating the large deformation behaviour of landslides.

Drilling technology of long horizontal section of shale oil

As an important supplementary energy resource, shale oil has attracted worldwide attention due to its huge reserves and rich comprehensive utilization levels. The world is rich in oil shale resources. According to statistics, if the oil shale of 33 countries and regions in the world is converted into shale oil, it will be about 400 billion tons. With the continuous maturity of horizontal well drilling and completion technology in shale oil gas reservoirs and the application of other advanced technologies in horizontal well drilling, mature shale oil gas drilling and completion matching technologies have gradually formed at home and abroad after years of research and drilling practice. In terms of measurement technology, China has been able to produce single-point, multi-point, wired, wireless inclinometers and MWD measuring instruments while drilling and has mastered their usage methods. In terms of control technology, various specifications and types of fixed-angle and ground-adjustable curved shell screw drilling tools have been produced in China. Large deformation analysis and trajectory prediction methods for lower drilling tool assemblies have been completed. Various lower drilling tool assemblies and their usage processes required for wellbore trajectory control have been improved and mastered. In the construction of inclined and horizontal sections, attention should be paid to the response law of drilling tool combinations to drilling pressure in different formations, especially the response law of composite drilling. Reasonable drilling tool combinations should be selected for the control of wellbore trajectory in stable and horizontal sections, especially in the long stable and horizontal sections.

Structural stability analysis of proposed Budhi Gandaki dam and optimization

High-rise arch dams are frequently employed in the construction of large storage-type hydropower projects due to their cost-effectiveness. This study presents the comparison in stress and deformation behavior of concrete dam and concrete face rock-fill dam under worst combination of loads. For illustrative purpose, the proposed double curvature arch dam of Budhigandaki Hydroelectric Project is chosen with some modifications. This study proposed the 3-D finite element method (FEM) for stress and deformation analysis of dam considering material non-linearity between concrete and rock-fill material following Drucker-Prager yield criteria. The proposed methodology is implemented through ANSYS 2021. The hydrodynamic pressure of reservoir water is modeled as added mass using Westergaard approach. The compressive and tensile stress developed in both types of dams are investigated and analyzed for different load combinations. The force acting at base of dam and deformation at crest level is also investigated. The results for both types of dam are found to be comparable which suggests that the wasteful volume of concrete can be replaced by consolidated soil (rock-fill) to decrease the overall construction cost of project.

Preliminary analysis of the irradiation deformation of a typical molten salt reactor graphite component

Nuclear graphite commonly serves as the moderator and constructs the coolant flowing channel in liquid fuel molten salt reactors. Under irradiation and high temperature, graphite components will experience obvious deformation due to irradiation creep, thermal expansion, dimensional change, elastic deformation, and thermo-mechanical properties change. The lifespan of graphite components is a limiting parameter of liquid fuel molten salt reactors, determining by the deformation of the graphite components. An improved approach based on the finite element method for graphite deformation analysis was proposed in this paper. Then this method was utilized to analyze a 10-year deformation history of a typical graphite component. The findings show that the stress-strain field of the graphite component significantly varies with the increasing irradiated neutron fluence. The dimensional change plays a primary role in influencing the deformation of the graphite components, determining the overall deformation trend. The irradiation creep plays a secondary role in influencing the deformation, alleviating the deformation of the graphite components to prolong the graphite lifespan. The improved method, which considers various factors like irradiation creep, thermal expansion, dimensional change, and elastic deformation, tends to provide more accurate results compared to the traditional method that focuses solely on the dimensional changes. Over 10 years, the contraction deformation of graphite components results in a reduction in graphite volume of up to 3.87%. The space for graphite contraction is filled with molten salt, resulting in a maximum increase of 22.49% in fuel volume. The alteration in volume of both graphite and fuel leads to a reduction in reactivity of up to 840 pcm.

A Novel Deformation Analytical Solution and Constitutive Model for Fractured Rock Masses

In order to study the deformation and stability of a fractured rock mass, existing research suggests that fracture deformation, which is usually obtained by evaluating the equivalent deformation modulus, dominates the deformation of a fractured rock mass. However, this parameter is difficult to obtain in theory and practice, which limits the application of rock mass deformation analysis methods. In order to calculate the deformation of fractured rock masses, the mass of the rock is regarded as a sponge-like material, and it is assumed that the deformation of a water-saturated fractured rock mass under external force load is approximately equal to the net flow of fracture water. Based on this assumption, firstly, the relationship between rock mass deformation and fracture flow is studied through a single-fracture rock mass model. The hydraulic properties of the fracture are characterized by the permeability coefficient, and the fracture deformation in the rock mass is equivalent to the fracture flow. The fracture deformation calculation formula is derived from the fracture hydraulics calculation formula, and this is compared with the measured data. The rationality of the calculation formula was verified. On this basis, the calculation formula for rock mass deformation, including multiple groups of fracture surfaces, is proposed, and the stress-strain constitutive relationship of a complex rock mass is established. The correctness of the calculation method was verified by comparing it with other theoretical calculation results.

Weighted radial basis collocation method for large deformation analysis of rubber-like materials

A nonlinear formulation, based on the total Lagrange description of the weighted radial basis collocation method (WRBCM), is proposed for the large deformation analysis of rubber-like materials where the materials are hyperelastic and nearly incompressible. The WRBCM based on the strong form collocation is a genuinely meshfree method that eliminates the need for meshing. As a result, it effectively circumvents challenges associated with mesh distortion during large deformation analysis. The proper weights that should be imposed on the boundary collocation equations are first derived to achieve the optimal convergence in hyperelasticity. In the WRBCM, the support of the shape function remains unchanged throughout material deformation, thereby guaranteeing the absence of tension instability during large deformation analysis. Additionally, by combining WRBCM with a least-squares solution, volumetric locking in nearly incompressible hyperelastic problems can be suppressed. This is due to the infinite continuity possessed by the radial basis approximation, which ensures the divergence-free condition. Several numerical examples are examined, demonstrating the high accuracy and exponential convergence of WRBCM in hyperelastic large deformation analysis. Moreover, no volumetric locking can be observed which further substantiates the effectiveness of applying nonlinear WRBCM to nearly incompressible hyperelastic problems.