Behavior Of Fractured Rock Mass Research Articles

Hydraulic properties of stressed granite fractures with heat-induced void alteration

During the extraction of geothermal heat, the changes in temperature and pressure environments can alter the mechanical and hydraulic behavior of fractured rock masses, affecting the overall transmissivity and heat extraction efficiency accordingly. This study carried out a series of experiments, including X-ray diffraction (XRD), scanning electron microscope (SEM), uniaxial compression tests, and surface morphological scanning, to explore the influence of reservoir temperature on the mechanical behavior of granite and fracture surface topography. The results indicate that as the temperature increases, the uniaxial compressive strength, elastic modulus, and Poisson's ratio of granite show similar variation patterns that increase as the temperature approaches 200 °C and then decrease. In addition, with the increase in temperature, the overall surface elevation and roughness parameters generally decrease due to surface asperity degradation, with the maximum mean mechanical aperture found at 200 °C. Flow simulations were conducted to further explore the influence of temperature and pressure environments on fracture transmissivity and flow fields. It is found that the normalized equivalent hydraulic aperture BN of the tested fractures decreases progressively as the stress increases, and more scattered distributions of BN are observed under higher compressive stresses. Moreover, with the continuous increase in temperature, the average BN slowly increases to its peak of ~0.78 at 200 °C, then it decreases to ~0.76 at 300 °C and remains nearly constant. These findings can be important for assessing heat production performances during the geothermal extraction process with spatially and temporally varying reservoir temperatures and pressures.

A novel DFN-DEM approach to simulate long-term behavior of crystalline rock under effects of glacial climate conditions

The safety assessment of nuclear waste repositories is a critical yet challenging task. Several processes acting on different time scales and multiphysical couplings must be taken into account. The complexity of such assessments often requires integrating different software into a single numerical workflow. This study focuses on the long-term behavior of fractured rock masses and the alteration of the hydrogeological system under changing global climate conditions. The investigated impacts include the response of the rock mass due to heating of a generic repository, development of permafrost, and advance and retreat of an ice-shield. To represent THM processes on a timescale of ∼100,000 years in crystalline rock, a novel DFN-DEM modelling approach has been developed. The modelling approach combines two numerical software tools. The thermomechanical calculations are carried out using the distinct element method (DEM) based tool 3DEC [1]. The flow field and the hydraulic heads in the fracture network are calculated with the DFN-tool DFN.Lab [2]. A proprietary script allows to couple and update parameters and variables that are needed to perform THM calculations linking the two different tools. The long-term THM simulations are tested on a generic model of crystalline rock that includes deterministic fault zones as well as a stochastic DFN as the key feature of the hydrogeological system. The modelling approach allows to analyze the behavior of the fracture network including fracture growth and the development of flow pathways within the fracture network as a response to the external THM impacts. The results of the simulations show that the superposition of the different THM processes favors the development of preferential flow pathways along large-scale faults during cold climate conditions.

Existence analysis of hydraulic conductivity representative elementary volume in fractured rocks based on three-dimensional discrete fracture network method

The complexity of fractures in rocks results in heterogeneity and anisotropy of their hydraulic properties. The existence of hydraulic conductivity representative elementary volume (KREV) is a fundamental question in comprehending the hydraulic behavior of fractured rock masses. This article introduces an analytical procedure for determining the existence of KREV in fractured rock masses, which considers the distribution of underground apertures using a discrete fracture network (DFN) model. The procedure follows four basic steps: inverse modeling to generate a 3D DFN; calibration of the effective aperture by combining the results of packer tests and flow simulation using finite difference methods; calculation of the equivalent conductivities in 10 domains and 31 different flow directions; analysis of the fit error between the conductivity ellipsoid to determine the existence of KREV. The proposed approach is applied to the fractured rocks surrounding the 3013 exploration adit near the underground powerhouse of the Three Gorges Project as a case study. The results show that most fractures in the study area have apertures ranging from 0.06 to 0.25 mm and follow a lognormal distribution. The KREV size is 14–16 times the fracture spacing. Investigation of this model has significant implications for understanding flow through fracture networks in related fields.

The correlation between blockiness and the existence of a hydraulic conductivity representative elementary volume of fractured rocks

Whether the hydraulic conductivity representative elementary volume (KREV) exists is a fundamental question for understanding the hydraulic behavior of fractured rock masses. The fracture density and size of rocks vary greatly, and are the two most important parameters affecting the existence of a KREV. The International Society for Rock Mechanics (ISRM) presented quantitative descriptions of fracture persistence and density, dividing the persistence into 5 rates and the density into 7 rates, defining 35 basic types of isotropic fractured rock masses with different persistence and densities. Based on ISRM classification suggestions, we construct an additional 40 anisotropic fractured rocks and conduct a systematic investigation of the KREVs of all 75 rock types. The 3D DFNs of the 75 rocks are established with the Monte Carlo method; the water flow in the DFNs is simulated with the finite difference method; the equivalent conductivities of each rock are calculated in 10 domain sizes and 21 different flow directions; and the optimum conductivity ellipsoid and the fitting errors of the equivalent directional conductivity vectors are analyzed to determine the existence and size of the KREVs. A KREV is more likely to exist in rock masses with a high fracture density and persistence. The effect of fracture density and persistence can be comprehensively represented by blockiness, defined as the ratio of the volume of isolated blocks formed by fractures to the total rock volume. A strong correlation is found between the blockiness and the existence of a KREV. A KREV always exists when the blockiness is higher than 0.5%, and its size is between 2 and 18 times the fracture spacing. A KREV may or may not exist in the range of 0.1% < B < 0.5%. When B < 0.1%, a KREV does not exist.

Coupled macro–meso damage constitutive model for fractured rocks based on logistic growth theory

Rock mass is a complex system contains large amounts of macroscopic and mesoscopic damage. The evolution of this internal macroscopic and mesoscopic damage under stress conditions has a significant impact on the stability of rock masses. However, most of the current damage constitutive models do not consider the coupled effects of damage at different scales, including mesoscopic and macroscopic damage in fractured rock masses, also unable to reflect the nonlinear characteristics shown in the process of rock damage. In order to investigate the effect of the nonlinear process of the macro- and mesoscopic damage evolution on the mechanical behavior of fractured rock masses, this study first divided the deformation and damage processes of fractured sandstone under uniaxial compression into three phases based on acoustic emission test data: the compaction phase, elastic phase, and damage phase. Subsequently, the mesoscopic damage variables for fractured sandstone in the compaction phase were derived from damage mechanics and nonlinear dynamics; the mesoscopic damage variables for fractured sandstone in the damage phase were derived from acoustic emission theory, micro-unit strength theory, and nonlinear dynamics; and the macroscale damage variables for fractured sandstone were derived from damage mechanics and fracture mechanics. The Lemaitre strain equivalence hypothesis was used to couple the mesoscopic and macroscopic damage variables, thereby constructing a coupled macro–meso formulation for the damage variables and a constitutive model for fractured sandstone under uniaxial compression. The results of comparisons with several sets of experimental data indicated that the damage constitutive model proposed in this study could accurately reflect the stress–strain relationship and damage evolution of fractured sandstone during uniaxial compression.

Hydromechanical coupling model for mechanical and hydraulic behavior of fractured rock mass in the framework of advanced general particle dynamics

AbstractIn this paper, hydromechanical coupling model is proposed to study the mechanical and hydraulic behavior of fractured rock mass in the framework of advanced general particle dynamics (GPD), and the relationship between stress and seepage is determined. Then, the proposed model is employed to investigate one‐dimensional seepage, and the numerical seepage field is in a good agreement with the analytical solution, implying the feasibility and accuracy of advanced GPD method. Finally, the proposed model is applied to analyze the mechanical and hydraulic behavior of surrounding rock mass around excavated tunnel under hydromechanical coupling conditions, and the numerical results obtained by the proposed model are in a good agreement with those obtained by PFC, which further verifies the correctness of the proposed model.

An analytical solution of equivalent elastic modulus considering confining stress and its variables sensitivity analysis for fractured rock masses

The equivalent elastic modulus is a parameter for controlling the deformation behavior of fractured rock masses in the equivalent continuum approach. The confining stress, whose effect on the equivalent elastic modulus is of great importance, is the fundamental stress environment of natural rock masses. This paper employs an analytical approach to obtain the equivalent elastic modulus of fractured rock masses containing random discrete fractures (RDFs) or regular fracture sets (RFSs) while considering the confining stress. The proposed analytical solution considers not only the elastic properties of the intact rocks and fractures, but also the geometrical structure of the fractures and the confining stress. The performance of the analytical solution is verified by comparing it with the results of numerical tests obtained using the three-dimensional distinct element code (3DEC), leading to a reasonably good agreement. The analytical solution quantitatively demonstrates that the equivalent elastic modulus increases substantially with an increase in confining stress, i.e. it is characterized by stress-dependency. Further, a sensitivity analysis of the variables in the analytical solution is conducted using a global sensitivity analysis approach, i.e. the extended Fourier amplitude sensitivity test (EFAST). The variations in the sensitivity indices for different ranges and distribution types of the variables are investigated. The results provide an in-depth understanding of the influence of the variables on the equivalent elastic modulus from different perspectives. • A new analytical solution of the equivalent elastic modulus for rock masses is proposed. • The confining stress is considered in the analytical solution. • The sensitivity of the variables in the analytical solution is analyzed.

Loading rate-dependent frictional resistance of a sawcut fracture in granite for prediction of thermoshearing

The coupled TM behavior of fractured rock masses should be evaluated for the long-term safety of the deep geological repository. Thermally induced fracture shear slip, i.e., fracture thermoshearing, might cause increase in fracture permeability. In this study, the thermally induced shear slip of a sawcut granite fracture was investigated in laboratory. Multistage biaxial shear test, consisting of mechanical shear test and thermoshearing test, was conducted on the true triaxial apparatus, and acoustic emission (AE) signals were recorded throughout the experiment. Effect of loading rate on frictional resistance of the fracture was investigated by conducting mechanical shear tests, and we found that friction coefficient of the fracture decreases in proportion to the increase in the logarithm of loading rate. Under mechanical loading rates of 1×10−3 MPa/s and 5×10−3 MPa/s, the failure envelopes with friction coefficients of 0.78 and 0.74 were obtained, respectively. Thermoshearing test was conducted via heating in the direction of the constant minimum principal stress while expansion was restricted in the other direction of the maximum principal stress. A maximum loading rate caused by thermal stress was observed at around 0.9×10−3 MPa/s. Shear slip of the fracture occurred during the heating, and this can be well predicted by the Mohr-Coulomb failure envelope, which was obtained from the mechanical shear test at a similar loading rate.

The effect of geometric characteristics on mechanical properties of asperities

The deformation and failure behavior of fractured rock mass is closely related to the unevenness of the fracture surface. The deformation behavior of asperities on rough fracture surfaces has not been studied comprehensively. This paper aims to study the effect of geometric parameters on the mechanical properties of asperities under normal load. In this work, the uniaxial compression experiment using the discrete element software PFC3D was used to investigate the strength and stiffness law of asperities. The results show that compressive strength and stiffness are less affected by the height-width ratio of spherical asperities. However, the curvature of the asperities tip has a significant impact on the peak compressive strength and stiffness. As the curvature of asperities decreases, the peak compressive strength and stiffness rise. In addition, the strength and stiffness of the unevenness of the surface are also affected by the size effect. The peak compressive strength and stiffness increase as the size of the unevenness of the surface grows. The results show that the mechanical properties of asperities are significantly affected by the curvature and the size effect.

Study on the effect of dynamic disturbance on creep behavior of frozen fractured red sandstone

The freezing method is an effective water shut-off method for shaft construction in water-rich Cretaceous strata in Northwest China. Blasting is an efficient excavation method for vertical shafts crossing the frozen stratum. The frozen rock wall is usually composed of ice and fractured rock mass and is influenced by both the in situ stress and blasting disturbance. To study the creep behavior of fractured rock masses under subzero temperatures and dynamic disturbances, a series of conventional triaxial creep and creep-disturbance tests were carried out. The results show that the flaw dip angle and dynamic disturbance had a significant influence on the creep failure characteristics of the specimens. The creep rate and failure strain of the accelerated creep stage of the specimens under dynamic disturbance were significantly greater than those of the specimens that did not undergo dynamic disturbance. Dynamic disturbance closed and recombined the microcracks, improved the short-term bearing capacity, increased the total creep time, and reduced the creep rate of the specimens. When the load or disturbance intensity reached a certain value, the crack propagation rate and creep rate of a specimen increased, the disturbance energy stored in the rock mass was released, and the specimen suddenly failed. Therefore, this disturbance creep phenomenon must be considered when constructing freezing vertical shafts in Northwest China. Moreover, timely support should be provided for exposed ice-filled fractured rock masses to guarantee construction safety and rock mass stability.

Physical reconstruction and mechanical behavior of fractured rock masses

Physical modeling of rock masses containing complex fracture geometries is an important but very challenging task in rock mechanics and rock engineering. In this work, a novel integration of 3D printing and water-soluble casting is presented for the preparation of rock-model specimens with fracture networks, which is similar to the lost-wax casting process. The fracture network is created with water-soluble polyvinyl alcohol (PVA) material by 3D printing. The intact rock matrix is prepared with cement paste. Uniaxial compressive tests combined with the digital image correlation (DIC) technique are conducted to investigate the mechanical properties and failure process of the prepared rock-model specimens. The differentiation rate of the effective variance is defined to recognize the precursory anomalies during the loading process. The mechanical anisotropy is further investigated by a series of rotated models. The results show that the proposed methodology has distinct advantages for replicating rocks with complex fracture geometries in terms of high accuracy for fabricating fracture networks, high repeatability of mechanical properties, and high strength and brittleness of rock matrices. Due to the presence of complex fracture geometries, the nonlinear mechanical responses of the fractured rock-model specimens, including strain-softening and anisotropy, are observed in our experiments.

Mechanical behavior and failure analysis of fracture-filled gneissic granite

Grouting reinforcement is a common way to strengthen fractured rock mass in rock engineering, which will transform the natural open flaws in rock mass into filled flaws. The existence of fillers will change the stress state of the flaws, thus affecting the mechanical properties and cracking behavior of fractured rock mass. In this paper, uniaxial compression experiments were carried out on granite specimens in four different filling states to study the effects of different filling materials on the strength, fracture behavior and strain state of flawed rock specimen. The experimental results show that compared with the unfilled specimen, the fillers can improve the strength of the specimen, delay the crack initiation and reduce the strain at the flaw tip, but these effects will weaken with the increase of the flaw inclination angle. In addition, the effect of fillers varies with different filling materials, and the effect of resin and gypsum fillers is significantly greater than that of silicone filler. Moreover, the mechanism of the interaction between filler and rock specimen is analyzed. The results reveal that the fillers can reduce the flaw tip stress, which is related to filling material parameters. This reduction of flaw tip stress will be more significant with the increase of the elastic modulus of the filling material, the friction angle and cohesion of the interface between rock and filling material.

Non-parallel double-crack propagation in rock-like materials under uniaxial compression

Coalescence among fractures would have influence on the stability of rock masses. Deep understanding of mechanical behavior of fractured rock masses is an important mean to identify failure mechanism of geological disaster. In this study, crack propagation processing was studied through loading pre-fractured specimens of concrete block, termed as rock-like material, in uniaxial compression tests. New non-parallel double-crack geometry was introduced to observe crack coalescence. The flaw combinations are different from the normally used flaw configurations. In addition, ultrasonic detection tests were performed on the test blocks. The stress and strain data of these tests and characteristic parameters of sound wave were recorded. The stress-strain curves of each test block under the uniaxial compression test were drawn, relations among deformation characteristics and crack angle of the crack specimens, and their overall strength were analyzed. It is found that strength of the specimen decreases as crack inclination increases under two crack inclinations. The highest uniaxial compressive strength is found in the specimen with the cracks at the same angle in different directions. Based on description of the crack initiation location, crack surface and the ultimate failure patterns, failure modes of eight subtype for test blocks are divided into three categories. It is expected that the study results could be beneficial for engineering application of jointed rock masses.

Modeling of rheological fracture behavior of rock cracks subjected to hydraulic pressure and far field stresses

Mathematical modelling of rheological fracture of rock cracks under the combined effect of hydraulic pressure and far field stresses has not been fully studied so far. The objectives of this study are to investigate the rheological fracture behavior and to establish a simple and practical model for rheological fracture of rock cracks under the combined effect of hydraulic pressure and far field stresses. Research results show that rheological fracture behavior of rock cracks is similar to the rock rheological process and can be decomposed into two stages: the decay and steady creep stages. By conducting a series of calculation analyses of the crack rheological fracture under different hydraulic pressures, it is found that wing crack propagation can be divided into two parts: the transient crack propagation at very high velocity and subcritical crack propagation at extreme low velocity. Moreover, both the transient crack propagation and subcritical crack propagation increase with an increase in the hydraulic pressure. Based on the introduction of an equivalent stress, an equivalent Burgers model for rock crack rheological fracture is proposed. The proposed equivalent Burgers model curves agree well with the theoretical curves under various hydraulic pressures, and generate a crack rheological propagation rate that is comparable to the theoretical analysis results. The proposed equivalent Burgers model lays the foundations for revealing the rheological behavior of fractured rock mass subjected to the combined action of hydraulic pressure and stresses.

Forensic Excavation of Rock Masses: A Technique to Investigate Discontinuity Persistence

True persistence of rock discontinuities (areas with insignificant tensile strength) is an important factor controlling the engineering behaviour of fractured rock masses, but is extremely difficult to quantify using current geological survey methodologies, even where there is good rock exposure. Trace length as measured in the field or using remote measurement devices is actually only broadly indicative of persistence for rock engineering practice and numerical modelling. Visible traces of discontinuities are treated as if they were open fractures within rock mass classifications, despite many such traces being non-persistent and actually retaining considerable strength. The common assumption of 100% persistence, based on trace length, is generally extremely conservative in terms of strength and stiffness, but not always so and may lead to a wrong prediction of failure mechanism or of excavatability. Assuming full persistence would give hopelessly incorrect predictions of hydraulic conductivity. A new technique termed forensic excavation of rock masses is introduced, as a procedure for directly investigating discontinuity persistence. This technique involves non-explosive excavation of rock masses by injecting an expansive chemical splitter along incipient discontinuities. On expansion, the splitter causes the incipient traces to open as true joints. Experiments are described in which near-planar rock discontinuities, through siltstone and sandstone, were opened up by injecting the splitter into holes drilled along the lines of visible traces of the discontinuities in the laboratory and in the field. Once exposed the surfaces were examined to investigate the pre-existing persistence characteristics of the incipient discontinuities. One conclusion from this study is that visible trace length of a discontinuity can be a poor indicator of true persistence (defined for a fracture area with negligible tensile strength). An observation from this series of experiments was that freshly failed surfaces through pre-existing rock bridges were relatively rough compared to sections of pre-existing weaker areas of geologically developed (though still incipient) discontinuities. Fractographic features such as hackle and rib marks were typical of the freshly broken rock bridges, whereas opened-up areas of incipient discontinuity were smoother. Schmidt hammer rebound values were generally higher for the rock bridge areas, probably reflecting their lower degree of chemical and physical weathering.

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

Fracture systems have strong influence on the overall mechanical behavior of fractured rock masses due to their relatively lower stiffness and shear strength than those of the rock matrix. Understanding the effects of fracture geometrical distribution, such as length, spacing, persistence and orientation, is important for quantifying the mechanical behavior of fractured rock masses. The relation between fracture geometry and the mechanical characteristics of the fractured rock mass is complicated due to the fact that the fracture geometry and mechanical behaviors of fractured rock mass are strongly dependent on the length scale. In this paper, a comprehensive study was conducted to determine the effects of fracture distribution on the equivalent continuum elastic compliance of fractured rock masses over a wide range of fracture lengths. To account for the stochastic nature of fracture distributions, three different 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 of fractured rock masses. To yield geologically realistic results, parameters for defining fracture distributions were obtained from different geological fields. The influence of the key fracture parameters and their relations to the overall elastic behavior of the fractured rock mass were studied and discussed. A detailed study was also carried out to investigate the validity of the use of a representative element volume (REV) in the equivalent continuum representation of fractured rock masses. A criterion was also proposed to determine the appropriate REV given the fracture distribution of the rock mass.

Numerical determination of strength and deformability of fractured rock mass by FEM modeling

The strength and deformability of fractured rock masses are important factors in the design and construction of civil and mining structures built in or on rock masses. The finite element method (FEM) was applied to study the mechanical behavior of fractured rock masses. A damage-softening statistical constitutive model of intact rock was implemented in FEM code in order to model the strain-softening behavior of rock masses. The FEM model was verified against a theoretical solution and resulted in good agreement. The FEM model was then applied to investigate the progressive failure process, scale effect and anisotropic characteristics of uniaxial compressive strength (UCS), and the deformation modulus of fractured rock masses. The numerical results showed that the representative elementary volume (REV) for strength and deformation modulus is 12 m with an acceptable variation of 10%, and the complete stress–strain curves of models greater than REV size were very similar to each other. A linear relationship was also found between the UCS and the deformation modulus. This result seems to support the idea that a rock mass has a critical strain corresponding to the UCS, regardless of the deformation modulus, scale and direction.

불연속면 연결구조의 삼차원 가시화 기법에 관한 연구

암반의 구조적 특성에 대한 확고한 이해는 지반구조물의 효과적인 설계 및 유지관리에 있어서 매우 중요한 요소이다. 이는 암반의 강도, 변형 및 수리지질학적 특성이 주로 암반에 존재하는 불연속면의 연결구조 특성에 좌우되기 때문이다. 그동안 암반의 구조적 특성에 대한 연구에 있어서 상당한 진전이 있었음에도 불구하고 불연속면 분포의 복잡성으로 인하여 암반의 삼차원적 구현 및 가시화에 기반한 지질공학적 해석은 드문 실정이다. 이 연구는 암반의 불연속면 및 불연속면의 연결구조를 삼차원적으로 구현하고 가시화하는 기법을 제시하였다. 이를 위하여 원판형으로 가정한 불연속면의 비선형 방정식을 유도하고 불연속면 교차선과 등가파이프의 위치를 산정할 수 있는 대수학적 알고리즘이 제시되었으며, 또한 연산과정을 수행하는 전산모듈이 작성되었다. 이 연구에서 개발한 불연속면 연결구조의 삼차원적 구현 및 가시화 기법은 불연속체 기반의 암반강도 및 변형성에 관한 연구 또는 수리지질학적 특성에 관한 연구를 수행함에 있어서 활용도가 높을 것으로 판단된다. A sound understanding of the structural characteristics of fractured rock masses is important in designing and maintaining earth structures because their strength, deformability, and hydraulic behavior depend mainly on the characteristics of discontinuity network structures. Despite considerable progress in understanding the structural characteristics of rock masses, the complexity of discontinuity patterns has prevented satisfactory analysis based on a 3-D rock mass visualization model. This paper presents the results of studies performed to develop rock mass visualization in 3-D to analysis the mechanical and hydraulic behavior of fractured rock masses. General and particular solutions of non-linear equations of disk-shaped fractures have been derived to calculated lines of intersection and equivalent pipes. Also, program modules have been developed to perform the calculations. The procedures developed for the 3-D fractured rock mass visualization model can be used to characterize rock mass geometry and network systems effectively. The results obtained in this study will be refined and then combined for use as a tool for assessing geomechanical problems related to strength, deformability and hydraulic behaviors of the fractured rock masses.

Strength characterization of rock masses, using a coupled DEM-DFN model

A discrete element model (DEM) is used to study the mechanical behaviour of a pre-fractured brittle medium subjected to triaxial loadings where progressive failure can occur. The initial discrete fracture network (DFN) is based on a fractal distribution and it is used to characterize the influence of clustering and size distribution of pre-existing fractures, on the strength of fractured rock masses. The proposed approach captures the progressive failure process occurring in the rock matrix as shearing displacement takes place along pre-existing discontinuities. The results show that the mechanical behaviour of fractured rock masses is mainly dependent on the fracture intensity. However, for a given fracture intensity, the strength can exhibit a 50 per cent variability depending on the size distribution of the pre-existing fractures. This difference can be attributed to the different mechanisms that involve sliding and crushing of blocks in the case of large interconnected fractures or progressive failure of the rock matrix through coalescence of cracks in the case of small unconnected fractures. Clustering of fractures was found to influence the spatial variability of the mechanical properties and therefore to have a scale effect on strength. The results outline the relevance of three parameters, the power-law exponent of the fracture size distribution, the clustering fractal dimension which fixes the fracture-to-fracture correlation number and the fracture intensity, to characterize the mechanical behaviour of rock masses.

Application of Manifold Method (MM) to the stability problems for cut slopes along the national roads

Recently one of the most challenging problems for civil engineers is how to construct new structures/infrastructures adjacent pre-existing ones and how to evaluate the effect of the new construction on the pre-existing structures (so-called neighbouring construction). The Manifold Method (MM) is one of the discontinuum based numerical approaches to simulate the mechanical behaviour of fractured rock masses including large deformation/displacement along fractures as well as stress/strain conditions of the rock blocks/masses. In this study, the MM was used to investigate the stability of the cut slope in the highly fractured rock masses along one of the national roads in Japan, focusing on the effects of new construction on the pre-existing structures/infrastructures. The effect of reinforcement during the construction such as rock bolts, anchors, etc. was also investigated and evaluated quantitatively by numerical simulations using MM.