Lined rock caverns (LRCs) are becoming the preferred option for air storage at sites where there are no natural cavities, such as salt caverns, and this storage technology is being developed and ...utilized in markets around the world. The stability of the overlying rock mass is one of the key factors to ensure the successful operation of LRCs. In this paper, a stability assessment method is presented that first calculates the potential fracture surfaces of the surrounding rock based on the limiting stress field and the Mohr–Coulomb damage criterion, and then, based on these fracture surfaces, solves for the factor of safety defined on the basis of the concept of strength reserve. Using this method, this study evaluates the stability of two types of LRCs, tunnel- and silo-type, under three different geological conditions. The results of the analysis show that the silo-type LRCs are more economical for engineering purposes. Also, this paper provides some guidance for engineers in site selection and preliminary design.
The numerical manifold method（NMM） is a partition of unity（PU） based method. For the purpose of obtaining better accuracy with the same mesh, high order global approximation can be adopted by ...increasing the order of local approximations（LAs）. This,however, will cause the ＂linear dependence＂（LD） issue, where the global matrix is rank deficient even after sufficient constraints are enforced. In this paper, through quadrilateral mesh to form the mathematical cover, a high order numerical manifold method called Quad4-COLS（NMM） is developed, where the constrained and orthonormalized least-squares method（CO-LS） is used to construct the LAs. The developed Quad4-COLS（NMM） does not need extra nodes or DOFs to construct high order global approximations, while is free from the LD issue. Nine numerical tests including five tests for linear elastic continuous problems and four tests for linear elastic fracture problems are carried out to validate the accuracy and robustness of the proposed Quad4-COLS（NMM）.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In southwestern China, the stability of high-steep slopes in large-scale hydropower projects has become a key technical challenge that constrains the safety of construction and operation. Based on a ...geological survey of the large-scale rock block in the Jinping-I Hydropower Station left bank, the entire system of the dam and its abutment slope is defined as the study subject. The mechanisms of interaction between the arch dam and the abutment slope during the construction stage, the impoundment stage and the structural plane strength-weakening stage are investigated using physical model tests. (1) During the excavation stage, the early-stage excavation has a significant impact on the huge rock block, whereas the impact of later-stage excavation is relatively small. (2) During the impoundment stage, the dam foundation is under hydraulic load. Therefore, the huge rock block moves away from the slope due to the arch thrust. (3) During the structural plane strength-weakening stage, both sides of the structural planes develop a relative displacement, and the massive rock block slips slightly. Moreover, the strain of the dam is slightly different from the situation in the normal impoundment stage. The majority of the downstream plane is under tension, indicating that a decline in the bedrock strength of the left bank dam abutment results in deformation of the dam towards the mountain body, the riverbed and the top part of the dam crest.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In the setting of the three-dimensional limit equilibrium method, a procedure for bounding the factor of safety is proposed under the constraint of the reasonable conditions on the system of forces ...suggested by Morgenstern and Price. No assumption is made regarding the internal forces but the system of forces resulted from the procedure satisfies the reasonable conditions as well as all the equilibrium conditions. The optimization problem proposed has weak nonlinearity but no numerical problems inherent in the methods of columns and can be solved using those conventional optimization techniques. Through some typical examples, it is illustrated that even for complicated failure surfaces the proposed procedure gives rise to a very narrow interval of the factor of safety with a low degree of computational complexity.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Formulations of a high-order numerical manifold method (HONMM) for crack problems are presented.•The derivatives of HONMM shape function are continuous among internal element edges and nodes.•The ...proposed HONMM is very suitable for solving crack propagation problems.•High accuracy for crack analysis can be obtained from the HONMM.
Recent attempts to solve solid mechanical problems using the numerical manifold method (NMM) are very fruitful. In the present work, a high-order numerical manifold method (HONMM) which is able to obtain continuous stress/strain field is proposed. By employing the same discretized model as the traditional NMM (TNMM), the proposed HONMM can yield much better accuracy without increasing the number of degrees of freedom (DOFs), and obtain continuous stress/strain field without recourse any stress smoothing operation in the post-processing stage. In addition, the “linear dependence” (LD) issue does not exist in the HONMM, and traditional equation solvers can be employed to solve the simultaneous algebraic equations. A number of numerical examples including four linear elastic continuous problems and five cracked problems are solved with the proposed method. The results show that the proposed HONMM performs much better than the TNMM.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Recently, fruitful results of geotechnical problems solved by the NMM (abbreviated form for the numerical manifold method) have been gained. In the present work, a free surface updating strategy is ...implemented into the NMM to simulate unconfined seepage flow in the soil-rock mixtures (SRMs). Several examples are employed to validate the effectiveness and correctness of the proposed numerical model. Results from the numerical examples indicate that the proposed model can predict the location of free surface with high accuracy, as well as capture the main feature of the unconfined seepage flow. In addition, the influence of rock blocks on the seepage flow in the SRMs can be captured.
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GEOZS, IMTLJ, KILJ, NLZOH, NUK, OILJ, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK
The NMM (numerical manifold method) was widely adopted to deal with many types of engineering problems involving moving boundaries, such as multiple crack propagation in rock masses. With regular ...triangular mathematical meshes, the NMM is further developed for two typical steady seepage problems, such as the confined seepage analysis and the unconfined seepage analysis. For unconfined seepage analysis, procedures to determine free surface location are introduced, and incorporated into the NMM code. Several classic numerical examples with analytical or reference solutions, and two challenge examples including a soil-rock-mixture (SRM) dam and a SRM slope are adopted to confirm capability and accuracy of the proposed numerical model for steady seepage problems. The results show that the exit gradient and free surface for steady seepage problems can be accurately calculated with the proposed numerical model. In addition, the existence of rock blocks have an impact to the distribution pattern of predicted contours of water head. More importantly, the proposed numerical model is able to calculate locations of free surface in SRM dam and SRM slope, which is very important in stability analysis of SRM dam and slope.
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GEOZS, IMTLJ, KILJ, NLZOH, NUK, OILJ, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK
To investigate the disintegration characteristics of the carbonaceous rocks in Guangxi Province, the typical carbonaceous rocks in the section exposed by the Hechi-Baise Expressway were investigated ...in this study. First, based on their mineral compositions and contents, the carbonaceous rocks were divided into four types: carbonate chert, carbonaceous argillaceous limestone, carbonaceous illite clay mudstone, and carbonaceous illite clay shale. Then, through indoor wet-dry cyclic disintegration test, the disintegration characteristics of the four types of rocks were studied. The test results showed the following: (1) the disintegration residues of the carbonate chert and the carbonaceous argillaceous limestone decrease linearly as the number of wetting-drying cycles increases. (2) The disintegration index of the carbonaceous illite clay mudstone and the carbonaceous illite clay shale decreases exponentially as the number of wetting-drying cycles increases. (3) As the number of wetting-drying cycles increases, the disintegration index curves of the carbonaceous illite clay mudstone and the carbonaceous illite clay shale samples gradually become stable until the disintegration of the samples is completed. (4) The disintegration of carbonaceous rocks is mainly affected by the clay content, followed by the structural form, but it cannot be ignored.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Hybrid distribution transformer (HDT) has powerful control ability, which is significant for the intelligentisation of the distribution network. A kind of HDT is presented here, the grid current ...control system of which is emphatic researched. Based on the mathematical model of ideal HDTs, a grid current control system is designed with quasi proportional-resonant controller (QPR). Using the characteristics that infinite gain and large bandwidth at the resonant frequency of QPR controller, the grid current system achieve the effects of unit power factor and sinusoidal symmetrical waveform. Tracking control with no static error of grid current was achieved in MATLAB. Compared with the traditional PI control, QPR controller can modulate AC signals in the static coordinate system, rather than rotary coordinate system. So the QPR controller has advantages of lower steady-state error, stronger anti-interference ability, and simpler calculation. Simulation results show that it has good dynamic and steady performance.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
•The MLS based numerical manifold method for the vibration and impact analysis of cracked bodies is derived.•A mass lumping scheme fit for all the Galerkin meshfree methods is proposed.•The proposed ...mass lumping scheme is shown to exceed in all the aspects the consistent mass formulation.
In the numerical manifold method (NMM), the mathematical patches composing the mathematical cover can take on any shape in addition to finite elements. In this study, the influence domains of those scattered nodes in the moving least squares (MLS) approximation serve as the mathematical patches. And accordingly, the MLS based NMM, designated by MLS-NMM, is derived, which owns the advantages of both NMM and MLS. Then, MLS-NMM is applied to analyze cracked bodies under dynamic loading, and a mass lumping scheme fit for MLS-NMM is proposed. The dynamic analyses of some typical cracked bodies are carried out, indicating MLS-NMM equipped with the proposed mass lumping scheme has more excellent numerical properties than that with the consistent mass formulation in the analysis of the time domain as well as the frequency domain.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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