Enriched finite element procedures for analyzing decoupled bolts installed in rock mass   总被引：1，自引：0，他引：1  

Debasis Deb  Kamal C. Das 《国际地质力学数值与分析法杂志》2011,35(15):1636-1655

Numerical procedures are developed to analyze interaction between fully grouted bolts and rock mass using ‘enriched finite element method (EFEM)’. A solid element intersected by a rock bolt along any arbitrary direction is termed as ‘enriched’ element. The nodes of an enriched element have additional degrees of freedom for determining displacements, stresses developed in the bolt rod. The stiffness of the enriched element is formulated based on properties of rock mass, bolt rod and grout, orientation of the bolt and borehole diameter. Decoupling at grout–bolt interface and elasto‐plastic behavior of rock mass have also been incorporated into the EFEM procedures. The results of this method are compared with analytical pull‐out test results presented by Li and Stillborg (Int. J. Rock Mech. Min. Sci. 1999; 36 :1013–1029). In addition, a numerical example of a bolted tunnel is provided to demonstrate the efficacy of the proposed method for practical applications. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Elastic properties of the incommensurate phase of akermanite,Ca2MgSi2O7     

Zhuang Li  Sai-Kit Chan  Subrata Ghose 《Physics and Chemistry of Minerals》1990,17(5):462-466

The crystal structure of akermanite, Ca₂Mg-Si₂O₇, consists of mixed tetrahedral sheets formed by [MgO₄] tetrahedra and [Si₂O₇] groups interleaved along the c axis with Ca²⁺ ions in eight-fold coordination. Above 358 K, the structure is tetragonal , and below it is incommensurate with modulations parallel to [110] and . The elastic stiffness moduli, C ^ij of the incommensurate phase at room temperature were measured from wave velocities in the 20–75 MHz carrier frequency range by the ultrasonic phase comparison method using optically clear synthetic single crystal plates (3×3×2 mm) oriented parallel to (100), (001), (110) and (101) planes. The C _ij values (GPa) are: C ₁₁ 159.40, C ₃₃ 149.43, C ₄₄ 30.26, C ₆₆ 58.10, C ₁₂ 76.58 and C ₁₃ 57.80. In (010) and (001) planes, the compressional modulus, V ²(L) from the longitudinal wave, L is considerably larger than the shear moduli, V ²(T₁, T ₂) both from the in-plane and perpendicular-to-plane shear waves, T ₁ and T ₂. The relatively small values of the shear moduli indicate the ease of tetrahedral rotations in response to in-plane and perpendicular-to-plane shears and may provide preconditions for structural changes involving shear-type atomic movements.  相似文献   

Phase transitions in leucite,KAISi2O6     

Dorian M. Hatch  Subrata Ghose  Harold T. Stokes 《Physics and Chemistry of Minerals》1990,17(3):220-227

An order parameter treatment of the phase transitions in leucite, KAlSi₂O₆, at approximately 950 and 920 K: (cubic) I4₁ acd(tetragonal) I4₁ a(tetragonal) is presented in terms of Landau theory and induced representation theory. The Al-Si order with decreasing temperature is taken as the primary order parameter to which other distortions (K⁺ ion displacements, strain components, etc.) couple linearly. The expected Al-Si ordering behavior and the associated K⁺ ion displacements for both transitions are derived and the resulting twin domain orientations are listed. The sequence of phase transitions results from a coupling of ₃ ⁺ and ₄ ⁺ representations. The Landau free energy for the five-dimensional reducible representation has been simplified to two components resulting in a linearquadratic coupling of the components. Possible phase diagrams are derived by free energy minimization. The cubic tetragonal transition is first-order, whereas the tetragonal-tetragonal transition may be second order. A tricritical point exists at which the first-order transition changes to second-order.  相似文献   

Rice-acreage estimation for Orrisa using remotely sensed data     

S. Panigrahy  J. S. Parihar  N. K. Patel  V. K. Dadhwal  T. T. Medhavy  B. K. Ghose  N. Ravi  K. C. Pani  B. K. Panigrahy  V. N. Sridhar  R. R. Mohanty  S. K. Nanda  D. P. Tripathy  P. K. Mishra  H. P. Bhatt  S. R. Oza  S. Sudhakar  K. S. Sudha  P. Kumar  N. K. Das 《Journal of the Indian Society of Remote Sensing》1991,19(1):17-26

Rice is one of the most important foodgrains grown in India. Attempts have been made to estimate kharif rice acreage of Orissa state since 1986 using digital remote sensing data from Landsat MSS/TM and/or IRS-1A. Accuracies of the estimates obtained have been evaluated against BES (Bureau of Economics and Statistics) estimate. This paper describes the methodology adopted for rice acreage estimation of Orissa state, the results obtained for three years, i.e. 1986–87, 1988–89 and 1989–90, and their accuracy.  相似文献   

Prof. R.C. Sinha (1920-2015)     

N. C. Ghose  M. K. Rao  A. M. Patwardhan  G. S. Roonwal 《Journal of the Geological Society of India》2016,87(6):750-750

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Paraelectric-antiferroelectric phase transition in titanite,CaTiSiO5     

C. Van Heurck  G. Van Tendeloo  Subrata Ghose  S. Amelinckx 《Physics and Chemistry of Minerals》1991,17(7):591-603

The paraelectric to antiferroelectric phase transition in titanite at ～500 K involves a displacement of the titanium atom from the center of the [TiO₆] octahedron in the paraelectric phase (A2/a) to an off-center position in the antiferroelectric (P2 ₁/a) phase. We have carried out a detailed single crystal high temperature x-ray diffraction study of the phase transition including structure refinements at 294, 350, 400, 430, 440, 450, 500, 600, and 700 K. The unit cell dimensions show a pronounced hysteresis effect in the 450–500 K range on heating and cooling during the first cycle along with a reduction of the transition temperature, T _c from 495 ± 5 K on heating to 445 ± 5 K on cooling. The hysteresis effect disappears on further heating and the superstructure reflections show residual intensities above T _c (445 K). An order parameter treatment of the phase transition is presented in terms of Landau theory and induced representation theory. The Ti-displacements parallel and antiparallel to a are taken as the primary order parameter η, which transforms as the Y ₂ ⁺ representation. A coupling of Y ₂ ⁺ with T ₁ ⁺ results in the linear-quadratic coupling of the spontaneous strain components, ? _ij with η. The Ti-displacements are coupled linearly to the Cadisplacements. Both sets of displacements predicted from induced representation theory are observed experimentally. The phase transition is initially driven by the soft mode at the zone boundary point Y ₂ ⁺ ; near T _c critical fluctuations set in and an order-disorder mechanism finally drives the phase transition, whereby parallel and antiparallel Ti-displacements related by [0, 1/2, 1/2] in adjacent domains are dynamically interchanged. Immediately above T _c , the high temperature (A2/a) phase is a statistical average of small dynamic antiphase domains of the low temperature (P2 ₁/a) phase. Vacancies and defects pinning the domain boundaries may drastically alter the transition behavior and affect the domain mobility.  相似文献   

Collapse loads for rectangular foundations by three-dimensional upper bound limit analysis using radial point interpolation method     

Debasis Mohapatra  Jyant Kumar 《国际地质力学数值与分析法杂志》2019,43(2):641-660

A three-dimensional kinematic limit analysis approach based on the radial point interpolation method (RPIM) has been used to compute collapse loads for rectangular foundations. The analysis is based on the Mohr-Coulomb yield criterion and the associated flow rule. It is understood that the internal plastic power dissipation function and flow rule constraints can be expressed entirely in terms of plastic strain rates without involving stresses. The optimization problem has been solved on basis of the semidefinite programming (SDP) by using highly efficient primal-dual interior point solver MOSEK in MATLAB. The results have been presented in terms of the variation of the shape factors with changes in the aspect ratio (L/B) of the footing for different values of soil internal friction angle (ϕ). Computations have revealed that the shape factors, s_c and s_q, due to effects of cohesion and surcharge increase continuously with (1) decrease in L/B and (2) increase in ϕ. On the other hand, the shape factor s_γ, due to the effect of soil unit weight, increases very marginally with an increase in L/B up to (1) ϕ = 25° for a rough footing and (2) ϕ = 35° for a smooth footing. Thereafter, for greater values of ϕ, the variation of s_γ with L/B has been found to be quite similar to that of the factors s_c and s_q. The variations of (1) nodal velocity patterns, (2) plastic power dissipation, and (3) maximum plastic shear strain rates have also been examined to interpret the associated failure mechanism.  相似文献   

A first-order phase transition in zektzerite,NaLiZrSi6O15: high-temperature single-crystal X-ray diffraction study     

A. M. Shaikh  Subrata Ghose 《Physics and Chemistry of Minerals》2015,42(9):747-759

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Hydrated goethite (α-FeOOH) (1 0 0) interface structure: Ordered water and surface functional groups     

Sanjit K. Ghose  Glenn A. Waychunas  Peter J. Eng 《Geochimica et cosmochimica acta》2010,74(7):1943-2587

Goethite(α-FeOOH), an abundant and highly reactive iron oxyhydroxide mineral, has been the subject of numerous studies of environmental interface reactivity. However, such studies have been hampered by the lack of experimental constraints on aqueous interface structure, and especially of the surface water molecular arrangements. Structural information of this type is crucial because reactivity is dictated by the nature of the surface functional groups and the structure or distribution of water and electrolyte at the solid-solution interface. In this study we have investigated the goethite (1 0 0) surface using surface diffraction techniques, and have determined the relaxed surface structure, the surface functional groups, and the three dimensional nature of two distinct sorbed water layers. The crystal truncation rod (CTR) results show that the interface structure consists of a double hydroxyl, double water terminated interface with significant atom relaxations. Further, the double hydroxyl terminated surface dominates with an 89% contribution having a chiral subdomain structure on the (1 0 0) cleavage faces. The proposed interface stoichiometry is ((H₂O)(H₂O)OH₂OHFeOOFeR) with two types of terminal hydroxyls; a bidentate (B-type) hydroxo group and a monodentate (A-type) aquo group. Using the bond-valence approach the protonation states of the terminal hydroxyls are predicted to be OH type (bidentate hydroxyl with oxygen coupled to two Fe³⁺ ions) and OH₂ type (monodentate hydroxyl with oxygen tied to only one Fe³⁺). A double layer three dimensional ordered water structure at the interface was determined from refinement of fits to the experimental data. Application of bond-valence constraints to the terminal hydroxyls with appropriate rotation of the water dipole moments allowed a plausible dipole orientation model as predicted. The structural results are discussed in terms of protonation and H-bonding at the interface, and the results provide an ideal basis for testing theoretical predictions of characteristic surface properties such as pK_a , sorption equilibria, and surface water permittivity.  相似文献   

Estimation of flow stresses in mylonitic quartzites of parts of Singhbhum shear zone,Bihar, eastern India     

Debasis Sen Gupta 《Journal of Earth System Science》1995,104(3):407-417

Recrystallized grain size was measured from quartzite mylonite specimens collected from parts of Singhbhum shear zone in eastern India. The specimens were collected along five traverses (Mushabani, Pathargora, Surda, Rakha and Jadugoda) across the elongation of the shear zone. The sheared quartzites range from protomylonite through mylonite to ultramylonite. The microstructural studies of the specimens reflect that dynamic recrystallization was the main deformation process. Estimation of flow stresses were derived from these specimens using empirical equations relating to flow stress and recrystallized grain size. The calculated stresses range from 12–28 MPa (Mercieret al 1977), 23–49 MPa (Twiss 1977), 20–68 MPa (Christie and Ord 1980), considering all the traverses. The results show that these values can only be used semiquantitatively.  相似文献