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71.
72.
本文对福建省水氡观测资料变化规律进行分析,并试图利用相对均方差、拟合噪声水平和相对年变幅等三项指标,对福建省8个水氡点的观测资料质量进行初步探索。 相似文献
73.
Localization of mining-induced horizontal fractures along rock layer interfaces in overburden: field measurements and prediction 总被引:3,自引:0,他引:3
V. Palchik 《Environmental Geology》2005,48(1):68-80
The locations of mining-induced horizontal fractures along rock interfaces in the overburden of Donetsk Coal Basin were identified using an original experimental device. The device traps methane from horizontal fracture zone (100–fold coal seam thickness) over an active longwall mining excavation. Presence or absence of horizontal fractures along rock layer interfaces is correlated with physical characteristics of the overburden, such as thickness, uniaxial compressive strength of overburden rock layers, location of rock layer interfaces and thickness of extracted coal seams. As a result, a combined criterion based on these physical characteristics is proposed to predict the presence of overburden horizontal fracturing in coal mine operations. 相似文献
74.
The strain developed due to creep is mainly proportional to the logarithm of the time under load, and is mostly proportional
to the stress and temperature. At higher temperature the creep rate falls slowly with respect to time, and the creep strain
is proportional to a fractional power of time, with the exponent increasing as the temperature increases and reaching a value
approximately one-third at temperatures of about 0.5°C. At these temperatures, the creep increases with stress according to
a power greater than unity and possibly exponentially. It increases with temperature as (−U/kT), where U is an activation energy and k is Boltzman’s constant. There are different methods to determine the creep strain and the energy of Jog (B) including experimental
methods, multivariate regression analysis, and by numerical simulation. These methods are less cumbersome and time consuming.
In the present investigation, artificial neural network technique has been used for prediction of the creep strain and energy
of Jog (B). Two different networks have been tested and validated. Both the networks have four input neurons and one hidden
layer with five neurons, and one output neuron. The data for different rocks at temperatures up to 750°C under conditions
of compressive or tortional stress are taken from the literatures. The training and testing data sets used were 163 and 14,
respectively. To deal with the problem of overfitting of data, Bayesian regulation has been used and network is trained with
suitable training epochs. The coefficients of correlation among the predicted and observed values are found high and they
improve the confidence of the users. The mean absolute percentage error obtained are also very low. 相似文献
75.
76.
《Geoforum》2017
The role of ‘quality of place’ (QoP) in attracting and retaining workers has been a significant concern of urban related policy makers and research communities over the past decade. This paper aims to address the significance of QoP factors in attracting and/or retaining global talent by presenting the findings and implications of a study into the relocation decisions of expatriate workers in Suzhou, China. Findings from a survey questionnaire indicate that global talent moving to Suzhou have been driven primarily by career-related opportunities instead of QoP factors. However, binary logit analysis shows that QoP factors have contributed positively towards the retention of global talent in the city. 相似文献
77.
Sealing layers are often represented by sedimentary sequences characterized by alternating strong and weak lithologies. When involved in faulting processes, these mechanically heterogeneous multilayers develop complex fault geometries. Here we investigate fault initiation and evolution within a mechanical multilayer by integrating field observations and rock deformation experiments. Faults initiate with a staircase trajectory that partially reflects the mechanical properties of the involved lithologies, as suggested by our deformation experiments. However, some faults initiating at low angles in calcite-rich layers (θi = 5°–20°) and at high angles in clay-rich layers (θi = 45°–86°) indicate the important role of structural inheritance at the onset of faulting. With increasing displacement, faults develop well-organized fault cores characterized by a marly, foliated matrix embedding fragments of limestone. The angles of fault reactivation, which concentrate between 30° and 60°, are consistent with the low friction coefficient measured during our experiments on marls (μs = 0.39), indicating that clay minerals exert a main control on fault mechanics. Moreover, our integrated analysis suggests that fracturing and faulting are the main mechanisms allowing fluid circulation within the low-permeability multilayer, and that its sealing integrity can be compromised only by the activity of larger faults cutting across its entire thickness. 相似文献
78.
Triaxial shear tests are performed to assess the effects of displacement velocity and confining pressure on shear strengths and dilations of tension-induced fractures and smooth saw-cut surfaces prepared in granite, sandstone and marl specimens. A polyaxial load frame is used to apply confining pressures between 1 and 18 MPa with displacement velocities ranging from 1.15 × 10−5 to 1.15 × 10−2 mm/s. The results indicate that the shearing resistances of smooth saw-cut surfaces tend to be independent of the displacement velocity and confining pressure. Under each confinement the peak and residual shear strengths and dilation rates of rough fractures increase with displacement velocities. The sheared-off areas increase when the confining pressure increases, and the displacement rate decreases. The velocity-dependent shear strengths tend to act more under high confining pressures for the rough fractures in strong rock (granite) than for the smoother fractures in weaker rocks (sandstone and marl). An empirical criterion that explicitly incorporates the effects of shear velocity is proposed to describe the peak and residual shear strengths. The criterion fits well to the test results for the three tested rocks. 相似文献
79.
This paper aims at developing a method for modeling rock mass with preexisting multiple discontinuities within the framework of the smoothed finite element method (SFEM). The discontinuity is simulated by an interface element with zero thickness, the stiffness matrix of which are derived explicitly based on the SFEM. An elastic damage constitutive relation with residual strength is introduced in order to describe the nonlinear mechanical behavior of the discontinuities. The computation codes of the present method were developed. The present method has been verified to be a sound approach for modeling discontinuous rock mass, inheriting the advantages of the SFEM. 相似文献
80.