Dynamic response of a pile considering the interaction of pile variable cross section with the surrounding layered soil          下载免费PDF全文

Liu Gao  Kuihua Wang  Si Xiao  Wenbing Wu 《国际地质力学数值与分析法杂志》2017,41(9):1196-1214

Assuming that the pile variable cross section interacts with the surrounding soil in the same way as the pile toe does with the bearing stratus, the interaction of pile variable cross section with the surrounding soil is represented by a Voigt model, which consists of a spring and a damper connected in parallel, and the spring constant and damper coefficient are derived. Thus, a more rigid pile–soil interaction model is proposed. The surrounding soil layers are modeled as axisymmetric continuum in which its vertical displacements are taken into account and the pile is assumed to be a Rayleigh–Love rod with material damping. Allowing for soil properties and pile defects, the pile–soil system is divided into several layers. By means of Laplace transform, the governing equations of soil layers are solved in frequency domain, and a new relationship linking the impedance functions at the variable‐section interface between the adjacent pile segments is derived using a Heaviside step function, which is called amended impedance function transfer method. On this basis, the impedance function at pile top is derived by amended impedance function transfer method proposed in this paper. Then, the velocity response at pile top can be obtained by means of inverse Fourier transform and convolution theorem. The effects of pile–soil system parameters are studied, and some conclusions are proposed. Then, an engineering example is given to confirm the rationality of the solution proposed in this paper. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Displacement analytical prediction of shallow tunnel based on unified displacement function under slope boundary     

Fanchao Kong  Dechun Lu  Xiuli Du  Chenpeng Shen 《国际地质力学数值与分析法杂志》2019,43(1):183-211

For slope condition of ground surface, the asymmetrical deformation about the vertical center line and the horizontal center line of the tunnel cross section can be formed. A unified displacement function expressed by the Fourier series is presented to express the asymmetrical deformation of the tunnel cross section. Five basic deformation modes corresponding to the expansion order 2 are a complete deformation mode to reflect deformation behaviors of the tunnel cross section under slope boundary. Such this complete displacement mode is implemented into the complex variable solution for analytically predicting tunneling-induced ground deformation under slope boundary. All of these analytical solutions are verified by good agreements of the comparison between the analytical solutions and finite element method results. A parameter study is carried out to investigate the influence of deformation modes of the tunnel cross section, geometrical conditions of the tunnel and the slope angle, and “Buoyancy effect” on the displacement field. Finally, the proposed method is consistent with measured data of the Hejie tunnel in China qualitatively. The presented solution can provide a simplified indication for evaluating the ground deformation under slope condition of ground surface.  相似文献   

Intensity of in‐lake processes in floodplain lakes within the Bug River zone of fluvial activity          下载免费PDF全文

Jarosław Dawidek  Beata Ferencz 《水文研究》2014,28(24):5965-5971

The paper presents a new approach to calculating the erosion and deposition values of floodplain lake basins, the erosion–deposition index (EDI). The EDI is a sum of the basin geometry indices (BGIs), which can be calculated for a separate cross section of the lake. The distribution of processes within the basin was investigated in two selected floodplain lakes with the use of BGIs. Field research was carried out in the Bug River valley from 1 November 2006 to 31 October 2011. The highest erosion was observed in the lakes located close to the parent river. Deposition processes were observed in lakes with high inflow of groundwater. The results showed that EDI values of 48 out of the 71 floodplain lakes ranged from ?0.2 to 0.2. Spatial distribution of erosion and deposition processes within the lake basins resulted from a velocity of water inflowing or flowing through the basin. This was observed especially in contrafluent–confluent lake. Inflow of rivers water via upstream crevasse occurred later than via downstream one, but energy of flowing water was higher, which favoured erosion of this part of the lake basin. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Structural geometry and controls on basement‐involved deformation in the northern Flinders Ranges,Adelaide Fold Belt,South Australia     

E. Paul  T. Flöttmann  M. Sandiford 《Australian Journal of Earth Sciences》2013,60(3):343-354

In the northern Flinders Ranges, Neoproterozoic and Cambrian sedimentary rocks were deformed and variably metamorphosed during the ca 500 Ma Cambro‐Ordovician Delamerian Orogeny. Balanced and restored structural sections across the northern Flinders Ranges show shortening of about 10–20%. Despite the presence of suitable evaporitic detachment horizons at the basement‐cover interface, the structural style is best interpreted to be thick‐skinned involving basement with only a minor proportion of the overall shortening accommodated along stratigraphically controlled detachments. Much of the contractional deformation was localised by the inversion of former extensional faults such as the Norwest and Paralana Faults, which both controlled the deposition of Neoproterozoic cover successions. As such, both faults represent major, long‐lived structures which effectively define the present boundaries of the northern Flinders Ranges with the Gawler Craton to the west and the Curnamona Craton to the east. The most intense deformation, which resulted in exhumation of the basement along the Paralana Fault to form the Mt Painter and Babbage Inliers, coincides with extremely high heat flows related to extraordinarily high heat‐production rates in the basement rocks. High heat flow in the northern Flinders Ranges suggests that the structural style not only reflects the pre‐Delamerian basin architecture but is also a consequence of the reactivation of thermally perturbed, weakened basement.  相似文献   

Reconstructing fluvial bar surfaces from compound cross‐strata and the interpretation of bar accretion direction in large river deposits          下载免费PDF全文

Renato P. Almeida  Bernardo T. Freitas  Bruno B. Turra  Felipe T. Figueiredo  André Marconato  Liliane Janikian 《Sedimentology》2016,63(3):609-628

The interpretation of fluvial styles from the rock record is based for a significant part on the identification of different types of fluvial bars, characterized by the geometric relationship between structures indicative of palaeocurrent and surfaces interpreted as indicative of bar form and bar accretion direction. These surfaces of bar accretion are the boundaries of flood‐related bar increment elements, which are typically less abundant in outcrops than what would be desirable, particularly in large river deposits in which each flood mobilizes large volumes of sediment, causing flood‐increment boundary surfaces to be widely spaced. Cross‐strata set boundaries, on the other hand, are abundant and indirectly reflect the process of unit bar accretion, inclined due to the combined effect of the unit bar surface inclination and the individual bedform climbing angle, in turn controlled by changes in flow structure caused by local bar‐scale morphology. This work presents a new method to deduce the geometry of unit bar surfaces from measured pairs of cross‐strata and cross‐strata set boundaries. The method can be used in the absence of abundant flood‐increment bounding surfaces; the study of real cases shows that, for both downstream and laterally accreting bars, the reconstructed planes are very similar to measured bar increment surfaces.  相似文献   

Smoothing and re-roughening processes: The geometric evolution of a single fault zone     

《Journal of Structural Geology》2016

The geometry of a fault zone exerts a major control on earthquake rupture processes and source parameters. Observations previously compiled from multiple faults suggest that fault surface shape evolves with displacement, but the specific processes driving the evolution of fault geometry within a single fault zone are not well understood. Here, we characterize the deformation history and geometry of an extraordinarily well-exposed fault using maps of cross-sectional exposures constructed with the Structure from Motion photogrammetric method. The La Quinta Fault, located in southern California, experienced at least three phases of deformation. Multiple layers of ultracataclasite formed during the most recent phase. Crosscutting relations between the layers define the evolution of the structures and demonstrate that new layers formed successively during the deformation history. Wear processes such as grain plucking from one layer into a younger layer and truncation of asperities at layer edges indicate that the layers were slip zones and the contacts between them slip surfaces. Slip surfaces that were not reactivated or modified after they were abandoned exhibit self-affine geometry, preserving the fault roughness from different stages of faulting. Roughness varies little between surfaces, except the last slip zone to form in the fault, which is the smoothest. This layer contains a distinct mineral assemblage, indicating that the composition of the fault rock exerts a control on roughness. In contrast, the similar roughness of the older slip zones, which have comparable mineralogy but clearly crosscut one another, suggests that as the fault matured the roughness of the active slip surface stayed approximately constant. Wear processes affected these layers, so for roughness to stay constant the roughening and smoothing effects of fault slip must have been approximately balanced. These observations suggest fault surface evolution occurs by nucleation of new surfaces and wear by competing smoothing and re-roughening processes.  相似文献   

Investigation of directional hydraulic fracturing based on true tri-axial experiment and finite element modeling     

《Computers and Geotechnics》2016

The initiation and propagation of directional hydraulic fracturing (DHF) was investigated based on true tri-axial experiment and finite element modeling. The influences of notch angle, notch length and injection rate on the DHF were investigated. The initiation and propagation of DHF was modeled by a 3D nonlinear finite element method. A comparison between experimental investigation and numerical modeling results indicates that there is a good correlation between unbalanced force (UF) and fracturing. UF can be used to predict the hydraulic fracture initiation and propagation.  相似文献   

Neotectonics of the Kharaulakh sector of the Laptev Shelf     

V.S. Imaev  L.P. Imaeva  O.P. Smekalin  A.V. Chipizubov  A.N. Ovsyuchenko  I.I. Kolodeznikov 《Russian Geology and Geophysics》2018,59(7):813-826

Seismotectonic deformation and crustal stress pattern have been studied comprehensively in major seismogenic structures of the Kharaulakh sector of the Verkhoyansk fold system and adjacent parts of the Chersky seismotectonic zone. The study focuses on neotectonic structures, deep structure, and systems of active faults, as well as tectonic stress fields inferred by tectonophysical analysis of Late Cenozoic faults and folds. The results, along with geological and geophysical data, reveal main strain directions and structural patterns of crustal stress and strain in the Arctic segment of the Eurasia-North America plate boundary. The area is a junction of mid-ocean and continental structures evolving in a mixed setting of extension, compression, and their various combinations. The rotation pole of the two plates is presumably located near Buor-Khaya Bay. In this case, extension is expected to act currently upon the neotectonic structures north of the bay and compression to control those in the south and southeast. This inference is consistent with the identified zoning of stress and strain in the Kharaulakh sector.  相似文献   

基于NCEP FNL资料的山西岢岚地区雨雪天气诊断可信度分析     

程胡华  王益柏  闻斌  武帅  智茂林  赵亮 《气象与环境学报》2019,35(2):23-31

基于山西岢岚地区2005—2014年共1218个雨雪天气日的NCEP FNL资料(1°×1°)与探空资料,采用偏差、绝对差、相关系数和偏差区间占有率的统计方法,对常规物理量(温度、相对湿度、纬向风和经向风)和诊断物理量(T_800-500、T_d800和TT_d700)进行统计分析。结果表明:常规物理量中的温度平均偏差值和绝对差值最小、相关系数值最大,分别为-0. 22℃、1. 02℃、0. 90,可信度最高;而相对湿度的平均偏差值和绝对差值最大、相关系数值最小,分别为12. 31%、19. 68%和0. 63,可信度最低;纬向风和经向风的可信度相差不大,略低于温度;诊断物理量T_800-500、T_d800和TT_d700的偏差值分别为-0. 08℃、1. 50℃和2. 79℃,绝对差值分别为1. 21℃、3. 33℃和4. 14℃,相关系数值分别为0. 95、0. 92和0. 74,偏差值为[-5,5]占总数百分比分别为98. 77%、80. 30%和75. 04%。即T_800-500可信度最高,TT_d700指数可信度最低。  相似文献   

VELOCITY–DISCHARGE RELATIONSHIPS DERIVED FROM DYE TRACER EXPERIMENTS IN GLACIAL MELTWATERS: IMPLICATIONS FOR SUBGLACIAL FLOW CONDITIONS     

PETER W. NIENOW  MARTIN SHARP  IAN C. WILLIS 《水文研究》1996,10(10):1411-1426

Repeated dye tracer tests were undertaken from individual moulins at Haut Glacier d'Arolla, Switzerland, over a number of diurnal discharge cycles during the summers of 1989–1991. It was hoped to use the concepts of at-a-station hydraulic geometry to infer flow conditions in subglacial channels from the form of the velocity–discharge relationships derived from these tests. The results, however, displayed both clockwise and anticlockwise velocity–discharge hysteresis, in addition to the simple power function relationship assumed in the hydraulic geometry approach. Clockwise hysteresis seems to indicate that a moulin drains into a small tributary channel rather than directly into an arterial channel, and that discharges in the two channels vary out of phase with each other. Anticlockwise hysteresis is accompanied by strong diurnal variations in the value of dispersivity derived from the dye breakthrough curve, and is best explained by hydraulic damming of moulins or sub/englacial passageways. Despite the complex velocity–discharge relationships observed, some indication of subglacial flow conditions may be obtained if tributary channels comprise only a small fraction of the drainage path and power function velocity–discharge relationships are derived from dye injections conducted during periods when the supraglacial discharge entering the moulin and the bulk discharge vary in phase. Analyses based on this premise suggest that both open and closed channel flow occur beneath Haut Glacier d'Arolla, and that flow conditions are highly variable at and between sites.  相似文献