Horizontal Displacement Distribution Research Articles

Late Quaternary Slip Behavior of the Jinqianghe Fault in the Middle Qilian–Haiyuan Fault Zone, Northeastern Tibetan Plateau

AbstractThe Qilian–Haiyuan fault zone in the northeastern Tibetan Plateau has been the source of strong earthquakes in the region. In its middle segment, the Jinqianghe fault is an important active fault within the Tianzhu seismic gap; however, little is known about its slip behavior. To present a new horizontal displacement distribution along this fault, we used WorldView‐2 stereo pairs and unmanned aerial vehicle‐based photogrammetry to construct digital elevation models to obtain a detailed tectono‐geomorphic interpretation and geomorphic offsets. The offset marker measurements yielded 135 geomorphic displacements and 8 offset clusters. Radiocarbon dating was used to establish the regional age sequence of the geomorphic units in offset fluvial terraces at four study sites. The displacements and ages linked the offset clusters with the geomorphic unit sequence; the Holocene strike‐slip rate of the Jinqianghe fault was estimated to 4.8–5.6 mm/a at ∼4–12 ka and 2.9–4.7 mm/a from ∼4 ka. Three recent earthquakes (with a recurrence interval of ∼1000 years) represent an active seismic period, revealing the potential seismic hazard along this fault because it has not ruptured in the last 1500 years.

Temporal-Spatial Characteristics of Ground and Pile Responses to Twin Shield Tunneling in Clays

This paper investigates the temporal-spatial characteristics of ground displacements as well as vertical and horizontal displacements and axial forces in existing piles induced by twin shield tunneling in clays. To that end, a case study and three-dimensional (3D) finite element (FE) analysis were performed. Based on the in situ monitoring data from the presented twin tunneling case history with existing piles beneath, the adopted 3D FE method was validated to be competent to yield reasonable simulation results. The validated 3D FE method was then used to analyze the effects of the distance between the tunnel and the pile, the distance between tunnel faces, and the pile length on the horizontal and vertical displacements and axial stresses in piles. It was found that the horizontal displacement distribution forms along the pile shaft for the front piles are similar to that for the back piles, whereas the magnitudes of the horizontal displacements of the front piles are slightly larger than that of the back piles. The interactions between piles in the pile group provide protection of the middle piles in the pile group against twin tunneling effects. With a reduction in the distance between the tunnel and the pile, the pile displacements and stresses increase nonlinearly. With an increase in the distance between tunnel faces, the maximum positive pile displacements and the maximum and minimum axial pile stresses increase, while the maximum negative pile displacements and the difference between the maximum and minimum axial pile stresses decrease.

ГЕОДИНАМІКА

Purpose. The aim of the research is mathematical analysis and forecasting of dispersive soils behaviour based on the study of inclinometric observations data in the area of the natural-technical system of the Dnister PSPP. Methodology. The research methodology is based on mathematical analysis and modelling of processes occurring in the mountain massif on which the Dnister PSPP is located, using the finite element method. Results. The paper presents an analysis of the results of geotechnical monitoring of the behaviour of dispersive soils, implemented on the basis of inclinometric measurements on the territory of the Dnister PSPP. Quantitative parameters of horizontal displacement distribution in inclinometric wells are established. They made it possible to detect negative dynamics in the geological horizons N1-2ap and N1p+v, which is apparently caused by technogenic load caused by the Dnister upper reservoir. The behaviour of dispersive soils under the influence of natural and technogenic loads has been modelled. Based on the simulation results, the change of the sign of deformations under the influence of additional load, which can be the filling of the Dnister upper reservoir, is confirmed. Obviously, the use of this method alone does not allow full detecting and tracking modern geological, seismic and geodynamic processes. A combination and detailed analysis of different monitoring methods (geophysical, geodetic, parametric, vibrometric, hydrogeological, temperature, visual-instrumental and others), as well as modelling the behaviour of the object under the influence of natural and technogenic factors is optimal. Such simulations could be used in the design of other objects of this type, so this is a promising area for further research. Originality. For the first time, a mathematical analysis and forecasting of the behaviour of dispersed soils in the area of the natural and technical system of the Dnister PSPP was conducted on the basis of studying the data of inclinometric observations. Practical significance. The proposed technique can be used in the design of other objects of this type, as modelling the behaviour of the object under the influence of natural and technogenic factors makes it possible to assess possible risks and prevent them.

Numerical Comparison on Deformation Characteristics of the Shored Mechanically Stabilized Earth Wall Between Reduced-Scale and Full-Scale Models

A reduced-scale shored mechanically stabilized earth (SMSE) wall test was employed to validate a proposed numerical model through comparing the top surface settlement, reinforcement strain, and horizontal earth pressure. On this basis, according to the model ratio, a full-scale model is established for comparison with the reduced-scale model. It was found that the anchor connection with reinforcements can obviously strengthen the stability of the walls. Due to the different influencing factors in the reduced-scale and full-scale models, there are obvious differences in the regularities of distribution of horizontal displacement, vertical earth pressure, horizontal earth pressure, and reinforcement strain between the reduced-scale and full-scale models.

Effect of mix component on the mechanical properties of coral concrete under axial compression

Typical influences of mix component on the properties of coral concrete (CC) were analyzed in this paper. Different types of fine aggregates (sea sand and river sand), mixing water (seawater and fresh water) and cementitious materials (cement and fly ash) were considered. An experimental system was developed involving uniaxial compression tests and the use of digital image correlation (DIC) method to investigate the deformation distribution and crack propagation of CC. The variations in failure pattern, strength and deformation of CC were studied. Test results indicated that the failure of CC adopting sea sand and seawater was brittle compared to CC using fresh water and river sand. It was found that axial stress-strain curve (SSC) of ordinary concrete (OC) was different from that of CC. The curvature and the descending slope of SSC obviously changed with the variation of mix components. The seawater improved the strength and elastic modulus of CC compared to fresh water, however, the effect of sea sand was negative. It was verified that prismatic compressive strength of CC with fly ash (FA) developed slowly in early stage, while it increased quickly in late stage. After using different types of aggregates, mixing water and cementitious materials, obvious changes were found in the crack propagation and the axial deformation distribution. However, typical influence of mix component on horizontal displacement distribution was negligible. The cracking of CC was seldom observed before the peak stress when compared to OC, and the seawater and sea sand accelerated the CC crack growth after the peak point. Finally, a numerical stress-strain expression of CC considering the influences of mix component was suggested, which could be used in the theoretical analysis and practical design.

Rational placement of measuring systems in high dams

To solve the problem of rational placement of measuring systems in concrete dams, the experience of full-scale observations of horizontal displacements and stresses in the body of the arch dam of Inguri HPP (Georgia) was used with the use of statistical processing of the results of observations and the Barlow-Hunter-Proshan mathematical model. The type of the law of distribution of horizontal displacements and arch stresses was established by analyzing the histograms of these measured indicators of the static state of the structure. It is established that the change of horizontal displacements along the dam height is well described by the one-sided normal distribution law, and the arch stresses in the controlled alignment - by the normal distribution law. The laws of distribution of random variables are established. Using the Barlow-Hunter-Proshan mathematical model enabled the use of economic criteria on the basis of the frequency characteristics of the indicators of trouble-free operation of the construction and obtain the recurrence relation for the sequence of coordinate points of the measuring systems. The results of calculations of the coordinates of the recommended location of straight plumb lines in the center console and tensometric rosettes in the measuring range of the Ingur dam at the level of 210 m for a rational placement scheme are presented. The calculation showed that the number of measuring systems installed in the body of the Ingur dam exceeds the optimum value.

Numerical study on static component generation from the primary Lamb waves propagating in a plate with nonlinearity

Under the discipline of nonlinear ultrasonics, in addition to second harmonic generation, static component generation is another frequently used nonlinear ultrasonic behavior in non-destructive testing (NDT) and structural health monitoring (SHM) communities. However, most previous studies on static component generation are mainly based on using longitudinal waves. It is desirable to extend static component generation from primary longitudinal waves to primary Lamb waves. In this paper, static component generation from the primary Lamb waves is studied. Two major issues are numerically investigated. First, the mode of static displacement component generated from different primary Lamb wave modes is identified. Second, cumulative effect of static displacement component from different primary Lamb wave modes is also discussed. Our study results show that the static component wave packets generated from the primary S0, A0 and S1 modes share the almost same group velocity equal to the phase velocity of S0 mode tending to zero frequency cplate. The finding indicates that whether the primary mode is S0, A0 or S1, the static components generated from these primary modes always share the nature of S0 mode. This conclusion is also verified by the displacement filed of these static components that the horizontal displacement field is almost uniform and the vertical displacement filed is antisymmetric across the thickness of the plate. The uniform distribution of horizontal displacement filed enables the static component, regardless of the primary Lamb modes, to be a promising technique for evaluating microstructural damages buried in the interior of a structure. Our study also illustrates that the static components are cumulative regardless of whether the phase velocity of the primary and secondary waves is matched or not. This observation indicates that the static component overcomes the limitations of the traditional nonlinear Lamb waves satisfying phase velocity matching condition to achieve cumulative second harmonic generation. This nature also enables the primary Lamb waves excited at a low center frequency to generate static component used for inspecting large-scale structures with micro-scale damages.

Displacement-based Mode Pushover Analysis of Self-anchored Cable-stayed Suspension Bridge

As being a typical multi-freedom degree system structure, self-anchored cablestayed suspension bridge is significantly affected by higher modes in the earthquake response. Traditional force-based pushover analysis of reverse triangle or uniform distribution patterns will lead* to a certain error for the results of pushover analysis of self-anchored cable-stayed suspension bridge. An improved method of displacement-based mode pushover analysis is presented in this paper by combining the two stage horizontal displacement pattern with mode pushover. This improved method can take the contributions of higher modes into account. And the applicability of the method can be verified commendably by the selected examples. Traditional force-based pushover analysis considers the seismic load is equivalent to lateral load. And it judges whether the deformation ability of the structure and component can meet the need of design and use function by analysing nonlinear response of structures under the monotonic increasing horizontal lateral load applied to the structure with a certain distribution mode. The selection of the lateral load distribution mode can directly affect the analysis results of the pushover method on the seismic performance of whole structure in traditional force-based pushover analysis. Moreover, the problem of stiffness degradation after failure is not taken into account in this traditional wide application method. Seismic hazard, experiment and theoretical analysis indicate structural collapse is mainly due to the lack of deformation capacity and energy dissipation capacity during severer earthquake. In this case, the deformation capacity and the displacement response of structure will have an certain impact on the damage degree of structural members. Therefore, it is more reasonable to use displacement control on structural seismic response during severer earthquake[4]. Compared with the traditional force-based design, the displacement of structure can reflect the nonlinear reactive state more during severer earthquake, it also can control the behavior of structure better in earthquake. Consequently, the displacement-based seismic design method has been greatly developed[5-10]. There are three commonly used displacement-based seismic design method: ductility factor design, capacity spectrum and direct displacement-based design method. The basic thought of displacement-based mode pushover analysis is as follows: first, put monotonic increasing lateral displacement to bear on structure directly according to a certain horizontal displacement distribution mode, second, the final failure pattern of structure is obtained by pushover the structure to the target displacement, after that, whether the deformation ability of structure and component can meet the need of design and use function can be analyzed.

Paleoseismology and slip rate of the western Tianjingshan fault of NE Tibet, China

We present results from a detailed investigation of the horizontal displacement distribution, timing of paleoearthquakes and left-lateral slip rate on the western Tianjingshan fault. Measurements of 240 offset streams and ridges confirm that the fault is left-lateral and record evidence of repeated ∼3–4m coseismic offsets along the 60–km–long fault. This suggests that ∼6 earthquakes may have occurred along the entire western Tianjingshan fault with repeated occurrence of earthquakes of Mw 7.2–7.5. Structural and stratigraphic relationships exposed in our five trenches in combination with previously reported studies further indicate that the fault has ruptured in as many as six paleoearthquakes since the late Quaternary. Paleoseismic data show that the average recurrence interval for Holocene earthquakes is approximately 5,000yr. The most recent earthquake along the western Tianjingshan fault occurred ∼1.2±0.1kyrBP, indicating that this fault segment did not rupture in the M 7.5 historical earthquake of 1709 that ruptured the central Tianjingshan fault. We estimate that the Holocene slip rate of the western Tianjingshan fault is ∼1.1–1.2mm/yr based on measurements of the age and offset of stream channels. Compared with the relatively fast slip rate of the Haiyuan fault (∼4–6mm/yr), we suggest that the Tianjingshan fault acts as an essential active fault accommodating the sinistral displacement and crustal shortening deformation in NE Tibet.

Numerical Modelling of the Mining Induced Horizontal Displacement

Abstract The paper presents results of numerical calculations and modeling of mining-induced surface deformation based on Finite Element Method (FEM). Applying the numerical method discussed to calculations allows us to assume a larger number of factors, such as rock mass structure, fracture network, rock properties, etc., which essentially affect the results obtained. On the basis of an elastic transversely isotropic model, an analysis of horizontal displacement distribution and surface subsidence was carried out for two sample regions of mines. The results of numerical calculations were later compared with the measured values. Such an analysis proved that the applied numerical model properly described distribution and values of subsidence and slope of subsidence trough, though there were serious differences in the values of calculated horizontal displacement, especially in areas of far influence range. In order to improve the matching, the influence of boundary conditions of the model on the value of calculated horizontal displacement was analyzed. The results are presented in graphs.

Analysis of horizontal displacement distribution caused by single advancing longwall panel excavation

The paper presents an analysis of the horizontal displacement of surfaces induced by exploitation in a longwall panel. The panel under discussion is No. 698 of Prosper Haniel coal mine, Germany. The author discusses both the distribution of displacement vectors, according to the theory assuming surface point displacement towards the center of gravitation (COG) zone of a selected deposit element, and the analysis of horizontal displacement measurements, based on the assumption that the value of horizontal displacement is proportional to the slope of the subsidence trough. Finally, the value of horizontal displacement coefficient B is estimated for particular longitudinal and transverse measurement section of the analyzed longwall No. 698.

The Elastoplastic Finite Element Analysis for the Deep Anti-Sliding Stability of Gravity Dam by the Method of Overloading

Combined with engineering requirements of the Qingyu reservoir, the ANSYS finite element software was used to establish an elastoplastic gravity dam calculation model which considered the mechanical properties of weak structural plane of rock in the dam foundation. An analysis based on not only the finite element iteration not converging,the plastic zones in dam foundation rock developing to through the foundation and the mutation in horizontal displacement of feature points, but also the discontinuous variation of the distribution of horizontal displacement of dam foundation rock, the dislocation between the above and below of weak layers and the leap of iterations were took as the criterions to get the deep anti-sliding stability safety factor of gravity dam by gradually increasing the load burdened on the upstream face of the dam. This thesis illustrated the principle of the elastoplastic finite element analysis for the deep stability of gravity dam by the method of overloading, demonstrated the feasibility of this method ,expanded the criterions to determine the safety factor and obtains the safety factor of this practical engineering under the elastoplastic overloading method.

Application of FVM Analysis for Elastic Characteristics on Cutting Process of a Composited Coating Iron

A composite material as a work piece is taken into account to investigate the elastic characteristics displaying during the cutting process. The magnitude of the elastic behaviors such as displacements and stresses reacts sensitively to the cutting angle and the vertical force increase, and the magnitude increases along the increments of the cutting angle and the vertical force increase. The buffering mechanism at the bond coat is described well by the fluctuation phenomenon for the horizontal displacement distribution profiles at the substrate. The variation of cutting angle under high vertical force yields profound influence on the behaviors of the longitudinal stress and the shear stress.

Development and validation of a 3D numerical model for TBM–EPB mechanised excavations

A 3D numerical model for mechanised excavations is presented, which is capable of simulating the overall process of excavation and construction of a tunnel when a TBM EPB (Tunnel Boring Machine–Earth Pressure Balance) is used. The main construction aspects of a mechanised excavation are modelled. Their influence on calculated ground displacements are investigated by means of a series of parametric analyses. With the aim of testing the performance of the proposed 3D numerical model, a series of 25 Class C predictions has been carried out. Case Histories related to the construction of the 1995–2003 Madrid Metro Extension Project were considered for this purpose. As a general rule, the results obtained with the Modified Cam–Clay model closely fit in situ measurements. When the Linear-Elastic or the Mohr–Coulomb models are used, it is not as easy to summarise the results obtained, as higher fluctuations are observed around in situ measured data. A good agreement is also shown when the distribution of horizontal displacements along depth is considered. For some sections, the mechanised excavation model is not capable of reproducing the high values of the surface settlements measured in situ. A closer look at the results shows that mixed face conditions are found for these cases, with the TBM excavating through layered soil formations having sharply different mechanical behaviour.

Dynamic Analysis of Response of Cofferdam with Steel Sheet Piles Induced by Earthquake Excitation

For its construction convenience and structure integrity, cofferdams are widely employed in port engineering. Past experience has shown that cofferdam are subjected to damage due to earthquake excitations. Numerical analyses with both response spectrum and step-by-step integration methods are conducted by using Lanczos eigenvalue extraction technique to obtain natural frequencies and modes, and solving dynamic equations with Newmark implicit method to consider geometric nonlinearity. The computational results show that the natural frequency of cofferdam system is low and the horizontal translation stiffness of cofferdam in positive direction is higher than that in negative direction. Under seismic excitation, the displacement response of inner steel sheet is much more obvious than that of outer one. And the distribution of horizontal displacements in steel sheets presents the characteristics that the corresponding values increase with their heights in the cofferdam system. On the contrary, the deviatonic stresses of cofferdam decrease with the augments of height.

Reevaluation of surface rupture parameters and faulting segmentation of the 2001 Kunlunshan earthquake (Mw7.8), northern Tibetan Plateau, China

The 14 November 2001,Mw= 7.8 Kunlunshan earthquake ruptured the westernmost part of the Kunlun Fault, northern Tibetan Plateau. The main segment affected by this event was the Kusaihu segment. Field investigations allowed us to constrain the length, the width, and the coseismic horizontal displacement distribution of the Kunlunshan earthquake rupture zone. The mapped surface rupture zone starts from 90.257°E in the west and ends at 94.795°E in the east with a total length of 426 km. It consists of three main sections, the western strike‐slip section, the transtensional section, and the eastern strike‐slip section. The rupture zone is oriented N100° ± 10°E on average. The distribution of the coseismic horizontal displacements is characterized by multiple peaks departing clearly from a general bell‐shaped distribution. Reassessment of the maximum coseismic horizontal left‐lateral displacement yields a value of 7.6 ± 0.4 m at the site (35.767°N, 93.323°E) consistent with independent measurements derived from interferometric synthetic aperture radar and seismology. From this site the horizontal displacement decreases unevenly to both the west and east. Coseismic vertical (reverse) displacement is also noted at the eastern end of the rupture but it remains much smaller than the horizontal component. The width of the rupture zone varies from site to site from several meters to few kilometers. The maximum width measured reaches 8 km along the Yuxi Feng subsection where a large number of shaking related cracks were well developed.

Further discussion on four-node isoparametric quadrilateral elements in plane bending

The aim of the study is: first—to show that the finite element method for plane bending is not sensitive to the distorted geometry of isoparametric quadrilateral elements, second—to close out further investigations on irregular elements based on Wilson incompatible functions employing ad hoc methods to force elements to pass the patch test, regardless of the type of the variational formulation used for the problem. A systematic review of papers dealing with finite four-node plane elements with two degrees of freedom at each node is presented. Selected results of the benchmark example of the mesh distortion test used by all cited authors are compared suggesting that no improvement has been made in more than two decades of intensive development of new elements and methods in the field. An attempt has been made to localize the pathological behaviour of irregular elements under consideration by calculating the areas of the elements after deformation for different values of the distortion parameter. It made possible to observe the mass density of the whole deformed system. The tip deflections at the lower and upper edge at the free end of the cantilever beam were depicted as well, illustrating unexpected physical phenomena of the longitudinal fibers deviating from being parallel. The horizontal displacement components at two common nodes of the adjacent elements have been compared with the analytical solution of the problem for the varying distortion parameter. The resulting horizontal displacement distribution along the common side of the elements has been shown to be the source of unreal behavior of all classes of irregular elements based on Wilson incompatible functions. Increasing the order of the interpolation functions for the displacement field, i.e. application of subparametric elements, makes the finite element method insensitive to element distortion. Copyright © 2000 John Wiley & Sons, Ltd.

Further discussion on four‐node isoparametric quadrilateral elements in plane bending

The aim of the study is: first—to show that the finite element method for plane bending is not sensitive to the distorted geometry of isoparametric quadrilateral elements, second—to close out further investigations on irregular elements based on Wilson incompatible functions employing ad hoc methods to force elements to pass the patch test, regardless of the type of the variational formulation used for the problem. A systematic review of papers dealing with finite four-node plane elements with two degrees of freedom at each node is presented. Selected results of the benchmark example of the mesh distortion test used by all cited authors are compared suggesting that no improvement has been made in more than two decades of intensive development of new elements and methods in the field. An attempt has been made to localize the pathological behaviour of irregular elements under consideration by calculating the areas of the elements after deformation for different values of the distortion parameter. It made possible to observe the mass density of the whole deformed system. The tip deflections at the lower and upper edge at the free end of the cantilever beam were depicted as well, illustrating unexpected physical phenomena of the longitudinal fibers deviating from being parallel. The horizontal displacement components at two common nodes of the adjacent elements have been compared with the analytical solution of the problem for the varying distortion parameter. The resulting horizontal displacement distribution along the common side of the elements has been shown to be the source of unreal behavior of all classes of irregular elements based on Wilson incompatible functions. Increasing the order of the interpolation functions for the displacement field, i.e. application of subparametric elements, makes the finite element method insensitive to element distortion. Copyright © 2000 John Wiley & Sons, Ltd.

Structure and deformational character of strike-slip fault zones

Strike-slip fault zones observed either in the field or in model experiments generally consist of several subparallel faults which make these zones complicated in geometry and kinematics. The geometry of a strike-slip fault or shear zone is dependent on arrangement (pinnate or en echelon), on step (left step or right step), and on the rank )smaller faults within larger faults) of the subparallel fault. The relations and interactions of these three factors create a variety of dynamic circumstances and tectonic settings within the strike-slip fault zones. These include pull-aparts in the release area between subparallel faults, push-ups in the jogs where the subparallel faults overlap, and pivotal movements, or rotation, of single faults along the whole fault zone. Each kind of tectonic setting is in itself characteristic, each setting consists of many subtypes, which are controlled chiefly by the geometric parameters of the subparallel faults. One of the most important phenomena revealed in the field work is two different kinds of evolution of strike-slip fault zones: one is the evolution of a zone with a tensile component, which is related to the growth of rock bridges, and the other, of one with a compressional component, which develops by the destruction of rock bridges. In this paper we discuss, on the basis of recent research on four strike-slip fault zones in China, the essential characteristics of strike-slip faults and the possible causes of the observed structural phenomena. Attention is focussed on the deformation, development, and distribution of horizontal displacements within strike-slip fault zones.