• Volume 39,Issue 5,2017 Table of Contents
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    • >地震工程
    • The Effect of Foundation Flexibility on System Response of Dynamic Soil-structure Interaction: An Analytical Solution

      2017, 39(5):799-810. DOI: 10.3969/j.issn.1000-0844.2017.05.0799

      Abstract (823) HTML (0) PDF 2.87 M (827) Comment (0) Favorites

      Abstract:The closed-form analytical solution for the effect of foundation flexibility on system response amplitude and system frequency of dynamic soil-structure interaction is presented. The wave function expansion method through a two-dimensional (2D) out-of-plane model, in which a single-degree-of-freedom (SDOF) system is supported by a semi-circular rigid-flexible composite foundation embedded into a homogeneous half-space subjected to plane SH waves, is used. The accuracy of the analytical solution is verified by comparing the results of the rigid foundation-SDOF model with the results of the flexible foundation-SDOF model. The numerical results are also performed and analyzed. It is shown that foundation flexibility has a strong effect on the system amplitude and system frequency. The analysis shows the dynamic response of the foundation and the relative response of the superstructure are very different to that of the rigid foundation results, especially for the case of small shear-velocity of the flexible layer and the small size of the rigid core. The displacement of the rigid core is always larger than that of the rigid foundation. Moreover, the rigid foundation assumption cannot provide the correct deformation of the structure near the base in the actual soil-structure interaction. The peak of the relative response of the superstructure is also always smaller than that of the rigid foundation, which means the rigid foundation may overestimate the effects of scattering of incident waves and the effective input motion of the foundation. The flexibility of the foundation also significantly affects the system frequency. When considering the flexibility in the analysis, the system frequency defined by the peak of the relative response of the superstructure will shift toward lower frequencies compared with that of the rigid foundation, and the amount of shift is highly dependent on the foundation flexibility. The larger the foundation flexibility, the larger the shift value is. The largest shift value can reach 38.9% of the rigid foundation system frequency.

    • Numerical Analysis of the Influence of Soil-structure Interface Parameters on the Seismic Dynamic Response of Underground Utility Tunnels

      2017, 39(5):811-819. DOI: 10.3969/j.issn.1000-0844.2017.05.0811

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      Abstract:To investigate the influence of soil-structure interface parameters on the seismic dynamic response of underground utility tunnels, in this study we built a dynamic finite element numerical model to probe the influence of changes in seismic input motion and interface reduction factors on the internal force and acceleration in utility tunnels. In the model, an optimized combination of boundary conditions was adopted wherein the excitation-applied side was a fixed boundary, the excitation-free side a viscous boundary, and the rest free-field boundaries. A small-strain stiffness model was employed as the constitutive soil model, a modified Goodman element was used to model the interface, and the dynamic load took into account three conditions:the effects of Rayleigh waves, the effects of bottom seismic waves (as those in Upland, California), and the combined effects of the two. The results showed that when the reduction factor remained unchanged, the structural internal force was greater under dynamic than under static force. Therefore, the situation wherein there is an increase in internal force under seismic loads should be considered in the design of utility tunnels. When the reduction factor increased, the extreme value of the sagging moment decreased, the extreme value of hogging moment increased, and the peak acceleration value increased. When the reduction factor remained the same, the extreme value of the structural internal force generated by bottom seismic waves was higher than that generated by Rayleigh waves. However, under the combined effect of Rayleigh and seismic waves, the extreme value of the structural internal force generated differed very slightly from that when only seismic waves were input. The research findings are expected to provide a reference for elaborate numerical simulations of the seismic response of underground utility tunnels and their seismic design.

    • Train-bridge Coupled Vibration Analysis of a Large-span Simply-supported Steel-truss Railway Bridge

      2017, 39(5):820-828,852. DOI: 10.3969/j.issn.1000-0844.2017.05.0820

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      Abstract:Over recent years, high-speed and heavy-load railways have developed in China. For a railway line, bridges are very important hubs along the line. Studies on the interaction between trains and bridges are very important for safe railway operations, especially for problems regarding the train-bridge coupled vibration of simply-supported steel-truss railway bridges, which have been widely used in recent years. In this paper, a 156-m-long simply-supported steel-truss bridge of the Huang Han-hou New Yellow River railway was studied. Numerical simulation using ANSYS and UM software is used together to study the train-bridge coupled vibration problems when a single locomotive, marshaling passenger coach, and freight coach pass the bridge. The results show that the lateral stiffness of the large-span steel-truss bridge is relatively small. The dynamic response parameters of the train and bridge all fell within the allowable limits when the different marshaling passenger coaches pass the bridge with the design speed. Compared with conditions of a single locomotive and marshaling passenger coach, the lateral and vertical accelerations of the bridge are obviously greater when the marshaling freight coaches pass.

    • Performance Analysis of Small Wild Goose Pagoda Seismic Reinforcement Based on Engineered Cementitious Composite

      2017, 39(5):829-835. DOI: 10.3969/j.issn.1000-0844.2017.05.0829

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      Abstract:Engineered cementitious composite (ECC), a new type of building material possessing high strength and excellent ductility, presents wide application prospects in strengthening engineering. This thesis takes advantage of these characteristics of ECC to put forward a protection scheme using ECC surfaces to reinforce the Small Wild Goose Pagod and improves its seismic performance of ancient pagoda. Using the finite element software ANSYS, the full size of the Small Wild Goose Pagoda is modeled via a monolithic masonry model. According to the national standard Code for Design of Masonry Structures and referencing the actual condition of the pagoda, the degree of damage to its bricks, and the multi-linear kinematic hardening model, the uniaxial stress-strain curve of the masonry is adjusted. The damage criterion of materials is further defined using five Willam-Warnke parameters. The El Centro seismic wave is selected as the ground motion input, and three levels of amplitude modulation are adopted. The maximum acceleration values of the three conditions are 70, 220, and 400 gal. The seismic response of the model was analyzed using dynamic time-history analysis methods, and the maximum displacement and acceleration of each layer are extracted. The story drift is also calculated. The criteria show that the pagoda is seriously damaged to the brink of collapse when the peak earthquake acceleration is 400 gal. The earthquake response of the pagoda notably decreased after establishment of the ECC reinforcement model of the Small Wild Goose Pagoda. The analysis results demonstrated that the ECC surface layer reinforcement can significantly enhance the overall ductility and bearing capacity of the tower, effectively improving its damage tolerance. This work provides a reference for the practical application of ECC in ancient tower seismic reinforcement for earthquake protection.

    • Seismic Response Analysis of Inter-story Isolation Structures Based on Wavelet Transformation

      2017, 39(5):836-842. DOI: 10.3969/j.issn.1000-0844.2017.05.0836

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      Abstract:In this study, ground motion acceleration time history was decomposed into multi-band wavelet components using the wavelet multi-resolution analysis method, and a dynamic response formula for an inter-story isolation structure under earthquake action was deduced using the complex modal method. The resulting seismic signals and displacement energies in a distinct frequency channel are discussed. The impact of earthquake energy distribution in the time-frequency domain on structural response was analyzed using wavelet time-frequency analysis tools, which provide a method of analyzing the nonlinear response of inter-story isolation structures. Finally, the elastic and elastoplastic responses of a typical inter-story isolation structure under earthquake excitation are analyzed using wavelet analysis. The results show that the elastic response can be the superposed seismic response of each wavelet component. Therefore, energy concentration of earthquake ground motion in the time domain can cause an adverse effect on inter-story isolation structures.

    • Influence of a Near-fault Velocity Pulse on the Seismic Response of a Mega Structural System

      2017, 39(5):843-852. DOI: 10.3969/j.issn.1000-0844.2017.05.0843

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      Abstract:The seismic responses of the seismic, isolation, and smart isolation systems of a mega structure were calculated and comparatively analyzed. Four groups of actual strong motion records with velocity pulses and corresponding synthetic time histories of ground motion with the same acceleration response spectra but without velocity pulses were used as ground motion inputs. Then, the influence of ground motion with and without velocity pulses on the mega structure under different control strategies was discussed. The results show that the seismic response of the mega structure's underground motion with a velocity pulse is greater than that without velocity pulse; in addition, the velocity pulse of near-fault ground motion has some negative impact on the seismic response of its seismic, isolation, and smart isolation systems. Though a mega structure with intelligent control system is more sensitive to ground motion with a velocity pulse, it can effectively reduce the displacement of the isolation layer.

    • Influence of Portal Elevation on Dynamic Response Characteristics of Loess Tunnel Portal Section

      2017, 39(5):853-858,869. DOI: 10.3969/j.issn.1000-0844.2017.05.0853

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      Abstract:The choice of portal elevation and gradient of upward slope values are critical to the safety and stability of the whole traffic line, especially, in the tunnel and bridge coupling process. To explore the dynamic response of tunnel portal section and upward slope under the influence of portal elevation and gradient of upward slope, models with different slope gradients and different portal elevations were constructed. These models were based on 3D numerical simulation, with the incident direction of seismic wave being parallel to the direction of the tunnel axis. Our results demonstrate that (1) Under seismic loads, with increasing distance from the tunnel portal, the displacement of the tunnel vault is gradually reduced, with the peak value of displacement located in the vault section of y=0 m (distance from the portal). Therefore, it is the portal section that is the most dangerous under the earthquake action, and it should receive the most attention when designing the whole tunnel line. (2) In this paper, Δmax is defined as the maximum displacement difference of the tunnel section. The change rule of Δmax indicates that with the increase of the gradient of upward slope, the portal elevation of tunnel should also be higher. The Δmax defined in this study may provide a new method to evaluate the seismic dynamic response. (3) By setting the contrast model, which is pure slope without tunnel, the influence of tunnel on the dynamic response of slope is studied. Firstly, the peak value of slope displacement is smaller than that with tunnel. Secondly, with increasing portal elevation, the tunnel will influence the dynamic response of the slope surface, due to the effects of portal elevation and slope gradient.

    • Effect of Different Ratios of Column-to-beam Flexural Strength on Seismic-collapse Resistance Behavior of Frame Structures

      2017, 39(5):859-869. DOI: 10.3969/j.issn.1000-0844.2017.05.0859

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      Abstract:In this study, we designed five fiber-reinforced concrete (FRC) frames and three reinforced concrete frames with different ratios of column-to-beam flexural strength (ηc-bua) and determined their failure modes and fragility curves using the pushover and increment dynamic analysis methods and the capacity evaluation software Perform-3D. The results show improved deformation and bearing capacities of FRC frames in which FRC is used at the beam and column ends, and that the deformation capacity of FRC frames increased over a greater range than the structural bearing capacity. The ηc-bua has a great effect on the failure mechanism of FRC frames. The ηc-bua also has some effect on the structural seismic response of the FRC frame, whereby the greater is its value, the lower is the probability of exceedance, which becomes more obvious when the expected failure is more serious. The collapse probability is less than 10 percent, which satisfies the requirement of the seismic design code for buildings when the ηc-bua value is greater than 1.2.

    • Discussion about Earthquake Resistance of the Bridges Crossing the Active Fault

      2017, 39(5):870-875,889. DOI: 10.3969/j.issn.1000-0844.2017.05.0870

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      Abstract:The connotation of bridges crossing the active fault (BCAF) was discussed in terms of time scale, fault activity and site effect. The great earthquake damage risks BCAF has to face was analyzed, and the reasons are summarized as "function" and "restriction" and so on. Based on the strong motion records of Imperial Valley earthquake collected by the El Centro array in 1979, the characteristics of strong earthquakes and the mechanism of earthquake ground motion of fault-rupture were analyzed, the ground motion distribution law on both sides of fault was studied, and a suggestion is put forward for the ground motion input direction of bridges crossing the strike-slip fault. The research results have reference significance for the promotion of seismic fortification of BCAF.

    • Study of Seismic Slope Permanent Displacements with Dynamic Critical Acceleration

      2017, 39(5):876-882. DOI: 10.3969/j.issn.1000-0844.2017.05.0876

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      Abstract:The Newmark permanent displacement, an important index for evaluating the stability of slopes in earthquakes, is extensively applied to seismic slope hazard assessment. However, because the critical acceleration is assumed to be constant and the variations of shear strength parameters on sliding surfaces are not considered in the traditional Newmark permanent displacement method, the permanent displacements of a slope are often underestimated. To solve this problem, this paper analyzes the change process of shear strength parameters on a sliding surface in detail based on geotechnical structure theory. A method to calculate the dynamic critical acceleration in which the dynamic change of cohesion is simulated by the Monte Carlo method on the basis of a certain probability distribution type of cohesion is presented. Sample calculations reveal the dynamic change processes of cohesion and critical acceleration of the slope sliding block in earthquake, and a new permanent displacement result is obtained. The displacement results conform to the normal displacement value of the seismic slope, and the implementation processes of dynamic cohesion and critical acceleration presented in this paper correspond to the seismic time history. Dynamic changes in shear strength parameters are solved to a certain extent, and the displacement problem encountered in the traditional Newmark permanent displacement calculation is addressed.

    • >场地地震效应及动力响应
    • Nonlinear Seismic Response Analysis of Soil Layers Based on FLAC3D

      2017, 39(5):883-889. DOI: 10.3969/j.issn.1000-0844.2017.05.0883

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      Abstract:To validate the effect of FLAC3D software on the seismic response analysis of soil, we used the No. 3 logging site (class Ⅱ site) in Xiangtang Town, Tangshan City as an experimental site and analyzed its seismic response using FLAC3D software and an equivalent linearization method. The calculation results show that FLAC3D software method is feasible. Then taking a class IV site in Tanggu District, Tianjin City as an example, the two methods are used to calculate the ground motion peak values and ground response spectra under different ground motion input intensities. The results show that the results calculated via FLAC3D and the equivalent linearization method have little difference when the intensity of input ground motion is relatively small; moreover, FLAC3D overcomes the problem of a long characteristic period of ground response spectrum when the input ground motion intensity is large. When using the equivalent linearization method, this problem occurs because of an underestimation in ground seismic response (high frequency) and an overestimation in soil nonlinearity. Therefore, the results obtained from the FLAC3D method may be more appropriate for engineering practice.

    • Equivalent Model for Dynamic Fluid Pressure Analysis of PCS Tanks in Nuclear Power Plants

      2017, 39(5):890-897,906. DOI: 10.3969/j.issn.1000-0844.2017.05.0890

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      Abstract:As a two-dimensional equivalent mass-spring model based on a rectangular or cylindrical liquid storage tank, the Housner model is used in seismic response analysis of liquid storage tanks with different geometric shapes. However, based on previous studies, this model is not suitable for fluid-structure coupling analysis of complex-shaped nuclear liquid storage structures. To analyze the passive containment cooling system water tanks (PCS tank for short) installed at the top of shield buildings in AP1000 and CAP1400 nuclear power plants, a three-dimensional equivalent mass-spring model is proposed through the introduction of volume correction parameters based on the Housner equivalent mass-spring model of a cylindrical tank. Then, several fluid-structure coupling finite element models of different tank systems, established with the finite element software ADINA, are used for modal analysis. The natural vibration characteristics of liquid sloshing in PCS and corresponding annular water tanks are calculated and analyzed with different box sizes and liquid depths. The calculation results from the integrated finite element and three-dimensional equivalent mass-spring models are compared, and it is found that the proposed three-dimensional equivalent mass-spring model of PCS tank can give reasonable estimated values of dynamic fluid pressure of liquid sloshing under different modes. It is concluded that the proposed model is suitable for dynamic fluid pressure analysis of a complex-shaped PCS tank. This model or method can also be applied to the dynamic fluid pressure analysis of other complex-shaped liquid storage tanks.

    • Determination and Sensitivity Analysis of the Parameters of Hardening Soil Model with Small Strain Stiffness

      2017, 39(5):898-906. DOI: 10.3969/j.issn.1000-0844.2017.05.0898

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      Abstract:Geotechnical construction disturbs soil mass, destructs soil fabrics, reduces soil strength, and causes soil deformation, all of which can result in the deformation and destruction of adjacent buildings. According to the value of soil shear strain, the soil surrounding a construction site can be divided into:strongly disturbed zone, disturbed zone, micro-disturbed zone, and undisturbed zone. Therefore, a soil constitutive model needs to consider the small strain characteristics and disturbance characteristics of the soil. Methods for determining key parameters of a hardening soil model with small strain stiffness (HS-Small model), including initial shear modulus and threshold shear strain, have been presented and analyzed. Drained triaxial tests and oedometer tests were performed on typical soils in Shanghai, and the corresponding model parameters were determined. The in situ testing methods are recommended for determining the initial elastic modulus of soils. Sensitivity analysis of the HS-Small model parameters, including initial shear modulus and threshold shear strain, revealed that the initial slope of the compression curve and the unloading-recompression curve increased with the increase of the initial elastic modulus. With increasing threshold shear strain, both the approximate straight segments of the compression curve and the unloading-recompression curve lengthened. Under same shear stress conditions, the shear strain of the soil decreased, while the interval range of the initial elastic modulus of the soil constantly increased.

    • Determination of the Category of Engineering Sites Disturbed by Humans

      2017, 39(5):907-912,918. DOI: 10.3969/j.issn.1000-0844.2017.05.0907

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      Abstract:Methods on using the test results of in situ shear wave velocity to determine the category of engineering sites that has been disturbed or transformed by humans have not been discussed in relevant codes or documents. Based on the revelation of engineering site category and the summary of actual experience for many years, this paper gives the theoretical basis and a practical method to solve the problem. It is necessary to evaluate whether the scope and depth of the disturbance is big enough to influence the effect of seismic waves on the site. The evaluation is done on the basis of site volume disturbed by humans. If the volume is large enough, for example, a three-dimensional block with a range of about 1 km2 and a depth of tens of meters, it is necessary to determinate the site category using in situ test shear wave velocity. If the volume of the site is not large enough, for example, only local disturbance, the in situ wave velocity cannot be directly used; the average wave velocity of disturbed layer should be replaced by 85% of the wave velocity in 1 m range below the disturbed layer. The reason is that a small amount of disturbance is not large enough to change the engineering category of the site but it may change the results of the in situ wave velocity test, thus leading to misjudgment.

    • >震例研究
    • Focal Mechanism Solution and Tectonic Stress Field of the Jiuzhaigou MS7.0 Earthquake

      2017, 39(5):913-918. DOI: 10.3969/j.issn.1000-0844.2017.05.0913

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      Abstract:The Jiuzhaigou MS7.0 earthquake occurred in Jiuzhaigou County, Sichuan Province on August 08, 2017. In this paper, the focal mechanism of the main shock was determined using gCAP and P-wave first motion methods based on the waveforms recorded at fixed stations in the China Earthquake Network Center. This proved to be consistent with the solutions published by Harvard CMT, the United States Geological Survey, and the China Earthquake Administration. We also determined the focal mechanisms of 28 small earthquakes that occurred in the region of the Jiuzhaigou MS7.0 earthquake from 2010 to 2016, and by the focal mechanisms the tectonic stress field in the area was inverted. The results show that the direction of the maximum and minimum principal stress axes was NWW and SSW, respectively, both in the horizontal direction. After the Jiuzhaigou MS7.0 earthquake, a series of aftershocks occurred, and, as they should continue for a certain time, we expect to eventually have more data for analysis of the changes in the tectonic stress field.

    • Discussion of the Earthquake Sequence and Earthquake Rupture Surface of Alxa Zuoqi MS5.8 in 2015

      2017, 39(5):919-924. DOI: 10.3969/j.issn.1013-0019.2017.05.0919

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      Abstract:This paper studies the MS5.8 earthquake that occurred in Alxa Zuoqi 2015. Based on the background seismicity and statistical analysis of the sequence, the HypoDD method was used to reposition the earthquake sequence. We examined the aftershocks distribution characteristics in space, and determined the MS5.8 earthquake fracture surface combined with epicentral intensity、focal mechanism solutions, and the results of the re-positioning. The results show the Alxa Zuoqi MS5.8 earthquake is the main aftershock, after relocation, the epicenter is 39.78°N(±0.72 km)、106.34°E(±0.76 km), focal depth is 13.2 km(±1.15 km). The distribution direction of the sequence dominance is near NS and NEE, and extends 18 km and 16 km respectively. The focal depth of the profiles display the overall east-dipping sequence; the focal depth gradually deepened from west to east. The regional stress field background characteristics、historical earthquake rupture characteristics、the main shock mechanism solutions, and serial repositioning information considered judgment, the fracture surface of Alxa Zuoqi MS5.8 earthquake should be near NS-direction surface.

    • Focal Mechanism, Focal Depth, and Seismogenic Structure of Oroqen M5.2 Earthquake Occurring on 10 June, 2008

      2017, 39(5):925-933. DOI: 10.3969/j.issn.1000-0844.2017.05.0925

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      Abstract:The M5.2 earthquake that occurred in Oroqen on 10 June, 2008, was the largest earthquake effecting northeastern Inner Mongolia in recent years. In this study, the focal mechanisms and focal depth of this earthquake are determined using the TDMT method, CAP method, PTD method, and sPn-Pn method. Results using the CAP and TDMT methods are inconsistent with each other, and show that the focal depth of the earthquake is shallow and that the source is located in the upper crust. Combined with existing data, the spatial and temporal distribution characteristics and tectonic stress characteristics of earthquakes in the area near the epicenter of this earthquake are analyzed, and the seismogenic structure of this M5.2 earthquake is discussed. Using a combination of the focal mechanism solution, earthquake distribution characteristics, and tectonic background, the M5.2 earthquake is determined as a dextral strike-slip faulting event with a NNE strike and a SWW principal compressive stress direction. The seismic activities of earthquakes in this area were significantly enhanced after the M5.2 earthquake. Focal mechanism solutions in the northern section of the Greater Khingan Range gradient zone show that the Greater Khingan Range fracture is controlled by NEE-SSW horizontal compressional stress, with a strike-slip feature.

    • The Earthquake Case Studies of the Hebei Solid Tide Parameters

      2017, 39(5):934-938. DOI: 10.3969/j.issn.1000-0844.2017.05.0934

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      Abstract:In this paper, based on the deformation observation data of five stations in Hebei, we use VENEDIKOV harmonic analysis method to calculate the MS > 4.0 earthquake phase and amplitude factor, tidal factor ect. We find that the strain tide factor of five deformation stations has a few weeks to half a year of abnormal period corresponding to the earthquakes. Kuancheng station has the shortest distance (the farest distance is 350 km, and the nearest distance is 100 km) from the epicenter of these MS>4.0 earthquakes. Therefore, based on the comprehensive analysis of Hebei strain stations, we use the strain tide factor of Kuancheng station as key data to briefly analyzed the earthquake cases of Hebei from 2005 to 2015. The results show that the corresponding rate of the earthquake and Kuancheng station reaches 60%, the false rate is 40%, the omission rate is only 14%, and the precursory anomaly reliability is higher, which can be used as a reference for precursory anomalies.

    • >工程地质与施工技术
    • Study of Treatment Measures for Landfill Site Foundation in Xi'an North EMU Depot

      2017, 39(5):939-945. DOI: 10.3969/j.issn.1000-0844.2017.05.0939

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      Abstract:With the rapid pace of urbanization, construction land is growing sparse, so it has become more common for landfills to be used as engineering sites. As such, to explore the physical and mechanical properties of various soil types in landfills and the necessary treatment measures to be taken, we studied the foundation treatment and construction of a landfill site in the Xi'an North EMU depot. Based on indoor tests and in-situ field measurements of the landfill soil, we quantitatively analyzed the engineering properties of miscellaneous fill ground. In this paper, we propose a reasonable foundation treatment plan. The related engineering operations verified that all the foundation parameters met the design requirements and achieved the desired effect after excavation, replacement, and dynamic consolidation of the foundation. Moreover, we also applied an innovative method of mixing quicklime into the solid waste, which prevents secondary pollution. Our research results can be used for reference in other landfill foundation treatment projects under similar conditions.

    • Application of Fuzzy Matter-element Model Based on Coefficients of Combined Weights to Evaluate Slope Stability

      2017, 39(5):946-950,980. DOI: 10.3969/j.issn.1000-0844.2017.05.0946

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      Abstract:In view of the complexity, uncertainty, and fuzziness of the factors involved in evaluating slope stability, based on the fuzzy matter-element theory, we calculated the objective and subjective weights of the influence factors using the analytic hierarchy process and the entropy weight method. Then, we established a fuzzy matter-element model based on the coefficients of combined weights that considers both objective and subjective factors. The problem of weight allocation can be avoided by employing our proposed method. A comprehensive evaluation can be made by using this matter-element model along with the subjective and objective weighting method, both of which make the best use of statistical information from samples, based on expert theories and experience, to obtain reasonable index weights. We conduct a case study to demonstrate that this method can not only accurately estimate the slope stability but also provides a new way to evaluate slope stability.

    • Vibration Analysis of Micro-rupture Process in the Qianjiangping Landslide in Zigui, Hubei Province

      2017, 39(5):951-956. DOI: 10.3969/j.issn.1000-0844.2017.05.0951

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      Abstract:In this study, based on the topographic, geological, and hydrological characteristics of the Qianjiangping landslide, we have built a vibration analysis model using the QUAKEW module of GeoStudio software. We set the dynamic elastic modulus and Poisson's ratio of the soil and rock; further, we processed and loaded the data of four rupture events recorded by Lujiashan seismic station. Then, we used the model to simulate the landslide creep and slide processes. The results show that the Qianjiangping landslide was under static load and also experienced a micro-rupturing process that involved following sub-processes in sequence:micro-rupture, creep slip, re-rupture, creep slip, and landslide. This model could provide some new ideas for feasibility studies on rock landslide forecasts.

    • Discrete Element Numerical Simulation on Stability of Bedding Shale Slope

      2017, 39(5):957-962. DOI: 10.3969/j.issn.1000-0844.2017.05.0957

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      Abstract:Slope,which is a natural geological integration,can be divided into two types-soil slope and rock slope.Qualitative analysis and quantitative analysis are often used in the slope stability assessment.DEM used in this paper belongs to quantitative analysis.The traditional approaches to slope stability assessment are hardly to reflect the unstability mode and destruction process.However,DEM owns apparent advantages on the analysis of non-continuum medium's deformation and destruction.Based on the bedding shale slope in debris deposit,the meso-parameters of PFC model was determinated by comparison of meso-parameters in simulated uniaxial compression test and macro mechanics parameters.It shows that the parameters used in the former simulations could be used in the subsequent stability assessment model of slope.Expasion method was used to establish the model in this paper.In this method,balls were generated in specified areas.Then the radius of balls were enlarged until contact forces were generated.Balls were driven to move around for balance and then the areas were filled with balls.A general study on stable state of the slope was carried out using DEM.Sliding process and sliding distance were also studied.The results show that:the completely weathered shale slipped down and deposited at the bottom of the slope.The strong weathered shale and intermediary weathered shale didn't slip.The sliding surface was a interface between completely weathered shale and strong weathered shale.Compression fractures are the primary fractures which only occur on the completely weathered layer.Owning to the small strength of the completely weathered shale layer,most parallel bonds break because of gravity.Grains' spilling out of the bottom makes the middle-upper grains slide downwards on account of lacking supports.Based on the analysis above,cutting slope should be adopted.The simulation results are in agreement with the stereographic method,and it can instruct the design and construction of the project.

    • >其他
    • Noise Characteristics Analysis of the High-rate GPS Coordinate Time Series

      2017, 39(5):963-968. DOI: 10.3969/j.issn.1000-0844.2017.05.0963

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      Abstract:To investigate the noise characteristics of the high-rate GPS coordinate time series, one-hour high-rate observations of eight CORS sites in the Sichuan basin from 8:00-9:00 Beijing time for three days, including the Lushan earthquake, are resolved and analyzed. The sidereal filtering and principle component analysis filtering are utilized to analyze and reduce the temporal and spatial noise separately; the power spectrum method is used to estimate the spectrum index. With the spectrum index from 1.6 to 2, we consider the high-rate coordinate time series are adjusted for white noise plus random walk noise characteristics. These results have important implications for the design of continuous GPS networks for crustal deformation and structural monitoring, and also for positioning and attitude determination of dynamic platforms.

    • Design and Implementation of the Middleware to Access Realtime Stream of Digitizers

      2017, 39(5):969-975. DOI: 10.3969/j.issn.1000-0844.2017.05.0969

      Abstract (662) HTML (0) PDF 8.74 M (898) Comment (0) Favorites

      Abstract:A digitizer is a key equipment in conducting studies on seismic networks; it acquires analogue signals from the seismometer and converts them into digital signals with the AD module. These signals are outputted via the Ethernet interface in the form of TCP/IP flow. Compared with the relational data set, TCP/IP flow has the following characteristics:continuous production, real-time arrival, and unlimited potential amounts. Based on these characteristics, researchers have proposed a method to access the layer between the data source and application, which can continuously and asynchronously collect data from the underlying part and send them to the upper layer. This hierarchical structure decouples the data producer process and consumer process, which improves the robustness and throughput of the whole system. However, the maximum number of concurrent connections that can be supported by the digitizer is usually limited; hence there is a need to develop an integrated data access service, which can provide a unified interface to access all kinds of data. Therefore, in this paper, the architecture design of a data-accessing-middleware is first introduced, and the implementation of each component is then proposed. In the end, the middleware is applied in the seismic station data monitoring system. The producer/consumer pattern is used to support concurrent and asynchronous communication. The whole system is divided into five components:digitizer adapter, stream buffer, stream adapter, data buffer, and data publisher. The instrument adapter establishes socket connections with the digitizer and obtains streams; it then writes the streams into the stream buffer without decoding. The stream buffer is a synchronized FIFO (First In First Out) queue. The stream adapter reads streams from the queue, extracts data, and writes them into the data buffer. The data buffer is also a synchronized FIFO queue, in which the data publisher reads data from the queue and publishes them in two ways:by storing them into the database or by sending them to a Java Message Service (JMS) provider. With this middleware, a system is developed to monitor the data quality of seismic stations. The system can collect real-time seismic wave data and health data from all seismic stations, and then provide these data to users through Web services. The health data include several parameters collected by the sensor inside the digitizer, including power input, power output, power battery, DSP temperature, clock difference, frequency difference, drive free space, and mass positions. When the value of the parameter is beyond the normal range, it can affect the availability of data, thus affecting the effectiveness of the station. The system provides methods and tools to track the data quality of stations for the engineers. Ultimately, this method can improve the efficiency of the maintenance work and promote further use of the accumulated health data.

    • Study on the Prevention and Control of Dynamic Disasters at an Isolated Island Working Face

      2017, 39(5):976-980. DOI: 10.3969/j.issn.1000-0844.2017.05.0976

      Abstract (688) HTML (0) PDF 4.56 M (694) Comment (0) Favorites

      Abstract:To study safe mining methods at an isolated island face, rock movement and stress conditions that could easily induce dynamic disasters under such conditions are analyzed theoretically, and criteria for safe mining in such locations are suggested. It was found that rational design of mining parameters can avoid dynamic disasters at isolated island faces. The results show that abutment pressure cannot be superposed and the working face is relatively safe if the length of the island face is larger than the sum of the abutment pressure ranges on adjacent faces. If the length of the adjacent face is larger than the fracture length of a key stratum, the overlying key stratum will fully collapse, and there will be no danger of dynamic pressure impact on the island face. Moreover, if a drifting roadway is located in a stable internal stress field, it has no danger of rock burst.

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