Abstract:The dynamic response law of pile foundations on liquefied soil is a perennial hot topic in the field of earthquake resistance engineering. In this work, the lateral dynamic response characteristics of pile groups in a nonliquefied soil layer and saturated sand layers with two different thicknesses are studied under the input of a sine wave with a certain peak acceleration and frequency through the model shaking table tests of 2×2 pile groups. Results show that under the input of the sine wave, the time histories of acceleration and displacement at the pile cap in nonliquefied sand are not significantly different from those of the input. The peak acceleration and peak displacement at the pile cap drastically increase in saturated sand with two different thicknesses. Specifically, the peak acceleration and peak displacement at the pile cap are magnified by 1.83 and 1.58 orders, respectively, in thin saturated sand, and by 2.18 and 1.91 orders, respectively, in thick saturated sand. Under the same input condition after liquefaction, the dynamic response of the pile cap is more remarkable in thick saturated sand than that in thin saturated sand.

Abstract:The local site effect should be considered when analyzing the seismic response of long-span suspension bridges because of the large span scale and different site conditions of pier column foundation. For such analysis, the finite element model of a certain long-span suspension bridge is established in this paper using the MIDAS/Civil finite element software. Considering the local site effect of ground motions, nine different calculation conditions are listed to carry out the time-history analysis of the long-span suspension bridge. By controlling the site classification of one tower pier and changing the site classification of another tower pier, the influence of site effect on the midspan displacement and bending moment of the bridge is analyzed. The results show that site effect has some impacts on the midspan displacement and bending moment of suspension bridges, and different site conditions have different levels of destruction on the same position of the bridge.

Abstract:Traditional analysis method for simulating the transverse vibration response process of high-rise buildings under the influence of a strong earthquake is associated with some problems, such as inaccurate calculation results and longer calculation time. This study aims to propose a new method for simulating the transverse vibration response process of high-rise buildings under strong earthquakes. This method is based on two methods, which are implicit and explicit methods. Both methods can be used to accurately calculate the transverse vibration displacement of high-rise buildings with different degrees of freedom and accurately simulate the deformation process of high-rise buildings during the transverse vibration response. The experimental results show that the proposed method can be applied to calculate the transverse vibration response of high-rise buildings under strong earthquakes with high accuracy and efficiency of operation.

Abstract:A novel fan-shaped disc energy dissipator (FDED) is proposed in this study. The working mechanism and characteristics of the FDED are illustrated, and its key points and theory of design are derived. The numerical method is used to analyze the seismic performance of the FDED and the influence of different design parameters on the performance of the FDED. Results show that the FDED has a feasible design principle and clear seismic performance. The fan-shaped construction enables the FDED to effectively amplify displacement. The FDED has a bilinear restoring force characteristic, stable energy dissipation performance, and an equivalent viscous damping coefficient that exceeds 50%. Although the change in rubber hardness is insensitive to the initial stiffness of the FDED, it influences the postyield stiffness and equivalent viscous damping coefficient of the FDED. Additionally, as rubber hardness increases, the postyield stiffness of the FDED increases, and the equivalent viscous damping coefficient decreases. The change in the thickness of the single rubber layer negligibly affects the seismic performance of the FDED. The yield force and energy dissipation performance of the FDED are mainly affected by lead-core diameter. Yield force increases and energy dissipation performance improves as lead diameter increases.

Abstract:Eccentricity has a considerable influence on the seismic effect of buildings. In this study, the seismic responses of three common frame structures under the action of eccentric torque were numerically simulated. The influence of eccentric structures on the seismic performance of buildings was analyzed through three-dimensional nonlinear simulation of a six-story building model. Maximum inter-story displacement was used as the measurement standard, and fragility curves were drawn to analyze the results. The results show that if the influence of accidental eccentric torque is ignored, then the seismic performance of the steel-structure system will be overestimated, thus affecting the safety assessment results. Conversely, if the influence of accidental eccentric torque is considered using 5% mass eccentricity of the entire floor, then the seismic performance of the steel-structure system will be underestimated.

Abstract:The traditional method for the analysis of the bearing capacity of steel plates in steel structures under external vibration analyzes the overall steel plate structure and stress characteristics to obtain the relationship between load and vibration frequency. This approach, however, provides results with high deviation because it ignores the stress-strain relationship between the steel plate and the concrete. A novel finite element analysis method for the analysis of the bearing capacity of steel structure plates under external vibration is proposed. The cross-section of the steel structure plate is simplified to the rectangular section of the concrete and the I-section of the corrugated steel plate. The interaction between the steel plate and the concrete is simulated and analyzed with the CONTACI2 contact element in ANSYS finite element software. The stress-strain relationship of the soil and steel plate and the stress-slip relationship of the interface module are analyzed. The load increment of the steel plate under external vibration is obtained through the force balance iterative method. Then, the finite element method is used to analyze the bearing capacity of the steel structure plate under external vibration. Experimental results show that the proposed method can accurately and efficiently realize the finite element analysis of the bearing capacity of steel structure plates under external vibration.

Abstract:Expert experience is required to determine reinforcement distribution when the traditional finite element analysis method is used to analyze the composite stress characteristics of reinforced concrete box girders in earthquake environments. However, such an approach is highly subjective and will cause the deviation of the analytical results of the obtained composite force characteristics. Therefore, an experimental model of the composite force of reinforced concrete box girders under earthquake conditions is constructed. In this work, the size of the experimental model is set in accordance with previously established experimental parameters and the national restrictions on the parameters of concrete bridges. The experimental model material is selected. The continuous support of the span beam is built with round steel and angular steel, and the experimental loading scheme is designed. Then, a scientific reinforcement scheme for the experimental model of the composite force of reinforced continuous box girders in an earthquake environment is obtained. Experimental results show that the experimental model can comprehensively and accurately analyze the composite force characteristics of reinforced concrete box girders in an earthquake environment.

Abstract:The traditional dynamic elastoplastic analysis method limits the results of studies on the seismic performance of buildings given that this approach fails to analyze the key nodes of the shear-wall transfer structure effectively. A method for analyzing the influence of the key nodes of shear-wall transfer structures on the seismic performance of buildings is proposed. The plane layout diagram of the shear-wall transfer structure is created, and the key nodes of the shear-wall transfer structure are determined. Then, the interstorey displacement and displacement angle of the key nodes and floor shear at the key nodes are analyzed. Elevating the key node position decreases the displacement of the maximum floor and the displacement angle. The fluctuation in the stiffness of the upper and lower floors of the building is obtained on the basis of differences in interstorey displacement, displacement angle, and force on the key nodes of different floors. Experimental results show that the proposed method can effectively and precisely analyze the seismic performance of buildings.

Abstract:The seismic performance of steel-strip refuge buildings under high-intensity earthquakes is improved through seismic design. The seismic fortification requirements of steel-strip refuge buildings under high-intensity earthquake are set, and the acceleration value and maximum earthquake affecting coefficient of the steel-strip shelter under different earthquake scenarios are given. SAP2000 is used to analyze the elastic-plastic dynamics of the steel-strip shelter, and reasonable parameters for plastic hinges are selected. The steel support is set around a building to analyze the seismic performance of the steel-strip shelter. Experimental results show that the steel-strip refuge building designed through the proposed method has good response and ductility under intense earthquakes. Moreover, the horizontal displacement angle of the building under the action of different seismic waves satisfies the seismic fortification criterion.

Abstract:The damage caused by underground fissure propagation prominently affects the stability of ground surface and underground buildings. Based on the damage caused by underground fissures to loess structures, the study of loess structural damage was combined with numerical simulations to analyze the development law of progressive failure of overlying strata due to underground fissures. The mechanical behavior of split-tunnel-lining structures was also discussed. The results show that during the process of underground fissure propagation, the dislocation displacement of the tunnel-lining structures in the ground-fissure area is smaller than that in a ground-fissure-free site. When the underground fissure extends from the bottom of the tunnel to the ground surface, the first section of the lining structure of the foot wall is particularly damaged. Tensile failure of the split-lining structure due to ground fissures is one of the key problems in the design of tunnel lining in ground-fissure areas.

Abstract:In strong earthquake environments, buildings are subjected to complicated lateral pressure force. In addition, given the different shapes of buildings and different sizes of force-bearing areas under earthquake conditions, strong earthquakes cause different impact sizes. This difference results in the stochastic complexity of lateral pressure. The traditional method for the detection of building pressure load has insufficient measurement ability for steel-bar load force and provides detection results that are prone to error. A method for the measurement of load on building steel bars under lateral pressure is proposed. The load variation characteristics of steel bars with different structures are tested and analyzed under the ideal elastic-plastic condition of the mechanical properties of the steel bars and different load conditions. Combined with the local pressure characteristics of the building, the method for the measurement of load on building steel bars under lateral pressure is designed and subjected to simulations. Results prove that the proposed method provides data with improved accuracy and has improved applicability.

Abstract:Steel Structure is widely used for industrial architecture because of its advantages of being light weight, higher strength, and better plasticity and toughness. Unfortunately, the poor performance that resists corrosion has been gradually found recently with the steel widely used. The seismic performance of structures in different service times is necessary to be evaluated since the corrosion of steel directly lead to the deterioration of seismic performance and stiffness of structure. In order to study the impact of corrosion on steel mechanical properties in the acidic atmospheric environment and then analysis the seismic vulnerability of multi-age steel structures, 105 standard steel material specimens corroded by artificial climate accelerated corrosion test technique were carried out under tensile test. Based on tensile test data, the linear regression relationship between the steel mechanical properties (yield strength, ultimate strength, elongation, elastic modulus) and weightlessness rate was established. At the same time, the corrosion rate and the initial corrosion time of steel bent frame structure were accounted for by using findings from related research. Based on the result of material performance of different corrosive steel in acidic atmospheric environment and combined with corrosion rate and the initial corrosion time, the analysis platform SAP2000 was employed to build numerical models of steel bent frame structures with different service times (30 years, 40 years, 50 years, 60 years).In order to eliminate the influence of uncertainty of seismic record, 24 seismic records had been chosen in this paper. The incremental dynamic analysis (IDA) was carried out on the models with PGA as the earthquake intensity index and maximum inter-story drift as the seismic demand index. The relationship of probabilistic seismic demand was obtained by IDA analysis for multi-age steel bent frame structures. The statistical parameters of the probabilistic seismic capacity model were evaluated using existing research. Consequently, seismic vulnerability curves of multi-age steel bent frame structures were established in accordance with seismic demand model and seismic capacity model. Furtherly, earthquake damage matrixes were obtained by seismic vulnerability curves. The results of this research provide support for seismic risk assessment of multi-age structures.

Abstract:The work proposes a nonlinear combination, two-parameter damage model of maximum deformation and hysteretic energy dissipation. Comparing the performance of the proposed model with that of existing damage models reveals that the proposed model can accurately reflect the earthquake damage mechanism. For comparison, the structural damage curves and seismic fragility curves of two single-parameter models (deformation and energy) and two two-parameter models (Niuditao model and the proposed model) are drawn in accordance with the incremental dynamic analysis results of an eight-story RC frame structure under the input of 50 seismic waves. Results show that structural collapse performance will be overestimated when the interstory drift angle is used as the sole structural damage index, whereas the exceedance probability of structural damage will be underrated if energy dissipation is used as the sole structural damage index. The proposed model can well balance the influence of maximum deformation and cumulative damage on structural damage.

Abstract:To investigate the antiprogressive collapse mechanism of hybrid structures with diffe-rent vertical stiffness values, remaining structures with initial failure are subjected to nonlinear static analysis, also known as the Pushdown method, through the alternate path method with ANSYS/LS-DYNA. The collapse failure mode of remaining structures, the relationship between load and deformation, the influence of the different positions of the initial failure column, and the number of steel frame layers on the antiprogressive collapse performance of the structure are analyzed. Results show that the failure mode of the remaining structures during collapse is characte-rized by typical ductile deformation and discontinuous displacement and stress distribution. Only the collapse of the remaining structure with side column failure experiences the beam action mechanism. By contrast, all other remaining structures experience the beam action mechanism, compressive arch action, and catenary action. The vertical bearing capacity of the remaining structure is negatively correlated with the height of the initial failure column and is positively correlated with the number of steel frame layers. The antiprogressive collapse capability of the remaining structure can be effectively improved by providing sufficient lateral restraint and increa-sing the number of alternate load paths in the remaining structures.

Abstract:To determine the influence of pile-soil interaction on the seismic fragility curves and post-earthquake traffic capacity of a 110 m-long, three-span continuous girder bridge, two diffe-rent finite element models that consider fixed pier bottoms and the pile-soil interaction were constructed. Then, 50 seismic waves with different intensities were selected as excitation. The ducti-lity ratio of the rotation angle and the shear strain of the bearing were calculated with the maximum displacements of the pier top and bearing as the target responses. Subsequently, the seismic fragility curves of the entire bridge were established through the wide-bound method, and a new formula for the calculation of average damage level was developed to estimate the post-earthquake traffic capacity of the girder bridge. Analytical results demonstrate that under the same seismic intensity, the peak displacement of the pier under pile-soil interaction is larger than that estimated by the consolidation model, which better agrees with the practical situation. With respect to the fragility curves of bridge components, the maximum damage exceedance probability of the bearing occurs when the pile-soil interaction is considered, but is not large different from the situation of fixed pier bottoms. Changes in traffic flow can be reasonably evaluated by using the seismic fragility curves of the entire bridge system. However, the traffic capacity assessment given by the consolidation model is unsafe. This result implies that the influence of pile-soil interaction on the seismic fragility of bridges cannot be ignored in class-Ⅲ sites.

Abstract:A linear rheological model obeying Hooke's law and Kelvin/Voigt's law was constructed in this study to ensure accurate analysis of the dynamic response and isolation capability of the base isolation system. Theoretical analysis and an experimental study of the dynamic characteristics of the model were conducted using the data of the 1977 Romanian earthquake. Then, the expressions of relevant parameters were established. The results show that the parameters are significantly influenced by the discrete variation of the viscous damping coefficient c and the continuous change of angular velocity ω. By comparing the experimental results, we determine that the established expressions are accurate. The dynamic isolation capability of the system can be evaluated using the maximum transfer force Q₀ and movement transmissibility T.

Abstract:The physical and mechanical characteristics of frozen soils are closely related to the temperature. The distribution and evolution law of a ground temperature field in a permafrost roadbed under climate warming does not only affect the static stability of embankment, but also affects the response characteristics and stability under dynamic loads such as earthquake and vehicle loads. Based on the field-measured temperature of roadbed slope, the distribution and evolution law of the ground temperature field in the permafrost roadbed of the Qinghai—Tibet Plateau under climate warming is systematically simulated in this paper. The results show that the difference of the freezing index of the shallow soil on the sunny-shady slope is more obvious than that of thawing index. The freezing index of the shady slope is about twice that of the sunny slope for the two embankments, while the melting index of the shady slope is about 0.83 times of that of the sunny slope. The seasonal freeze-thaw process of the roadbed body and the active layer at sunny-shady slopes do not correlate. The maximum difference in the freezing-thawing period of the two slopes can be as much as one month for the roadbed in ES orientation. After the roadbed construction, the artificial permafrost table beneath the shady slope has a certain uplift under the three orientations. While beneath the sunny slope, the artificial permafrost table only uplifts for the roadbed in NS orientation. Then, because of the climate warming and the significant heat absorption of asphalt pavement, the artificial permafrost table declines quickly both under the sunny and shady slopes, and the maximum decline rate can reach 20 cm/a. With the decline of the artificial permafrost table, thawed bulb develops within the permafrost subgrade. The thickness of the thawed bulb is greater beneath the sunny slope than beneath the shady slope, with a maximum difference of 2.5 m. The seasonal freezing-thawing process of roadbed body and the artificial permafrost table buried depth and asymmetry of temperature field distribution should be considered in future designs and studies on the static and dynamic stability of the permafrost roadway embankment.

Abstract:In this work, Holocene-era soft soil deposits in the Pearl River Delta were sampled. The differences in the compression and shear deformation properties of undisturbed and reconstituted soils were determined through uniaxial compression tests, consolidated-undrained triaxial tests, and unconsolidated-undrained triaxial tests. Comparing the compression curves of undisturbed and reconstituted samples revealed that the void ratio of the two soils decreases as pressure increases and is closely related to compression method. The consolidation coefficient of the undisturbed soil sample decreases exponentially as pressure increases, whereas that of the reconstituted soil sample increases linearly with pressure. The results of the triaxial shear test showed that under the same consolidation pressure, the strength of undisturbed samples is lower than that of reconstituted samples. The stress-strain curves of soil samples reflect the occurrence of strain hardening. The influence of confining pressure on the reconstituted soil sample is smaller than that on the undisturbed soil sample.

Abstract:Nowadays, the microscopic analysis of the evolution process mechanism of loess liquefaction is a hot topic. In this study, we attempt to investigate the nature and influence factors of loess liquefaction through dynamic tests. We use the CT scanning test to study the macroscopic change of loess liquefaction. The results show that the primary cause of liquid level rise is the water absorption of alkalescent salt cement. When specimens become highly saturated, the cementing material between the particles surrounding the soil macropores is destroyed. Then, the effective stress is zero and the soil is liquefied. The difference in the microstructure of soil can also influence the increase in liquid level and the failure strength of soil. Liquefaction tests on three kinds of loess (low-cohesive silt, silty sand, and silty clay) indicate that the dynamic loading time of the low-cohesive silt is the shortest. In other words, the liquefaction of low-cohesive silt is most severe and the silty sand is in medium liquefaction; by comparison, the silty clay is difficult to liquefy. The analysis of soil microstructure parameters with scanning electron microscope indicated that the chemical element (Ca/Fe) ratios of the cements around the soil particles, and the particle size distribution and pore size of the soil particles affect the degree of liquefaction.

Abstract:The traditional dynamic modulus method for subgrade analysis provides results with high deviation because it mainly focuses on the seismic performance of a single roadbed and not the seismic performance of composite subgrades. A seismic test method for the subgrade analysis of Guangzhou Rail Transit Line 21 is proposed. After the analysis of geological conditions, the soil liquefaction of the original subgrade is assessed through the standard penetration test. On this basis, the Swedish strip method is used to test the seismic performance of the original subgrade. Results show that the liquefied soil of the subgrade has low safety and poor seismic stability. Thus, the composite roadbed should be reinforced. The seismic performance of the reinforced subgrade is tested through the circular sliding method. Experimental results show that the proposed method has strong antijamming performance and high accuracy.

Abstract:An M_S7.0 earthquake occurred in Jiuzhaigou County, Sichuan Province, on August 8, 2017, before which we had made some predictions.According to the recurrence periods of 44 years and 7 years, we predicted in 2016 that an M7.5 earthquake will happen in Sichuan Province in 2017.On July 28, 2017, based on the geomagnetic anomalies observed by instruments, we predicted that an M6~7 earthquake was imminent.A retrospective analysis after the Jiuzhaigou earthquake shows that combining our prediction with the landslides that occurred in Maoxian County, Sichuan Province before the earthquake can result in a good impending earthquake prediction.Moreover, combining the date of the 1973 Luhuo earthquake with the recurrence period of 44 years and 180 days can lead to an accurate estimation of the date of Jiuzhaigou earthquake shock.

Abstract:In this study, 66 groups of three、|component acceleration records of the M_S7.0 earthquake that occurred in Jiuzhaigou County, Sichuan Province, China, on August 8, 2017 recorded by China Strong Motion Net Center (CSMNC) are analyzed and processed, including the base lines correction and filtering, used for comparing the characteristics of the amplitude and response spectra of the strong motion records. The results show that the peak ground acceleration (PGA) value ranges from 0.98~185 gal, and the largest PGA was recorded by the closest station, 51JZB station. The instrumental intensity of the earthquake ranges from 0.93~6.8, and the comparison between the instrumental intensity and the seismic intensity map of Jiuzhaigou M_S7.0 earthquake indicates that the instrumental intensity and macroseismic survey intensity differs in 1 degree. According to the comparison among the observation data, the ground motion attenuation relationship proposed by Huo Junrong, and the ground motion parameter zoning map of China (fifth generation), it is found that the attenuation relationship of Huo Junrong is more suitable for the acceleration attenuation of the Jiuzhaigou earthquake. The horizontal PGA contour map was drawn using the Kreager interpolation method, and the contours near the epicenter show NW distribution.

Abstract:The M_W6.6 earthquake occurred in Jiuzhaigou County, Sichuan Province, on August 8, 2017. The focal mechanism solution shows that the earthquake was a left-lateral strike-slip earthquake. In this study, the observation data from GPS continuous stations around the epicenter are processed to obtain a high-rate GPS dynamic deformation and static co-seismic horizontal displacement. Through 1 Hz GPS data measurements, dynamic deformation is only observed at the Songpan station in Sichuan Province and Wudu station in Gansu Province within 100 km of the epicentre. The co-seismic horizontal displacement observed by the Songpan station, the nearest continuous station to the epicenter, is 7.4 mm. The co-seismic rupture model inferred based on a small amount of GPS static co-seismic displacement shows that the maximum slippage of the earthquake is 376 mm, the seismic moment is 7.25×10¹⁸ N·m, and the equivalent moment magnitude is M_W6.6. The co-seismic three-dimensional deformation field obtained by forward calculation shows that the maximum horizontal displacement of this earthquake can reach 4~5 cm, and the vertical displacement can reach a maximum of 1.5 cm in a four-quadrant distribution. The co-seismic deformation can be observed in 10 mobile GPS stations in the region.

Abstract:About 50~60 million years ago, the Indian subcontinent plate collided with Eurasia plate, which resulted in the Tibetan Plateau, the highest and most active in the world. The Xigaze region of southern Tibet, which crosses the Yarlung Zangbo River suture zone, is the most significant tectonic boundary in southern Tibet. Geoscientists have conducted several studies on the evolution of geological structure, rocks and sedimentary stratigraphy, and paleoclimate and paleoenvironment in southern Tibet, and large amounts of geophysical data have been collected from this region. However, the studies on active structure and the active faults data collected from the Xigaze area are rather insufficient. In this study, based on detailed field geomorphology surveys, trench studies, and optically stimulated luminescence (OSL) data, we investigated the activities of Ladui—Naidong and Biding—Jiashela faults, which lie in the suburban area of the Xigaze city. The trench profile near Dari village and the OSL ages obtained from this trench indicate that the Ladui—Naidong fault possibly ceased to be active approximately 30 ka ago, indicating that the fault is not a Holocene active fault. Our result on Ladui—Naidong fault activity directly contradicts those of previous studies, which claim the fault is a Holocene active fault, based on scanning electron microscopy (SEM) analysis on the quartz surface of fault gouge. Likely, the trench excavated near Nadang village suggests that the fault was deeply buried and did not reach the surface area. From the uninfluenced strata OSL ages, it can be deduced that the Biding-Jiashela fault ceased to be active at least 50 ka ago. In addition, the earthquake distribution and shallow artificial seismic survey results suggest that the two target faults are less active or inactive, which further confirms our geological observations. In the regional scale, the other E-W-striking faults also seem to be inactive, while the N-S-striking fault systems, such as Shenzha—Dingjie and Yadong—Gulu rifts, are very active. Such structural framework is probably because of the long, complicated tectonic evolutional history and the particular geological stress background.

Abstract:The tectonic geometry and kinematic dissipation of the active faults in southeast Gansu can be better understood by exploring the quantitative data of the Wudu—Kangxian fault. Based on the data from surveying and prospecting of active faults and geological mapping in Longnan City, Gansu Province, using a differential GPS, this study mainly investigates the dislocations of scarp, water system, and river terraces discovered by remote sensing image interpretation, field geological survey, fault dislocation measurement, and other basic methods. Taking some typical dislocation points for example, the ages of related terraces in the study area and adjacent Bailongjiang area were collected. The average slip rates of the west and east segment of Wudu—Kangxian fault were estimated to be 1.1 mm/a and 1.06 mm/a, respectively. According to the assessment principle and method of the maximum magnitude of potential earthquakes, using an empirical formula of M-L, it is calculated that an earthquake with magnitude 7 may occur in this area.

Abstract:In this paper, the gravity changes of one year scale before and after the Minxian—Zhangxian M6.6 earthquake on July 22, 2013 are analyzed using the mobile gravity observation data from 2010 to 2014 in southeast Gansu network, and then the relationship between the gravity and b-value anomalies in southeast Gansu and the Minxian—Zhangxian M6.6 earthquake is discussed considering the b-value image and global navigation satellite systems result. The results indicate the following: (1) The gravity anomaly in the study area underwent a spatiotemporal evolution from regional negative gravity change to constant negative change, positive change of turn and increase, earthquake occurrence, and then recovery after the earthquake; (2) before and after the Minxian—Zhangxian M6.6 earthquake, the b-value curve shows characteristics of low value-high value-reduction and shock; (3) the Minxian—Zhangxian M6.6 earthquake occurred in a high gradient zone of gravity change near the "0" contour line and the low b-value region.

Abstract:Considering the Alxa Left Banner M5.8 earthquake that occurred on April 15, 2015, the continuous digital seismic waveform data recorded by Wuhai, Dongshengmiao, and Shizuishan seismic stations from 00:00 April 1 to 23:00 April 15, 2015 were analyzed using Fourier transform, and the variation of maximum envelop amplitude within 0~0.25 Hz was tracked. The results reveal the following. (1) Before the M5.8 earthquake, the seismic waveform recorded by Wuhai, Dongshengmiao, and Shizuishan stations near the epicenter all show that the frequency spectrum shifts to low frequency. (2) The tracking forms of maximum envelop amplitude with low frequency anomaly in the three stations are different. Before the earthquake, only the tracking form in Wuhai station shows obvious continuous unsteady anomaly, which continues for about 120 hours. (3) The tracking forms of maximum envelop amplitude in the three stations are quite different with their distance from epicenter.

Abstract:In this study, seismic wave data of January 2009 to November 2015 are collected from China National Seismographic Network, and 16 156 Pg wave travel times from 1 820 seismic events (M_L=1.8~6.7 and epicentral distances less than 800 km) are selected to study the 3D Q-value distribution characteristics of P-wave in the southwestern Ordos margin. The results show that Q-values are relatively lower along the fault zones with "L" shape distribution in the southwestern Ordos margin, while on both sides of this zone, the Q-values are higher and vary greatly in their distribution. In the research area, the resistivity and velocity layers are significantly low in the Haiyuan and Tianshui—Lixian regions which have low Q-values, but the Weiyuan—Dingxi—Tongwei—Xiji region, which has higher Q-values, lacks a low resistivity layer. In addition, the Weihe Basin and Tianshui—Lixian region with a high heat flow have low Q-values, but surrounding areas have higher Q-values. There is a significant vertical deformation gradient belt and gravity change isoline along the Lintong—Chang’an—Fucheng—Pucheng fault. Moreover, the distribution of horizontal deformation along the fault is characterized by distinct stripped variations. The low Q-values in this area indicate that Q-value distribution is related to the vertical and horizontal deformations and gravity changes in the crust.

Abstract:In studies of post-earthquake areas using the traditional methods of 2D seismic damage images, the visual effect of the image is not ideal because of the limited shooting angle. Therefore, a method of 3D virtual reconstruction of post-earthquake regions based on 3D laser scanning technology is proposed in this paper. The post-earthquake area is measured by a 3D laser scanner, and the point cloud data of the region is obtained. First, the Cyclone software is used to merge the point cloud data, and the whole point cloud image of the post-earthquake region is obtained, and then the point cloud data of the map are processed and encapsulated. Finally, a sketch model is used to implement the mapping on the point cloud data, and then the 3D image of the post-earthquake region can be virtually reconstructed with ideal visual communication effect. Experimental results show that the proposed method has high accuracy and good visual effect for 3D reconstruction of post-earthquake area images.

Abstract:Construction sites pose dangers in a high-intensity earthquake environment. The traditional AHP algorithm is often used to analyze the risk of construction sites but provides poor analysis results because it ignores earthquake resistance. Therefore, a risk modeling method for construction sites under high-intensity earthquakes is proposed. First, the TOPSIS method is used to obtain the indexes of earthquake risk assessment, and the matter element analysis model of risk assessment index is constructed. The comprehensive weight of the seismic risk assessment index is obtained on the basis of the combination weighting of the AHP-entropy weight method. Then, the Bayesian network is used to deduce the risk parameters of construction sites under high-intensity earthquakes. A risk assessment model of construction sites is constructed by using the dividing standard and the calculating method of earthquake magnitude in accordance with the risk evaluation criteria and acceptance principle of building construction sites. The model can be used to complete the modeling analysis of the risk of construction sites under high-intensity earthquakes. Experimental results show that the designed model can accurately analyze the hazards of construction sites under high-intensity earthquakes and ensure the safety of the whole construction site. Therefore, the model has important application values.

Abstract:The traditional BIM estimation model of post-earthquake construction schedules ignores the effect of lean management on the construction schedule, thus wasting construction costs and affecting the later stages of the construction schedule. In this work, an evaluation model of post-earthquake construction schedule is constructed on the basis of BIM and lean management. In the proposed model, the evaluation of post-earthquake building schedule is subdivided. Then, three-dimensional calculation is implemented on the basis of BIM, and the submodel of schedule planning is used to obtain subproject quantities. The main schedule plan of building construction is determined, and the construction schedule plan is established. Construction state is simulated and refined by using the schedule control submodel in virtual and practical construction. On the basis of simulation and practical results, the planning construction cost, actual construction cost, and earned value curve of the post-earthquake construction project are analyzed and compared, and the construction schedule and cost of the project are obtained. Experimental results show that the proposed model can accurately estimate the schedule and costs of post-earthquake construction projects.

Abstract:The traditional model used for computing the costs of post-earthquake reconstruction projects is based on the back-propagation neural network. It requires a complex computation process and provides low convergence efficiency and low-accuracy results. In this work, a model based on the improved genetic algorithm for computing the costs of post-earthquake reconstruction projects is proposed. The cost model is optimized in accordance with the factors that influence the cost of post-earthquake reconstruction projects, and the cost function model is established with superior cost simulation data. The data of the cost function model are analyzed on the basis of the T coefficient, and the data parameters of the cost function model are determined on the basis of the binary calculation law. Then, data parameters with high precision are obtained through formula calculus, and accurate cost data are obtained. Experimental results show that the designed model can accurately and quickly estimate the cost of post-earthquake reconstruction projects.

Abstract:The demand of earthquake relief materials for different disaster sites can be met by utilizing a mathematical model of earthquake disaster relief based on real-time updating of information to optimize the number of rescue points and delivery time. According to the characteristics of earthquake disaster relief, this paper presents the design and implementation of a mathematical model for earthquake disaster relief that considers time. First, the main factors affecting the demand of earthquake relief materials are analyzed by using the model to forecast the demand, and then the model for calculating the demand for earthquake relief materials is constructed, and the model for grading earthquake relief materials demand based on fuzzy comprehensive evaluation is established. Second, considering time constraint and uncertain demand, the earthquake relief materials are studied and a multi-objective optimization mathematical model of earthquake disaster relief which considers time constraints is constructed. The experimental results show that the model can reduce the delay to reach the disaster site and improve the material demand satisfaction rate while meeting the time constraints.

Abstract:Recently, 3D seismic technology has become an important method in coalfield exploration, and great progress has been achieved. However, the prediction of water content in coal seam roof using 3D seismic technology is rarely discussed. In this study, a neural network inversion was carried out based on the logging constrained inversion. Seismic attributes, such as wave impedance, were converted to porosity and resistivity, which were closely related to water content. Taking the mining area of Huaibei coalfield as a case study, the water abundance of 10# coal seam roof in the study region was predicted by the neural network inversion of porosity and resistivity. The results show that a water-rich subsided column develops in the north of mining area, which is consistent with the borehole detection results. There is unconformity contact between the 10# coal seam roof and the Quaternary aquifer in the west of mining area, which is predicted as a water-abundant area by the PPN inversion. The neural network inversion can effectively predict the water abundance characteristics of a coal seam roof, thus providing an important guarantee for coalmine safety production.

Abstract:The earth-rockfill dam body can easily generate seepage when water level is below the dam. To study the influence of the dam body reinforcement on the seepage pressure, a finite element numerical simulation was conducted based on an actual reservoir, under three cases of an earth-rockfill dam before and after reinforcement. Seepage gradients, the discharge per unit width, and quasi drift were obtained. The research results show that the safety factors of upstream slope under the three cases after reinforcement significantly increased, and the discharge per unit width can reach 0.636 m³/d, which is far greater than the standard value.