Propagation Characteristics of Seismic Wave While Transiting Interlining in Soil Medium

Based on the theory of wave and the Snell theorem, propagation characteristics of seismic wave, three kinds of elastic body waves, is studied when they pass through soil/elastic solid medium including elastic thin plan intercalation in half-space. The analytic solution of the amplitude rate is the rate of the amplitude of the wave behind the intercalation to that of the incident wave. Compared with the field data, the analytic results are beneficial, affected by soft clay stratum, at the Nankai District of Tianjin Municipality caused by the 1976 Tangshan earthquake (had a magnitude of 7.8). In this area, however, damage of the buildings was generally minor, about 50%, with the Heping District near Nankai

Three-dimensional nonlinear analysis of seismic ground response of soft soils in Shanghai

Reduced order bounding surface model was employed to study 3-D seismic ground response of site considering the nonlinearity of soft soils in Shanghai. A nonlinear procedure for response analysis of horizontal layered sites subjected to multidirectional earthquake loading was used to study vertical and horizontal ground responses, respectively, under unidirectional and multidirectional base excitations (Taft). Also, the development of ratio of vertical and horizontal peak acceleration and the effects of the variation of groundwater table on the characteristics of seismic responses were studied. The study results show that the characteristics of vertical seismic ground response are much different from those of horizontal seismic ground response; the amplification effect is greatly increased under multidirectional base excitations compared with that under unidirectional base excitations; greatly difference is induced by the rise of groundwater table between vertical and horizontal seismic response, as result of the rise of groundwater table, seismic amplification effect at ground surface increases in horizontal direction, but decreases in vertical direction，which are important for geotechnical engineering aseismic design in Shanghai region

A New GNSS Spoofing Signal Power Control Algorithm for Receiver Sensors in Acquisition Phase and Subsequent Control

Satellite navigation spoofing technology has become a hotspot of interference technology research because of its significant threat and high concealment. In a spoofing scenario, suppressive interference is typically used to ensure that the target receiver sensor is in the unlocked and reacquisition state, and then spoofing is implemented. This method has a high feasibility, and the power of the spoofing signal affects the concealment and efficiency of spoofing. Currently, there is limited research involving the GNSS spoofing signal power control. Moreover, there is no systematic complete power control scheme, most of which is limited to qualitative or simulation, and the actual application effect is still unclear. Therefore, a new GNSS spoofing signal power control algorithm under the power constraints of the receiver sensor in the acquisition phase and the subsequent control is proposed. The experimental platform is designed to prove that compared with the conventional spoofing signal high power control algorithm, the new GNSS spoofing signal power control algorithm shortens Doppler frequency fluctuation time by 72.2% and reduces the range by 75.9%. The carrier-to-noise ratio of the received signal is less than the threshold of the receiver sensor, and the range of three-dimensional coordinates of Earth-Centered, Earth-Fixed (ECEF) is significantly reduced during the spoofing signal taking over receiver sensor, this shows that the new design of the GNSS spoofing signal power control algorithm can make spoofing behavior more hidden, and it will make it more difficult for the target receiver sensor to detect spoofing behavior. The designed algorithm can take over the receiver sensor stealthily with the help of suppressing interference and then pull the bias positioning results, which has good feasibility and effectiveness

A Slowly Varying Spoofing Algorithm on Loosely Coupled GNSS/IMU Avoiding Multiple Anti-Spoofing Techniques

When satellite navigation terminal sensors encounter malicious signal spoofing or interference, if attention is not paid to improving their anti-spoofing ability, the performance of the sensors will be seriously affected. The global navigation satellite system (GNSS) spoofing has gradually become a research hotspot of the jammer because of its great harm and high concealment. In the face of more and more sensors coupling GNSS and inertial measurement unit (IMU) to varying degrees and configuring a variety of anti-spoofing techniques to effectively detect spoofing, even if the spoofer intends to gradually pull the positioning results, if the spoofing strategy is unreasonable, the parameters of the coupled filter output and spoofing observation measurement will lose their rationality, which will lead to the spoofing being detected. To solve the above problems, in order to effectively counter the non-cooperative target sensors of assembling loosely coupled GNSS/IMU using GNSS spoofing, based on the analysis of the influence mechanism of spoofing on the positioning of loosely coupled GNSS/IMU, a slowly varying spoofing algorithm to avoid loosely coupled GNSS/IMU with multiple anti-spoofing techniques is proposed in this paper, and a measurement deviation determination method to avoid multiple anti-spoofing techniques is proposed, which can gradually pull the positioning results of the coupled system and successfully avoid the detection of anti-spoofing techniques of innovation sequence monitoring and a rationality check on parameters. Simulation experimental results show that the proposed algorithm gradually changes the positioning of loosely coupled GNSS/IMU, the north and east displacements achieve the purpose of spoofing, and error with expected offset is −0.2 m and 2.3 m, respectively. Down displacement also basically achieves the purpose of spoofing, and error with the expected offset is 13.2 m. At the same time, the spoofer avoids the detection of multiple anti-spoofing techniques, does not trigger the system alarm, and realizes the purpose of spoofing; thus, the effectiveness and high concealment of the spoofing algorithm are verified

Two Regional Deployment Algorithms of Distributed GNSS Forwarding Spoofer for Multiple Receiver Sensors

Global navigation satellite system (GNSS) spoofing technology is an effective way to protect sensitive facilities and control foreign objects. To realize effective distributed GNSS forwarding spoofing for multiple receiver sensors in the area, the following research work is carried out: first, the GNSS forwarding spoofing model is established, including a forwarding spoofing mathematical model and an asynchronous traction spoofing method; second, the function scope of forwarding spoofing is fully evaluated; third, two forwarding spoofer area deployment algorithms for multi-spoofer multi-target (MSMT) are proposed—the multi-target same-point spoofing algorithm (MSPSA) is suitable for the same-point spoofing of multiple receiver sensors, and the multi-target different-point spoofing algorithm (MDPSA) is suitable for the different-point spoofing of multiple receiver sensors; and four, the experimental tests of MSPSA and MDPSA for MSMT were carried out. The experimental results show that MSPSA and MDPSA can respectively give the most appropriate deployment scheme of spoofing according to the various needs of the spoofer. For example, the number of spoofing devices is 1, the total distance between each spoofer and each receiver is 40,345.1 m, and the critical spoofing rate (CSR) and spoofing success rate (SSR) are both 100%. The performance of the spoofing deployment scheme can meet the needs of the spoofer

Radial Consolidation Solution of Plastic Wick Drain Combined Vacuum Preloading

A system of radial consolidation by combining the plastic wick drain with the vacuum preloading is one of the most popular way for soft ground improvement, which can not only reduce the height of surcharge preloading on dam, but also reduce the lateral displacement of soil. The consolidation solution of plastic wick drains and vacuum preloading based on the nonlinear relationship can well forecast and analyze this kind of ground improvement. In the process of analytical solution, the relationship between the void ratio and the mean effective stress, as well as the horizontal permeability coefficient under one-dimensional consolidation is considered to be semi logarithmic linear, rather than previously thought one-dimensional linear. Because of disturbing on soil around PVD in smear zone, permeability around PVD in the zone distributes in parabolic form. Besides, the effect of vacuum preloading on consolidation is taken into consideration. This analytical solution is verified through degradation method and compared with test results. Finally, the effects of κ, Ck /Cc are analyzed on consolidation. The results indicate that consolidation rate increases with the increasing of Ck /Cc and decreasing of κ

Prediction of ground vibration under combined seismic and high-speed train loads considering earthquake intensity and site category

Based on a two-and-half-dimensional finite element model (2.5D FEM), the layered ground vibration under combined seismic and high-speed train loads was investigated. On this basis, the effect of site category and earthquake intensity on ground vibration under the combined action of two dynamic loads was analyzed. Numerical examples indicated that ground vibration displacement due to combined loads decreases with the increase of soil stiffness, while the influence of soil stiffness on the ground vibration is small when the hardness of the subsoil is large. The peak ground displacement (PGD) is a reasonable seismic intensity index for predicting the ground vibration displacement at the track center under the combined loads, which has a higher accuracy for hard ground. In view of this, an equivalent shear wave velocity and PGD-based prediction formula was proposed to estimate the ground vibration under combined seismic and high-speed train loads. Reliability of the prediction formula was verified through comparison with results of numerical tests, indicating that the prediction formula has good applicability to different site conditions and seismic events. Compared with the previous study, it demonstrated that the prediction method provided an effective means for estimating ground vibration caused by a high-speed train load during earthquakes

Effect of rise of ground water table on seismicground response of soft soil in Shanghai

A dynamic model is developed based on the results of geological investigations as well as laboratory and field tests in Shanghai. The Biot\u27s dynamic consolidation theory and reduced order bounding surface model are coupled to study the effect of the rise of groundwater table on the seismic ground response of soft soil undergoing 3-D seismic base excitations (which are obtained from Taft). The effect of the rise of groundwater table on the horizontal and vertical amplification factors, the ratio of vertical to horizontal peak acceleration, the characteristics of acceleration and response spectrum at ground surface as well as the maximum pore water pressure and pore water pressure ratio along the depth of soil layer are studied. The results show that the rise of groundwater table has dramatically different influences on the horizontal and vertical amplification effect as well as the characteristics of acceleration andresponse spectrum at ground surface. As the result of the rise of groundwater table, the amplification effect increases in horizontal direction but decreases in vertical direction. The ratio of vertical to horizontal acceleration decreases. The filtering effect on the acceleration with high frequency and the amplification effect on the acceleration with long period increase. The range of liquefiable soil near ground surface extends and hazard risk increases

Ground vibration analysis caused by China railway high- speed with track geometric irregularities

A semi-analytical approach, considering the effects of track geometric irregularities on the wheel/rail force, is presented in this paper to simulate the ground vibration induced by moving train loading. The; train is studied as a secondary suspension mechanical system. The track and the attached sleepers are simplified as Euler beams resting on infinite half-space. Based on the compatibility condition of deformation, combining with the 2.51) FEM for layered soil, the semi-analytical solutions of dynamic wheel/rail forces are obtained implicitly. Detailed analyses and discussions of the wheel/rail forces and ground vibration are carried out. The results show that the track geometric irregularities exert an important influence on dynamic wheel/rail forces and ground vibration. With the track geometric irregularity unchanged, the wheel/rail forces linearly increase with the increasing train speed; With the wavelength of the track geometric irregularities unchanged, the wheel/rail forces and ground vibration acceleration increases with the increasing track irregularity amplitude; With the track irregularity amplitude unchanged, the wheel/rail forces and ground vibration acceleration decreases with the increasing wave length of track irregularities

Effect of multidirectional earthquake loading on seismic compression of sand

Dynamic simple shear tests on different types of sand under multidirectional earthquake loading are simulated by means of the finite element method. The reduced order bounding surface model is employed and its parameters are determined based on the results obtained from laboratory dynamic simple shear tests. 148 groups of ground motions with multi-components from far and/or near fields of moderate and/or strong earthquake events at different site conditions are used as input motions for strain controlled and stress controlled dynamic simple shear tests. Effect of multidirectional earthquake loading on seismic compression of sand for different earthquake magnitudes site-to-source distances and properties of sand is studied. The results show that the ratio of vertical strain induced by multi-components of seismic loading and that induced by one component of seismic loading are greatly associated with earthquake magnitude, site-to-source distance and properties of sand, the ratio of vertical strain increases with the increasing earthquake magnitude and relative density of sand, and decreases with the increasing site-to-source distances. Great limitation exists in the method considering the effect of multidirectional earthquake loading on seismic compression proposed by Pyke et al (1975) due to its lack of considering the effect of characteristics of seismic loading and properties of sand. Also, the ratios obtained from stress controlled and strain controlled simple shear tests are greatly different and the mean ratios from the former are larger than those from the latter