Full-waveform inversion is a promising tool to produce accurate and high-resolution subsurface elastic models. Accurate estimation of the source wavelet is required for most full-waveform inversion algorithms to obtain reliable inversion results. We develop a novel source-independent waveform inversion method to avoid source wavelet estimation in full-waveform inversion. We define an amplitude-semblance objective function in full-waveform inversion to remove the source wavelet effect. Compared with other source-independent FWI methods, our new method does not require an optimized reference trace. Meanwhile, our approach can better handle the inconsistence of source wavelets for different sources. We verify our method using the Marmousi model. The results show that our source-independent full-waveform inversion can produce accurate velocity models even if the source signature is incorrect.
Presentation Date: Thursday, October 18, 2018
Start Time: 8:30:00 AM
Location: 207C (Anaheim Convention Center)
Presentation Type: Oral
Huang, Daomin (Huazhong University of Science and Technology) | Tang, Guoyuan (Huazhong University of Science and Technology) | Xu, Guohua (Huazhong University of Science and Technology) | Liu, Zhi (Ship Design and Research Institute of Wuhan)
In this paper, the dynamic model of rigid-flexible coupling system for an underwater manipulator based on element coupling deformation is established, in which three reference frames (global frame, floating frame, and element translate frame) are used to describe the configuration of the point in flexible body. A robust sliding mode control is presented for the position control and tracking control of the manipulator. The simulations are performed and the results show that the presented controller has good performance to track some moving underwater object or approach some fixed target point.
There is no doubt that the development and protection of the ocean cannot be separated from research on marine engineering equipment. Underwater manipulators are playing important roles in ocean explore. Study of underwater manipulator is an active field and may have a far-reaching impact on human beings in ocean explore.
Since the sphere of human activity become further and deeper in ocean space, it is essential for technological advances in underwater manipulator systems to enable new and promising marine operations, processes and exploration. Some manipulating modes of large scale of work space are mandated for underwater vehicle to facilitate it to fulfill tasks. As is well known, the load capability of an underwater vehicle is limited and its manipulator of large-scale should be made of lightweight components and parts. For the type of manipulator whose arms are characterized as slender rod, flexibility should be taken into account to set up its dynamic model and to control it (Bauchau and Han, 2014; Carrera, Gaetano and Petrolo,2011).
In the field of aerospace, the manipulators of large scale are used widely in outer space to fulfill some specific tasks such as grasping, repairing, and so on. The astronauts to operate these systems should be trained on some mimic system that is used to be built on the earth, especially in some underwater environment.
Zhu, Ming-xing (Jiangsu Electric Power Design Institute (JSPDI) Co., Ltd. of China Energy Engineering Group) | Lu, Hong-qian (Jiangsu Electric Power Design Institute (JSPDI) Co., Ltd. of China Energy Engineering Group) | Wang, Lei (Jiangsu Electric Power Design Institute (JSPDI) Co., Ltd. of China Energy Engineering Group) | Gong, Wei-ming (Southeast University)
Determining the response of the laterally loaded piles analytically is one of the challenging problems due to the complexity of soil-pile interaction models and the difficulty to solve governing difference equations. In this paper, a general solution for laterally loaded piles is proposed for multilayered soil systems with any forms of p-y curves. The generalized solution of laterally loaded pile was formulated based on the transfer matrix approach. The elastic and plastic transfer matrix coefficients for pile segment at any depth were analytically obtained through Laplace transformation. Validations of the proposed method are performed through comparison between our predictions with the results from existing methods. Good agreements are reached which implies that the proposed method can be employed as an alternative method to effectively evaluate the response of laterally loaded piles. Moreover, a parametric study on pile bending stiffness is performed to investigate its influence on the ultimate capacity of laterally loaded piles in the same soil profile. We found that these three piles with different bending stiffness would have the same limit state distribution of soil resistance along the pile with the same rotation center below soil surface, which will yield identical ultimate lateral bearing capacity and corresponding maximum bending moment (Mmax) for the piles. Under the concept of the maximum bending moment (Mmax), it would be more rigorous to define a rigid pile when plastic moment Mp along the pile exceeds Mmax and to define a flexible pile when Mp is less than Mmax, especially for piles in multilayered soil deposits.
Piles are extensively used as foundations not only to transfer vertical loads from upper structures to surrounding soils, but also to bear horizontal forces and moments simultaneously. In offshore engineering (e.g., offshore wind turbine and oil production platforms), the piles are mainly designed to resist the lateral loads mainly from the wind to the upper structure, water pressure and seismic activity to the foundation (Basu et al., 2008). The subgrade reaction concept of laterally loaded piles was introduced since the piles behave as Winkler model against lateral loads. To determine the pile responses rigorously is one of the challenging problems due to the complexity of soil-pile interaction and difficulty of solving the governing fourth order differential equation on the basis of subgrade reaction approach.
In this study, the wave run-up over a simplified semi-submergible platform with two columns in regular wave is predicted numerically using a three-dimensional particle method in order to investigate the wave run-up and wave impact on the columns of the platform. A series of fully-nonlinear regular waves are generated by a flap-type wave- maker in a numerical wave tank, and the reflected waves from the opposite side of wave-maker are induced to be intentionally dissipated in the beach region including wave absorbers. The results of the present simulation for time-series of wave run-up and impact pressure acting on the columns of the platform are compared with those of the grid- based simulations and experiments performed by MARIN.
The area for developing fossil fuel has gradually expanded to the deep sea because demands for fossil fuel from developing countries have been gradually increased. There are many types of offshore structures operated in deep sea, such as semi-submersible, spar and ship-shaped vessels. Especially, semi-submersible offshore structure has been usually operated in the deep ocean of harsh environment because the structure represents good performance in heave motion. However, these offshore structures have been continuously subjected to severe wave impact loads caused by environmental conditions due to long operating time in a local place. In addition, there were some reports on failure of semi-submersible structure operated in offshore, such like Alexander Kielland in 1980(ALK, 1981; Moan, 1981; Moan and Holland, 1981), Ocean Ranger in 1982 (OR, 1984), P-36 in 2001 (P-36, 2003). Therefore it is of significant to predict accurately wave impact loads on semi-submersible structure for safe and economical design of the structure.
The MPS (Moving Particle Semi-implicit) method is a Lagrangian meshless method developed by Koshizuka and Oka (1996) to simulate incompressible fluid flows. However, its energy conservation properties have not been examined rigorously. In this paper, the effect of a few enhanced schemes in improving the energy conservation properties of MPS method is investigated by considering a set of appropriate Ocean Engineering related tests. It will be shown that an improved MPS benefitting from five enhanced schemes, referred to as, MPS -HS -HL -EC S-GC -DS with the Wendland kernel, provides relatively accurate energy conservation compared with the standard MPS. Furthermore, it tends to have the same level of performance in energy conservation with HMPS (Hamiltonian MPS; Suzuki et al., 200 7) that theoretically should result in exact energy conservation.
Nguyen , QuocPhi (Hanoi University of Mining and Geology, Vietnam) | Phi , TruongThanh (Institute of Marine Geology and Geophysics, Vietnam) | Nguyen, AnhNguyet (Institute of Marine Geology and Geophysics, Vietnam) | Lam, VanAnh (Ban Ve Hydropower Joint Stock Company, Vietnam)
The study aims to apply statistical approaches for landslide susceptibility mapping for natural and cut slopes at two study areas in Vietnam. A landslide database from two study areas with 837 natural and 82 cut slopes was used to produce susceptibility maps to predict the landslide hazard in the future. The distribution of landslides was identified from field surveys, research reports and remote sensing images. By means of Likelihood Ratio (LR), Weight of Evidence (WoE) and Certainty Factor (CF) approaches, the tendency to landslide occurrences was assessed by relating landslide inventory (dependent variable) to a series of causal factors (independent variables) which were managed in the GIS environment. The developed models produced reliable susceptibility maps of study areas and the probability level of landslide can be divided by four different classes (low, medium, high and very high). The overall performance achieved by the LR, WoE and CF analyses was assessed on validation datasets in both two study areas with Kappa statistic (KIA) > 0.7, area under curve (AUC) > 0.85 could be considered very satisfactory for landslide susceptibility zonation. All three models give over 80% of accuracy, in which WoE give best results. Landslide zonation map shows high and very high classes account for only 25% of total area of Quang Ngai province, but they can explain for nearly 90% of existing landslide locations. The weights of statistical approaches can also provide the important level of causal factors, relatively. In which, 3 most affluent factors for natural slopes are geological engineering conditions, landuse and the rock type (lithology) of the slopes, for man-made slopes are the angle of cut slope, weathering depth and the strength of slope materials.
Landslides are more widespread than any other geological event and many factors can cause a slope to fail, such as natural occurrences or man-made activities. Landslide hazard mapping was defined as the quantitative prediction of the spatial distribution of slopes which are likely to be failure (Guzzetti et al., 1999). The causal factors that have been used for landslide hazard analysis can usually be grouped into geomorphology (topographic conditions), geology (rock types, structures, strength of slope materials), land use/land cover and hydrogeology (drainage state and ground water). However, the contributing factors are behaved differently for natural and cut slopes. A natural slope is different from a cut slope (road cuts, excavations, open-pit mining, etc.) in that the effects of rock types, fracture networks inside the rocks, the strength and weathering property of slope materials, the contribution of water on the surface or in the ground may undergone the test of time that will reveal tendencies of slumping, cracking and finally collapsing. On cut slopes, the slope angle, weathering depth, slope cover type, the property of upslope terrain, slope reinforcement, etc. may play an important role in their stability. A cut slope may expose soils that respond poorly to weathering elements, especially when the soil profile of slopes is not uniform and homogenous.
Kato, M. (Hokkaido University) | Park, H. (National Institute of Advanced Industrial Science and Technology) | Takahashi, M. (Research Institute of Innovative Technology for the Earth) | Kaneko, K. (National Institute of Advanced Industrial Science and Technology)
Deformation of rock masses and fluid flow through reservoirs are important when designing sites for geological nuclear waste disposal, carbon dioxide capture and storage, and an enhanced geothermal system. To estimate the behavior of the rock and pore fluid, the poroelastic and hydraulic parameters of high-porosity, low-permeability sedimentary rocks were evaluated simultaneously from triaxial compression tests with instantaneous change of axial stress, confining pressure, or pore pressure. The experimental results of the fluid discharges from the specimen during the tests were used in theoretical interpretations. Thus, besides analyzing the behavior of the pore water, the transient response of the rock deformation corresponding to the pore water movement can be analytically evaluated. Accordingly, the hydraulic constants can be evaluated from the transient strain data of the triaxial compression tests with instantaneous change of stress or pore pressure. The hydraulic constants obtained from the triaxial compression tests agreed well with those from the transient pulse permeability tests. Furthermore, a simple coupling model introduced in this study provided a good representation of the time-dependent rock deformation with pore water movement.
A constitutive model that couples elastic-plastic and damage theories is developed to predict the mechanical behavior of a shale from the Mont Terri rock laboratory (Opalinus Clay). The framework of continuum damage mechanics allows to predict the degradation of the elastic parameters with strains, while the coupling with plasticity correctly reproduces the irreversible strains typical of hard clayey materials. The yield surfaces (one for damage and one for plasticity) are postulated and the evolution equations of the internal variables are derived throughout the application of normality rule. Thermodynamic consistency of the model is investigated. The plastic behavior is described with a non-linear strain hardening function and is coupled with an isotropic damage model suitable for brittle and quasi-brittle geomaterials. The model is integrated with an implicit scheme that guarantees convergence and accuracy. Numerical simulations carried out with the proposed model in triaxial conditions well reproduced observed behavior from experiments.
In this paper, we develop the absorbing boundary condition (ABC) combined with wide-angle wave equations based on the ideas of arbitrarily wide-angle wave equations (AWWEs) (Guddati, 2006) and the hybrid ABC (Liu and Sen, 2010). We introduce the finite difference scheme of AWWEs for the hybrid ABC. Numerical modeling results show significant absorption of our ABC which can achieve good results with fewer boundary grids.
A number of tsunamis have occurred during last decades in the East Sea surrounded by Korea, Japan and Russia. One of the main tsunami disaster prevention policies is to create a tsunami hazard map. In this study, by using a numerical model based on the shallow-water theory, tsunami run-up heights at Samcheok Port are computed for probable maximum tsunamis. A tsunami hazard map is made based on these tsunamis.