Kyushu University Academic Staff Educational and Research Activities Database
List of Presentations
GUANGQI CHEN Last modified date:2019.11.29

Professor / Geotechnic, Department of Civil & Structural Engineering, Graduate School of Engineering / Division for Experimental Natural Science / Faculty of Arts and Science


Presentations
1. Guangqi CHEN, Long ZHANG, Chengwen CAI, Chunmei FAN, Qiang XU, SIMULATION OF EARTHQUAKE GROUND MOTIONS USING DDA, The International Conference for the Decade Memory of the Wenchuan Earthquake with the 4th International Conference on Continental Earthquakes, 2018.05, Earthquake ground motions, such as acceleration time series and peak ground acceleration (PGA), are important and necessary data in earthquake engineering. Although these data can be obtained by seismic observations, they need to be simulated for the regions where records were not available during a past earthquake or for a future potential earthquake. For example, acceleration time series and PGA are necessary in hazard assessment of landslides induced by a potential earthquake on a specific active fault. However, there is no practical simulation system established for this purpose. In this study, we propose two methods. The one is developing a practical system for simulating earthquake ground motions based on the so-called stochastic finite-fault method (SFFM). The other is to estimate PGA in a specific location using 3D-DDA simulation technique based on some extreme ground motions.

Development of a practical system for simulating earthquake ground motions based on SFFM
The key issues in simulating earthquake ground motion are how to consider the source effect, path effect and site effect. Up to now, the effect of asperity, one of the important factors in estimating source parameters, and the effect of volcanic zone on estimating path parameters have not been well investigated. Also, how to estimate the site effect for the location without seismic sensors remains an unsolved problem although site amplification can be estimated based on the seismic observations from both the surface and borehole sensors at the same station. For these reasons, this study aims at developing a practical system for simulating earthquake ground motions based on SFFM, especially, paying attention to volcanic zone and asperity. The system consists of four modules: (1) a module for estimating the site amplification based on a new method proposed even for the location without strong ground-motion observations; (2) a module for estimating shear-wave attenuation based on a new analysis approach which can distinguish volcanic zone from non-volcanic; (3) a module for estimating slip distribution field by considering the characteristics of the asperity on a fault; (4) the SFFM module for calculating ground motions. Also, the system is applied to simulate the PGA distribution for landslide hazard assessment in Aso-bridge region, Kumamoto, Japan. It is shown that the assessment accuracy is improved using the simulated PGA than the conventional assumed PGA based on landslides induced by the 2016 Kumamoto earthquake.

Estimation of PGA using 3D-DDA numerical simulation based on extreme ground motion phenomenon
The 2016 Kumamoto Earthquake induced a number of landslides and one of the largest scale landslides is located at Aso bridge area on the Futagawa Fault. In order to study the landslide, it is necessary to know the ground motion or PGA (Peak Ground Acceleration) there. Although there are four seismic stations around the area, no records can be directly used because of geotechnical side effect which is expected very large due to near the seismic fault. Meanwhile, we noticed another extreme ground motion phenomenon that several vehicles were toppled near the landslide. Therefore, this study aims at inversing the PGA around the landslide by simulating the phenomenon of toppled vehicles using 3D DDA (Discontinuous Deformation Analysis). At first, the car model for DDA simulation is made. The mechanism of vehicle toppled phenomenon is clarified by investigating 1) the effect of the seismic frequency; 2) the effect of the parameters of a car such as weight distribution, gravity center, tire’s Young’s Modulus, parking direction. And then, the PGA for Aso bridge area is estimated based on the above discussions by the use of the seismic waves recorded at the station KMMH16 that is also close to the Futagawa Fault..
2. Guangqi CHEN, Long ZHANG, Chengwen CAI, Chunmei FAN, Qiang XU , SIMULATION OF EARTHQUAKE GROUND MOTIONS, The 5th International Symposium on Mega Earthquake Induced Geo-disasters and Long Term Effects, 2018.05, Earthquake ground motions, such as acceleration time series and peak ground acceleration (PGA), are important and necessary data in earthquake engineering. Although these data can be obtained by seismic observations, they need to be simulated for the regions where records were not available during a past earthquake or for a future potential earthquake. For example, acceleration time series and PGA are necessary in hazard assessment of landslides induced by a potential earthquake on a specific active fault. However, there is no practical simulation system established for this purpose. In this study, we propose two methods. The one is developing a practical system for simulating earthquake ground motions based on the so-called stochastic finite-fault method (SFFM). The other is to estimate PGA in a specific location using 3D-DDA simulation technique based on some extreme ground motions.

1. Development of a practical system for simulating earthquake ground motions based on SFFM
The key issues in simulating earthquake ground motion are how to consider the source effect, path effect and site effect. Up to now, the effect of asperity, one of the important factors in estimating source parameters, and the effect of volcanic zone on estimating path parameters have not been well investigated. Also, how to estimate the site effect for the location without seismic sensors remains an unsolved problem although site amplification can be estimated based on the seismic observations from both the surface and borehole sensors at the same station. For these reasons, this study aims at developing a practical system for simulating earthquake ground motions based on SFFM, especially, paying attention to volcanic zone and asperity. The system consists of four modules: (1) a module for estimating the site amplification based on a new method proposed even for the location without strong ground-motion observations; (2) a module for estimating shear-wave attenuation based on a new analysis approach which can distinguish volcanic zone from non-volcanic; (3) a module for estimating slip distribution field by considering the characteristics of the asperity on a fault; (4) the SFFM module for calculating ground motions. Also, the system is applied to simulate the PGA distribution for landslide hazard assessment in Aso-bridge region, Kumamoto, Japan. It is shown that the assessment accuracy is improved using the simulated PGA than the conventional assumed PGA based on landslides induced by the 2016 Kumamoto earthquake. The following conclusions have been obtained
① The site amplification of 53 KiK-net stations in the Kyushu region are calculated. Compared with the S/B method, the H/V method is not suitable to be used in Kyushu Island due to the significant amplification in the vertical component.
② A method for estimating the site amplification in the region without SGM stations is developed and made as a module.
③ A method for estimating the S-wave attenuation considering the volcanic effect is proposed and made as a module.
④ The accuracy of the PGA estimated based on the slip distribution fields inversed from different kinds of data is discussed. A combination of the three results is proposed to improve the accuracy of simulated PGA.
⑤ An approach for generating the slip distribution field for a potential earthquake with an expected magnitude on a specific fault is proposed and made as a module.
⑥ A practical system for simulating earthquake ground motions paying attention to volcanic zone and asperity on a fault is developed and successfully applied to the landslide hazard assessment.

2. Estimation of PGA using 3D-DDA simulation based on extreme ground motion phenomenon
The 2016 Kumamoto Earthquake induced a number of landslides and one of the largest scale landslides is located at Aso bridge area on the Futagawa Fault. In order to study the landslide, it is necessary to know the ground motion or PGA (Peak Ground Acceleration) there. Although there are four seismic stations around the area, no records can be directly used because of geotechnical side effect which is expected very large due to near the seismic fault. Meanwhile, we noticed another extreme ground motion phenomenon that several vehicles were toppled near the landslide. Therefore, this study aims at inversing the PGA around the landslide by simulating the phenomenon of toppled vehicles using 3D DDA (Discontinuous Deformation Analysis). At first, the car model for DDA simulation is made. The mechanism of vehicle toppled phenomenon is clarified by investigating 1) the effect of the seismic frequency; 2) the effect of the parameters of a car such as weight distribution, gravity center, tire’s Young’s Modulus, parking direction. And then, the PGA for Aso bridge area is estimated based on the above discussions by the use of the seismic waves recorded at the station KMMH16 that is also close to the Futagawa Fault. The following conclusions have been obtained in this study.
① The extreme ground motion of car toppled phenomenon has been successfully simulated by using 3D-DDA.
② The mechanism of toppled car has been clarified. It has been found that two kinds of factors may contribute to the phenomenon. One factor is the vehicle condition such as the weight distribution, the gravity center and the Young’s modulus. The other is the external factor including the seismic frequency, parking directions and the vertical component of ground motions.
③ The PGA for the study area has been estimated as about 16.3 m/s2 from the DDA simulation of the car toppled phenomenon based on the seismic waves recorded at the station KMMH16. It has been found the PGA is 1.41 times of the records at the near station. Therefore, the amplified seismic waves recorded at the station KMMH16 can be used for the study on the large scale landslide analysis in Aso bridge area in the future..
3. Guangqi Chen, Wei Wang, Hong Zhang, Yingbin Zhang, Numerical simulation of landslide-dam using a 3D DDA and SPH coupled solid-fluid simulation technique, THE SEVENTH CHINA-JAPAN GEOTECHNICAL SYMPOSIUM, 2018.03.
4. Guangqi Chen, Some common problems and solutions in practical DDA application, 13th International Conference on Analysis of Discontinuous Deformation, 2017.12, It is offen heard that DDA (Discontinuous Deformation Analysis) is an excellent numerical method but using it requres advanced technical capabilities and a good experience. This is because a lot of things have not been discussed in DDA theroy book and there is no commerical software including all the improvments and extensions made by a lot of researchers. In this study, some key issues in 2D DDA, such as multi joint sets, panelty spring, dynamic and static DDA, maximum allowed displacement, are discussed. The common problems are analyzed and the solutions are proposed. Also, one of the problems in application of 3D DDA-SPH to landslide-dam formation and failure is discussed and the solution is proposed.
(1) The modification of both the model and DDA program is required for a DDA model with different joint sets. Otherwise, the correct analysis cannot be made. (2) No penetration should be stated as small penetration. A proper spring stiffness is necessary and it is related to loadings on the contacted blocks but not related to E. Using a large spring stiffness can result in a large random force, which makes instable, due to the error of calculated penetration. (3) There would be no need to distinct dynamic and static analysis if a proper initial processing is done. (4) The parameter Pmad is one very important parameters and the improper value can lead some strange phenomena and a method is proposed to clarify it. (5) A natural river can be modelled in 3D DDA-SPH..
5. Guangqi Chen, DEVELOPMENT OF A 3D COUPLED SOLID-FLUID SIMULATION TECHNIQUE USING DDA AND SPH AND APPLICATION TO LANDSLIDE INDUCED CHAIN DISASTERS, 2017 Forum on Simulation and Analysis Techniques for Hazard Mitigation and Prevention of Civil and Hydraulic Systems, 2017.12, 1. Some applications of 2D DDA to landslide disaster prevention.
2. Landslide induced chain disasters.
3. Development of a program for simulating debris flow.
4. Devlopment of a coupled solid-fluid program using 3D DDA and SPH.
5. Application of the 3D DDA-SPH to landslide-dam simulation.
.
6. GUANGQI CHEN, An approach of landslide risk assessment in Japan by considering global climate change
, THE 15TH INTERNATIONAL SYMPOSIUM ON GEO-DISASTER REDUCTION , 2017.08, 1.The approach of landslide risk mapping for the project
①Develop a tool for landslide risk mapping
 ②Assess landslide risk over the whole Japanese territory
 ③Evaluate the risk increase with extreme climate change
2.Improvements on the landslide risk mapping approach
 ①A new model for rainfall infiltration
 ②Development of a real time hazard mapping method
 ③Develop a GIS-based 2d & 3d stability analysis based on circular and ellipse slip surface
Further studies from the project
.
7. GUANGQI CHEN, Tsukasa KAWAKAMI, Yingbin ZHANG, Mechanism analysis of earthquake induced extreme motions: Clarifying extreme acceleration
, The 51th US Rock Mechanics/Geomechanics Symposium , 2017.06, Earthquake induced extreme motions are classified as the extreme large acceleration, the extreme large velocity and the extreme large displacement. In this paper, a sudden braking model is proposed for the mechanism of the extreme large acceleration, i.e. the extreme large acceleration can easily occur when a moving body is suddenly braked. The model is verified by theoretical analysis, laboratory experiments and numerical simulation using DDA. It is successful to reproduce the unprecedented vertical surface acceleration of nearly four times gravity, recorded at the West Ichinoseki station during the 14 June 2008 Iwate-Miyagi earthquake (Ms6.9) in Japan, by DDA simulation. .
8. Yingbin ZHANG, GUANGQI CHEN, Shaking table test for estimating the effects of seismic loading on the mobility of rockfall, The 51th US Rock Mechanics/Geomechanics Symposium , 2017.06.
9. GUANGQI CHEN, Mechanism clarification of earthquake induced extreme motions, International Workshop on the 2016 Kumamoto Earthquake (IWKE), 2017.03.
10. GUANGQI CHEN, Mechanism clarification of earthquake induced extreme motions
, International Workshop on the 2016 Kumamoto Earthquake , 2017.03.
11. GUANGQI CHEN, Next generation numerical simulation technique for discontinuous rock mechanics, The Second International Academic Conference on Discontinuous Rock Mechanics, 2016.11.
12. GUANGQI CHEN, Development of a solid-fluid simulation technique for analysis of landslide induced chain disasters, The 14th International Symposium on Geo-disaster Reduction, 2016.10, Landslide can create a landslide dam when its debris fill into and stop a river; while the dam is being filled, the surrounding water level rises and causes back-flooding (upstream flooding). Because of its rather loose nature and absence of controlled spillway, a landslide dam can easily collapse catastrophically and lead to debris flow or downstream flooding. Also, the landslide debris can be removed into a valley or a ravine by excessive precipitation to form debris flow. These secondary disasters occur as a disaster chain, i.e. “disaster triggering disaster”. Therefore, it is very important and necessary to cut the disaster chain in an early stage. This paper majorly focuses on the study of landslide dam.
Many studies have been made to analyze the formation and failure of a landslide dam. Most of them majorly use statistical methods or empirical formulas to assess the possibility of formation and failure based on geomorphological parameters of the dam and river. However, the formation of a landslide dam is not only related to geomorphological parameters but also to kinematic coupling between the river flow and the movement of the landslide mass. Particularly, the formation and failure of landslide dam always involves complicated solid-fluid interaction. Therefore, the kinematic characteristics and interaction process of river flow and landslide mass should be well analyzed. With the development of computer and computation sciences, various numerical methods have been developed and shown their powerful capabilities in simulating the solid and fluid dynamics. Among them, Discontinuous Deformation Analysis (DDA) shows great advantages in simulating rigid body movements from theory to practice, and Smoothed Particle Hydrodynamics (SPH) is very capable to model the free surface flow. Although there have been some studies on the coupling of DDA with SPH, the practical simulation technique for landslide dam formation and failure is still unavailable because of the following three unsolved key issues: (1) how to produce a river flow with steady motion under the SPH framework; (2) how to simulate a large-scale landslide movement over a complicated 3D topography; (3) how to accomplish the simulation involving large-scale, complicated solid and fluid phases and their interaction in practical landslide dam formation and failure.
In this study, a practical 3D coupled solid-fluid simulation technique is developed by using DDA and SPH to analyze the formation and failure characteristics of the landslide dam. At first, an Open Channel Model with Steady Flow (OCMSF) and a Particle Recycling Method (PRM) are proposed to solve the first issue. Then, an Ordered Blocky Method (OBM) is developed to solve the second issue. Also, the coupled DDA-SPH method is validated by a laboratory experiment, and a series of typical examples are performed to analyze the formation and failure characteristics of the landslide dam. Finally, a Three-stage Simulation Strategy (TSSS) is proposed to solve the third issue. The developed simulation technique is successfully applied to simulate a practical landslide dam and its effectiveness and practicality are validated..
13. GUANGQI CHEN, Stability analysis of toppling slope using the extended NMM, The 50th US Rock Mechanics/Geomechanics Symposium , 2016.06, The original numerical manifold method (NMM) is extended for stability analysis of a toppling slope with complex sliding surface and cohesion and tensile strengths existing in discontinuities. The extended NMM is shown effective by reproducing a centrifuge test. With NMM simulation, the commonly used Goodman and Bray’s analytical method is shown adaptable to a toppling slope model with a simple sliding surface without cohesion and tensile strengths in the discontinuities. It is shown that the deformation of the sliding body has no significant effect on the result. The relationship between dip angle and critical friction angle is investigated. A real toppling slope is simulated and the necessary cohesion and friction angle are verified.
14. Wang W., GUANGQI CHEN, Modeling of open channel flow for landslide dam formation using smoothed particle hydrodynamics method, The symposium on advanced technology of prediction and preventive measures of landslides, Fukuoka 2015 , 2015.12.
15. Jing P., GUANGQI CHEN, Simulation of dynamic block displacement using 3D-DDA method, The symposium on advanced technology of prediction and preventive measures of landslides, Fukuoka 2015, 2015.12.
16. Zhou S., GUANGQI CHEN, Integration of Bivariate Statistics and Analytic Hierarchy Process Methods in Regional Landslides Susceptibility Mapping: A case study of Tsushima Island, The symposium on advanced technology of prediction and preventive measures of landslides, Fukuoka 2015, 2015.12.
17. Han Z., GUANGQI CHEN, A method for estimating the bed-sediment entrainment in debris flow, THE 15TH ASIAN REGIONAL CONFERENCE ON SOIL MECHANICS AND GEOTECHNICAL ENGINEERING, 2015.11.
18. Wang W., GUANGQI CHEN, Modeling of landslide generated waves in Three Gorges Reservoir, China using SPH method , THE 15TH ASIAN REGIONAL CONFERENCE ON SOIL MECHANICS AND GEOTECHNICAL ENGINEERING, 2015.11.
19. GUANGQI CHEN, Hazard mapping of landslide-dam induced by earthquake , THE 15TH ASIAN REGIONAL CONFERENCE ON SOIL MECHANICS AND GEOTECHNICAL ENGINEERING, 2015.11.
20. Jing P., GUANGQI CHEN, Simulation of the bolt mechanism using three dimensional discontinuous deformation analysis
, 12th International Conferences on Analysis of Discontinuous Deformation, 2015.10.
21. Wang W., GUANGQI CHEN, Numerical modeling of landslide generated impulsive waves using coupled DDA-SPH method, 12th International Conferences on Analysis of Discontinuous Deformation, 2015.10.
22. GUANGQI CHEN, Development of a practical solid-fluid coupling simulation technique using DDA and SPH, 12th International Conferences on Analysis of Discontinuous Deformation, 2015.10.
23. GUANGQI CHEN, Development & application of DDA & MM, DDA Workshop in Asian Rock Mechanics Symposium , 2014.10.
24. Jing P., GUANGQI CHEN, Application of 3D-DDA to simulate the kinematic behavior of rock slope, DDA Workshop in Asian Rock Mechanics Symposium, 2014.10.
25. FAN F., GUANGQI CHEN, Mechanism analysis of toppling failure using numerical manifold method, DDA Workshop in Asian Rock Mechanics Symposium, 2014.10.
26. Han Z., GUANGQI CHEN, Development of Cellular Automaton Model for Simulating the Propagation Extent of Debris Flow at Alluvial Fan: A Case Study of Yohutagawa, Japan, The TC105 ISSMGE International Symposium on Geomechanics from Micro to Macro, 2014.09.
27. Zhang H., GUANGQI CHEN, A new discontinuous model for three dimensional analysis of fluid-solid interaction behavior, The TC105 ISSMGE International Symposium on Geomechanics from Micro to Macro, 2014.09.
28. Kawakami T., GUANGQI CHEN, Vertiffivation of earthquake trampoline effect on ground movement by shaking table test, 大韓土木学会―日本土木学会―台湾公共工程学会ジョイントセミナー2014, 2014.08.
29. GUANGQI CHEN, Hazard mapping for earthquake induced geo-disaster chain, The Sixth Japan - Taiwan Joint Workshop on Geotechnical Hazards from Large Earthquakes and Heavy Rainfall , 2014.07.
30. Zhou S., GUANGQI CHEN, GIS-based support vector machine modeling of landslides triggered by April 20, 2013 Lushun earthquake, Sichuan, China, The 6th Japan-Taiwan Workshop on Geotechnical Hazards from Large Earthquakes and Heavy Rainfall, 2014.07.
31. Jing P., GUANGQI CHEN, Application of three-dimensional deformation analysis to simulate characteristics of planar translational slope failure, The 6th Japan-Taiwan Workshop on Geotechnical Hazards from Large Earthquakes and Heavy Rainfall, 2014.07.
32. Han Z., GUANGQI CHEN, Numerical Simulation of Post-entrainment Debris Flow at Alluvial Fan Using FLO-2D Model, The 6th Japan-Taiwan Workshop on Geotechnical Hazards from Large Earthquakes and Heavy Rainfall, 2014.07.
33. GUANGQI CHEN, Risk Assessment on earthquake induced landslide chain disasters , The 2nd IACGE International Conference on Geotechnical and Earthquake Engineering, 2013.10.
34. Hong Zhang, GUANGQI CHEN, Y. Zhang, L. Zheng, Mechanism of shallow rainfall-induced landslide and simulation of initiation with DDA, The 11th International Conference on Analysis of Discontinuous Deformation (ICADD11), 2013.08, [URL].
35. Fusong FAN, GUANGQI CHEN, Y. Zhang, L. Zheng, Study on soil arching effects of stabilizing piles using numerical methods, The 11th International Conference on Analysis of Discontinuous Deformation (ICADD11), 2013.08, [URL].
36. Guruh Samodra, GUANGQI CHEN, Y. Zhang, L. Zheng, Combining GIS and DDA for preliminary rockfall risk assessment in Gunung Kelir area Yogyakarta Indonesia, The 11th International Conference on Analysis of Discontinuous Deformation (ICADD11), 2013.08, [URL].
37. T. Kawakami, GUANGQI CHEN, Y. Zhang, L. Zheng, Stability analysis of breakwater in terms of seepage flow using DDA, The 11th International Conference on Analysis of Discontinuous Deformation (ICADD11), 2013.08, [URL].
38. GUANGQI CHEN, Y. Zhang, L. Zheng, Practical applications of DDA to disaster prevention, The 11th International Conference on Analysis of Discontinuous Deformation (ICADD11), 2013.08, [URL], Some of practical applications of DDA to disaster prevention in Kyushu University are introduced. The first application is to analyze stability of breakwater by considering tsunami induced seepage. A local piping mode and global failure mode are clarified by DDA simulations. The second application is to analyze stability and simulate cave-in phenomenon for sand beach. An approach of using DDA to continuous material like sand ground is proposed by generating proper artificial mesh. The bearing capacity and arch function are clarified for the sand ground with a cave. The cave-in phenomenon is reshown by DDA simulations. The third application is to clarify the mechanism of extreme earthquake wave based on so-called trampoline effect and ping-pong model. The extreme waveform with a PGA of more than 4000 gal recorded in Japan is reshown by DDA simulation. These applications will play an important role in disaster prevention in future. .
39. L. Zheng, GUANGQI CHEN, Y. Zhang, Rock mass stability analysis based on contact mode using DDA, The 11th International Conference on Analysis of Discontinuous Deformation (ICADD11), 2013.08, [URL].
40. Y. Zhang, GUANGQI CHEN, L. Zheng, Detailed investigation of near-fault earthquake loading induced displacement of sliding system by the Discontinuous Deformation Analysis (DDA), The 11th International Conference on Analysis of Discontinuous Deformation (ICADD11), 2013.08, [URL].
41. Zheng Han, GUANGQI CHEN, Yange Li, A numerical simulation of volumetric enlargement for seismic debris flow using integrated DDA and KANAKO 2D, The 11th International Conference on Analysis of Discontinuous Deformation (ICADD11), 2013.08, [URL].
42. Yanqiang Wu, GUANGQI CHEN, Zaisen Jiang, The mathematical algorithm of multi-point constraints in the simulations of three-dimensional Numerical Manifold Method, The 11th International Conference on Analysis of Discontinuous Deformation (ICADD11), 2013.08, [URL].
43. Yana FAN, GUANGQI CHEN, Susceptibility analysis of earthquake induced landslide-dam based on GIS, the 47th U.S. Rock Mechanics and Geomechanics Symposium, 2013.06.
44. GUANGQI CHEN, Y. Zhang, L. Zheng, Stability Analysis of Breakwater Under Seepage Flow Using DDA, ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering, Nante, France, 2013.06.
45. GUANGQI CHEN, Earthquake induced a chain of disasters, ATC3 TAIWAN-JAPAN COLLABORATIVE RESEARCH WORKSHOP ON NATURAL DISASTERS, 2011.09.
46. GUANGQI CHEN, Application of DDA simulations to landslide analysis, 2011 International Workshop on Geotechnical Engineering , 2011.07.