The topographic effect of ground motion based on Spectral Element Method

Liu, Xinrong,Jin, Meihai,Li, Dongliang,Hu, Yuanxin,Song, Jianxue Techno-Press 2017 Geomechanics & engineering Vol.13 No.3

A Spectral Element Method for 3D seismic wave propagation simulation is derived based on the three-dimensional fluctuating elastic dynamic equation. Considering the 3D real terrain and the attenuation characteristics of the medium, the topographic effect of Wenchuan earthquake is simulated by using the Spectral Element Method (SEM) algorithm and the ASTER DEM model. Results show that the high PGA (peak ground acceleration) region was distributed along the peak and the slope side away from the epicenter in the epicenter area. The overall distribution direction of high PGA and high PGV (peak ground velocity) region is parallel to the direction of the seismogenic fault. In the epicenter of the earthquake, the ground motion is to some extent amplified under the influence of the terrain. The amplification effect of the terrain on PGA is complicated. It does not exactly lead to amplification of PGA at the ridge and the summit or attenuation of PGA in the valley.

Experimental and numerical study on pre-peak cyclic shear mechanism of artificial rock joints

Xinrong Liu,Yongquan Liu,Yuming Lu,Miaomiao Kou 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.74 No.3

The pre-peak cyclic shear mechanism of two-order asperity degradation of rock joints in the direct shear tests with static constant normal loads (CNL) are investigated using experimental and numerical methods. The laboratory testing rock specimens contains the idealized and regular two-order triangular-shaped asperities, which represent the specific geometrical conditions of natural and irregular waviness and unevenness of rock joint surfaces, in the pre-peak cyclic shear tests. Three different shear failure patterns of two-order triangular-shaped rock joints can be found in the experiments at constant horizontal shear velocity and various static constant normal loads in the direct and pre-peak cyclic shear tests. The discrete element method is adopted to simulate the pre-peak shear failure behaviors of rock joints with two-order triangular-shaped asperities. The rock joint interfaces are simulated using a modified smooth joint model, where microscopic scale slip surfaces are applied at contacts between discrete particles in the upper and lower rock blocks. Comparing the discrete numerical results with the experimental results, the microscopic bond particle model parameters are calibrated. Effects of cyclic shear loading amplitude, static constant normal loads and initial waviness asperity angles on the pre-peak cyclic shear failure behaviors of triangular-shaped rock joints are also numerically investigated.

Numerical Analysis on the Mechanical Performance of Supporting Structures and Ground Settlement Characteristics in Construction Process of Subway Station Built by Pile-Beam-Arch Method

Xinrong Liu,Yongquan Liu,Zhongping Yang,Chunmei He 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.5

Pile-Beam-Arch (PBA) method is an effective approach to control the surface settlement induced by excavation to construct the subway station, especially when the station is located in the urban area with dense buildings. Based on the numerical analysis model of practical engineering, the whole construction stages of the subway station built by PBA method are simulated in this paper. The mechanical performance of supporting structures (such as piles, beams, arches, secondary lining and backfill concrete) and surface settlement characteristics during construction are investigated. The results show that the pre-supporting system of piles, beams and arches is formed in the stage of soil excavation under main tunnel arch; Station hall plate and backfill concrete are two key structures to ensure the support stiffness of PBA supporting system. In addition, compared to the bottom-up method, the top-down method for the secondary lining construction can obviously reduce the internal force of supporting structures and the surface settlement. Combined with in-situ monitoring data, three increase stages of surface settlement and the corresponding settlement ratio are gained and the characteristic of surface settlement trough is also analysed. This study is helpful for further understanding the support mechanism of PBA method and the increase law of the ground settlement during the construction of the station built by PBA method.

Coffin-Siris syndrome in two chinese patients with novel pathogenic variants of ARID1A and SMARCA4

Liu Mingjie,Wan Linlin,Wang Chunrong,Yuan Hongyu,Peng Yun,Wan Na,Tang Zhichao,Yuan Xinrong,Chen Daji,Long Zhe,Shi Yuting,Qiu Rong,Tang Beisha,Tang Beisha,Chen Zhao 한국유전학회 2022 Genes & Genomics Vol.44 No.9

Background: Coffin-Siris syndrome (CSS) is a rare congenital syndrome characterized by developmental delay, intellectual disability, microcephaly, coarse face and hypoplastic nail of the fifth digits. Heterozygous variants of different BAF complex-related genes were reported to cause CSS, including ARID1A and SMARCA4. So far, no CSS patients with ARID1A and SMARCA4 variants have been reported in China. Objective: The aim of the current study was to identify the causes of two Chinese patients with congenital growth deficiency and intellectual disability. Methods: Genomic DNA was extracted from the peripheral venous blood of patients and their family members. Genetic analysis included whole-exome and Sanger sequencing. Pathogenicity assessments of variants were performed according to the guideline of the American College of Medical Genetics and Genomics. The phenotypic characteristics of all CSS subtypes were summarized through literature review. Results: We identified two Chinese CSS patients carrying novel variants of ARID1A and SMARCA4 respectively. The cases presented most core symptoms of CSS except for the digits involvement. Additionally, we performed a review of the phenotypic characteristics in CSS, highlighting phenotypic varieties and related potential causes. Conclusions: We reported the first Chinese CSS2 and CSS4 patients with novel variants of ARID1A and SMARCA4. Our study expanded the genetic and phenotypic spectrum of CSS, providing a comprehensive overview of genotype-phenotype correlations of CSS.

Robust Adaptive Fault-tolerant Containment Control of Networked Heterogeneous Agent Systems with Multiple Active Leaders and Mismatched Affine Uncertainties

Heng Liu,Xin Wang,Xinrong Yang,Xiaona Yang 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.1

This paper investigates the problem of robust fault-tolerant containment control for a class of multiagent systems in which multiple active leaders and linear heterogeneous follower subsystems with mismatched affine uncertainties and actuator faults are distributed on a communication network. It first introduces a group of distributed adaptive intermediate estimators, based on which each following agent can estimate the desired containment trajectory objective. Then, by utilizing adaptive parameter estimation approach and S-procedure technique, a decentralized fault-tolerant tracking control algorithm is designed to guarantee all practical states of followers asymptotically track the desired containment trajectory even in the case of actuator faults and heterogeneous affine uncertainties. Interestingly, the main advantage of proposed fault-tolerant containment strategy is that, not only the faulty information from follower subsystems cannot affect neighbor agents, but also both actuator faults and heterogeneous affine uncertainties can be compensated in local subsystem. Finally, a numerical example is given to illustrate the effectiveness of the designed containment control protocol.

Study on rock fracture behavior under hydromechanical loading by 3-D digital reconstruction

Miaomiao Kou,Xinrong Liu,Yunteng Wang 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.74 No.2

The coupled hydro-mechanical loading conditions commonly occur in the geothermal and petroleum engineering projects, which is significantly important influence on the stability of rock masses. In this article, the influence of flaw inclination angle of fracture behaviors in rock-like materials subjected to both mechanical loads and internal hydraulic pressures is experimentally studied using the 3-D X-ray computed tomography combined with 3-D reconstruction techniques. Triaxial compression experiments under confining pressure of 8.0 MPa are first conducted for intact rock-like specimens using a rock mechanics testing system. Four pre-flawed rock-like specimens containing a single open flaw with different inclination angle under the coupled hydro-mechanical loading conditions are carried out. Then, the broken pre-flawed rock-like specimens are analyzed using a 3-D X-ray computed tomography (CT) scanning system. Subsequently, the internal damage behaviors of failed pre-flawed rock-like specimens are evaluated by the 3-D reconstruction techniques, according to the horizontal and vertical cross-sectional CT images. The present experimental does not only focus on the mechanical responses, but also pays attentions to the internal fracture characteristics of rock-like materials under the coupled hydro-mechanical loading conditions. The conclusion remarks are significant for predicting the rock instability in geothermal and unconventional petroleum engineering.

Shear Behavior of Marlstone Containing Parallel Fissure under Normal Unloading

Zhiming Yin,Xinrong Liu,Zhongping Yang,Yanlei Wang 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.4

Shear tests under normal unloading were carried out to further study the shear mechanical behavior of marlstone containing parallel fissures. The results reveal that the failure on the rock bridge is tensile failure except for the limited extrusion failure at the tip of the prefabricated fissure. The failure on both sides is generally tensile-shear mixed failure, in which the tensile failure is mainly concentrated in the middle of both sides. In general, it can be summarized as a tensile-shear failure mode of STS-T-STS (S means shear failure, T means tension failure). The failure normal stress of the specimens gradually increases and then decreases with the increase of the fissure inclination, increases with an increase in the initial normal/shear stress, and decreases with the increase of the unloading rate. Strong dilation occurred in the shear process of the specimens, which shows obvious arch effect. The variation law of dilatancy deformation and horizontal deformation in the stage of normal stress unloading is just opposite to that of the failure normal stress. The increasing effect of high shear stress on shear deformation is greater than that of dilatancy deformation, while the inhibiting effect of high normal stress on dilatancy deformation is greater than that of the shear deformation.

Influences of Principal Stress Rotation on the Deformation of Saturated Loess under Traffic Loading

Sui Wang,Zuliang Zhong,Xinrong Liu,Yiliang Tu 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.5

This study focuses on the undrained behavior of saturated remolded loess under long-term traffic loading in Lishi, China. In this work, a series of stress-controlled monotonic and cyclic hollow cylinder tests were conducted. In the monotonic tests, the samples were sheared under different inclinations of the major principal stress. According to the results, the saturated remolded loess clearly shows strength anisotropy and shear dilation features. In the cyclic tests, the experimental results show that the evolutions of the pore pressure and generalized shear strain are highly dependent on the principal stress rotation (PSR). The evolution of the strain can be categorized into stable and destructive types. For the stable type, the change in pore pressure increases with the number of loading cycles and then becomes stable. The change in the difference in pore pressure is approximately the same under the same vertical stress ratio. The development of pore pressure shows the hysteresis property, the PSR decreases the degree of the pore pressure hysteresis.

U-shaped relationship between urea level and hepaticU-shaped relationship between urea level and hepatic decompensation in chronic liver diseases decompensation in chronic liver diseases

Huapeng Lin,Grace Lai-Hung Wong,Xinrong Zhang,Terry Cheuk-Fung Yip,Ken Liu,Yee Kit Tse,Vicki Wing-Ki Hui,Jimmy Che-To Lai,Henry Lik-Yuen Chan,Vincent Wai-Sun Wong 대한간학회 2022 Clinical and Molecular Hepatology(대한간학회지) Vol.28 No.1

Background/Aims: We aimed to determine the association between blood urea level and incident cirrhosis, hepatic decompensation, and hepatocellular carcinoma in chronic liver disease (CLD) patients. Methods: The association between blood urea level and liver fibrosis/liver-related events were evaluated on continuous scale with restricted cubic spline curves based on generalized additive model or Cox proportional hazards models. Then, the above associations were evaluated by urea level within intervals. Results: Among 4,282 patients who had undergone liver stiffness measurement (LSM) by transient elastography, baseline urea level had a U-shaped association with LSM and hepatic decompensation development after a median follow-up of 5.5 years. Compared to patients with urea of 3.6–9.9 mmol/L, those with urea ≤3.5 mmol/L (adjusted hazard ratio [aHR], 4.15; 95% confidence interval [CI], 1.68–10.24) and ≥10 mmol/L (aHR, 5.22; 95% CI, 1.86–14.67) had higher risk of hepatic decompensation. Patients with urea ≤3.5 mmol/L also had higher risk of incident cirrhosis (aHR, 3.24; 95% CI, 1.50–6.98). The association between low urea level and incident cirrhosis and hepatic decompensation was consistently observed in subgroups by age, gender, albumin level, and comorbidities. The U-shaped relationship between urea level and LSM was validated in another population screening study (n=917). Likewise, urea ≤3.5 mmol/L was associated with a higher risk of incident cirrhosis in a territory-wide cohort of 12,476 patients with nonalcoholic fatty liver disease at a median follow-up of 9.9 years (aHR, 1.27; 95% CI, 1.03–1.57). Conclusions: We identified a U-shaped relationship between the urea level and liver fibrosis/incident cirrhosis/hepatic decompensation in patients with CLD.

A modified shear strength reduction finite element method for soil slope under wetting-drying cycles

Tu, Yiliang,Zhong, Zuliang,Luo, Weikun,Liu, Xinrong,Wang, Sui Techno-Press 2016 Geomechanics & engineering Vol.11 No.6

The shear strength reduction finite element method (SSRFEM) is a powerful tool for slope stability analysis. The factor of safety (FOS) of the slope can be easily calculated only through reducing effective cohesion (c′) and tangent of effective friction angle ($tan{\varphi}^{\prime}$) in equal proportion. However, this method may not be applicable to soil slope under wetting-drying cycles (WDCs), because the influence of WDCs on c′ and $tan{\varphi}^{\prime}$ may be different. To research the method of estimating FOS of soil slopes under WDCs, this paper presents an experimental study firstly to investigate the effects of WDCs on the parameters of shear strength and stiffness. Twelve silty clay samples were subjected to different number of WDCs and then tested with triaxial test equipment. The test results show that WDCs have a degradation effect on shear strength (${\sigma}_1-{\sigma}_3)_f$, secant modulus of elasticity ($E_s$) and c′ while little influence on ${\varphi}^{\prime}$. Hence, conventional SSRFEM which reduces c′ and $tan{\varphi}^{\prime}$ in equal proportion cannot be adopted to compute the FOS of slope under conditions of WDCs. The SSRFEM should be modified. In detail, c′ is merely reduced among shear strength parameters, and elasticity modulus is reduced correspondingly. Besides, a new approach based on sudden substantial changes in the displacement of marked nodes is proposed to identify the slope failure in SSRFEM. Finally, the modified SSRFEM is applied to compute the FOS of a slope example.