Modeling or rock slope stability and rockburst by the rock failure process analysis (RFPA) method

Chun'an Tang,Shibin Tang 한국암반공학회 2011 한국암반공학회 학술대회 및 세미나 자료집 Vol.2011 No.9

Brittle failure of rock is a classical rock mechanics problem. Rock failure not only involves initiation and propagation of single crack, but also is a complex problem associated with initiation, propagation and coalescence of many cracks. As the most important feature of rock material properties is the heterogeneity, the Weibull statistical distribution is employed in the rock failure process analysis (RFPA) method to describe the heterogeneity in rock properties. In this paper, the applications of the RFPA method in geotechnical engineering and rockburst modeling are introduced with emphasis, which can provide some references for relevant researches.

Survival benefit of patients with early-stage ovarian carcinoma treated with paclitaxel chemotherapeutic regimens

Chien-An Chen,Chun-Ju Chiang,Yun-Yuan Chen,San-Lin You,Shu-Feng Hsieh,Chao-Hsiun Tang,Wen-Fang Cheng 대한부인종양학회 2018 Journal of Gynecologic Oncology Vol.29 No.1

Objective: Adjuvant chemotherapy was introduced in patients with early-stage ovarian cancer (OC). The benefit of standard chemotherapeutic regimens including taxane has not been established. Methods: Patients with early-stage OC from the National Health Insurance Research database of Taiwan who received platinum plus cyclophosphamide (CP) or platinum plus paclitaxel (PT) for 3–6 cycles were recruited, and the disease-free survival (DFS) and overall survival (OS) were determined. Results: A total of 1,510 early-stage OC patients, including 841 who received CP regimen and 699 who received PT regimen, were included. The 2 groups had a similar estimated probability of 5-year DFS (PT vs. CP, 79.0% vs. 77.6%; p=0.410) and OS (84.6% vs. 84.3%; p=0.691). Patients >50 years of age who received the CP regimen had a lower 5-year DFS than the patients ≤50 years of age who received the CP (p<0.001) or PT regimens (p=0.001). Additionally, patients >50 years of age who received the CP regimen had a worse 5-year OS compared with the other 3 groups (p=0.019) (p=0.179 for patients >50 years of age in the PT group; p=0.002 for patients ≤50 years of age in the CP group; and p=0.061 for patients ≤50 years of age in the PT group). Patients with the CP or PT regimen for 3–5 cycles had a similar 5-year DFS and OS compared to 6 cycles (p>0.050). Conclusion: Chemotherapeutic regimens with taxane could be recommended for early-stage OC patients >50 years of age.

Study on Progressive Damage and Failure of Sandstone Samples subjected to Cyclic Disturbance Loads using a Modified Triaxial Test System

Xu Chen,Chun’an Tang,Xiangyong Kong 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.5

The deep-buried rock may experience external disturbance loads and bear overstress simultaneously in the process of free surface formation of excavation. However, the mechanical behaviors and responses under these complex stress conditions are still poorly understood. The main purpose of this paper focuses on investigating effect of frequency and amplitude of external disturbance load on stress-strain behaviors of rock samples, progressive damage evolution and failure characteristics. Using a newly developed triaxial test system at Huaqiao University a series of disturbance tests with different frequencies (5 Hz, 10 Hz, and 20 Hz) and different amplitudes (1.0 MPa, 2.5 MPa, and 5.0 MPa) was carried out on sandstone samples at the axial stress level of 85% of uniaxial compressive strength. According to the experimental results, the frequency and amplitude of the axial disturbance stress have important effects on time duration until failure, and the changing trends of axial and radial strain versus time in disturbance loading phase are extremely similar with regime I and regime II—transient creep and steady-state creep—in idealized one-dimensional creep curve. Furthermore, damage variable defined in terms of residual strain method can well reflect the gradual increase in damage degree of rock samples in disturbance loading tests under different disturbance frequencies and different amplitudes conditions. The fragmentation degree and ductility characteristics of the failure of rock sample gradually increase with the disturbance frequency and amplitude.

Analysis of the shear failure process of masonry by means of a meso-scopic mechanical modeling approach

Wang, Shuhong,Tang, Chun'an,Jia, Peng Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.24 No.2

The masonry is a complex heterogeneous material and its shear deformation and fracture is associated with very complicated progressive failures in masonry structure, and is investigated in this paper using a mesoscopic mechanical modelling, Considering the heterogeneity of masonry material, based on the damage mechanics and elastic-brittle theory, the newly developed Material Failure Process Analysis (MFPA) system was brought out to simulate the cracking process of masonry, which was considered as a three-phase composite of the block phase, the mortar phase and the block-mortar interfaces. The crack propagation processes simulated with this model shows good agreement with those of experimental observations by other researchers. This finding indicates that the shear fracture of masonry observed at the macroscopic level is predominantly caused by tensile damage at the mesoscopic level. Some brittle materials are so weak in tension relative to shear that tensile rather than shear fractures are generated in pure shear loading.

Impact of rock microstructures on failure processes - Numerical study based on DIP technique

Yu, Qinglei,Zhu, Wancheng,Tang, Chun'an,Yang, Tianhong Techno-Press 2014 Geomechanics & engineering Vol.7 No.4

It is generally accepted that material heterogeneity has a great influence on the deformation, strength, damage and failure modes of rock. This paper presents numerical simulation on rock failure process based on the characterization of rock heterogeneity by using a digital image processing (DIP) technique. The actual heterogeneity of rock at mesoscopic scale (characterized as minerals) is retrieved by using a vectorization transformation method based on the digital image of rock surface, and it is imported into a well-established numerical code Rock Failure Process Analysis (RFPA), in order to examine the effect of rock heterogeneity on the rock failure process. In this regard, the numerical model of rock could be built based on the actual characterization of the heterogeneity of rock at the meso-scale. Then, the images of granite are taken as an example to illustrate the implementation of DIP technique in simulating the rock failure process. Three numerical examples are presented to demonstrate the impact of actual rock heterogeneity due to spatial distribution of constituent mineral grains (e.g., feldspar, quartz and mica) on the macro-scale mechanical response, and the associated rock failure mechanism at the meso-scale level is clarified. The numerical results indicate that the shape and distribution of constituent mineral grains have a pronounced impact on stress distribution and concentration, which may further control the failure process of granite. The proposed method provides an efficient tool for studying the mechanical behaviors of heterogeneous rock and rock-like materials whose failure processes are strongly influenced by material heterogeneity.

Parallel computation for debonding process of externally FRP plated concrete

Xu, Tao,Zhang, Yongbin,Liang, Z.Z.,Tang, Chun-An,Zhao, Jian Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.38 No.6

In this paper, the three dimensional Parallel Realistic Failure Process Analysis ($RFPA^{3D}$-Parallel) code based on micromechanical model is employed to investigate the bonding behavior in FRP sheet bonded to concrete in single shear test. In the model, the heterogeneity of brittle disordered material at a meso-scale was taken into consideration in order to realistically demonstrate the mechanical characteristics of FRP-to-concrete. Modified Mohr-coulomb strength criterion with tension cut-off, where a stressed element can damage in shear or in tension, was adopted and a stiffness degradation approach was used to simulate the initiation, propagation and growth of microcracks in the model. In addition, a Master-Slave parallel operation control technique was adopted to implement the parallel computation of a large numerical model. Parallel computational results of debonding of FRP-concrete visually reproduce the spatial and temporal debonding failure progression of microcracks in FRP sheet bonded to concrete, which agrees well with the existing testing results in laboratory. The numerical approach in this study provides a useful tool for enhancing our understanding of cracking and debonding failure process and mechanism of FRP-concrete and our ability to predict mechanical performance and reliability of these FRP sheet bonded to concrete structures.

Parallel computation for debonding process of externally FRP plated concrete

Tao Xu,Yongbin Zhang,Z.Z. Liang,Chun-an Tang,Jian Zhao 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.38 No.6

In this paper, the three dimensional Parallel Realistic Failure Process Analysis (RFPA3D-Parallel) code based on micromechanical model is employed to investigate the bonding behavior in FRP sheet bonded to concrete in single shear test. In the model, the heterogeneity of brittle disordered material at a meso-scale was taken into consideration in order to realistically demonstrate the mechanical characteristics of FRP-to-concrete. Modified Mohr-coulomb strength criterion with tension cut-off, where a stressed element can damage in shear or in tension, was adopted and a stiffness degradation approach was used to simulate the initiation, propagation and growth of microcracks in the model. In addition, a Master-Slave parallel operation control technique was adopted to implement the parallel computation of a large numerical model. Parallel computational results of debonding of FRP-concrete visually reproduce the spatial and temporal debonding failure progression of microcracks in FRP sheet bonded to concrete, which agrees well with the existing testing results in laboratory. The numerical approach in this study provides a useful tool for enhancing our understanding of cracking and debonding failure process and mechanism of FRP-concrete and our ability to predict mechanical performance and reliability of these FRP sheet bonded to concrete structures.

Experimental observation and realistic modeling of initiation and propagation of the rock fracture by acoustic emission

Shuhong Wang,Chung-in Lee,Seok-won Jeon,Heekwang Lee,Chun-an Tang 한국암반공학회 2006 한국암반공학회 학술대회 및 세미나 자료집 Vol.- No.-

It is well known that acoustic emission (AE) is indicator of rock fracturing or damage as rock is brought to failure under the uniaxial compressive loads. In this paper, an experimental study on the source location of acoustic emission on the cylindrical specimens of granite under uniaxial compression test was made. The AE source location was made by measuring the six channel AE data. Comparing to this experiment, the numerical method is applied to model the initiation and propagation of fracture by AE using a numerical code, RFPA (Realistic Failure Process Analysis). This code incorporates the mesoscopic heterogeneity in Young's modulus and rock strength characteristic of rock masses. In the numerical models, values of Young's modulus and rock strength are realized according to a Weibull distribution in which the distribution parameters represent the level of heterogeneity of the medium. The results of the simulations show that RFPA can be used not only to produce acoustic emission similar to those measurements in our experiments, but also to predict fracturing patterns under uniaxial loading condition.

Where Are Landscape Designers' Spatial Abilities in the Brain? An fMRI Study

Shih-Han Hung,Chia-Yi Huang,Tsung-Ren Huang,Shih-An Tang,Yu-Ping Tsai,Chun-YenChang 인간식물환경학회 2023 인간식물환경학회지 Vol.26 No.5

Background and objective: To effectively understand and communicate their work, landscape designers should possessexcellent spatial abilities. Neurological methods have confirmed that activation of the occipital lobe, parietal cortex, andprefrontal cortex affect the judgment of space; however, few studies have measured spatial abilities in landscape design. This study aimed to identify the potential role of various brain regions during spatial interpretation processes by landscapedesigners, particularly the effect of stimulating the frontal lobe on enhancing design capabilities. Methods: This study tested the spatial abilities of landscape designers when transforming a planar drawing into a sectionaldrawing and the brain regions activated in this process. The subjects were asked to identify the correct option whenmatching given section lines in a planar drawing. The correct answer rate and response time were used to score brainactivation during spatial task processes. A total of 16 valid subjects were divided into high- and low-accuracy groupsaccording to the correct answer rate. Results: The results for the high-accuracy group showed that the left inferior frontal gyrus was activated during spatialdesign tasks. In contrast, the findings for the low-accuracy group revealed that the left middle occipital gyrus was activatedfor processing visual information. Conclusion: The findings suggest that the frontal lobe plays a role in allowing landscape designers to make planar tocross-sectional inferences via mental rotations and categorical spatial relations. The findings offer implications forlandscape designers in stimulating the frontal lobe and enhancing their design capabilities.