• Title/Summary/Keyword: geotechnical parameter

Search Result 285, Processing Time 0.028 seconds

Experimental investigation of blocking mechanism for grouting in water-filled karst conduits

  • Zehua Bu;Zhenhao Xu;Dongdong Pan;Haiyan Li;Jie Liu;Zhaofeng Li
    • Geomechanics and Engineering
    • /
    • v.34 no.2
    • /
    • pp.155-171
    • /
    • 2023
  • Aiming at the grouting treatment of water inflow in karst conduits, a visualized experiment system for conduit-type grouting blocking was developed. Through the improved water supply system and grouting system, and the optimized multisource information monitoring system, the real-time observation of diffusion and deposition of slurry, and the data acquisition of pressure and velocity during the whole process of grouting were realized, which breaks through the problem that the monitoring element is easy to fail due to slurry adhesion in conventional test system. Based on the grouting experiments in static and flowing water, the diffusion and deposition behavior of the quick-setting slurry under different working conditions were analyzed. The temporal and spatial variation behavior of the pressure and velocity were studied, and the blocking mechanism of the grouting were further revealed. The results showed that: (1) Under the flowing water condition, the counter-flow diffusion distance of slurry was negatively correlated with the flow water velocity and the volume ratio of cement and sodium silicate (C-S ratio), and positively correlated with the grouting volume. The slurry deposition thickness was negatively correlated with the flowing water velocity, and positively correlated with the grouting volume and C-S ratio. (2) The pressure increased slowly before blocking of the flowing water and rapidly after blocking in karst conduits. (3) With the continuous progress of grouting, the flowing water velocity decreased slowly first, then significantly, and finally tended to be stable. According to the research results, some engineering recommendations were put forward for the grouting treatment of the conduit-type water inflow disaster, which has been successfully applied in the treatment project of the China Resources Cement (Pingnan) Limestone Mine. This study provided some guidance and reference for the parameter optimization of grouting for the treatment projects of water inflow in karst conduits.

Model Tests for Deriving Failure Parameter during Levee Overflow (제방 월류시 붕괴매개변수 도출을 위한 모형실험)

  • Kim, Jin-Man;Cho, Won-Beom;Choi, Bong-Hyuck;Oh, Eun-Ho
    • Journal of the Korean Geosynthetics Society
    • /
    • v.14 no.2
    • /
    • pp.11-21
    • /
    • 2015
  • According to the damage investigation in 2002, the failures of river levee were caused by overflow, erosion, and unstable body conditions due to piping, inappropriate embanking materials, and poor compaction. Especially, overflow was identified as a main reason that induces levee failure by 39.5% from the distribution of failure types. The major parameters, such as levee collapsing angle (${\theta}$), levee collapsing rate (k) affect inundation velocity and area size during the analysis of inundation modeling, however, domestic research effort on this area is still insufficient. In this paper authors conducted levee failure experiments of 4 levee height types, 0.20 m, 0.25 m, 0.30 m, and 0.40 m based on theassumption of Froude Similarity (${\lambda}_{Fr}=1$). As a result, the authors suggested a levee failure mechanism according to the levee heights (H), a collapse extension lengthwhich is around, levee collapse angle (${\theta}$), levee collapse rate (k).

Determination of Deformation Modulus of Rock Mass with Measured Tunnel Displacement (측정된 터널변위에 의한 암반 변형계수의 결정)

  • Park, Jae-Woo;Park, Eun-Gyu;Kim, Gyo-Won
    • The Journal of Engineering Geology
    • /
    • v.17 no.4
    • /
    • pp.655-664
    • /
    • 2007
  • The major geotechnical parameters employed in tunnel design are deformation modulus, Poisson's ratio, friction angle, cohesion, etc. Among these parameters, the deformation modulus is the most significant parameter in tunnel deformation. However, determination of the modulus for rock mass by means of tests is very difficult due to factors affecting including discontinuities and sample size, etc. Thus input values used in the numerical analysis are generally determined by empirical method. A numerical analysis on tunnel was conducted with geotechnical parameters determined through the geological field mapping, laboratory tests, and evaluation of boring data, and some discrepancy between the computed result and tunnel displacements measured was found. Thus, further analyses by changing the deformation modulus of rock mass were performed to determine a relationship between the modulus and computed displacement. Data from two tunnel sites were used to verify the applicability of the proposed method and a correlative equation between deformation modulus and tunnel displacement is proposed. The deformation modulus of rock mass was around 30-40% of young's modulus of intact rock in these cases.

A Quantitative Physical Parameter for Detection of Ultimate Failure State of Soil Using CEL Method in Finite Element Analysis (CEL 기법을 이용한 유한 요소 해석에서 지반의 극한 파괴 상태 감지를 위한 정량적 물리량 기준)

  • Kim, Seongmin;Lee, Ju-Hyung;Jung, Young-Hoon
    • Journal of the Korean Geotechnical Society
    • /
    • v.34 no.12
    • /
    • pp.59-69
    • /
    • 2018
  • In order to use the limit equilibrium theory, it is necessary to find a slip line under the ultimate failure condition. The strength reduction method using the Lagrangian finite element method defines the ultimate failure state at a time when the numerical solution cannot converge within the certain number of the iteration. When the coupled Eulerian-Lagrangian (CEL) method is used, however, such definition is inappropriate because the numerical solution of the CEL method can converge even under the ultimate failure condition. In this study, an objective condition designating the ultimate failure state in the finite element analysis adopting the CEL method was proposed. In the problem of the bearing capacity of the undrained soft ground subjected to the strip footing loading, we found that the rate of the plastic dissipated energy is highly sensitive at the load of the theoretical limit of the ultimate failure state.

Determination of Site Classification Method in the Korean Peninsula Based On NYCDOT2008(2008 New York City DOT Seismic Design Guidelines) (NYCDOT2008 기준을 이용한 국내 지반의 지반분류방법 결정)

  • Kang, Ho-Deok;Kim, Ki-Sang;Sun, Chang-Kuk;Kim, Myung-Mo
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • 2010.03a
    • /
    • pp.777-784
    • /
    • 2010
  • In the current Korean seismic design guide, the site classification and the corresponding site coefficients were determined based on the UBC-1997 (Uniform Building Code). In order to develop the current site classification system, it is important to compare the local site conditions in Korea to other countries which have similar seismic design guides. In the eastern United States, New York City(40degrees 45minutes north latitude, 73degrees 59minutes west longitude) suggested that current design guidelines are unsuitable to shallow bedrock depth sites. So the 3-parameter methods are performed for new criteria in New York City. In this study, site response analyses were performed at 181 study sites using one-dimensional equivalent linear to evaluate the site-specific earthquake ground motions at inland areas in the Korean peninsula and reclassify the results according to similar ground motions using the 3-parameter methods. It is effective that multi-parameter methods for Korean site characteristics in comparison with single parameter method.

  • PDF

Parameter Effect on Elastic Modulus of Discontinuity Rock-mass Based on Homogenization Method (균질화 이론에 근거한 불연속성 암반의 탄성계수에 영향을 미치는 불연속면의 조사 인자에 관한 연구)

  • Baek, Yong
    • Journal of the Korean Geotechnical Society
    • /
    • v.16 no.4
    • /
    • pp.63-70
    • /
    • 2000
  • The quantitative analyses and the mechanical interpretation of discontinuity planes are the most important factor for the study of strength and deformation properties of rock masses containing discontinuity planes. However, the relationship between the factors investigated in the field and the actual mechanical properties of discontinuity planes is not fully understood. The main purpose of this study is to investigate the effects of density, length, and spacing of joints on elastic modulus of rock masses as these values vary. A new parameter which has a direct relation with the elastic modulus of discontinuity planes is also preposed in this study. The combination of finite element methods and homogenization methods has been used for the numerical analyses of a uintcell with discontinuity planes, which is generated using random-number generation methods. The elastic modulus of the discontinuity plane is found from the numerical analyses. The final results propose not only the relation between the investigation parameters of discontinuity planes and the elastic modulus of rock masses but also a new parameter, an effect area ratio having a linear relation with the elastic modulus of rock masses.

  • PDF

Embankment and Excavation Behaviour with Shear Parameters of Soft Clayey Soil in FEM (점성토의 유한요소해석에서 전단파라미터에 따른 성토 및 굴착 거동)

  • Kim, Byung Il;Choi, Chanyong;Hong, Kang Han;Han, Sang Jae
    • Journal of the Korean Geotechnical Society
    • /
    • v.34 no.2
    • /
    • pp.5-17
    • /
    • 2018
  • In this study, the in-situ stress, strength and stress-strain characteristics with shear parameters (UU, CU, ${\bar{CU}}$) are analytically evaluated and the stability analyses are carried out under loading/unloading conditions. The in-situ stress and the stress-strain behaviour may become different according to input shear parameters in finite element analyses with construction step, Especially, if the internal friction angle in Mohr-Coulomb model is set to zero, the in-situ stress and the stress-strain behaviour might not be properly predicted. The results from CU parameter of total stress analysis have no significant difference with the results from CU of effective stress analysis. Therefore, in the numerical analysis for soft ground, CU parameters can be applied to predict in-situ stress and stress-strain behaviors. In addition, the calculation method was proposed to determine the shear parameter of Mohr-Coulomb model, which is corresponding to the shear strength equivalent to that of in-situ soil.

Quantification of Surface Topography Using Digital Image Analysis

  • Lee, Seok-Won
    • Journal of the Korean Geotechnical Society
    • /
    • v.15 no.3
    • /
    • pp.131-149
    • /
    • 1999
  • It was found that surface roughness has a first-order effect on the interface shear strength and accordingly it should be accurately quantified if its role is to be properly understood. To quantify the surface topography, first of all, a variety of commonly used surface roughness parameters and profiling methods were reviewed in this study. Based on this review, the normalized roughness parameter. $R_n$(Uesugi and Kishida, 1986), the profile roughness parameter, $R_L$, and the surface roughness parameter, $R_n$(Dove and Frost, 1996), were selected to be appropriate candidates of roughness parameters and the digital image analysis based Optical Profile Microscopy(OPM) method(Dove and Frost, 1996) to be an appropriate profiling method for this study. Using a smooth and three textured HDPE geomembranes which encompass the range of textures and texture patterns commonly used, a series of roughness measurements on virgin and previously used geomembranes were performed. The results showed that both $R_L\; and\; R_S$ values appropriately reflect the degree of texturing for the geomembranes used in this study, however, $R_n$ value showed limited ranges of variation which may not be sufficient to permit distinction between roughness values for certain conditions. The results of this study will be extended to the investigation of the influence of surface roughness on interface strength in future study.

  • PDF

Experimental Study on the Consolidation Characteristics of Kwang-Yang Clay by Large Block sampling (대형자연시료를 이용한 광양점토의 압밀특성에 관한 실험적 연구)

  • Kim, Jong-Kook;Yu, Seong-Jin;Chae, Young-Su
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • 2005.10a
    • /
    • pp.429-436
    • /
    • 2005
  • In this study, we have compared with the differences between the extent of sampling disturbance and consolidation characteristics by experiments, which are consolidation test and have been performed with Kwang-Yang clay samples. The effects on sampling disturbance to consolidation characteristics of soft clay have been inverstigated by using soil samples obtained from large block sampling and piston sampling methods. Through a few experiments, we've got important results which are that the consoilidation parameter of large block sample(Pc, Cc, Cv) is much larger than the value of parameter of piston sample. We've also found the fact that the large block sample using the large size sampler is much better than piston sample in the quality of goods to lessen the effects on disturbance of sampling. When compared to the parameter of consolidation along with the methods of experiment, we found that the result performed by large size consolidation test is the greatest one and CRS is much better than standard consolidation test to seek for proper parameter.

  • PDF

Significance of seabed interaction on fatigue assessment of steel catenary risers in the touchdown zone

  • Elosta, Hany;Huang, Shan;Incecik, Atilla
    • Structural Engineering and Mechanics
    • /
    • v.57 no.3
    • /
    • pp.403-423
    • /
    • 2016
  • The challenges involved with fatigue damage assessment of steel catenary riser (SCR) in the touchdown zone (TDZ) are primarily due to the non-linear behaviour of the SCR-seabed interaction, considerable uncertainty in SCR-seabed interaction modelling and geotechnical parameters. The issue of fatigue damage induced by the cyclic movements of the SCR with the seabed has acquired prominence with the touch down point (TDP) interaction in the TDZ. Therefore, the SCR-seabed response is critical for reliable estimation of fatigue life in the TDZ. Various design approaches pertaining to the lateral pipe-soil resistance model are discussed. These techniques have been applied in the finite element model that can be used to analyse the lateral SCR-seabed interaction under hydrodynamic loading. This study investigates the sensitivity of fatigue performance to geotechnical parameters through a parametric study. In this study, global analyses are performed to assess the influence of vertical linear seabed springs, the lateral seabed model and the non-linear seabed model, including trench evolution into seabed, seabed normalised stiffness, re-penetration offset parameter and soil suction resistance ratio, on the fatigue life of SCRs in the TDZ.