• Title/Summary/Keyword: limestone cavity

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A design and construction for reinforcement of bridge foundations on the limestone cavities (교량기초를 위한 석회암 공동지반의 지반보강 설계 및 시공)

  • 박종호;최용기;한현희;김태훈;박용원
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.03a
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    • pp.205-212
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    • 2002
  • Carbonate rocks such as limestone are susceptible to solution and show numerous solution cavities. For the construction of the structures such as bridge foundations and tunnel on the limestone cavities, the geological unconformities developed in the bed rocks, cavity systems and the filling types of solution deposits should be surveyed and analyzed. And also, the stability of structures on the limestone cavities must be taken into consideration in the view of the geotechnical engineering. As a result of analysis of the foundation settlement, an economic and effective reinforcement method is to be proposed and the construction by the proposed method is to be accompanied with verification of reinforcement effect. This paper is a case study of design and construction for the reinforcement of bridge foundations on the limestone cavity covered with thick bedded colluvial soils.

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A Study of the Deformation Characteristics in Limestone Cavity Area by Finite Element Method (유한요소해석에 의한 석회암 공동지반의 변형특성에 관한 연구)

  • Chun, Byung-Sik;Park, Hyeong-Jun
    • Journal of the Korean GEO-environmental Society
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    • v.6 no.1
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    • pp.63-72
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    • 2005
  • From the geological and engineering point of view, the limestone is so rigid that it is able to act as a bedrock but if there are some unstable elements which are solubility cavity and cracking zone in the ground, the settlement and bearing capacity of a structure will be required to long-term stability investigations and countermeasures about those problems. When comparing the allowable bearing capacity, the results of Bell's method and the Bowles' method are similar but the results of Hoek-Brown's method are very larger than the others. For weathered limestone, stability is changed by size and depth of the cavity of limestone, but soft and hard rock are stable regardless of size and depth of the cavity.

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The Characteristic of Strength for a Lime Stone in Donghae Area and Harden Cement Milk of Super Injection Grouting (동해 석회암과 SIG 고결체의 강도특성)

  • Park, Young-Ho;Kim, Nak-Young;Hong, Sa-Myun;Yook, Jeong-Hoon;Kim, Ki-Seog
    • Proceedings of the Korean Geotechical Society Conference
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    • 2004.03b
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    • pp.137-145
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    • 2004
  • Limestone zone in korea have been distributed to diagonal line so that it is wide from the Gangwondo to the Jeonlanamdo. The limestone cavity and fractured zone were formed by chemical weathering. Limestone cavity and fractured zone was reinforced with cemented milk(w/c=60%)by high pressure jet grouting by tripple -pipe to establish bridge foundation on the ground condition like limestone cavity. To analyze property of limestone and solid of cement milk(w/c=65%), mixed solid of cement, core NX size in the limestone cavity and fractured zone and compressive strength. Seismic tomograpy exploration was pcrforn1cd to analyze deformation modulus of limestone. The analysis suggests that deformation modulus of limestone has effect on uniaxial compressive strength, seismic velocity, seismic elasticity modulus. Average static elasticity modulus of limestone is $5.08{\times}10^5kgf/cm^2$, cement and coal mixed solid is $0.25{\times}10^5kgf/cm^2$, $0.095{\times}10^5kgf/cm^2$. Average seismic velocity of limestone is 5.240m/sec, cement and coal mixed solid is 2,211.3m/sec, 1,447.5m/sec. Average uniaxial compressive strength of limestone was $1,221.3kgf/cm^2$ and limestone specimen mixed with cement milk and solid of cement milk mixed with coal were $125.22kgf/cm^2$, $35kgf/cm^2$ each other. Average friction angle of limestone was $49.14^{\circ}$ and limestone specimen mixed with cement milk and solid of cement milk mixed with coal were $38.39^{\circ}, 25.83^{\circ}$ each other. Average cohesion of limestone was $137.7kgf/cm^2$ and limestone specimen mixed with cement milk and solid of cement milk mixed with coal were $23.5kgf/cm^2$, $15.5kgf/cm^2$ each other. Average deformation modulus of limestone was $2.84{\times}10^5kgf/cm^2$ and limestone specimen mixed with cement milk and solid of cement milk mixed with coal were $0.4{\times}10^5kgf/cm^2, 0.12{\times}10^5kgf/cm^2$ each other. It was analyzed that the elasticity and uniaxial compressive strength, seismic velocity of solid of cement milk mixed limestone pieces and coal had an highly interrelation regardless of existence of limestones pieces and coal but it had shown that limestones had an lower interrelation. In case of field seismic velocity and deformation of limestone, SIC solid of cement milk mixed with coal and limestone pieces had an highly interrelation.

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Petro-mineralogical and Solubility Characterization in Soluble Rocks (용해성 암석의 용식 진전에 대한 암석-광물학적 특성 연구)

  • 정의진;윤운상;여상진;김정환;이근병;노영욱
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.03a
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    • pp.253-260
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    • 2002
  • Chemical weathering processes related with mineralogical characters and ground water condition are very essential engineering problems in soluble rock masses. Detailed geological mapping were performed and 8 samples were collected from the 2 formations including various rock faces to deduce the possibility of the limestone cavity formation and their mechanism. Petrological descriptions and various petro-mineralogical experiments such as XRD analysis, clay mineral analysis, absorptivity test, impurity analysis were conducted to evaluate the cavity making processes. Laboratory solubility test for rock specimen were also carried out under the strong acid (pH=1) condition. From the experimental data and geological mapping data, it is found that the formation of limestone cavities in limestones are strongly related with geological structures such as beddings, cleavages and the contents of impurities rather than CaCO$_3$contents. In case of dolomites, rock textures, grain size, amounts and types of clay minerals as well as geological structures are major controlling factors of cavity forming processes

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Influence of limestone cavity on tunnel stability (석회암 공동이 터널의 안정에 미치는 영향)

  • Jin, Seong-Kyu;Yang, Moon-Sang;Choi, Deog-Chan;Park, Kwang-Joon
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.4 no.2
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    • pp.113-121
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    • 2002
  • This study is focused on establishing influence zone caused by tunnelling in limestone site. Therefore, the numerical analysis using the FLAC2D was performed considering various locations and magnitudes of cavities. To reduce the stress concentration, the shape of cavities was designed to ellipse. This parametric study reveals that the cavities located at crown part and edge part of tunnel greatly have influenced on stability of tunnel. The effect of distance between tunnel and cavity which is larger than 1-0D (Tunnel diameter) dose not directly related to stability of tunnel, but the nearer a cavity location was, the larger displacement and stress of reinforcement occured within 0.25D.

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A Study on the Failure Cause of Large Scale Rock Slope in Limestone Quarries (석회석 광산에서 발생한 대규모 암반사면의 붕괴원인 분석에 관한 연구)

  • Lee, Sang-Eun;Kim, Hak-Sung;Jang, Yoon-Ho
    • Tunnel and Underground Space
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    • v.24 no.4
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    • pp.255-274
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    • 2014
  • The target of this study is large scale rock slope collapsed by around 7 pm on August, 2012, which is located at ${\bigcirc}{\bigcirc}$ limestone quarries of Gangneung city, Gangwondo. The slope prior to the collapse is formed as the height of about 200 m and the average inclination of $45^{\circ}$. The estimated amount of the collapse is about $1,500,000m^3$ with respect to the slope after the collapse. Geotechnical and field investigations such as boring, geophysical prospecting, surface geological survey, geological lineaments, borehole imaging, metric 3D imaging, experimental and field test, mining work by year, and daily rainfall were performed to find the cause of rock slope failure. Various analyzes using slope mass rating, stereonet projection, limit equilibrium method, continuum and non-continuum model were conducted to check of the stability of the slope. It is expected that the cause of slope failure from the results of various analysis and survey is due to the combined factors such as topography, rainfall, rock type and quality, discontinuities, geo-structural characteristics as the limestone cavity and fault zones, but the failure of slope in case of the analysis without the limestone cavity is not occurred. Safe factor of 0.66 was obtained from continuum analysis of the slope considering the limestone cavity, so the ultimate causes of slope failure is considered to be due to the influence of limestone cavity developed along fault zone.

Analysis of Ground Subsidence on Gyochon Residential Region of Muan City (무안 교촌리주거지역 지반침하 안정성 분석)

  • Han, Kong-Chang;Cheon, Dae-Sung;Ryu, Dong-Woo;Park, Sam-Gyu
    • Tunnel and Underground Space
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    • v.17 no.1 s.66
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    • pp.66-74
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    • 2007
  • The analysis of ground subsidence stability was conducted for the residential area located on the limestone corrosion zone. For the investigation of the cavity distribution in limestone region, various geophysical investigations such as electroresistivity tomography, electromagnetic prospecting are carried out. Geotechnical field tests with drilling are also carried out for the evaluation of the ground characteristics. Based upon their results, numerical modeling is performed for the simulation and prediction of the ground subsidence with the conditions of cavity geometry and groundwater level. The main factor to cause the ground subsidence is estimated as the draw down of the groundwater level below soil overburden, which disturbs the mechanical equilibrium of ground and drives washing away the overburden soil through the cavity and solace subsidence. It seemed that it is essential to maintain the groundwater level continuously above the shallow cavity for the prevention of the ground subsidence on the limestone corrosion zone.

Stability Investigation of a Foundation Located above Limestone Cavities Using Scaled Model Tests (석회암공동 상부 기초의 안정성 검토를 위한 모형실험 연구)

  • Kim, Jong-Woo;Heo, Seok
    • Tunnel and Underground Space
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    • v.26 no.6
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    • pp.493-507
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    • 2016
  • Scaled model tests were performed to investigate the stability of a foundation located above limestone cavities. Cavity shape was assumed to be an ellipse having 1/3 for the ratio of minor to major axis lengths. 12 different test models which have various depths, locations, inclinations, sizes and numbers of cavity were experimented and they were classified into 5 different groups. Crack initiation pressure, maximum pressure, deformation behaviors, failure modes and subsidence profiles of test models were obtained, and then the influences of those parameters on the foundation stability were investigated. No cavity model showed a general shear failure, whereas the models including various cavities showed the complicated three different failure modes which were only punching failure, both punching and shear failures, and double shear failure. The stability of foundation was found to be decreased as the cavity was located at shallower depth, the size and number of cavity were increased. Differential settlements appeared when the cavity was located under the biased part of foundation. Furthermore, subsidence profiles were found to depend on the distribution of underground cavities.

Characteristics of Lime-cavities and Survey Design for Bridge Foundation in the Karst Area (석회 공동의 특성과 카르스트 지역 내 교량 기초를 위한 조사 설계)

  • 윤운상;김학수;최원석
    • Proceedings of the Korean Geotechical Society Conference
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    • 1999.03a
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    • pp.399-406
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    • 1999
  • Recently, the construction of the several highway bridges in the karst area have encountered severe problems associated with cavities and sinkholes. To solve this problems, it is important to understand the distribution characteristics of cavities in the construction site on limestone area. This paper briefly describes the different types, the distribution control factors and the infill sediment types of lime-cavities in the study area, bridge site in the karst area and propose the effective method of survey design. Cavity system may be divided into two main groups, 1)'slot and cave system'and 2)'sinkhole and cave system'. And the shape, the size and the distribution pattern of cavity are controlled by three main factors - rock type, geological structure and ground water condition. Additionally, infill sediment may be considered as one of the important design factors for foundation design and divided into four types by sediment properties. There are geophysical thechnics and geologic survey and drilling test, etc. by the survey method to interpretate characteristics of cavity system, and this methods are optimally designed at the site investigation stage.

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Numerical Investigation on Load Supporting Mechanism of a Pile Constructed above Underground Cavity (공동이 존재하는 암반에 시공된 말뚝기초의 하중지지 메카니즘에 관한 수치해석 연구)

  • Choi, Go-Ny;Yoo, Chung-Sik
    • Journal of the Korean Geotechnical Society
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    • v.27 no.1
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    • pp.5-16
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    • 2011
  • This paper presents the results of a three-dimensional finite element analysis on load supporting mechanism of pile constructed above underground cavity in limestone rock formation. Considering a wide range of cavity conditions, the behavior of pile was studied using the bearing capacity, rock yielding pattern, stress distribution and deformation of pile head and the cavity. The results indicate that the load transfer mechanism of pile, rock yielding pattern and the reduction of bearing capacity of pile significantly vary with the location, size and length of cavity. Based on the results, graphical solutions defining the reduction of the bearing capacity with specific cavity conditions were suggested.