펄디난드 이. 바우터스타
(Doctor Couse-Pusan National Univ. Research of RIIT-PNU)
,
박이근
(Researcher of RIIT, Pusan National Univ.)
,
임종철
(Dept. of Civil Engrg., Pusan National Univ.)
,
이영남
(Research & Dev't Department, Hyundai Construction)
개착식 터널라이닝의 파괴 원인은 물리적 요인과 공학적 요인으로 나눌 수 있다. 물리적 요인으로서는 재료특성, 보강재 부식 등이 있으며, 공학적 요인은 수압과 교통진동 등이 있다. 본 연구에서는 공학적 요인 중 부가하중 즉, 공사를 완료한 뒤에 라이닝의 변형 및 파괴를 유발하는 증가 토압에 초점이 맞추어져 있다. 증가 토압은 되메움토의 다짐 불량, 자중 및 강우에 의한 침하, 교통하중에 의한 진동 등이 원인이 되어 발생한다. 본 연구는 모래 지반에 $1.0D{\sim}1.50D$ 깊이에 개착식으로 시공하는 원형의 강성 터널에 작용하는 토압에 관한 것으로 진동다짐의 영향을 모형 실험에서 충분히 반영하기 위하여 100Hz의 진동주파수를 사용하였다. 본 연구에서는 개착식 터널 라이닝에 작용하는 토압과 주변 지반의 변형 양상을 파악하고 기존 토압 계산공식을 검토하기 위해 실내 터널모형실험을 실시하였으며, 개착식 터널 라이닝에 작용하는 측정 토압과 토압공식에 의해 산출한 토압을 비교 분석하여 기존 공식에 대한 안전율을 제시하였다.
개착식 터널라이닝의 파괴 원인은 물리적 요인과 공학적 요인으로 나눌 수 있다. 물리적 요인으로서는 재료특성, 보강재 부식 등이 있으며, 공학적 요인은 수압과 교통진동 등이 있다. 본 연구에서는 공학적 요인 중 부가하중 즉, 공사를 완료한 뒤에 라이닝의 변형 및 파괴를 유발하는 증가 토압에 초점이 맞추어져 있다. 증가 토압은 되메움토의 다짐 불량, 자중 및 강우에 의한 침하, 교통하중에 의한 진동 등이 원인이 되어 발생한다. 본 연구는 모래 지반에 $1.0D{\sim}1.50D$ 깊이에 개착식으로 시공하는 원형의 강성 터널에 작용하는 토압에 관한 것으로 진동다짐의 영향을 모형 실험에서 충분히 반영하기 위하여 100Hz의 진동주파수를 사용하였다. 본 연구에서는 개착식 터널 라이닝에 작용하는 토압과 주변 지반의 변형 양상을 파악하고 기존 토압 계산공식을 검토하기 위해 실내 터널모형실험을 실시하였으며, 개착식 터널 라이닝에 작용하는 측정 토압과 토압공식에 의해 산출한 토압을 비교 분석하여 기존 공식에 대한 안전율을 제시하였다.
Damage of cut-and-cover tunnel lining can be attributed to physical and mechanical factors. Physical factors include material property, reinforcement corrosion, etc. while mechanical factors include underground water pressure, vehicle loads, etc. This study is limited to the modeling of rigid circul...
Damage of cut-and-cover tunnel lining can be attributed to physical and mechanical factors. Physical factors include material property, reinforcement corrosion, etc. while mechanical factors include underground water pressure, vehicle loads, etc. This study is limited to the modeling of rigid circular cut and cover tunnel constructed at a depth of $1.0{\sim}1.5D$ in loose sandy ground and subjected to a vibration frequency of 100 Hz. In this study, only damages due to mechanical factors in the form of additional loads were considered. Among the different types of additional, excessive earth pressure acting on the cut-and-cover tunnel lining is considered as one of the major factors that induce deformation and damage of tunnels after the construction is completed. Excessive earth pressure may be attributed to insufficient compaction, consolidation due to self-weight of backfill soil, precipitation and vibration caused by traffic. Laboratory tunnel model tests were performed in order to determine the earth pressure acting on the tunnel lining and to investigate the applicability of existing earth pressure formulas. Based on the difference in the monitored and computed earth pressure, a factor of safety was recommended. Soil deformation mechanism around the tunnel was also presented using the picture analysis method.
Damage of cut-and-cover tunnel lining can be attributed to physical and mechanical factors. Physical factors include material property, reinforcement corrosion, etc. while mechanical factors include underground water pressure, vehicle loads, etc. This study is limited to the modeling of rigid circular cut and cover tunnel constructed at a depth of $1.0{\sim}1.5D$ in loose sandy ground and subjected to a vibration frequency of 100 Hz. In this study, only damages due to mechanical factors in the form of additional loads were considered. Among the different types of additional, excessive earth pressure acting on the cut-and-cover tunnel lining is considered as one of the major factors that induce deformation and damage of tunnels after the construction is completed. Excessive earth pressure may be attributed to insufficient compaction, consolidation due to self-weight of backfill soil, precipitation and vibration caused by traffic. Laboratory tunnel model tests were performed in order to determine the earth pressure acting on the tunnel lining and to investigate the applicability of existing earth pressure formulas. Based on the difference in the monitored and computed earth pressure, a factor of safety was recommended. Soil deformation mechanism around the tunnel was also presented using the picture analysis method.
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가설 설정
(a) Existing earth pressure formulas has the tendency to underestimate the earth pressure acting on the tunnel lining.
제안 방법
3.4.1.2 Model Tests with Varying Slope Roughness To determine the effect of slope roughness on the soil behaviour, earth pressure and other geometric factors, 2 types of sand paper (#100 and #400) and acetate were used to model the roughness of the slope surface.
During the preliminary tests, frequencies of 50 Hz, 75 Hz and 100 Hz were used at various duration of time. A frequency of 100 Hz with a vibration period of 10 minutes was selected from the preliminary test since at this frequency up to a period of about 10 minutes there was a rapid increase in density.
At a constant drop height the density of sand will also vary with the speed of sand drop. In order to determine the variation of sand density with the drop height and speed of drop height, Sand Drop Height Density Test and Sand Drop Velocity Density Test were performed. The variation of the density of J나munjin Standard Sand with the drop height and drop velocity is shown below.
In this study, a bi-directional load cell was installed on each segment of the 8-segment transverse tunnel model to monitor the earth pressure. The surface of the bi-directional load cell is covered with Sandpaper #100 (Refer to Photo 2 and Photo 3).
5 and Photo 7, the control box houses the analog frequency controller, timer and automatic shutdown switch. Since the exact frequency and vibration time can be accurately controlled, the tests in this study were performed at uniform condition.
, 2002), clays (Britto, 1979) and other materials like aluminum rods (Yuasa, 1988) were used. Tests were performed either in soil tanks of different shapes and sizes or in tests pits. In most cases rectangular soil tanks were 나sed (Adachi et al.
The surface of the bi-directional load cell is covered with Sandpaper #100 (Refer to Photo 2 and Photo 3). The correction coefficient test was performed in order to determine whether there is coupling effect on the vertical and horizontal direction of the load cell. Based on the test result, the correction coefficient was determined and was applied to the test results obtained from the tunnel model test.
The earth pressures around the tunnel (1.0D-100, 1.5D-100, 1.5D-400 & 1.5D-ACE) were monitored, compared and analyzed. The monitored earth press니re for each test was compared with the computed earth pressure using Terzaghi*s Earth Pressure Formula, Bierbaumer's Formula, Marston- Spangler's Ditch Type and Projecting Type Formula and Terzaghi's Modified Earth Pressure Formula.
5D-ACE) were monitored, compared and analyzed. The monitored earth press니re for each test was compared with the computed earth pressure using Terzaghi*s Earth Pressure Formula, Bierbaumer's Formula, Marston- Spangler's Ditch Type and Projecting Type Formula and Terzaghi's Modified Earth Pressure Formula. The ratio between the monitored and computed earth pressure will serve as the factor of safety to be used in the earth pressure computation for tunnel lining design of a Cut and Cover Tunnel.
대상 데이터
10 mm stainless steel at a scale of 1:20. It has a diameter (D) of 180 mm and is made of 8 segments. The bi-directional load cell is installed on each segment in order to measure the earth pressure acting on the crown, shoulder and sides of the tunnel.
The plane strain soil tank used in this study has an internal dimension of 720 mm (H) x 1490 mm (L) x 400 mm (W) and an internal volume of V = 0.429m3. The soil tank is supported by 2 springs and 4 braces.
The transverse tunnel model used in this study is made of 10 mm stainless steel at a scale of 1:20. It has a diameter (D) of 180 mm and is made of 8 segments.
데이터처리
The correction coefficient test was performed in order to determine whether there is coupling effect on the vertical and horizontal direction of the load cell. Based on the test result, the correction coefficient was determined and was applied to the test results obtained from the tunnel model test. It can be seen in Fig.
이론/모형
Due to these reasons there is a necessity to investigate the earth pressure acting on the cut and cover tunnel lining. Earth pressure monitored from the laboratory model tests was compared with earth pressure computed using Terzaghi (1956), Bierbaumer (1913), Marston-Spangler's Ditch and Projecting Type (Spangler, 1948) and Terzaghi's Modified Earth Pressure Formula in order to determine the most appropriate earth pressure computation method. Depending on the earth pressure method, a factor of safety was recommended and the behaviour of soil around the tunnel was investigated.
(1992), was used to analyze the behaviour of soil around the tunnel based on the pictures taken before and after vibration. The picture taken during the laboratory model test was interpreted using Micro station and analyzed using Deformation Analysis for Laboratory model Test introduced - DALT (Park 2003). Through this analysis the soil behaviour was determined.
tunnel. The pictures were interpreted using Micro station and analyzed using the DALT (Park, 2003).
성능/효과
time. A frequency of 100 Hz with a vibration period of 10 minutes was selected from the preliminary test since at this frequency up to a period of about 10 minutes there was a rapid increase in density. After a period of 10 minutes the increase in density was very minimal and becomes constant.
3 and Photo 4. In this study the 90~95% compaction which is implemented in the field was not considered in order to obtain a large range of soil density variation.
17 (b) shows the redrawn contour diagram. It was determined from these tests that the soil displacement behaviour is also similar to the displace ment mechanism of Marston-Spari읺er s Pr이 ecting Type earth pressure theory regardless of the slope roughness and soil cover.
참고문헌 (19)
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김상윤 (2004), 개착식 터널의 라이닝에 작용하는 토압의 산정 및 경감대책에 관한 실험적 연구, 부산대학교 석사학위논문
김은섭, 이상덕 (1999), '지하 박스구조물에 작용하는 토압에 관한 실험적 연구', 한국지반공학회논문집, 제 15권, 제 6호, pp.235-246
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Britto, A. M. (1979), Thin walled buried pipes, Doctorate Course Thesis, University of Cambridge
Komiya, K., Shimizu, E., Watanabe, T. and Kodama, N. (2000), 'Earth pressure exerted on tunnels due to the subsidence of sandy ground', Geotechnical Aspect of Underground Construction in Soft Ground, Balkema, Rotterdam, pp.397-402
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Nakai, T. and Zang, F. (1999), 'Numerical simulation of excavation simulation in model tunnels', 34th Soil Engineering Conference, pp.622-623
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Terzaghi, K. (1956), Theoretical Soil Mechanics, John Wiley & Sons, Inc., pp.69-76
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