이상덕 이용준 2011-02 11716 https://aurora.ajou.ac.kr/handle/2018.oak/9891 학위논문(박사)--아주대학교 일반대학원 :건설교통공학과,2011. 2 터널의 기계화 시공은 열악한 건설 환경에서 환경 친화적인 사회적 요구에 따라 적용 빈도가 증가하는 추세이다. 특히 터널과 주변지반의 안정성 확보가 어려운 연약지반에서 저토피로 터널을 굴착할 때에는 기계화 시공의 일종인 쉴드공법이 많이 활용되고 있으며 결과도 매우 성공적이다. 이수가압식 쉴드공법은 이수압을 적정 수준으로 관리하면 사질토에서 특히 우수한 적용성을 보이지만, 적정 이수압보다 낮은 이수가압은 이수 유출 및 지반변형의 원인이 되기도 한다. 따라서 이수가압식 쉴드공법에서는 초기 막장압보다 큰 초과 이수압을 가하여 막장의 안정을 유지하고 있다. 그러나 너무 높은 이수압은 전방 지반의 수동 파괴를 유발하므로 이수가압식 쉴드공법에서 이수압 조절은 매우 중요하다. 전방 지반의 수동 파괴 위험성을 배제하고 이수압을 증가시키는 방법으로 막장 전방에 수평 차수층을 설치하는 방안이 있으나 그 위치와 규모 및 효과가 잘 알려져 있지 않다. 따라서 본 연구에서는 포화된 사질토에서 막장 전방에 차수 그라우팅을 적용할 경우에 발생하는 효과를 규명하기 위하여 2차원 모형실험을 실시하였다. 실험에서는 차수층의 위치와 길이를 변화시키면서 이수의 유출이나 지반 파괴 이전까지 이수압을 가하여 최대 이수압과 지반 변위 및 이수의 유출로 인한 파괴 형상을 측정하여 분석하였다. 또한 이수압 증가 시 지반 내에서 발생하는 물의 흐름을 확인하기 위하여 침투류 해석을 실시하였다. 모형실험을 위하여 챔버 내부 이수압의 조절과 측정이 가능한 2차원 모형 쉴드 실험기(1.2m×1.2m×0.5m, L×H×W)를 제작하고, 토피고(H=0.5D∼2.0D)와 전방 차수층의 높이(S=0.5D∼1.5D) 및 길이(L=0.5D∼2.0D)를 변화시키면서 실험을 수행하였다. 침투류 해석에서는 이수 침투로 인한 막장 전방 지반 내의 간극수 흐름을 확인하기 위하여 초과 이수압과 동일한 위치수두를 적용하여 막장 전방으로 물의 흐름이 발생하도록 하였다. 예비실험으로 실시한 초기 막장압 실험 결과, 초기 막장은 주동상태였으며 예비실험에서 측정된 막장압은 이론값과 매우 유사하였다. 이수가압 실험 결과, 전방 차수층이 없는 경우에 최대 이수압과 초과 이수압은 토피고에 선형비례하였으며, 전방에 차수층이 존재하는 경우에는 차수층이 없는 경우보다 이수압을 크게 가할 수 있어서 전방 차수층이 막장 안정성을 증대시킬 수 있다는 것을 확인할 수 있었다. 막장 안정성 증대에 가장 큰 영향을 주는 적정 차수 그라우트 층의 규격은 길이 1.0∼1.5D, 설치높이 1.0D로 나타났다. 초기 막장압 대비 최대 이수압의 비로 막장의 자립 안전율()을 제안할 수 있으며, 전방 차수층을 적정 위치에 설치할 경우 초기 막장압보다 3.5∼4.0배 크게 이수압을 가할 수 있는 것으로 나타났다. 또한 모형실험과 동일 조건으로 수행한 2차원 침투류 해석 결과의 흐름 벡터와 압력 분포로부터 천단 이수 유출 현상과 이수의 수평 확산 경향을 설명하였으며 차수층의 간극수 흐름 방해 현상을 확인할 수 있었다. 제 1 장 서 론 1 1.1 연구 배경 1 1.2 연구 동향 2 1.3 연구 목적 및 필요성 3 1.4 연구 내용 및 범위 4 제 2 장 이론적 배경 6 2.1 터널의 기계화 시공 6 2.1.1 기계화 시공법의 발달 6 2.1.2 기계화 시공법의 정의 7 2.1.3 기계화 시공법의 분류 8 2.1.4 터널 굴착 공법의 선정 9 2.2 이수가압식 쉴드공법 11 2.2.1 공법의 특징 11 2.2.2 적용 지반조건 11 2.2.3 쉴드공법 적용 시 차수 그라우팅 기술 11 2.3 기본이론 14 2.3.1 내적 안정 모델(Internal Stability Model) 14 2.3.2 외적 안정 모델(External Stability Model) 16 2.3.3 지지매개체 손상 모델(Loss of Support Medium) 24 2.4 경험 막장압 28 2.5 이수가압 시 막장면 거동 29 2.6 쉴드 굴진 시 지표침하 31 제 3 장 모형실험 32 3.1 개요 32 3.2 모형지반 33 3.2.1 사질토 33 3.2.2 차수층(불투수 Seam층) 36 3.2.3 이수(슬러리) 38 3.3 예비실험(초기 막장압 측정) 39 3.3.1 초기 막장압 측정 실험기 39 3.3.2 실험 변수 42 3.3.3 실험 방법 44 3.4 이수가압 모형 실험 48 3.4.1 이수가압 모형 실험기 48 3.4.2 실험 변수 51 3.4.3 실험 방법 60 제 4 장 실험 결과 및 분석 65 4.1 예비실험 결과(초기 막장압 측정) 65 4.1.1 실험 결과 및 분석 65 4.1.2 이론 초기 막장압과의 비교 67 4.2 이수가압 실험 70 4.2.1 서 론 70 4.2.2 사질토 73 4.2.3 전방 차수층을 포함하는 사질토 80 제 5 장 수치해석 107 5.1 수치해석 조건 및 방법 107 5.1.1 침투류 해석의 기본이론 107 5.1.2 적용 물성치 및 해석 조건 110 5.2 해석 결과 및 분석 114 5.2.1 비교 실험 침투류 해석 114 5.2.2 차수층의 영향 검토 침투류 해석 116 5.2.3 막장면과의 이격거리 영향 검토 침투류 해석 131 5.3 해석 결론 135 제 6 장 결 론 136 참 고 문 헌 139 부 록 A. 예비실험 (초기 막장압 측정) 143 B. 이수가압 실험 (비교군) 144 C. 이수가압 실험 (Seam층의 위치, 크기 변수) 148 D. 이수가압 실험 (Seam층과 막장의 이격거리 변수) 174 E. 이수가압 실험 사진 179 F. 침투류 해석 결과도 214 Abstract 234|- List of Figures - <Fig. 2.1> NATM and TBM(slurry or EPB shield) method modelling and shape of section 8 <Fig. 2.2> Flowchart of choosing tunnel excavation method 10 <Fig. 2.3> Ranges of grain size distribution where use of slurry shields is possible or difficult (Krause, 1987) 12 <Fig. 2.4> Forces included in the Micro-stability analysis 15 <Fig. 2.5> Unsupported opening in vertical hold (Broms & Bennemark., 1967) 17 <Fig. 2.6> Schmatisation of partially unlined tunnel 18 <Fig. 2.7> Conical failure mechanisms 18 <Fig. 2.8> Circular and spherical failure mechanisms 19 <Fig. 2.9> Log-spiral shaped sliding wedge 20 <Fig. 2.10> Wedge and silo model 21 <Fig. 2.11> Three-dimensional earth pressure coefficient obtained by Jancsecz & Steiner 21 <Fig. 2.12> Minimum for stability on the tunnel face (after Kovari, 1994) 23 <Fig. 2.13> Change of safety rate according to slope () 24 <Fig. 2.14> Blow-out model including friction at boundaries 25 <Fig. 2.15> Balthaus model for the safety against blow-out 26 <Fig. 2.16> Three cases of slurry in&#64257;ltration (M&uuml;ller, 1977) 30 <Fig. 2.17> Reliable mechanism to tunnel face of EPB shields 30 <Fig. 3.1> Grain size distribution 33 <Fig. 3.2> Result of direct shear test 35 <Fig. 3.3> Liquid limit test 36 <Fig. 3.4> Grain size distribution 37 <Fig. 3.5> Specification of initial tunnel face pressure measuring device 39 <Fig. 3.6> Front panel 40 <Fig. 3.7> Load-cell 40 <Fig. 3.8> Reaction force system 40 <Fig. 3.9> Loading plate 40 <Fig. 3.10> Loading system 40 <Fig. 3.11> Device of initial tunnel face pressure measuring tests 41 <Fig. 3.12> Case of the tunnel face pressure measuring tests 42 <Fig. 3.13> Procedure of the tunnel face pressure measuring tests 45 <Fig. 3.14> Connection of the tunnel face pressure measuring device and lower ground composition 46 <Fig. 3.15> Ground composition by stages 46 <Fig. 3.16> Ground composition extend to depth of the test 47 <Fig. 3.17> Loading by stages 47 <Fig. 3.18> Front view of slurry pressure testing mockup 48 <Fig. 3.19> Shield model 49 <Fig. 3.20> Shield model overview 49 <Fig. 3.21> Section A-A' 49 <Fig. 3.22> Measuring device of slurry pressure tests 50 <Fig. 3.23> Slurry pressure measuring tests(depth of cover=1.0D) 52 <Fig. 3.24> Slurry pressure measuring tests(depth of cover=1.5D) 53 <Fig. 3.25> Slurry pressure measuring tests(depth of cover=2.0D) 55 <Fig. 3.26> Slurry pressure measuring tests(pure sandy ground) 56 <Fig. 3.27> Slurry pressure measuring tests by tunnel face apart distance 59 <Fig. 3.28> Procedure of earth pressure testing 61 <Fig. 3.29> Ground preparation composition 61 <Fig. 3.30> Composition of clayer seam layer 62 <Fig. 3.31> Ground preparation and installation of measurement device 62 <Fig. 3.32> Slurry injection in chamber 63 <Fig. 3.33> Retreat of front panel 63 <Fig. 3.34> Slurry pressure loading and measurement 64 <Fig. 4.1> Initial tunnel face pressure according to the depth of cover 66 <Fig. 4.2> Schematic of tunnel face pressure acting circular section 67 <Fig. 4.3> Comparison with the initial tunnel face pressure (experiment vs. theory) 69 <Fig. 4.4> Macrography of slurry out-flow(H20S00L00) 71 <Fig. 4.5> Maximum slurry pressure according to the depth of cover 73 <Fig. 4.6> Surface displacement in the maximum slurry pressure(S00L00) 75 <Fig. 4.7> Surface outflow of slurry(H05S00L00) 75 <Fig. 4.8> Surface outflow of slurry(H10S00L00) 76 <Fig. 4.9> Surface outflow of slurry in excess maximum slurry pressure (H10S00L00) 76 <Fig. 4.10> Slurry seepage in the ground and surface displacement 77 <Fig. 4.11> Distribution of the tunnel face pressure 79 <Fig. 4.12> Maximum slurry pressure according to size of seam(H10S05) 81 <Fig. 4.13> Surface displacement in the maximum slurry pressure(H10S05) 81 <Fig. 4.14> Increase of slurry pressure according to size of seam(H10S05) 82 <Fig. 4.15> Deformation of seam layer and state of slurry outflow(H10S05) 83 <Fig. 4.16> Maximum slurry pressure according to size of seam(H15S05) 84 <Fig. 4.17> Surface displacement in the maximum slurry pressure(H15S05) 84 <Fig. 4.18> Increase of slurry pressure according to size of seam(H15S05) 85 <Fig. 4.19> Deformation of seam layer and state of slurry outflow(H15S05) 86 <Fig. 4.20> Maximum slurry pressure according to size of seam(H15S10) 87 <Fig. 4.21> Surface displacement in the maximum slurry pressure(H15S10) 88 <Fig. 4.22> Increase of slurry pressure according to size of seam(H15S10) 88 <Fig. 4.23> Deformation of seam layer and state of slurry outflow(H15S10) 89 <Fig. 4.24> Maximum slurry pressure according to size of seam(H20S05) 90 <Fig. 4.25> Surface displacement in the maximum slurry pressure(H20S05) 91 <Fig. 4.26> Increase of slurry pressure according to size of seam(H20S05) 91 <Fig. 4.27> Deformation of seam layer and state of slurry outflow(H20S05) 92 <Fig. 4.28> Maximum slurry pressure according to size of seam(H20S10) 93 <Fig. 4.29> Surface displacement in the maximum slurry pressure(H20S10) 94 <Fig. 4.30> Increase of slurry pressure according to size of seam(H20S10) 94 <Fig. 4.31> Deformation of seam layer and state of slurry outflow(H20S10) 95 <Fig. 4.32> Maximum slurry pressure according to size of seam(H20S15) 96 <Fig. 4.33> Surface displacement in the maximum slurry pressure(H20S15) 97 <Fig. 4.33> Surface displacement in the maximum slurry pressure(H20S15) 97 <Fig. 4.35> Deformation of seam layer and state of slurry outflow(H20S15) 98 <Fig. 4.36> Increase the maximum slurry pressure(sandy ground based) 99 <Fig. 4.37> Range of maximum slurry pressure 100 <Fig. 4.38> Distribution increase rate of maximum slurry pressure 101 <Fig. 4.39> Increase slurry pressure according to distance seam layer and tunnel face (H15S05) 103 <Fig. 4.40> Maximum slurry pressure according to distance seam layer and tunnel face (H15S05) 104 <Fig. 4.41> Maximum increase rate of slurry pressure according to distance seam layer and tunnel face 104 <Fig. 4.42> Distribution increase rate of maximum slurry pressure 105 <Fig. 4.43> Maximum slurry pressure by departed distance of seam layer and tunnel face 106 <Fig. 5.1> Results of seepage analysis on comparison tests 115 <Fig. 5.2> Results of seepage analysis (H10S05) 117 <Fig. 5.3> Results of seepage analysis (H15S05) 119 <Fig. 5.4> Results of seepage analysis (H15S10) 121 <Fig. 5.5> Results of seepage analysis (H20S05) 123 <Fig. 5.6> Results of seepage analysis (H20S10) 126 <Fig. 5.7> Results of seepage analysis (H20S15) 129 <Fig. 5.8> Results of seepage analysis (H15S05G) 133 |- List of Tables - <Table 2.1> Classification of mechanized tunnelling method (ITA Working Group, 2000) 9 <Table 2.2> Classification of the grouting method on surface 13 <Table 2.3> Overview of stability models (DUP science, 2001) 16 <Table 2.4> Support pressure used in several Japanese tunnelling projects (slurry supported) 28 <Table 3.1> Unit weight and water content of sandy ground 33 <Table 3.2> Results of grain size distribution test 33 <Table 3.3> Results of specific gravity tests in sandy ground 34 <Table 3.4> Properties of test in sandy ground 34 <Table 3.5> Quantitative symbol of coarse-grained soil 34 <Table 3.6> Results of direct shear test 35 <Table 3.7> Properties of sandy ground 36 <Table 3.8> Plasticity characteristics of clayey seam layers 36 <Table 3.9> Results of grain size distribution test 37 <Table 3.10> Properties of clayey seam layer 38 <Table 3.11> Properties of bentonite used for test 38 <Table 3.12> Loading step 40 <Table 3.13> Device for initial tunnel face pressure measurement 41 <Table 3.14> Case of the tunnel face pressure measuring tests 43 <Table 3.15> Device for slurry pressure tests 50 <Table 3.16> Comparative specification of frontal impermeable layer 51 <Table 3.17> Experiment variable(including clayer seam layer) 52 <Table 3.18> Experiment variable(pure sandy ground) 56 <Table 3.19> Case of slurry pressure measuring tests according to height and length of seam layer 57 <Table 3.20> Case of slurry pressure measuring tests according to tunnel face apart distance 59 <Table 4.1> Variable of initial tunnel face pressure measuring model tests 65 <Table 4.2> Results of initial tunnel face pressure measuring model tests (load, kgf) 66 <Table 4.3> Results of initial tunnel face pressure measuring model tests (pressure, kPa) 66 <Table 4.4> Prerequisite of initial face support pressure in theory 68 <Table 4.5> Comparisons of initial face support pressure (model test / calculation of theory, kPa) 68 <Table 4.6> Initial face support pressure with overburden (closed form solutions considering active earth pressure) 72 <Table 4.7> Analysis of initial face support pressure with depth (closed form solutions considering active earth pressure) 78 <Table 5.1> Analysis condition 110 <Table 5.2> Permeability of the numerical analysis 110 <Table 5.3> Position head of the numerical analysis 111 <Table 5.4> Steps of numerical analysis 111 <Table 5.5> Case of numerical analysis on slurry pressure measuring tests (pure sandy ground) 112 <Table 5.6> Case of numerical analysis on slurry pressure measuring tests (including clayer seam layer) 112 <Table 5.7> Case of numerical analysis on slurry pressure measuring tests according to tunnel face apart distance 113 kor The Graduate School, Ajou University 아주대학교 논문은 저작권에 의해 보호받습니다. 포화 사질토에서 전방 차수층이 쉴드터널 초과 이수압에 미치는 영향 Lee Yong Jun Thesis 아주대학교 일반대학원 Lee Yong Jun 일반대학원 건설교통공학과 2011. 2 Master http://dcoll.ajou.ac.kr:9080/dcollection/jsp/common/DcLoOrgPer.jsp?sItemId=000000011716 이수가압식 쉴드 초기 막장압 최대 이수압 초과 이수압 차수층 The demand for the application of the mechanized tunnelling method has been increased because of its environment-friendly construction conditions. It could be successfully applied to excavate a shallow tunnel in a soft ground where it is extremely difficult to secure the stability of the tunnel and the environments. Slurry type shield would be very effective for the tunnelling in a sandy ground, when the slurry pressure would be properly adjusted. Low slurry pressure could cause a tunnel face failure or a ground settlement in front of the tunnel face. Thus, the stability of tunnel face could be maintained by applying an excess slurry pressure that is larger than the active earth pressure of tunnel face. However, the slurry pressure should be increased properly since an excessively high slurry pressure could cause the passive failure of the frontal ground. It is possible to apply the high slurry pressure without passive failure if a horizontal impermeable layer is located in the ground in front of the tunnel face, but its location, size, and effects are not clearly known yet. In this research, two-dimensional model tests were carried out in order to find out the effect of a horizontal impermeable layer for the slurry shield tunnelling in a saturated sandy ground. In tests slurry pressure was increased until the slurry flowed out of the ground surface or the ground fails. Location and dimension of the impermeable layer were varied. In addition, seepage analyses to check the water flow in the ground were conducted during the slurry pressure was increased. Model tests were carried out in the two-dimensional shield test device (1.2m×1.2m×0.5m, L×H×W), in which the slurry pressure inside the chamber could be controlled. The cover of the tunnel was varied(H=0.5D∼2.0D), and the location and the dimension of the impermeable layer was varied in height S=0.5D∼1.5D, and in length L=0.5D∼2.0D. Seepage analyses were conducted in order to check the pore water flow in the ground in front of the tunnel face in the same potential head as the excess slurry pressure. As results, it was found out that the tunnel face was in an active state, and the earth pressure at the tunnel face in the experiment was very similar to that of the theoretical values. The maximum and the excess slurry pressure in sandy ground were linearly proportional to the cover depth. Larger slurry pressure could be applied to increase the stability of the tunnel face when the impermeable layer was located in the ground above the tunnel crown in front of the tunnel face. The most effective length of the impermeable grouting layer was 1.0∼1.5D, and the location was 1.0D above the crown level. The safety factor F could be suggested as the ratio of the maximum slurry pressure to the active earth pressure at the tunnel face. It could also be suggested that the slurry pressure in the magnitude of 3.5∼4.0 times larger than the active earth pressure at the initial tunnel face could be applied if the impermeable layer was constructed at the optimal location. The flow vector and the pressure distribution showed that slurry flowed out of the crown of tunnel face and the slurry tends to diffuse horizontally, but it could be interrupted by the impermeable layer.