Effect of the Earth Pressure Coefficient on the Support System in Jointed Rock Mass

Son, Moorak,Adedokun, Solomon,Hwang, Youngcheol Korean Geo-Environmental Society 2015 한국지반환경공학회논문집 Vol.16 No.2

This paper investigated the magnitude and distribution of earth pressure on the support system in jointed rock mass by considering different earth pressure coefficients, rock types and joint inclination angles. The study mainly focused on the effect of the earth pressure coefficients on the earth pressure. Based on a physical model test (Son & Park, 2014), extended studies were conducted considering rock-structure interactions based on the discrete element method, which can consider the joints characteristics of rock mass. The results showed that the earth pressure was highly influenced by the earth pressure coefficients as well as the rock type and joint inclination angles. The effects of the earth pressure coefficients increased when the rock suffered more weathering and has no joint slide. The test results were also compared with Peck's earth pressure for soil ground, and clearly showed that the earth pressure in jointed rock mass can be greatly different from that in soil ground. This study indicated the earth pressure coefficients considering the rock types and joint inclination angles are important parameters influencing the magnitude and distribution of earth pressure, which should be considered when designing the support systems in jointed rock mass.

Effect of the Earth Pressure Coefficient on the Support System in Jointed Rock Mass

Moorak Son,Solomon Adedokun,Youngcheol Hwang 한국지반환경공학회 2015 한국지반환경공학회논문집 Vol.16 No.2

This paper investigated the magnitude and distribution of earth pressure on the support system in jointed rock mass by considering different earth pressure coefficients, rock types and joint inclination angles. The study mainly focused on the effect of the earth pressure coefficients on the earth pressure. Based on a physical model test (Son & Park, 2014), extended studies were conducted considering rock-structure interactions based on the discrete element method, which can consider the joints characteristics of rock mass. The results showed that the earth pressure was highly influenced by the earth pressure coefficients as well as the rock type and joint inclination angles. The effects of the earth pressure coefficients increased when the rock suffered more weathering and has no joint slide. The test results were also compared with Peck’s earth pressure for soil ground, and clearly showed that the earth pressure in jointed rock mass can be greatly different from that in soil ground. This study indicated the earth pressure coefficients considering the rock types and joint inclination angles are important parameters influencing the magnitude and distribution of earth pressure, which should be considered when designing the support systems in jointed rock mass.

토압 분리형 교대에 작용하는 수평토압 분석

이세희,김미나,조국환 한국철도학회 2018 한국철도학회논문집 Vol.21 No.5

As bridge and tunnel construction comprise a large proportion of railway construction, the importance oftransition zones has increased. In this study, a reinforced segmental retaining wall was constructed to separate abutmentand backfill. This was done by stacking up geosynthetic tubes. At the object field, the earth pressure acting on abutmentwas measured. Accordingly, the distributions of earth pressure and geotechnical properties were derived from the measuredearth pressure. The measured earth pressure and Rankine earth pressure showed a lot of differences, whereas themeasured earth pressure and silo earth pressure appeared similar because the lateral earth pressure decreases non-linearlywith depth. Therefore, the most similar to the measured lateral earth pressure distribution was derived by changingthe geotechnical properties to estimate the silo earth pressure. Using the derived results, the lateral earth pressure actingon a separated abutment is suggested, depending on the space between abutment and backfill.

복합지반 굴착 시 기반암의 깊이와 절리경사에 따라 흙막이벽체에 작용하는 토압

이상덕,배상수 한국지반공학회 2016 한국지반공학회논문집 Vol.32 No.10

Stability of the braced earth wall in the composite ground, which is composed of the jointed base rocks and the soil strata depends on the earth pressure acting on it. In most cases, the earth pressure is calculated by the empirical method, in which base rocks are considered as a soil strata with the shear strength parameters of base rocks. In this case the effect of the joint dips of the jointed base rocks is ignored. Therefore, the calculated earth pressure is smaller than the actual earth pressure. In this study, the magnitude and the distribution of the earth pressure acting on the braced wall in the composite ground depending on the joint dips of the base rocks and the ratio of soil strata and base rocks were experimentally studied. Two dimensional large-scale model tests were conducted in a large scale test facility (height 3.0 m, length 3.0 m and width 0.5 m) by installing 10 supports in a scale of 1/14.5. The test ground was presumed with the base rock ratio of the composite ground of 65%:35% and 50%:50% and with the joint dips for each base rock layer, 0°, 30°, 45° and 60°, respectively. And then finite element analyses were performed in the same condition. As results, the earth pressure on the braced wall increased as the base rock layer’s joint dips became larger. And earth pressure at the rock layer increased as the rock rate became larger. The largest earth pressure was measured when the base rock rate was 50% (R50) and the rock layer's joint dips was 60°. Based on these results, a formular for the calculation of the earth pressure in the composite ground could be suggested. Distribution of earth pressure was idealized in a quadrangular form, in which the magnitude and the position of peak earth pressure depended on the rock ratio and the joint dips.

제주 지역의 지반 특성을 고려한 흙막이벽의 측방토압 적용에 관한 연구 Ⅱ -어스앵커 공법 시공 사례-

김도형,이동욱,김승현,고권문 한국지반신소재학회 2023 한국지반신소재학회 논문집 Vol.22 No.2

This paper describes the comparative results of measured and predicted values for the horizontal displacement of earth retaining wall based on two field cases, in order to evaluate the application of lateral earth pressure to earth retaining wall supported by earth anchor in Jeju. The prediction of lateral earth pressure acting on the earth retaining wall was performed by elasto-plastic analysis using Rankine earth pressure, Hong & Yun lateral earth pressure, Terzaghi & Peck modified lateral earth pressure, and Tschebotarioff lateral earth pressure. As a result, the predicted value of the maximum horizontal displacement for site A was about 10 to 12 times greater than the measured value, and in the case of site B, the predicted value was evaluated as about 9 to 12 times greater than the measured value. That is, both sites showed a similar increase rate in the maximum horizontal displacement by the predicted value compared to the measured value. In all field construction cases, the maximum horizontal displacement by measured values occurred in the sedimentary layer, soft rock layer, and clinker layer, and the horizontal displacement distribution was shown in a trapezoidal shape. The maximum horizontal displacement by the predicted value occurred around the clinker layer, and the horizontal displacement distribution was elliptical. In the ground with a clinker layer, the measured value showed a very different horizontal displacement tendency from the predicted value, because the clinker layer exists in the form of a rock layer and continuous layer. In other words, it is unreasonable to apply the existing prediction method, which is overestimated, because the characteristics of the earth pressure distribution in Jeju show a tendency to be quite different from the predicted earth pressure distribution. Therefore, it is necessary to conduct a research on the lateral earth pressure in the realistic Jeju that can secure more economic efficiency. 본 연구에서는 제주 지역에서 어스앵커로 지지된 흙막이벽의 측방토압 적용을 평가하기 위하여, 2개의 현장 시공 사례를기반으로 수평변위에 대한 계측값과 예측값을 비교하였다. 흙막이벽에 작용하는 측방토압의 예측은 Rankine 토압, Hong & Yun 측방토압, Terzaghi & Peck 수정측방토압, Tschebotarioff 측방토압을 이용하여 탄소성해석을 실시하였다. 그 결과, A현장에 대한 최대 수평변위의 예측값은 계측값에 비하여 약 10배~12배로 화인되었으며, B현장의 경우에는 예측값이 계측값보다약 9배~12배로 평가되었다. 즉, 2개 현장 모두 계측값에 비해 예측값에 의한 최대 수평변위가 유사한 증가율을 보였다. 모든현장 사례에서 계측값에 의한 최대 수평변위는 퇴적층, 연암층 및 클링커층에서 발생하였고, 수평변위 형상은 사다리꼴 형태에나타냈다. 그리고 예측값에 의한 최대 수평변위는 클링커층 주변에서 발생하였으며, 수평변위 형상은 타원형으로 나타났다. 클링커층이 혼재되어 있는 지반에서 계측값이 예측값과 매우 다른 수평변위 경향을 보이는 원인으로는 클링커층이암반층과 연속된 지층의 형태로 존재하기 때문으로 판단되었다. 즉, 예측되는 토압 분포와 상당히 다른 경향을 보이는 제주지역의 토압 분포 특성을 고려하면 과다하게 평가되는 기존의 예측방법을 적용하는 것은 다소 무리가 있을 것으로 판단되기때문에, 보다 경제성을 확보할 수 있는 현실적인 제주 지역의 측방토압에 관한 연구가 수행될 필요가 있다.

Earth pressure on a vertical shaft considering the arching effect in c-𝜙 soil

Lee, In-Mo,Kim, Do-Hoon,Kim, Kyoung-Yul,Lee, Seok-Won Techno-Press 2016 Geomechanics & engineering Vol.11 No.6

A new earth pressure equation considering the arching effect in $c-{\phi}$ soils was proposed for the accurate calculation of earth pressure on circular vertical shafts. The arching effect and the subsequent load recovery phenomenon occurring due to multi-step excavation were quantitatively investigated through laboratory tests. The new earth pressure equation was verified by comparing the test results with the earth pressures predicted by new equation in various soil conditions. Resulting from testing by using multi-step excavation, the arching effect and load recovery were clearly observed. The test results in $c-{\phi}$ soil showed that even a small amount of cohesion can cause the earth pressure to decrease significantly. Therefore, predicting earth pressure without considering such cohesion can lead to overestimation of earth pressure. The test results in various ground conditions demonstrated that the newly proposed equation, which enables consideration of cohesion as appropriate, is the most reliable equation for predicting earth pressure in both ${\phi}$ soil and $c-{\phi}$ soil. The comparison of the theoretical equations with the field data measured on a real construction site also highlighted the best-fitness of the theoretical equation in predicting earth pressure.

제주 지역의 지반 특성을 고려한 흙막이벽의 측방토압 적용에 관한 연구 Ⅰ -스트럿 공법 시공 사례-

김도형,이동욱,최희복,고권문 한국지반신소재학회 2023 한국지반신소재학회 논문집 Vol.22 No.2

This paper describes the comparative results of measured and predicted values for the horizontal displacement of earth retaining wall based on two field cases, In order to examine the application of lateral earth pressure to the earth retaining wall considering the typical ground characteristics (clinker layer) in Jeju. The prediction of the lateral earth pressure causing the horizontal displacement of the retaining wall was performed by elasto-plastic analysis using Rankine earth pressure, Terzaghi & Peck modified lateral earth pressure, and Tschebotarioff lateral earth pressure. As a result, it was confirmed that the maximum horizontal displacement predicted at site A was about 5 times larger than the measured value, and the ground with maximum horizontal displacement occurred by the prediction was found to be the clinker layer. In the case of site B, the predicted value was 4 to 7 times larger than the measured value. In addition, the ground with maximum horizontal displacement and the tendency of horizontal displacement were very different depending on the prediction method. This means that research on lateral earth pressure that can consider regional characteristics needs to be continued, because it is due to the multi-layered ground characteristics of the Jeju area in which bedrock layers and clinker layers are alternately distributed, 본 연구에서는 제주 지역의 대표적인 지반 특성(클링커층)을 고려한 흙막이벽의 측방토압 적용을 고찰하기 위해 2개의 현장사례를 이용하여 수평변위에 대한 계측값과 예측값을 비교하였다. 흙막이벽의 수평변위 발생에 기인하는 측방토압 예측은Rankine 토압, Terzaghi & Peck 수정측방토압, Tschebotarioff 측방토압을 이용하여 탄소성해석을 실시하였다. 그 결과, A현장에서 예측된 최대 수평변위는 계측값에 비하여 약 5배가 큰 것으로 확인되었으며, 예측에 의한 최대 수평변위 발생 지반은클링커층으로 나타났다. 그리고 B현장의 경우에는 예측값이 계측값에 비하여 4배에서 최대 7배까지 크게 나타났으며, 최대수평변위가 발생한 지반과 수평변위 발생 경향은 예측 방법에 따라 매우 다른 경향을 보였다. 이는 암반층과 클링커층이교호되어 분포되는 제주 지역의 다층지반 특성에 기인한 것이라 판단되기 때문에, 지역 특성을 고려할 수 있는 측방토압에관한 연구가 지속될 필요가 있음을 의미한다.

국내 다층지반의 지반물성치 및 토압에 관한 고찰

구자갑,김운학,최정호,유영화,정양규 한경대학교 2004 論文集 Vol.26 No.1

This paper study on soil properties and earth pressure at the domestic multi layer. Reliable predictions of the movement of earth retaining structures and the ground adjacent to the braced walls in urban excavation are often difficult due to many variable factors. Also, Unpredictable behavior of ground and retaining structure due to variation of the above factors may cause considerable damage to the adjacent structures, and cost many of human lives as a results of retaining wall failure. The earth pressure at the retaining walls was measured at total 13 numbers sites and Peck's empirical earth pressures adapted at the design stage. The geotechnical properties by this research was proposed as a preliminary design guide line in urban excavation where controling ground movement and safety assurance of adjacent structure. The earth pressure of rock masses were found to be 70.14% of Peck's earth pressure and the earth pressure of soil were found to be 44.4% of Peck's earth pressure. It is indicated that the design earth pressures of a retaining wall is

Evaluation of the seismic earth pressure for inverted T-shape stiff retaining wall in cohesionless soils via dynamic centrifuge

Jo, Seong-Bae,Ha, Jeong-Gon,Lee, Jin-Sun,Kim, Dong-Soo Elsevier 2017 Soil dynamics and earthquake engineering Vol.92 No.-

<P><B>Abstract</B></P> <P>In the design procedure of a retaining wall, the pseudo-static method has been extensively used and the dynamic earth pressure has been calculated based on force equilibrium using the Mononobe–Okabe method that is an extension of the Coulomb's earth pressure theory. According to the Mononobe–Okabe method, the resultant total dynamic thrust would act at a height of 0.33H. The Seed and Whitman method that is a modification of the Mononobe–Okabe method, suggests that the dynamic thrust would be applied at 0.6H above the base. There is no clear empirical basis for the distribution of the dynamic earth pressure, and recent experimental research studies have shown that the dynamic earth pressure has a triangular shape, and that the dynamic thrust is applied at 0.33H above the base. Moreover, pseudo-static methods do not consider the effects of the inertial force of the wall itself on the structural behavior. Two dynamic centrifuge tests were designed and conducted to evaluate the magnitude and distribution of the dynamic earth pressure and the inertial effect of the wall itself on an inverted, T-shape, stiff retaining wall with a dry medium sand backfill. Results from two sets of dynamic centrifuge experiments show that the dynamic earth pressure has a triangular shape for critical states during the earthquake, and that the inertial force of the wall significantly influences the structural moment. Moreover, the deformation pattern, the rigidity of the retaining wall, and the frequency contents of the input motions cause the phase difference between the wall and the soil. Correspondingly, this phase difference influences the dynamic earth pressure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Distribution of dynamic earth pressures measured by transducers is triangle shape. </LI> <LI> Phase difference depend on deformation, wall rigidity and frequency of input. </LI> <LI> Phase difference between wall and soil influence the dynamic earth pressure. </LI> <LI> Inertial force of the wall should be accounted for when designing cantilever wall. </LI> <LI> Mononobe–Okabe method is an upper bound for coefficient of dynamic earth pressure. </LI> </UL> </P>

Variation of Earth Pressure Acting on the Cut-and-Cover Tunnel Lining due to Geotextile Mat Reinforcement

바우티스타,박이근,임종철,주인곤 한국지반공학회 2007 한국지반공학회논문집 Vol.23 No.3

Excessive earth pressure is one of the major mechanical factors in the deformation and damage of Cut-and-Cover Tunnel lining in shallow tunnels and portals of mountain tunnels (Kim, 2000). Excessive earth pressure may be attributed to insufficient compaction and consolidation of backfill material due to self-weight, precipitation and vibration caused by traffic (Komiya et al., 2000; Taylor et al., 1984; Yoo, 1997). Even though there were a lot of tests performed to determine the earth pressure acting on the tunnel lining, unfortunately there were almost no case histories of studies performed to determine remedial measures that reduce differential settlement and excessive earth pressure. In this study the installation of geotextile mat was selected to reduce the differential settlement and excessive earth pressure acting on the cut-and-cover tunnel lining. In order to determine settlement and earth pressure reduction effect (reinforcement effect) of geotextile mat reinforcement, laboratory tunnel model tests were performed. This study was limited to the modeling of rigid circular cut-and-cover tunnel constructed at a depth of 1.0D~1.5D in loose sandy ground and subjected to a vibration frequency of 100 Hz. Model tests with varying soil cover, mat reinforcement scheme and slope roughness were performed to determine the most effective mat reinforcement scheme. Slope roughness was adjusted by attaching sandpaper #100, #400 and acetate on the cut slope surface. Mat reinforcement effect of each mat reinforcement scheme were presented by the comparison of earth pressure obtained from the unreinforced and mat reinforced model tests. Soil settlement reduction was analyzed and presented using the Picture Analysis Method (Park, 2003).