< Previous98 자연,터널그리고 지하공간특별기고다. 직접지급청구권의 발생 범위 및 수급자의 주의사항1) 직접지급청구권의 효력은 직접지급 요청이 발주자에게 도달한 시점을 기준으로 기 당시 시공이 완료된 부분에 대하여 발생하고 요청 이후의 하도급대금에 관하여는 직접지급청구권이 발생하지 않습니다.7)2) 수급자가 발주자의 동의없이 원사업자와의 합의에 따라 변경‧ 추가공사를 한 부분에 대하여는 발주자가 직접지급의무를 부담하지 않는다고 본 사례8)가 있습니다.3) 수급자의 직접지급사유가 발생하기 전에 원사업자의 채권자가 원사업자의 발주자에 대한 공사대금채권을 압류 또는 가압류한 경우 직접지급청구권을 주장할 수 없고, 원사업자의 착오로 수급자들에게 하도급대금을 지급하였다면 오히려 수급자들이 원사업자들의 압류채권자들에게 부당이득으로 반환해야 한다는 판례가 있습니다.9)[사례1 : 당사자들의 합의에 의한 지급약정을 근거로 하도급법 제14조 제1항에 다른 하도급 대금의 직접지급청구권의 발생을 충족하였다고 보기 어렵다고 한 사례]1) 사안도급인인 갑 주식회사, 수급인인 을 주식회사, 하수급업체 대표인 병 주식회사 등이 을 회사의 워크아웃 신청으로 중단되었던 공사를 재개하기 위한 사업약정을 체결하면서 갑 회사가 하수급업자 등에게 하도급대금 등을 직접 지급하기로 하였고, 이에 따라 하수급인인 정 주식회사와 갑 회사, 을 회사가 직접지급 합의서를 작성하였는데, 정 회사가 갑 회사 등을 상대로 하도급대금의 지급을 청구하는 전소를 제기하면서 직접지급 합의서에는 기재되어 있지 않은 을 회사와 변경계약한 증액대금도 함께 지급할 것을 청구하였으나, 법원이 갑 회사가 직접지급 합의서에 따른 최초의 하도급대금만을 지급할 의무가 있음을 전제로 증액대금의 지급약정 등에 관한 정 회사의 주장을 배척하자, 정 회사가 을 회사를 흡수합병한 무 주식회사를 상대로 증액대금의 지급을 구하는 소를 제기한 사안2) 쟁점수급사업자인 원고가 발주자에게 하도급대금의 직접지급을 요청함으로써 원사업자의 하도급대금의 지급의무가 소멸하였는지 여부.7) 대법원 2012. 5. 10. 선고 2010다24176 판결8) 대법원 2018. 6. 15. 선고 2016다229478 판결9) 대법원 2014. 11. 13. 선고 2009다67351 판결Vol. 21, No. 1 99하도급대금의 직접지급청구권에 관하여3) 대법원의 판단전소 소장에 기재된 문언의 내용, 사업약정과 직접지급 합의의 경위와 내용, 증액대금에 관한 변경계약의 경위, 전소에서 증액대금과 관련하여 당사자들이 했던 주장과 이에 관하여 법원이 심리‧ 판단한 내용과 범위, 소제기의 경위, 전소판결에 관한 당사자들의 불복 여부, 정 회사의 진정한 의사와 갑 회사가 인식한 내용 등을 종합적으로 고찰해 보면, 정 회사는 전소에서 사업약정과 지급합의에 기하여 갑 회사가 정 회사에 지급하기로 한 하도급대금을 청구한 것이고, 그것이 동시에 증액대금에 관한 구 하도급거래 공정화에 관한 법률상 직접지급청구권의 발생요건인 같은 법 제14조 제1항 제3호에 따른 직접지급의 요청에 해당한다고 보기는 어렵다.[사례2 : 원사업자의 압류채권자와 수급사업자와의 관계]1) 발생순서① 발주자가 원사업자 을의 100원짜리 도급대금채권에 대하여 원사업자의 채권자 A가 집행채권 40원으로 40원 압류 ② 수급사업자 병의 원사업자 을에 대하여 30원 직접지급청구③ 원사업자의 채권자 B가 집행채권 90원으로 90원 압류사례2 순서도100 자연,터널그리고 지하공간특별기고2) 해결발주자 갑은 ①의 압류에 의하여 묶어둔 40을 제외한 60중 30을 수급채권자 병에게 지급하고 ③의 압류에 의한 나머지 10원도 묶어두어야 합니다. 한편 도급대금채권 중 병에게 지급한 30을 제외한 70에 대하여는 A와 B가 각 40대 90 비율로 나누어 가지게 됩니다. 2.4 건설산업기본법에 의한 직접지급청구권 존부가. 관련규정 : 건설산업기본법 제35조, 동법 시행령 제34조의4, 동법 시행규칙 제29조나. 하도급법과의 관계 및 직접지급청구권 인정여부건설산업기본법상의 하도급 관련 규정은 하도급법이 적용되지 않은 경우에만 적용됩니다.(하도급법 제34조)건설산업기본법 제35조는 발부자가 하수급인에게 공사대금중 상당한 금액을 직접 지급하고 지급채무를 면할 수 있는 것이지, 하수급인이 발주자에게 공사대금을 직접 청구할 수 있는 권리가 보장되는 조항은 아닙니다.2.5 기타 청구근거이 외에도 민간건설공사 표준도급계약 일반조건과 계약예규인 공사계약일반조건(기획재정부 회계예규 제16호)에도 일정한 경우 도급인이 하도급 공사대금을 하수급인에게 직접 지급하도록 하고 있습니다.3. 마치며가. 수급사업자께서는 직접지급청구의 사유가 발생하면 지체하지 말고 직접지급청구권을 적극적으로 행사하길 바랍니다. 나. 분쟁으로 생계를 이어가는 직업이지만, 저의 생계를 위해서 분쟁이 발생하기를 결코 원하지는 않습니다. 건설분쟁없는 대한민국을 기원합니다.[본 기사는 저자 개인의 의견이며 한국터널지하공간학회의 공식입장과는 무관합니다.]Vol. 21, No. 1 101Simplified Failure Mechanism for the Prediction of Tunnel Crown and Excavation Front Displacements1. IntroductionWith over 200km (125miles) of rail and nearly 4million daily passengers Mexico City Metro is one of the world’s largest underground transportation systems. A 25.4km (15.8mi) long route was proposed as part of the expansion project of the Mexico City metro system. The new line (L-12) was planned to pass through 22 new stations between localities Tlahuac and Mixcoac. The 7.7km (4.8mi) long tunnel represents the capital’s first new route in a decade, and service thousands of passengers on a daily basis.Because of Mexico City’s difficult subsoil formation, this project was considered one of the most challenging projects for all fields of engineering, especially for geotechnical engineers. The L-12 was planned to connect Southeast Mexico City to West of Mexico City. The new L-12 was designed to be part underground and part above ground. The underground construction techniques encompassed Tunneling using a TBM (Tunnel Boring Machine) and the NATM (New Austrian Tunneling Method), and cut-and-cover using braced Diaphragm walls. The above ground structures consisted of superficial and elevated sections. The above ground sections were selected to avoid construction and excavation difficulties due to the presence of high plastic clays.This paper presents details regarding Mexico City’s geotechnical aspects including a preliminary crown deformation calculation for a tunnel section using the simplified method for tunnel stability. Although, advanced tools and software such as FLAC3D were implemented during the design phase, for purposes of this paper the discussion has been limited to the simplified design method only.Simplified Failure Mechanism for the Prediction of Tunnel Crown and Excavation Front DisplacementsRozbeh B. MoghaddamGRL EngineersMintae KimTexas Tech University해외전문가기고102 자연,터널그리고 지하공간2. Mexico City Metro SystemWith 195 stations, 12 lines, and approximately 227km (141mi) of route, Mexico City’s Metro system is the second largest in North America and 5th largest in the world, (APTA 2014). The public transportation system Mexico City, added its first Metro system line in 1969 serving 16 stations and ever since it has been expanded based on the City’s population demand. Due to the regional subsidence and the high deformability of Mexico City’s clay layers, the train carts are rubber-tired-based system on rolling pads instead of traditional steel-wheel based system with flanges on steel tracks, (SCT 2016).The Metro construction took place in different historic times in Mexico City starting in 1967. Between 1967 and 1972 lines 1, 2, and 3 were constructed. During these years the 1968 summer Olympics, 1968 Tlatelolco massacre, and the 1970 World Cup were debuted in Mexico. Between 1977 and 1982 expansions to line 3 and the construction of lines 4 and 5 took place. From 1983 to 1985 when the earthquake occurred, lines 1, 2, and 3 were significantly expanded, and the construction of lines 6 and 7 started. On the morning of 19 September 1985, an 8.1 magnitude in the scale of Richter, hit Mexico City. Majority of buildings and streets were significantly damage. Due to its geometry, the Metro underground structures did not suffer major damage proving a safe mean of transportation during the time of crisis in Mexico City. Between 1985 and 1987 and 1988 and 1994 line 7 was completed, and lines 8 and 9 were constructed, respectively. Also, in 1988 a new line referred to as Line A (with fewer stations) was introduced to leverage the eastern suburbs of Mexico City. Between 1994 and 2014, Line B and Line 12 were added to the Mexico City metro system. Each line is identified with color and numbers, and each station has been named after historic figures, locations, and events in Mexico. With 24 stations serving as connecting stations, the Metro system covers the majority of the downtown (El Centro) and suburbs of the city, Figure 1. Line 12 was proposed to connect the west and southwest location of the city to the Mexico City’s southeast. Considering new residential developments in the southeast region, the need for transportation systems other than local bus routes resulted in the planning and design of the Line 12, (SCT 2016). Line 12 was planned to connect the station Mixcoac (an existing station corresponding to the Orange line 7) to a newly planned station, Tlahuac. The route will include three connecting stations with lines 2, 3, and 8 to provide direct access to the north, Center, and east of the city, Figure 1. Vol. 21, No. 1 103Simplified Failure Mechanism for the Prediction of Tunnel Crown and Excavation Front Displacements<Figure 1> Mexico City Underground Map (Retrieved from SCT 2016)3. Mexico City Soil profile and GeologyThe Valley of Mexico (El Valle de Mexico) is located at the southern part of the Mexican plateau with an average altitude of 4650m (15256ft) above sea level. It has the shape of an extended bowl spreading in a 해외전문가기고104 자연,터널그리고 지하공간north-south direction. The Valley is surrounded by the Pachuca range in the north, the Ajusco range in the south, the Sierra Nevada in the east, and the Sierra Madre Occidental in the west. Two mountain ranges known as Guadalupe and Santa Catarina are extending into the basin creating two curtains in the central-north and south of the Valley and Mexico City is located in the middle of these ranges. The lowest elevation in the Valley is approximately 2200m (7220ft) above sea level which is the final destination of many small rivers flowing into the Valley.During a 17th century excavation for the Mexico City’s deep sewage system, a large accumulation of fossils and sediments were encountered. This finding suggested that this path was part of the outlet in the north side of the basin during the early Pleistocene which was blocked by fossils and sediments. In the south a heavy volcanic activity mainly from Popocateptl created another block to the southern outlet, (Zeevaert 1983), explaining the high-water elevation in the valley during the Pleistocene and further clarifying how the deepest part of the Valley was filled with water-transported materials. Furthermore, high water elevation caused the disintegration of andesitic rocks of the surrounding hills represented by accumulation of residual clays, pyroclastic materials, gravel, and sands at the bottom of the basin which created layers of gravel, sand, and silty clays with hundreds of meters in thickness. In the center of Mexico City, the upper surface of these layers is encountered at the depth of approximately 35m (115ft) below the ground surface. Above these layers, fine-grained lake sediments are located which it is believed to be the product of the volcanic effusion containing fine fractions of basaltic lava and very fine water-transported materials. Along with the effusion, steam explosions created dense volcanic clouds containing volcanic ashes which later on came down as rain covering the entire Valley. The volcanic ash decomposed into bentonite clay with approximately 20% of montmorillonite, (Zeevaert 1983). During this process, heavier particles such as volcanic glass were trapped in between fine particle layers forming thick glass layers. At the end of volcanic effusion era and up to present times, a fill largely containing coarse pyroclastic material and residual clays were eroded from surrounding hills and accumulated in the Valley. The result of the above described geological events is the multi-layered subsurface conditions of Mexico City. The Mexico City’s subsoil conditions in the downtown area can be delineated following the description presented by Rosenblueth and Ovando (1991) in one of their research project sites. In general, the subsurface material consists of an archeological deposit extending from the ground surface up to a depth of 6.0m (20ft) followed by 3.0m (10ft) of fine alluvial sediments. From 9.0m (30ft) to 33.0m (108ft) a silty clay deposit is located with an average water content of 300% and a soft to medium consistency. This layer contains numerous sand layers product of the volcanic activity and rains discussed above. A series of Vol. 21, No. 1 105Simplified Failure Mechanism for the Prediction of Tunnel Crown and Excavation Front Displacementscemented sand and silt deposits forms the next layer located between 33.0m (108ft) and 38.0m (125ft) with a water content varying from 10% to 20% and a compactness of dense to very dense. From 38.0m (125ft) to 48.0m (158ft) a lacustrine deposit containing green clayey silt, with an average water content of 200% and medium consistency is encountered. In the middle of this stratum, a well-defined 1.0m (3.30ft) thick white volcanic glass is located. For depths greater than 48.0m (158ft) different alluvial sediments are encountered which becomes coarser and denser with depth.<Figure 2> Mexico City Geotechnical Zones (Retrieved from Santoyo et al. 2004)해외전문가기고106 자연,터널그리고 지하공간Based on the geological events, the urban area of Mexico Valley is traditionally divided in three main geotechnical zones (Marsal and Mazari 1975): Foothills (Zone I), Transition (Zone II) and Lake (Zone III), Figure 2. In the foothills, very compact but heterogeneous volcanic soils and lava are found. These materials contrast with the highly compressible soft soils of the Lake Zone. Generally, in between these Zones, a Transition Zone is found where clayey layers of lacustrine origin alternate with sandy alluvial deposits, Figure 2.Typical soil profile including soil characteristics were presented by Marsal and Mazari (1975), Figure 3. A representative borehole (Pc-28) corresponds to the Lake Zone has been considered to illustrate the Mexico City’s subsurface profile and the water content variation, Figure 3. Three clayey layers are to be distinguished, denominated upper (Formaci(n Arcillosa Superior, FAS), lower (Formaci(n Arcillosa Inferior, FAI) and deep deposits (Dep(sitos Profundos, DP). The FAS are separated from the FAI by a hard layer (Capa Dura, CD), comprising a 3-m (10-ft) thick sandy clayey stratum.<Figure 3> Typical Soil Profile in Mexico City Downtown (Marsal and Mazari, 1975)Vol. 21, No. 1 107Simplified Failure Mechanism for the Prediction of Tunnel Crown and Excavation Front Displacements4. Tunnel Mixcoac DesignFor purposes of this paper and to illustrate the simplified design method, the tunnel corresponding to Mixcoac Station has been selected. Mixcoac station is located in the vicinity Zone I and II which is referred to as the Transition Zone, Figure 2. A common soil profile for this part of Mexico consists of lacustrine clayey layers alternated with sandy alluvial deposits. At the location of the tunnel section highly cemented granular deposits with unit weight of 1.7ton/m3 (106pcf), internal angle of friction of 25° to 28°, a cohesion of 8 to 10ton/m2 (11 to 14psi), and a Young’s modulus of 420 to 1000kg/cm2 (6 to 14ksi) were encountered, Figure 4.<Figure 4> Dimensions of Mixocac Tunnel portalThe tunnel portal was a horseshoe section with a cross diameter, D, of 13.0m (43ft) and height, A, of 13.0m (43ft). The failure mechanism considered for the simplified design approach and the stability of the excavation front consisted of a static analysis to determine the equilibrium at the front of the excavation based on three main failure zones, Figure 5.Next >