The Experts below are selected from a list of 5184 Experts worldwide ranked by ideXlab platform

Jianxiu Wang - One of the best experts on this subject based on the ideXlab platform.

  • physical model test of transparent soil on coupling effect of cut off wall and pumping wells during foundation Pit dewatering
    Acta Geotechnica, 2019
    Co-Authors: Jianxiu Wang, Xiaotian Liu, Shaoli Liu, Yanfei Zhu, Weiqiang Pan, Jie Zhou
    Abstract:

    Water level is decreased during foundation Pit Excavation to avoid water inrush under confined water pressure. Cut-off wall is often used as waterproof curtain to partially cut off the dewatered aquifer. When a foundation Pit is located in a built-up area and the underlying confined aquifer is not cut off, the drawdown must be minimized outside the Pit to avoid land subsidence in buildings and pipelines. The coupling effect of the cut-off wall and pumping well is used to control the drawdown outside the foundation Pit. However, the coupling mechanism is not intuitively well understood because of the limitations of existing experimental methods. In this study, transparent soil was introduced to model the coupling mechanism in the physical model test. High-purity fused silica and mixed paraffin oil were used as skeleton and fluid to simulate the confined aquifer and groundwater. Industrial solid dye and paraffin oil were used as tracers. A camera was used to collect flow information. Tests were performed for the combinations of cut-off wall and partially penetrating pumping wells. The insertion depth ratio of the cut-off wall most effectively influenced the drawdown. The layout of the pumping wells in horizontal direction influenced water level distribution and flow rate. The optimal depth of the pumping wells was 1–5 m above the bottom of the cut-off wall, and the optimal horizontal distance between the cut-off wall and the pumping wells was 25% of the Pit width. Non-Darcy flow was observed within the range of 0–10 m around the bottom of the cut-off wall. These results were significant in understanding the cut-off wall and pumping well coupling effect on foundation Pit dewatering.

  • numerical study of dewatering in a large deep foundation Pit
    Environmental Earth Sciences, 2013
    Co-Authors: Jianxiu Wang, Bo Feng, Taiping Guo, Guangyun Yang, Junwu Tang
    Abstract:

    During foundation Pit Excavation, groundwater is often the most important factor that affects Pit stability. Dewatering is widely used in Pit Excavation to avoid uplift of Excavation floors due to high water pressure. The characteristics of seepage in small-scale deep foundation Pits of high-rise buildings or in the long narrow foundation Pits of subway stations have been extensively investigated. However, the characteristics of seepage in large-scale deep Excavations have not been studied. This paper investigates the large deep Excavation of the buildings in Oriental Fisherman’s Wharf. The total area of the construction site is 33,917 m2. Single-well and group-well field pumping tests were performed and a numerical simulation by 3D finite difference method (FDM) was carried out. The simulation used results from the field pumping tests. The permeability parameters of the confined aquifer were then revised, based upon comparisons of simulation and observation results. Subsequently, dewatering schemes were simulated by FDM forward analysis. The simulation results show that dewatering schemes can minimize seepage and uplift in large Excavation Pits, though settlement outside the Pit may need treatment measures.

Jie Zhou - One of the best experts on this subject based on the ideXlab platform.

  • physical model test of transparent soil on coupling effect of cut off wall and pumping wells during foundation Pit dewatering
    Acta Geotechnica, 2019
    Co-Authors: Jianxiu Wang, Xiaotian Liu, Shaoli Liu, Yanfei Zhu, Weiqiang Pan, Jie Zhou
    Abstract:

    Water level is decreased during foundation Pit Excavation to avoid water inrush under confined water pressure. Cut-off wall is often used as waterproof curtain to partially cut off the dewatered aquifer. When a foundation Pit is located in a built-up area and the underlying confined aquifer is not cut off, the drawdown must be minimized outside the Pit to avoid land subsidence in buildings and pipelines. The coupling effect of the cut-off wall and pumping well is used to control the drawdown outside the foundation Pit. However, the coupling mechanism is not intuitively well understood because of the limitations of existing experimental methods. In this study, transparent soil was introduced to model the coupling mechanism in the physical model test. High-purity fused silica and mixed paraffin oil were used as skeleton and fluid to simulate the confined aquifer and groundwater. Industrial solid dye and paraffin oil were used as tracers. A camera was used to collect flow information. Tests were performed for the combinations of cut-off wall and partially penetrating pumping wells. The insertion depth ratio of the cut-off wall most effectively influenced the drawdown. The layout of the pumping wells in horizontal direction influenced water level distribution and flow rate. The optimal depth of the pumping wells was 1–5 m above the bottom of the cut-off wall, and the optimal horizontal distance between the cut-off wall and the pumping wells was 25% of the Pit width. Non-Darcy flow was observed within the range of 0–10 m around the bottom of the cut-off wall. These results were significant in understanding the cut-off wall and pumping well coupling effect on foundation Pit dewatering.

Gargini Alessandro - One of the best experts on this subject based on the ideXlab platform.

  • Use of the Conduit Flow Process for the simulation of passive mitigation measures against the piezometric damming effect at the new underground High Speed railway station of Florence
    2016
    Co-Authors: Filippini Maria, S. Menichetti, F. Palmiero, L. Ranfagni, Martina, Mario Lloyd Virgilio, Gargini Alessandro
    Abstract:

    The new High Speed railway station of the city of Florence will be located below ground level inside a huge Excavation, 25 m b.g.s deep, 450 m long and 50 m wide; the Pit, already built, is surrounded by concrete cutoff walls causing a piezometric damming effect against the main aquifer of the Arno River. As permanent mitigation measure against the piezometric mounding, the design of the station considers a series of drain pipes drilled horizontally on up and down gradient sides of the Pit and connected by blind wall tubes. A numerical finite differences model has been implemented with the Modflow code, in order to quantify the expected damming effect and to properly design the drain-based mitigation measures (i.e. frequency and length of the drains). One of the major challenges of the numeric approach was the coupling between the groundwater flow in the porous medium and the water flow towards and through the drains and the blind wall tubes connecting the sides of the Excavation. Thus, the drains were simulated using a recently published Modflow Process originally developed for karst conduits (Conduit Flow Process - CFP), which allows combining the groundwater flow in the porous medium with laminar or turbulent flow into pipes. In order to guarantee an acceptable head differential between both sides of the Excavation, the results showed that the system should permit a discharge flow rate of about 0.026 m3/s, considering a hydraulic gradient equal to 0.5% (i.e. hydraulic gradient from the averaged piezometric distribution before Pit Excavation). Conductance turned out to be the most influent parameter towards the effectiveness of the drainage system

A. Gargini - One of the best experts on this subject based on the ideXlab platform.

  • Use of the Conduit Flow Process for the simulation of passive mitigation measures against the piezometric damming effect at the new underground High Speed railway station of Florence”
    2016
    Co-Authors: M. Filippini, M. Martina, S. Menichetti, F. Palmiero, F.a. Rota, L. Ranfagni, A. Gargini
    Abstract:

    The new High Speed railway station of the city of Florence (Italy) will be located below ground level inside a huge Excavation, 25 m b.g.s deep, 450 m long and 50 m wide+ the Pit, already built, is surrounded by concrete cut-off walls causing a piezometric damming effect against the main aquifer of the Arno River. As permanent mitigation measure against the piezometric mounding, the design of the station considers a series of drain pipes drilled horizontally on up and down gradient sides of the Pit and connected by blind wall tubes. A numerical finite differences model has been implemented with the Modflow code, in order to quantify the expected damming effect and to verify the design hypothesis of the drain-based mitigation measures (i.e. frequency and length of the drains). One of the major challenges of the numeric approach was the coupling between the groundwater flow in the porous medium and the water flow towards and through the drains and the blind wall tubes connecting the sides of the Excavation. Thus, the drains were simulated using a recently published Modflow Process originally developed for karst conduits (Conduit Flow Process – CFP), which allows combining the groundwater flow in the porous medium with laminar or turbulent flow into pipes. In order to guarantee an acceptable head differential between both sides of the Excavation, the results showed that the system should permit a discharge flow rate of about 0.026 m3 s, considering a hydraulic gradient equal to 0.5% (i.e. hydraulic gradient from the averaged piezometric distribution before Pit Excavation). The drain Conductance turned out to be the most influent parameter towards the effectiveness of the drainage system

L. Ranfagni - One of the best experts on this subject based on the ideXlab platform.

  • Use of the Conduit Flow Process for the simulation of passive mitigation measures against the piezometric damming effect at the new underground High Speed railway station of Florence”
    2016
    Co-Authors: M. Filippini, M. Martina, S. Menichetti, F. Palmiero, F.a. Rota, L. Ranfagni, A. Gargini
    Abstract:

    The new High Speed railway station of the city of Florence (Italy) will be located below ground level inside a huge Excavation, 25 m b.g.s deep, 450 m long and 50 m wide+ the Pit, already built, is surrounded by concrete cut-off walls causing a piezometric damming effect against the main aquifer of the Arno River. As permanent mitigation measure against the piezometric mounding, the design of the station considers a series of drain pipes drilled horizontally on up and down gradient sides of the Pit and connected by blind wall tubes. A numerical finite differences model has been implemented with the Modflow code, in order to quantify the expected damming effect and to verify the design hypothesis of the drain-based mitigation measures (i.e. frequency and length of the drains). One of the major challenges of the numeric approach was the coupling between the groundwater flow in the porous medium and the water flow towards and through the drains and the blind wall tubes connecting the sides of the Excavation. Thus, the drains were simulated using a recently published Modflow Process originally developed for karst conduits (Conduit Flow Process – CFP), which allows combining the groundwater flow in the porous medium with laminar or turbulent flow into pipes. In order to guarantee an acceptable head differential between both sides of the Excavation, the results showed that the system should permit a discharge flow rate of about 0.026 m3 s, considering a hydraulic gradient equal to 0.5% (i.e. hydraulic gradient from the averaged piezometric distribution before Pit Excavation). The drain Conductance turned out to be the most influent parameter towards the effectiveness of the drainage system

  • Use of the Conduit Flow Process for the simulation of passive mitigation measures against the piezometric damming effect at the new underground High Speed railway station of Florence
    2016
    Co-Authors: Filippini Maria, S. Menichetti, F. Palmiero, L. Ranfagni, Martina, Mario Lloyd Virgilio, Gargini Alessandro
    Abstract:

    The new High Speed railway station of the city of Florence will be located below ground level inside a huge Excavation, 25 m b.g.s deep, 450 m long and 50 m wide; the Pit, already built, is surrounded by concrete cutoff walls causing a piezometric damming effect against the main aquifer of the Arno River. As permanent mitigation measure against the piezometric mounding, the design of the station considers a series of drain pipes drilled horizontally on up and down gradient sides of the Pit and connected by blind wall tubes. A numerical finite differences model has been implemented with the Modflow code, in order to quantify the expected damming effect and to properly design the drain-based mitigation measures (i.e. frequency and length of the drains). One of the major challenges of the numeric approach was the coupling between the groundwater flow in the porous medium and the water flow towards and through the drains and the blind wall tubes connecting the sides of the Excavation. Thus, the drains were simulated using a recently published Modflow Process originally developed for karst conduits (Conduit Flow Process - CFP), which allows combining the groundwater flow in the porous medium with laminar or turbulent flow into pipes. In order to guarantee an acceptable head differential between both sides of the Excavation, the results showed that the system should permit a discharge flow rate of about 0.026 m3/s, considering a hydraulic gradient equal to 0.5% (i.e. hydraulic gradient from the averaged piezometric distribution before Pit Excavation). Conductance turned out to be the most influent parameter towards the effectiveness of the drainage system