Scale effect and value criterion of the permeability of the interlayer staggered zones in the basalt of Jinsha River basin, China

Zhou, Zhifang; Lin, Min; Guo, Qiaona; Chen, Meng

doi:10.1007/s10040-018-1777-3

“…Zone C 2 is developed in the Tuff layer P 2 β 2 4 which is mainly composed of gravel, rock fragments, and a small amount of medium-dense brown-red mud; it will become soft and plastic when exposed to water. In summary, the permeability of the mud filling is weak, while the gravel and rock fillings are strong [17].…”

Section: Field Applicationmentioning

confidence: 93%

“…The interlayer staggered zones are special fractures, which have been caused by the localization of shear within relatively narrow zones in fault rocks [16]. They are mainly filled by low-permeability fillings (mud and debris) and the high-permeability fillings (gravel and fractured surrounding rock), and the internal structure is loose, with fractured rocks and high content clay in it [17]. As a result, the interlayer staggered zone has a great influence on the stability of engineering works, such as dam breaks, water inrush in underground excavations, seepage deformation, and leakage in dam foundations [18].…”

Section: Introductionmentioning

confidence: 99%

An Analytical Solution for Non-Darcian Flow on a Constant Head Packer Test in the Interlayer Staggered Zone

Shen

¹

,

Zhou

²

,

Chen

³

et al. 2021

Geofluids

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Groundwater flow in an aquifer has frequently been found to be non-Darcian by performing in situ tests. A novel analytic model is proposed in this study for describing the unsteady non-Darcian flow in a confined aquifer by taking advantage of the observed flow rate and injection pressure during the constant head packer test. A linearization approximation of the Izbash equation is used to approximate the nonlinear term in the governing equation. This analytic model is applied to describe the non-Darcian flow in the interlayer staggered zone at the Baihetan hydropower station, China. The test results inversed by the genetic algorithm show that non-Darcian flow happened during the test under the injection pressure 0.3 MPa with the power index n is 1.278, non-Darcian hydraulic conductivity k 1 is 1.613 × 10 − 5 cm/s and the specific storage S s is 9.757 × 10 − 5 m-1, respectively. The sensitivity analysis indicated that when the power index n or the specific storage S s is larger, and the hydraulic head will increase more slowly and needs longer to stabilize, but the non-Darcian hydraulic conductivity k 1 shows the opposite trend. Moreover, the hydraulic head is more sensitive to the power index n compared to other parameters at late times. The findings of this study reveal the non-Darcian flow during the constant head packer test and provide a simple and fast way to estimate parameters for more accurate seepage field simulation.

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“…Duan et al [15] proposed a comprehensive in situ monitoring scheme for rock mass with interlayer shear zone and analyzed some collapse and plastic extrusion failure problems induced by interlayer shear zone combined with monitoring data and mechanical test results. Zhou et al [16] revealed the scale effect and value standard of permeability of interlayer shear zone of basalt by numerical and analytical methods. Guo and Huang [17] analyzed the seepage characteristics of interlayer shear zone C 2 in underground powerhouse area by finite element groundwater flow system.…”

Section: Introductionmentioning

confidence: 99%

Deformation and Failure Analyses of the Surrounding Rock Mass with an Interlayer Shear Zone in the Baihetan Underground Powerhouse

Yuan

¹

,

Shi

²

,

Zhou

³

et al. 2021

Advances in Civil Engineering

2

0

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In the process of underground cavern excavation, the existence of the interlayer shear zones or large faults often makes the surrounding rock tend to be unstable or even deformed. Under the influence of interlayer shear zone C2, different degrees of deformation and failure occurred in many parts during the excavation of the Baihetan left bank underground powerhouse. Based on field monitoring and numerical calculation, this paper studies the deformation and failure characteristics of the rock mass with C2 in the whole excavation process and the failure mechanisms are analyzed. The results show that C2 has poor mechanical properties. In the process of excavation, it mainly induces two failure modes: rock collapse and shear deformation, which specifically leads to rock collapses, large deformation and shotcrete cracking in the main powerhouse, and shear deformation in the omnibus bar caves. In addition, the similarities and differences between this study and other studies on the deformation and failure of surrounding rock of underground powerhouse in recent years are discussed, and the relevant treatment measures for C2 are given. The above research results can be a reference for other related studies.

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“…Weeks [16] and Guo et al [5] showed that heavy rainfall events might produce the Lisse effect in which heavy rainfall produced air confinement and an increase in air pressure that led to a rise of water level in observation wells. Although vertical infiltration in the unsaturated zone is more common and extensively studied, horizontal air-water flow is also expected to occur in many geological circumstances [6,[18][19][20]. For example, the tide-induced air-water flow in coastal areas is a typical two-dimensional air-water flow system.…”

Section: Introductionmentioning

confidence: 99%

“…They reported that in such an air-confined system, the vertical air flux tends to be dominant in the upper low-permeability layer and the horizontal air flux is expected to be dominant in the lower relatively high-permeability layer, and both the vertical and horizontal airflow would gradually attenuate landward and upward. More importantly, in volcanic rock reservoir areas, the horizontal fault zones or interlayer staggered zones consisting of mud, debris, and gravel are often formed in river mountains due to tectonic activity [19,20]. In natural condition, most horizontally developed interlayer staggered zones are initially in the unsaturated state.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of Water Infiltration in Unsaturated Horizontal Sand Columns under Various Air Confinement Conditions

Chen

¹

,

Zhou

²

,

Sleep

³

et al. 2019

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The process of water infiltration into initially dry sand was studied in horizontal sand columns under various airtight conditions. To investigate the interrelations among water inflow behavior, air pressure, air confinement effect, and vent effectiveness in unsaturated porous media experiencing dynamic infiltration, a total of five dynamic infiltration experiments with fixed inlet water pressure were performed with different air vents open or closed along the column length. Visualizations of the infiltration process were accompanied by measurements of water saturation, air pressure, and accumulated water inflow. In a column system with an open end, the absence of air pressure buildup reveals that the vent at the column end can significantly reduce the internal air pressure effects during infiltration, and the air phase can be ignored for this case. However, in columns with a tight end, the coupled air and water flow processes can be divided into two completely different periods. Before the water front passed by the most distant open vent, the internal air pressure effects on retarding dynamic infiltration are negligible, similar to the open end case. After this period, the open vents can certainly influence the inflow behavior by functioning as air outlets while they cannot equilibrate pore air pressure with the atmospheric pressure. The remaining air ahead of the front will be gradually confined and compressed, and the significant increase in air pressure highlights the great role of air pressure buildup in reducing the water infiltration rate. The closer the last open vent was to the water inlet, the higher was the increase in air pressure and the greater was the delaying effect on water infiltration. This work may extend the experimental study of water infiltration into the unsaturated soils with different airtight conditions and provide experimental evidence on these coupled mechanisms among the water and air phases in soils.

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Scale effect and value criterion of the permeability of the interlayer staggered zones in the basalt of Jinsha River basin, China

Cited by 10 publications

References 23 publications

An Analytical Solution for Non-Darcian Flow on a Constant Head Packer Test in the Interlayer Staggered Zone

An Analytical Solution for Non-Darcian Flow on a Constant Head Packer Test in the Interlayer Staggered Zone

Deformation and Failure Analyses of the Surrounding Rock Mass with an Interlayer Shear Zone in the Baihetan Underground Powerhouse

Experimental Study of Water Infiltration in Unsaturated Horizontal Sand Columns under Various Air Confinement Conditions

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