scholarly journals Research on a Critical Hydraulic Gradient of Piping in Noncohesive Soils

2021 ◽  
Vol 2021 ◽  
pp. 1-6
Author(s):  
Can-Hong Zhang ◽  
En-Yue Ji ◽  
Bao-Tian Wang
Keyword(s):  
Water Flow ◽  
Drag Force ◽  
Moving Objects ◽  
Cohesive Soil ◽  
Interaction Force ◽  
Hydraulic Gradient ◽  
Force Analysis ◽  
Important Condition ◽  
Critical Hydraulic Gradient ◽  
Soil Piping

The critical hydraulic gradient of cohesive soil is an important condition for judging soil piping. For force analysis of movable particles in pore channels of soil, this study proposes to consider the influence of surrounding particles on the drag force of movable particles by water flow. According to the principle of relative motion, considering the interaction force between moving objects in still water, the value of the drag force of water flow that is affected by surrounding particles is calculated, to derive the method of the critical hydraulic gradient. This calculation method is suitable for the results of previous piping tests, and the method is accurate and concise.

scholarly journals Study on Critical Hydraulic Gradient Theory of Flow Soil Failure in Cohesive Soil Foundation

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Mei Zhou ◽  
Faning Dang ◽  
Yutao Li ◽  
Jiulong Ding ◽  
Jun Gao
Keyword(s):  
Shear Strength ◽  
Cohesive Soil ◽  
Hydraulic Gradient ◽  
Gradient Theory ◽  
Clay Layer ◽  
Soil Thickness ◽  
Seepage Failure ◽  
Critical Hydraulic Gradient ◽  
Comparison Results ◽  
Soil Foundation

The current formula of critical hydraulic gradient is not adapted to solve critical hydraulic gradient of cohesive soil. Assume that the seepage failure mode of the cohesive soil foundation was cylindrical or inverted circular truncated cone, based on the calculation formula of the critical hydraulic gradient of Terzaghi, the analytical formula of the critical hydraulic gradient considering the influence of the shear strength of the soil was derived. Then, the seepage failure process of the clay layer was simulated numerically, and the effects of the clay layer thickness, failure radius, and shear strength indexes on the critical hydraulic slope were analyzed. The comparison results show that the numerical test results are in good agreement with the calculated results of the new formula. In addition, the critical hydraulic gradient of sandy loam and loess under different working conditions was studied severally by a self-made permeation failure instrument. The results show that the critical hydraulic gradient decreases with the increase of soil thickness and failure radius, and the maximum error between the test and the corresponding formula results is no more than 16%.

scholarly journals Evaluation of Water Retention Capacity of Bulkheads in Underground Coal Mines

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Yuan Hang ◽  
Lichuang Jin ◽  
Binbin Yang ◽  
Ning Li ◽  
Shichong Yuan ◽  
...  
Keyword(s):  
Water Flow ◽  
Safety Factor ◽  
Water Pressure ◽  
Decisive Role ◽  
Surrounding Rock ◽  
Hydraulic Gradient ◽  
Water Retention Capacity ◽  
Retention Capacity ◽  
Critical Hydraulic Gradient ◽  
Conducting Pathway

The mechanism of water flow in and around the bulkheads and the surrounding rock is studied for Panel No. 21102 in the Sanhejian coal mine in Xuzhou, China. Based on an analysis of the properties of the bulkheads and the surrounding rock, three types of water conducting pathways are identified: (1) a water conducting pathway at the interface between the bulkhead and the surrounding rock; (2) a water conducting pathway in the faults of the rock; and (3) a water conducting pathway in the fractures of the rock. The possibility of these three pathways for water flow at Panel No. 21102 is analyzed, and the connectivity coefficient of the water conducting pathway is determined. The expression for calculating the critical hydraulic gradient of the rock by using the connectivity coefficient in the water conducting pathways is presented which is based on the permeability and integrity of the rock. The ratios of the critical hydraulic gradient to the steady state hydraulic gradient are calculated for 13 mines in China. An acceptable safety factor in controlling the water flow for the bulkhead is found to be 1.68. When the safety factor is less than 1.68, water leakage has occurred in a number of cases. Finally, changes in the water pressure in the bulkheads with time and changes in the seepage flow with time in the surrounding rock are analyzed. It is found that there is a good correlation between the rate of water flow and water pressure which confirms that water pressure plays a decisive role in controlling seepage from the rock in and around the bulkheads.

scholarly journals Impacts of Consolidation Time on the Critical Hydraulic Gradient of Newly Deposited Silty Seabed in the Yellow River Delta

2021 ◽  
Vol 9 (3) ◽  
pp. 270
Author(s):  
Meiyun Tang ◽  
Yonggang Jia ◽  
Shaotong Zhang ◽  
Chenxi Wang ◽  
Hanlu Liu
Keyword(s):  
Yellow River ◽  
Yellow River Delta ◽  
Hydraulic Gradient ◽  
River Delta ◽  
Theoretical Formula ◽  
The Yellow River ◽  
The Yellow River Delta ◽  
Critical Hydraulic Gradient ◽  
Seepage Flows ◽  
The Yrd

The silty seabed in the Yellow River Delta (YRD) is exposed to deposition, liquefaction, and reconsolidation repeatedly, during which seepage flows are crucial to the seabed strength. In extreme cases, seepage flows could cause seepage failure (SF) in the seabed, endangering the offshore structures. A critical condition exists for the occurrence of SF, i.e., the critical hydraulic gradient (icr). Compared with cohesionless sands, the icr of cohesive sediments is more complex, and no universal evaluation theory is available yet. The present work first improved a self-designed annular flume to avoid SF along the sidewall, then simulated the SF process of the seabed with different consolidation times in order to explore the icr of newly deposited silty seabed in the YRD. It is found that the theoretical formula for icr of cohesionless soil grossly underestimated the icr of cohesive soil. The icr range of silty seabed in the YRD was 8–16, which was significantly affected by the cohesion and was inversely proportional to the seabed fluidization degree. SF could “pump” the sediments vertically from the interior of the seabed with a contribution to sediment resuspension of up to 93.2–96.8%. The higher the consolidation degree, the smaller the contribution will be.

Slip Length Measurement of Water Flow on Graphite Surface Using Atomic Force Microscope

2014 ◽  
Vol 941-944 ◽  
pp. 1581-1584 ◽  
Author(s):  
Da Yong Li ◽  
Da Lei Jing ◽  
Yun Lu Pan ◽  
Khurshid Ahmad ◽  
Xue Zeng Zhao
Keyword(s):  
Atomic Force Microscope ◽  
Water Flow ◽  
Drag Force ◽  
Silicon Surface ◽  
Slip Length ◽  
Graphite Surface ◽  
Length Measurement ◽  
Hydrodynamic Drag ◽  
Experimental Measurements ◽  
Atomic Force

In this paper, we present experimental measurements of slip length of deionized (DI) water flow on a silicon surface and a graphite surface by using atomic force microscope. The results show that the measured hydrodynamic drag force is higher on silicon surface than that on graphite surface, and a measured slip length about 10 nm is obtained on the later surface.

The Analysis of Horizontal Extension Capability in Horizontal Wells

2014 ◽  
Vol 1010-1012 ◽  
pp. 1745-1749
Author(s):  
Wei Kai Liu ◽  
Ming Xing Song ◽  
Zi Yi Xu ◽  
Xue Hong Zhang
Keyword(s):  
Drag Force ◽  
Field Data ◽  
Horizontal Wells ◽  
Element Model ◽  
Force Analysis ◽  
Gap Element ◽  
Field Works ◽  
Set Up

It is critical to understand whether the available drilling assembly could meet the requirements of drilling design during the design and drilling of horizontal wells. This paper pointed out several limitations on horizontal extension capability of horizontal wells and provided judging criteria of the limit of horizontal extension based upon the characteristics of horizontal wells, and set up the gap element model analyzing torque and dragged of whole drill strings in horizontal wells. According to the force analysis of drill strings in bores given the foundation for regularities in the distribution of torque and drag force along the axis, on the basis of those above mentioned models and theories, a software was made to calculate the torque and drag force of a well, which compared with the field data, the average discrepancies of theoretical values are below 20% that could meet the needs in field works.

Development of Bubble Departure Diameter Model Based on Force Analysis

2017 ◽  
Author(s):  
Ye Tian ◽  
Wei Huang ◽  
Pengfei Li ◽  
Simin Cao ◽  
Yan Sun
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Drag Force ◽  
Bubble Dynamics ◽  
Hydrodynamic Pressure ◽  
Surface Tension Force ◽  
Force Analysis ◽  
Pressure Force ◽  
Model Based ◽  
Unsteady Drag Force

Bubble departure diameter has significant effect on bubble dynamics and heat transfer in boiling system, and it is difficult to be measured in a boiling system. Therefore, a method to predict bubble departure diameter is necessary to study of bubble dynamics and heat transfer in boiling system. A new theoretical model based on force analysis is proposed for the prediction of bubble departure diameter in vertical boiling system in this paper. Surface tension force, unsteady drag force, quasi-steady drag force, shear lift force, buoyancy force, hydrodynamic pressure force and contact pressure force are taken into account to build the model. Chen’s experimental data is used to validate the model, the averaged relative deviation between the predict results of the model and the experimental data is less than ±14.8%.

Sign in / Sign up

Export Citation Format

Share Document