An analysis of passive earth pressure modification due to seepage flow effects

Using an assumed vertical retaining wall with a drainage system along the soil-structure interface, this paper analyses the effect of anisotropic seepage flow on the development of passive earth pressure. Extremely unfavourable seepage flow inside the backfill, perhaps due to heavy rainfall, will dramatically increase the active earth pressure while reducing the passive earth pressure; thus increasing the probability of instability of the retaining structure. In this paper, a trial and error analysis based on limit equilibrium is applied to identify the optimum failure surface. The flow field is computed using Fourier series expansion, and the effective reaction force along the curved failure surface is obtained by solving a modified Kötter equation considering the effect of seepage flow. This approach correlates well with other existing results. For small values of both the internal friction angle and the interface friction angle, the failure surface can be appropriately simplified with a planar approximation. A parametric study indicates that the degree of anisotropic seepage flow affects the resulting passive earth pressure. In addition, incremental increases in the effective friction angle and interface friction both lead to an increase in the passive earth pressure.National Key Basic Research Program of China (No. 2015CB057801), the National Key R & D program of China (No. 2016YFC0800204), and Natural Science Foundation of China (Nos. 51578499 & 51761130078)

Exercise and the nitric oxide vasodilator system

<p>a) Schematic overview of the two-compartment perfusion model explains the FEAST technique, adapted from Wang <i>et al</i>. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133717#pone.0133717.ref006" target="_blank">6</a>] b) shows raw perfusion-weighted maps and c) perfusion maps after post-processing for a representative subject. Note that the signal intensity is lower after crushing (ΔM') than before (ΔM) and that crushed CBF (CBF_crushed) is weighted toward the micro-vascular CBF whereas non-crushed CBF (CBF_non-crushed) is weighted toward both micro- and macro-vascular CBF. ATT = arterial transit time, ∝ = proportional to.</p

Proportion of arterial transit time (ATT)−values (y-axis) measured by FEAST that is equal to the post-label delay (PLD), for bin sizes 1–250 ms (x-axis), for flow territories perfused by the anterior (ACA), middle (MCA) and posterior cerebral artery (PCA).

<p>Proportion of arterial transit time (ATT)−values (y-axis) measured by FEAST that is equal to the post-label delay (PLD), for bin sizes 1–250 ms (x-axis), for flow territories perfused by the anterior (ACA), middle (MCA) and posterior cerebral artery (PCA).</p

Flow territories.

<p>ACA (green), MCA (red) and PCA (blue) refer to the standard flow territories perfused by the bilateral anterior, middle and posterior cerebral arteries respectively, whereas the shadings represent their subdivision into proximal, intermediate and distal flow territories, based on arterial transit times.</p

Regression coefficients for age and gender (n = 186).

<p>For each ROI, estimated cross-sectional regression coefficients and <i>p</i>-values are shown. †<i>p</i><0.01. ACA, MCA and PCA refer to the flow territories perfused by the anterior, middle and posterior cerebral arteries respectively, corresponding to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133717#pone.0133717.g002" target="_blank">Fig 2</a>. CBF = cerebral blood flow, M>F stands for higher mL/100g/min in men compared to women, ATT = arterial transit time</p><p>Regression coefficients for age and gender (n = 186).</p

Distributions of perfusion parameters (n = 186).

<p>Shown are the median ± mean absolute deviation from median (with the coefficient of variation (CV) between parentheses) of cerebral blood flow (CBF) and arterial transit time (ATT). ACA, MCA and PCA refer to the flow territories perfused by the anterior, middle and posterior cerebral arteries respectively, corresponding to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133717#pone.0133717.g002" target="_blank">Fig 2</a>. Difference (4^th column) shows whether the median or CV differed (Y) or not (N) (<i>p</i><0.01) between CBF_crushed and CBF_non-crushed.</p><p>Distributions of perfusion parameters (n = 186).</p