Slope Stabilizing Piles and Pile-Groups: Parametric Study and Design Insights

This paper uses a hybrid method for analysis and design of slope stabilizing piles that was developed in a preceding paper by the writers. The aim of this paper is to derive insights about the factors influencing the response of piles and pile-groups. Axis-to-axis pile spacing (S), thickness of stable soil mass (Hu), depth (Le) of pile embedment, pile diameter (D), and pile group configuration are the parameters addressed in the study. It is shown that S = 4D is the most cost-effective pile spacing, because it is the largest spacing that can still generate soil arching between the piles. Soil inhomogeneity (in terms of shear stiffness) was found to be unimportant, because the response is primarily affected by the strength of the unstable soil layer. For relatively small pile embedments, pile response is dominated by rigid-body rotation without substantial flexural distortion: the short pile mode of failure. In these cases, the structural capacity of the pile cannot be exploited, and the design will not be economical. The critical embedment depth to achieve fixity conditions at the base of the pile is found to range from 0.7Hu to 1.5Hu, depending on the relative strength of the unstable ground compared to that of the stable ground (i.e., the soil below the sliding plane). An example of dimensionless design charts is presented for piles embedded in rock. Results are presented for two characteristic slenderness ratios and several pile spacings. Single piles are concluded to be generally inadequate for stabilizing deep landslides, although capped pile-groups invoking framing action may offer an efficient solution.     

Simplified Design of Hydraulically Efficient Power-Law Channels with Freeboard

A power-law channel section is very versatile. It can model a wide range of familiar man-made or natural channel shapes. However estimating the wetted perimeter of a power-law channel section is difficult. The problem gets complicated further when considering the freeboard in the design process. In this paper, the wetted perimeter is estimated using the isoperimetric theorem which results in a simple and accurate expression for the wetted perimeter that does not lead to discontinuity in the optimal solution. For unconstrained optimum power-law channels, it is shown that the exponent and side slope at the water surface have values of 0.314 and 0.352, respectively, independent of either the maximum side slope or the relative freeboard. The analyses have also shown that the most hydraulically efficient power-law channel sections come closest to the semicircle. They tend to be U shaped and narrow with small relative freeboard ( ? 0.30). A design procedure and two design charts are presented together with two illustrative examples to demonstrate the simplicity of the method.     

Design of Hydraulically Efficient Power-Law Channels with Freeboard

A power-law channel is a generalized form of the parabolic channel. The exponent of the governing equation is a variable that for certain maximum permissible side slopes can be determined by maximizing the cross-sectional area of flow (or minimizing the wetted perimeter). Using this exponent rather than the constant allows a hydraulically more efficient open channel section to be designed. In earlier work on power-law channels freeboard was neglected to simplify the analysis. However as pointed out by several authors, a channel without freeboard is of academic interest only and not practical. All open channels are in practice designed and constructed with freeboard as a factor of safety. In this paper freeboard has been introduced as an additional parameter to be taken into account when designing a power-law channel. The work from this paper is applied to an earlier example of a parabolic channel to demonstrate a practical design.     

New Relation for the Computation of Settling Velocities and Diameters of Spheres

Single relations that can be used to calculate both the terminal settling velocities of spheres and the equivalent diameter of particles from their settling velocities are developed. The literature going back to Newton is reviewed and the relations developed tabulated. It is shown how the standard drag curve has developed into the dimensionless velocity versus dimensionless diameter curve. No relations that cover the full range that can conveniently be used for both velocity and diameter calculation were found, however a relation by Concha and Almendra covers most of the range.

The standard drag curve data are constructed by utilizing 535 data points available in the literature in a Reynolds number range of 2.4 × 10^?5 to 2 × 10⁵. The settling velocities are corrected for experiments in finite width columns that do not satisfy the infinite medium dimensions. The data are converted to the dimensionless diameter and dimensionless velocity terms, which is more convenient for calculation purposes.

The data are analyzed using piecewise cubic functions. Data from sources with excessive scatter and a few outliers are removed leaving 443 data points. The resulting piecewise cubic can be used to obtain velocity from diameter or diameter from velocity. To give an algebraic expression a hyperbola is fitted to the data giving an expression that can be solved to give explicit relations for both dimensionless velocity and dimensionless diameter. This provides an accuracy that compares well with expressions given in the literature.     

Calbindin D-28k and monoamine oxidase A immunoreactive neurons in the nucleus basalis of Meynert in senile dementia of the Alzheimer type and Parkinson''s disease

The lungs must be kept "dry" for efficient gas exchange. The mechanisms that contribute to clear alveoli from fetal lung fluid at birth are still present during adult life and allow recovery from alveolar flooding. It has recently been shown with the use of different approaches in vitro, as well as in vivo, that alveolar epithelium performs solute-coupled fluid transport. Fluid absorption from alveoli occurs chiefly as a result of active transepithelial Na+ transport. The mechanisms of Na+ transport have been partly elucidated; Na+ enters alveolar cells through apical Na+ channels and Na(+)-coupled solute transporters and is pumped out at the basolateral membrane by a Na(+)-K(+)-adenosinetriphosphatase (ATPase). Transepithelial Na+ transport and fluid absorption are stimulated by beta-adrenergic agonists, with adenosine 3',5'-cyclic monophosphate being the likely intracellular second messenger. K+ is probably secreted into alveoli because its concentration in the epithelial lining fluid is larger than expected for passive distribution. K+ channels have been described that, in conjunction with Na(+)-K(+)-ATP-ase, might provide pathways for active transport. Active proton secretion or bicarbonate absorption have been reported, which may explain the low pH of the alveolar epithelial lining fluid. It is probable that active solute transports are the main determinants of epithelial lining fluid depth and composition. A challenge for the future is to understand how this homeostasis is achieved.     

Nondestructive Analysis of a Concrete Tunnel Model Using a Newly Proposed Combined Stress Wave Propagation Method

This paper summarizes the measured properties of a three-layer model concrete tunnel lining using a newly proposed combined stress wave propagation (CSWP) method. The spectral analysis of surface waves (SASW) and impact echo (IE) methods were used in combination to determine the in-place dynamic properties of the tunnel lining and to locate embedded voids. Simultaneously, the free-free resonant column (FFRC) method was independently used to determine the dynamic properties of the materials used to construct the concrete tunnel lining. Finally, a direct P-wave (DPW) measurement was used to compare and verify measurements recorded using the CSWP method. Results indicate that the combination of the SASW and IE methods, along with FFRC measurements, provides a more efficient procedure that leads to the accurate determination of the P-wave and shear wave velocities, depths of layers, and locations of embedded voids without the need to make any assumptions of material properties. Thus, more physical properties can be found using this proposed procedure than by using the techniques independently, and the procedure is more efficient than performing each task separately.     

Hydraulically Efficient Power-Law Channels

A power-law channel is a generalized form of a channel and includes parabolic and triangular cross sections. For an exponent m<0.5 in the power law, the relative wetted perimeter has been estimated from a series expansion truncated to four terms. For values of the exponent m ≥ 0.5 the relative wetted perimeter has been estimated using an appropriate non-linear interpolation expression. A table to estimate relative wetted perimeter based on these expressions is presented for design purposes. With these expressions for relative wetted perimeter, and using the Lagrange method of undetermined multipliers, for any given maximum side slope, the area and/or wetted perimeter is minimized subject to the equality constraint of a uniform flow (Mannings) equation. Using this technique, for any given side slope, the exponent of the power-law channel can be determined and hydraulically efficient power-law channels can be designed. Optimized power-law channels are compared with trapezoidal and parabolic channels. The existing parabolic design of the Pehur High Level Canal, Pakistan is compared with an optimum power-law channel.     

高炉顶压发电机组液压控制油站的国产化改造

分析了15MW高炉顶压压差发电设备旁通阀组液压控制油站存在的问题．对德国配套设备进行了改造，使液压控制油站实现稳定运行．实现了旁通阀组的正常稳定动作．保证了高炉及压差发电设备的安全稳定运行。     

Hydraulics of Rectangular Dropshafts

A dropshaft is an energy dissipator connecting two channels with a drop in invert elevation. The hydraulics of vertical rectangular shafts was systematically investigated in seven configurations. A particular emphasis was on the effects of shaft pool, outflow direction, and drop height, while geometrically similar shafts (scale 3.1:1) were studied using a Froude similitude. The results demonstrate that rectangular dropshafts with 90° outflow are the most efficient energy dissipators. The shaft pool and drop height have little effect on the rate of energy dissipation. Recirculation time results exhibited marked differences between flow regimes and the longest dimensionless residence times were observed at low flow rates. Although basic flow characteristics were similar between model and prototype, observations of dimensionless bubble penetration depths and recirculation times showed some discrepancy, highlighting limitations of the Froude similitude for studies of air entrainment and residence times in dropshafts.     

考虑固壁作用力的微可压缩流体纳微米圆管流动分析

针对流体在纳微米尺度下的流体流动规律不符合泊肃叶规律的理论依据不足的难题,研究了纳微米圆管中流体的流动,将流体的微可压缩和固壁对流体的作用同时考虑进来,并将固壁对流体的作用采用固壁作用力的形式引入到流体力学方程,采用涡函数流函数将方程解耦,并用正则摄动法求得一阶精度的压力和速度的解析解.结果发现:固壁作用力导致零阶径向压力的出现,一阶压力的增强和一阶速度的降低;量纲一的体积流量偏离了不可压缩流体的体积流量,偏离效应受流体的微可压缩性和固壁作用力的共同影响.体积流量在同尺度下偏离泊肃叶流动的流量大小随着可压缩系数和流体中和壁面产生作用的离子浓度增大而增大,随着纳微米圆管管径减小而增大,纳微米圆管管径低于某一尺寸时,流体将不能流动.通过研究表明:纳微米尺度下产生微尺度效应的原因是流体的微可压缩性和壁面力的共同影响.      

露天矿山胶带运输系统保护装置的优化及应用

德兴铜矿铜厂采区利用BC01, BC02B, BC03等胶带机运输废石,胶带机能否安全稳定运行,是制约矿山高质量发展的重要因素。胶带系统在运行过程中,不可避免会遇到突发性故障,此时若胶带输送机未能及时停机,不仅会对设备造成一定程度的损坏,而且还有可能酿成较大的事故。为此,通过优化设计一种运输胶带斜式清扫器,解决了小块废石损伤胶带及滚筒的问题,实现了回程胶带小块废石清扫;采用移动胶带纠偏装置,解决了移动胶带易跑偏的难题,实现了移动胶带跑偏的自动调节;采用移动胶带驱动滚筒陶瓷包胶方式,有效降低了移动胶带打滑的故障率。胶带运输系统保护装置的优化与应用至关重要,可以解决废石胶带运输的安全运行瓶颈,实现废石胶带系统安全高效运行。     

Short and long waves in the cochlea

Mathematically, it is attractive to model cochlear dynamics as a one-dimensional problem. This implies the hypothesis that the (smallest) wavelength is large compared to the cross-section of the cochlear channels. It is suspected that this hypothesis is not justified at and near the place where the wavelength is smallest. For several types of model the response is computed with due allowance for short waves. The results show that in the pertinent region short waves completely dominate the response. Several consequences of this finding are discussed.     

金堆城露天矿台阶爆破技术中交叉网络的应用

随着宽孔距、小排距技术的应用，解决了12m高台阶的爆破难题，提高了设备的效率。但是随着岩石的硬度越来越大，原有的斜线起爆网络和V型掏槽网络使得爆破后岩石的大块率增大。为了解决这个问题，采用排间交叉起爆、掏槽交叉起爆、斜线交叉起爆的网络方式，降低了大块率，形成了贯通性的岩体结构面，提高了铲装效率，取得了明显的经济效益。     

Analyzing Turbulence Intensity in Gravel Bed Channels

In this paper, the results of an experimental investigation of the turbulence intensity in gravel bed channels are described. The runs were carried out by measuring, with an acoustic Doppler velocimeter, the turbulence intensity profile along six verticals of a given cross section in a laboratory flume. The analysis of the measured intensity distributions has shown the existence of two different regions, above and below the tops of the roughness elements, in which different intensity profiles occur. Furthermore, the measured profiles have shown a maximum of the turbulence intensity that decreases for increasing values of the roughness height, confirming that the turbulence damping efficiency increases when the roughness elements protrude inside the flow. The applicability of Nezu’s relationship (derived for a hydraulically smooth bed) for the experimental intensity profiles above the roughness elements is positively tested. Finally a new intensity distribution for a rough bed, applicable to the whole water depth, is proposed. In this profile, two coefficients having a known physical meaning (the maximum turbulence intensity and the depth at which this maximum is located) appear.     

Kinematics of Overhanging Slopes in Discontinuous Rock

The kinematics of overhanging rock slopes and the mechanical constraints associated with this specific slope geometry were studied. Investigation of the problem began with a generalized rigid body analysis and was followed by a numerical discontinuous deformation analysis, both of which were performed in two dimensions. It was found that eccentric loading and hence the development of tensile stresses at the base of overhanging rock slopes control their stability. Global slope instability, which is typically manifested in a forward rotation failure mode, may ensue if a through-going vertical discontinuity, typically referred to as “tension crack,” transects the slope at the back. The transition from stable to unstable configurations depends on the distance between the tension crack and the toe of the slope. On the basis of the analysis, a simple threefold stability classification—stable, conditionally stable, and unstable—is proposed. In addition, geometrical guidelines, based on standard field mapping data, for the above stability classification are provided. Finally, the optimal reinforcement strategy for overhanging slopes is explored. The stability of overhanging slopes is determined by their eccentricity ratio, defined by the ratio between the base (B) and top (L) lengths: er = B/L. It was found that an overhanging slope with eccentricity ratio of er<0.38 is unstable and requires reinforcement. With an eccentricity ratio between 0.38相似文献   

石膏围岩隧道衬砌结构破坏模式及时变可靠度模型

石膏围岩具有很强的膨胀性和腐蚀性,在隧道全寿命周期内均会引起衬砌结构自身强度劣化及受力增加,严重影响隧道二次衬砌结构可靠性.针对石膏围岩膨胀特性和腐蚀性对隧道二次衬砌结构的影响分别建立了二次衬砌结构膨胀破坏模式和腐蚀破坏模式;考虑石膏围岩膨胀性和腐蚀性对隧道衬砌结构的综合影响,建立了石膏围岩隧道二次衬砌结构综合破坏模式;基于结构体功能函数,推导出能够初步考虑围岩膨胀性和腐蚀性的隧道衬砌结构可靠度指标计算公式;并分别建立了三种破坏模式下的时变可靠度分析模型.采用石膏围岩隧道衬砌结构综合破坏模式下的时变可靠度模型对礼让隧道进行了分析,得到其在使用寿命100 a内的可靠度指标变化规律.根据计算结果可以优化石膏围岩隧道衬砌结构的抗腐蚀、抗膨胀和支护结构设计参数,并对石膏围岩隧道使用寿命周期内的合理维护及维修提供依据.研究成果可推广应用于隧道衬砌结构的可靠度研究中.      

Mass Angle of Repose of Open-Graded Rock Riprap

Mass angle of repose (that is, the angle at which a mass of sliding particles will come to rest) is a fundamental material property that is needed to design drainage channel linings composed of open-graded riprap stone, also called dumped rock riprap, which protect earthen slopes from erosion by flowing water. Multiple regression analysis of measurements at 74 stockpiles of dumped natural and crushed rock shows the angle to depend primarily on rock particle angularity and, to lesser extents, on the gradation and the median particle diameter of the stone mixture, the angle increasing with angularity, mixture nonuniformity, and particle size. Uncomplicated expressions are developed from the data to calculate the expected mass angle of repose of open-graded rock riprap along with prediction intervals.     

Evaluation of Stream Grade Control Structures in Loess Soil Region

Grade control structures are used extensively to control river channel degradation. Although their use is widespread, the durability and performance of these structures, namely, sheet pile, H-pile, rock sill, and concrete block weirs have not been systematically evaluated. In this study, stream grade control structures in a loess area (western Iowa) were quantitatively evaluated with a performance number system to determine their field conditions and durability. For these evaluations, two dimensionless parameters (erosion control ratios and discharge ratios) were developed to correlate field observations and measurements. Structures that experienced small flows performed relatively well, whereas those that carried large discharges had poor performance. The stability of riprap decreases as the discharge ratio increases. Better riprap performance was obtained at structures with greater erosion control ratios. Based on these evaluations, problems associated with the structures were identified. In-channel movement of rock riprap was found to be a prevalent problem. Considerations for future designs and construction are recommended. The evaluation method and procedure can be applied to loess soil regions in the central United States and other regions worldwide. The information gathered can be used to guide field surveying and modeling studies.     

Stability and Erosion in Grassed Channels

Grass is a cost-effective form of erosion control. Since grass prevents erosion, the relationship between grass properties and erosion rate in grassed open channels is highlighted and analyzed within the context of channel stability. The deformation of grass caused by the flow’s momentum has been taken into consideration. Results are in good agreement with the available experimental erosion rate data for grassed channels. The purpose of this paper is to show that the amount of deformation of a grass channel lining due to flow can be used to estimate the erosion rate, and, as a result, lining deformation can be used as an indicator of channel stability. The method is simple enough to be useful for design.