دانلود رایگان ترجمه مقاله برآورد پارامتریک سازه های نگهبان میخ کوبی خاک در خاک چسبنده و غیر چسبنده – الزویر 2015

ارزیابی پارامتری سازه های نگهبان میخ کوبی خاک در خاک های چسبنده و غیر چسبنده

Parametric assessment of soil-nailing retaining structures
in cohesive and cohesionless soils

1. Introduction

Soil nailing is an in situ construction technique used for enhancing the stability of retaining walls, slopes, and excavations. Because of advantages such as low cost, easy construction, mature construction techniques, and short construction period it has been widely used in engineering. It can be used to allow the safe over-steepening of new or existing soil slopes or as a remedial measure to treat unstable natural soil slopes. The method involves the insertion of reinforcing elements (i.e., nails) into the slope. General-purpose reinforcing bars (‘rebar’), but also hollow-system or proprietary solid bars are available. Hollow bars may be drilled and grouted simultaneously by a sacrificial drill bit, pumping grout down the hollow bar as drilling progresses; solid bars are usually installed into pre-drilled holes and then grouted into place using a separate grout line. Nails work predominantly in tension, under certain circumstances, but may also work in bending and/or shear. Nails are integrated tightly with the soil around them; therefore they can form a type of composite soil. Such composite soils rely mainly on the frictional force of the contact surface. The details of a typical nail and tension anchors are presented in Figs. 1 and 2. Many observations have been made on the performance of experimental retaining walls reinforced with dynamically driven nails [1–4]. Yin et al. [5] presented a simplified analytical method for calculating the maximum shear stress of the nail-soil interface. In order to examine the effects of several important parameters on the maximum shear stress of the nail-soil interface, they conducted an extensive parametric study. It was observed that when there was no grouting pressure, maximum shear stress increased with decreasing drill-hole radius or increasing failure surface distance, overburden pressure, or dilation angle. Zhang et al. [6] used centrifuge model tests and investigated failure and deformation of a nailing-reinforced slope. They performed a series of centrifuge model tests under vertical-surface loading conditions, considering different nail lengths and slope gradients. The deflection of nails increased with the increasing load pressure, and showed diverse features in distribution in the lower and upper parts of the slope. Ng and Lee [7] also used a three-dimensional parametric to study soil nails for stabilizing tunnel faces. Cheuk et al. [8] investigated on numerical experiments of soil nails in loose fill slopes subjected to rainfall infiltration effects. Davies and Morgan [9] studied on the serviceability of soil nailed slopes. They evaluated the influence of the effective stress on the serviceability of nailed cut slopes. Their experiments showed that the nail loads can increase remarkably when an earth structure is subjected to a reduction in effective stress. Such reduction will normally occurs from an increase in pore water pressure. Wu et al. [10] studied the influence of cohesion (C) and internal-friction-angle (u) values on a slope reinforced by a soil-nailing wall in a thick miscellaneous fill site. They concluded that the internal friction angle and cohesion of the soil (i.e. shear strength parameter of the soil) have great influence on the stability of the soil nailing slopes. Their analysis shows that if c and u values are reasonably chosen, the slope reinforced by soil nailing wall will be much safer. Cheuk et al. [11] investigated the effect of soil-nail orientations on stabilizing mechanisms of loose-fill slopes. They recommended the use of steeply inclined nails throughout the entire slope to prevent global instability, although stating this could lead to significant slope movement, especially with prevailing sliding failure. Dong et al. [12] explored seismic analysis and design methods for soil-nailing retaining walls. Their analysis model provides a new approach for seismic design and seismic analysis of soil-nailing retaining walls. Zhang et al. [13] discussed extensively the relationship between stability and deformation of soil-nailing structure. They offered a new idea and method to determine deformation of similar supporting structures. The new method has some significance for improving the specifications of foundation pits. They also calculated the deformation of soil-nailing structures. Zhang et al. [14] evaluated the load-deformation behaviour of soil nails using a hyperbolic pull-out model. They studied the interaction mechanism of a soil nail and the surrounding soil and its influential factors. Accordingly, a hyperbolic shear stress– shear strain relationship was proposed using a pull-out model to define the load-deformation behaviour of a cement-grouted soil nail. The proposed model was efficient and accurate, as the laboratory soil-nail pull-out test results in the literature were highly consistent with simulation results. Wang and Wu [15] proposed a new technique to calculate the seismic active earth pressure of soil-nailing retaining structures. Their results show that lateral pressure of supporting structures under earthquake ground motions can be effectively reduced with soil nails. Seo et al. [16] investigated the optimization of soil-nailing retaining wall design considering three failure modes: shear failure, the pull-out failure, and face failure. They theoretically verified the mechanical behaviour of face failure, shear failure, and pull-out failure. The proposed design procedure of soil nailing presented here could be a more satisfactory design procedure in the actual field. In the last decades the technology of shorting systems, particularly soil-nailing retaining structure, has significantly improved. Some of the most recent technology is mentioned above. The main objective of the present research is to assess the behaviour of soil-nailing retaining structures after a parametric assessment of the measured data from numerical simulation for a real-scale soil-nailing retaining structure.