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In this study, a latex membrane with a diameter of 50 mm and thickness of 0.5 mm is used to encase an injection hole. The gap between the membrane and the nail rod is fixed to achieve compaction grouting and to prevent fracturing and permeating; hence, a regular grout bulb is easily formed and locked into the soil matrix to provide a pullout force for a compaction-grouted soil nail. For this type of soil nail, two series of physical model tests for an embedded soil nail and a soil nail with a predrilled hole (the soil sample was moistened and could sustain the hole without collapsing during the placement of the nail rod) were conducted to study the influence of the installation methods on the performance of a compaction-grouted soil nail. The results of the two series of tests were compared, and some conclusions were drawn: First, the aforementioned installation methods for a soil nail had little impact on the mass of injected grout, whereas the shape of the cured grout bulb showed some differences based on the type of soil response. Second, compared with that of an embedded soil nail, the pullout force of a postplaced soil nail remarkably decreased because the hole drilled for installation led to a gap between the soil nail and the surrounding soil. In addition, the loss rate correlated with the grouting pressure (i.e., the diameter of the grout bulb). Third, because of the lower soil densification, dilation, and squeeze effect, a slower growth rate (with increasing grouting pressure) of the pullout force (i.e., resistance) was found for the postplaced soil nail relative to that of the embedded soil nail, during which the efficiency of the increasing pullout force decreased. [ABSTRACT FROM AUTHOR]

An important research topic in reinforcing deep soft soil slopes is the pullout distribution of a long anchor with multiple grout bulbs under various factors. The nonlinear variation between the compaction effect and grout bulb diameter was first quantitatively described using an exponential model. The pullout force of a long anchor with multiple grout bulbs was then calculated using a modified model considering the compaction effect. After verification based on the model test data, a parametric analysis was carried out on the elastic modulus of the anchor rod, grout bulb diameters, bulb numbers, and bulb sequences. The results indicated that a larger elastic modulus leads to a more obvious hardening behavior and a lower mobilized displacement of the pullout force. The grout bulb diameter significantly influences the ultimate pullout force and the mobilized displacement of the pullout force. Although the bulb number affects the ultimate pullout force and the distribution of the pullout force, the mobilized displacement of the pullout force does not change. For a long anchor with multiple grout bulbs, the sequence of the bulb diameters has a significant impact on the ultimate pullout force and the distribution and mobilized displacement of the pullout force. [ABSTRACT FROM AUTHOR]

This paper presents a work to define four fundamental concepts, namely, buoyant force, submerged unit weight, seepage force, and critical hydraulic gradients, for saturated geomaterials including soils, rocks, and concrete under normal and high pressures using the general effective stress (GES) concept along with Terzaghi's effective stress. In particular, four typical GES expressions are used for this purpose, and their impacts on the definition of the four concepts are compared based on available experimental evidence in the literature. The results suggest that (1) Terzaghi's effective stress can be physically validated in the context of Archimedes' principle for soils under normal conditions; (2) the generalized buoyant force on the unit volume of saturated geomaterials is the product of the unit weight of pore fluid and the GES coefficient tensor; and (3) the generalized seepage force theoretically acts in the direction of pore fluid flow only when the GES coefficient tensor is proportional to the permeability coefficient tensor. These four fundamental concepts have a profound significance for geotechnical applications with GES and thus merit further validation with adequate laboratory and in situ observations. [ABSTRACT FROM AUTHOR]

Stress conditions and preflaws are prominent conditions influencing the cuttability of deep hard rock. This study aims to investigate the cuttability of intact, prefractured, and drilled rocks under biaxial confining stress, uniaxial confining stress, and stress-free conditions using a conical cutter in rock fragmentation tests on true triaxial loading apparatus. Peak cutter force and penetration depth at rock initial fracture and final failure of the rock specimen were used to reflect rock cuttability. The results show that the rock cuttability increases with stress in one direction decreasing under biaxial confining stresses, and presents a decreasing trend followed by an initial increase as uniaxial confining stress increases. The prefractures and boreholes in rock can further improve the rock cuttability, compared with intact rock. A series of cuttability improvement measures were proposed to provide a suitable condition for the application of nonexplosive mechanized mining in hard rock. Finally, comparative field tests were performed on a single-face entryway and a peninsula-shaped pillar, in which the mean value of cutting efficiency increased from 32.6 to 107.7 t/h, and the dust production and cutter wearout failure reduced significantly. [ABSTRACT FROM AUTHOR]