In situ tests were performed on three types of micropiles under static compressive loading: straight, expanded-base, and double-expanded. The results show that the ultimate compressive bearing capacity of the expanded-base and double expanded micropiles is 1.40 times and 1.49 times greater than that of the straight micropile, respectively, indicating that incorporating an expanded section effectively enhances the ultimate bearing capacity of a single pile. The middle expanded section of the double-expanded micropile engages more of the surrounding soil in bearing the upper load, considerably increasing the side friction over that for the other two types of micropiles at the same depth. Under the ultimate load, the proportion of the load carried via the end resistance is 42
To mitigate dynamic hazards, such as rock bursts and roof collapse, induced by deep mining disturbances, we integrated laminated rubber—known for its superior impact resistance and energy absorption—into a novel low-strain energy-absorbing rockbolt. We quantitatively evaluated the buffering effects of laminated rubber on rock specimens under impact loading via split Hopkinson pressure bar tests, focusing on three key metrics: the degree of rock fragmentation, energy absorption rate, and dynamic failure duration. With an impact energy of 600 J, increasing the number of rubber layers from two to six (corresponding to thicknesses of 6–36 mm) substantially enhanced the buffering performance. Specifically, the rock fragmentation fractal dimension decreased by 28
Recently, granular anchor piles (GAPs) have emerged as a sustainable alternative for resisting uplift forces on foundations. The aim of this study is to design and analyze the behavior of GAP using finite element-based software PLAXIS 3D. The influences of the pile length, axial capacity of the anchor rod, concrete layer placement, and relative density of the granular material were analyzed. The results demonstrated that the pull-out force for GAP significantly increased when the axial capacity of the anchor rod increased, but improved negligibly beyond 250 MN. The inclusion of a concrete layer increased the value of the pull-out force for GAP. Additionally, the designed GAP was compared with other uplift-resisting piles: underreamed and helical piles. The anchorage diameter of all three pile types was held constant for comparison and the effect of the number of anchorages in the pile was analyzed. For all cases, the response of GAP ranged between those of underreamed and helical piles. However, the pull-out capacity of GAP was closer to that of underreamed piles at L/d = 5 and L/d = 10 for single and double arrangements of anchorage, respectively.
A novel technology designed to enhance the reliability and stability of post-grouting at the bottom of bridge-pile foundations is proposed in this paper. Based on a pile-foundation construction project, static load tests are conducted under distinct operational conditions: composite post-grouting and non-grouting. The investigation examines the dynamic variations in grouting parameters during the grouting process and validates the efficacy of composite post-grouting through an examination of bearing-capacity improvement. The findings reveal that the pile-bottom composite post-grouting technology can effectively improve the reliability and stability of pile grouting, eliminate sediments, form an expanded head at the bottom of the pile, and improve the bearing capacity of the pile foundation, with a noteworthy 29.5
An improved stability analysis method for embankments supported by the piles in cement-improved soil is proposed in this paper. Based on the bending moments and distribution of tension damage in inner piles at the sliding moment, it is inferred that the failure modes of the piles in cement-improved soil are substantially different from those of flexible piles. The most likely failure modes are divided into two types according to the pile locations, bending failure inside the slope foot and soil sliding upward which results in excessive deformation outside the slope foot. Thicker cement soil helps to delay inner pile cracking under bending. An analysis method for the safety factor is proposed after the determination of the resistance contribution of piles in different failure modes. Safety factors calculated by this method are the most accurate according to the numerical simulation results.
