Experimental Study on Lateral Bearing Mechanical Characteristics and Damage Numerical Simulation of Micropile

Abstract

The construction site of the foundation pit support project in the urban area is narrow. Micropile has the advantages of flexible pile position layout, strong site adaptability, and fast construction speed, which can effectively control the horizontal displacement of the foundation pit and ensure the safety of surrounding buildings. However, the lateral bearing capacity of micropile is weak. In order to study the lateral force characteristics and failure characteristics of micropile, laboratory tests on the flexural and tensile strength of reinforced concrete micropiles with different diameters and with or without external steel pipes were performed. The authors studied the lateral force characteristics and failure characteristics of various types of micropiles. Based on numerical simulation software ABAQUS, the measured yield strength of the specimen was used as the loading force. And taking the occurrence and development of concrete damage into consideration, the loading process was simulated. The result shows the following: (1) the micropile specimens with external steel pipe had better flexural performance than the bare micropiles and the mechanical characteristics of the specimens changed from brittleness to plasticity; (2) the degree of concrete damage is greatly reduced after the external steel pipe is attached, and the bearing capacity of the micropile specimen of the same diameter is increased by 70% after the external steel pipe is added; and (3) the specimens were mainly damaged due to tensile damage. The calculation formula for the lateral bearing capacity of the concrete-filled steel tube micropile considering the damage is proposed through fitting analysis. The calculation formula, the finite element calculation value, and the calculation formula proposed by other scholars are compared with the authors' test and the test data of other scholars. The meta-calculation results, experimental results, and formula calculation results proposed by the authors have high accuracy.

Horizontal and Uplift Bearing Characteristics of a Cast-In-Place Micropile Group Foundation in a Plateau Mountainous Area

“…This indicates that the transfer of lateral friction resistance increases gradually from top to bottom. As shown in Figure 10, at the ultimate load, Part 3 exhibits the highest average lateral friction resistance (45-63 kPa), followed by Part 1 with a slightly lower average lateral friction resistance (21-33 kPa), and Part 2 shows the lowest average lateral friction resistance (11)(12)(13)(14)(15)(16).…”

“…In recent years, researchers both domestically and internationally have conducted extensive investigations into the force mechanisms of micropiles, employing prototype tests, model tests, and numerical simulations, and yielding noteworthy findings. Theoretical analyses of micropiles typically rely on three primary methods: the p-y curve method [6][7][8], the load-structure method [9], and the finite element method [10][11][12]. All these approaches serve for both qualitative and quantitative assessments of micropile bearing capacity.…”

Development of Expanded Steel Pipe Pile to Enhance Bearing Capacity

“…The increase in the strength of materials and the development in construction technology have resulted in the use of micropiles composed of small-diameter steel pipes recently. Micropiles are advantageous because of their characteristics, such as flexible pile placement, short construction period, and strong field applicability, owing to the use of light construction equipment [4]. In addition, a small borehole volume minimizes the effect of construction materials on the ground environment [5].…”

“…However, the slender ratio increases corresponding to the increase in micropile length, thereby increasing the risk of buckling. The low resistance to bending of micropiles was evaluated through experiments [4]. In addition, it was confirmed through numerical analysis that as the slender ratio increased, the bending deformation increased [22].…”

Numerical Analysis on the Bending Capacity of the Concrete-Filled Micro-Steel-Tube Piles

“…Micropile is a bored pile with a diameter typically in 150-300 mm range and internal steel-bar reinforcement, which is usually used to underpin existing structures, reduce di erential settlements, and serve as the main foundation components [1][2][3][4]. As the extension of the micropile, concrete-lled micro-steel-tube (CFMST) pile, generally refers to cast-in-place pile with a pile diameter of less than 300 mm and using construction techniques such as drilling and pressure grouting.…”