The existence of flaws in brittle rocks or rock‐like materials has an obvious influence on the material mechanical properties and cracking behavior of civil engineering projects. In this work, the two‐dimensional particle flow code PFC^2D was used to study the deformation and strength properties, failure processes, and acoustic emission (AE) characteristics of mudstone with a single preexisting flaw. First, the procedure to construct a parallel bond model is introduced. The Weibull distribution is used to reflect the mechanical heterogeneity of rocks. Then, the microscopic parameters used in PFC^2D are calibrated to the macroproperties of mudstone obtained from laboratory tests under the uniaxial compression. The results indicate that the increases of the flaw inclination lead to the increasing uniaxial compressive strength and elastic modulus. In terms of microcrack evolution, the initiation, propagation, and coalescence of microcracks are closely related to the force chain. Specifically, an “X” shaped tension force chain concentrated area around the preexisting flaw is founded, which is the most prone area for microcracks to initiate. With an increase in flaw inclination, the b value of AE also shows an increasing trend. By incorporating the AE event numbers into a damage variable, this paper derives a constitutive model, which is verified by numerical results on brittle rocks with a single preexisting flaw under uniaxial compression.

In the installation of pre-bored grouted planted (PGP) piles and other composite pile foundations, cement is commonly used in the grouting stage. However, the cement-production process generates significant CO₂ emissions, which are not favorable for achieving low-carbon societal goals. This study explores the use of industrial solid waste (mineral powder and gypsum powder) mixed with cement as a grouting material in test pile TP1, while traditional cement grout was used in test pile TP2. Both test piles were instrumented with optical fiber sensors along their shafts. The findings indicate that the ultimate load-bearing capacity of TP1 was approximately 93% of that of TP2, signifying a 7% reduction when mineral and gypsum powder were added to cement. Additionally, TP1’s peak surface friction in various soil layers ranged from 1.29 to 2.79 times that of the bored pile, whereas TP2’s peak surface friction was about 1.42 to 3.10 times higher. The cement consumption for TP1 was roughly 65% less than for TP2, and the cost of grouting materials for TP1 was reduced by 35%. This study confirms that utilizing solid waste in the grouting stage of PGP piles is feasible, and optimizing material proportions may enhance future performance.

Pre-bored grouted planted pile has been increasingly applied in infrastructure construction in soft soil areas in recent years owing to its high bearing performance, low construction disturbance, and reduced slurry discharge. However, the synergistic load-bearing mechanism between the inner core pile and the surrounding cement soil is relatively complex, and the design calculation methods provided in existing studies and specifications for this pile type remain incomplete. Therefore, based on field tests, this study investigates the compressive bearing performance and load transfer behavior of pre-bored grouted planted piles, and further develops calculation methods for bearing capacity and settlement. The results show that, in this test field, due to grouting and slurry penetration reinforcement, the ultimate shaft resistance at the cement soil–soil interface is significantly improved, reaching 1.49–3.21 times the recommended values for bored cast-in-place piles in current codes. The enlarged base effectively enhances pile tip bearing capacity, while a nodular core pile near the pile base promotes the mobilization of base resistance. Furthermore, shaft resistance and base resistance models, together with their corresponding calculation methods, are established by considering both the enhancement effect of grouting on interface shaft resistance and the contribution of the enlarged pile base. Calculation methods for total bearing capacity and settlement are also summarized based on the two field test piles at this test site. The findings of this study can provide experimental support, theoretical basis and methodological reference for the bearing mechanism analysis, bearing capacity and settlement calculation, and engineering application of pre-bored grouted planted piles and similar composite pile foundations. Because the conclusions are based on only two field test piles at a single site, further validation with more field test data under different geological conditions is still needed.