# Study on the Bearing Characteristics of Composite Foundations with Permeable Concrete Piles
## 1 Introduction  
In coastal regions, foundations predominantly comprise soft soils characterized by high water content, high compressibility, poor permeability, and low shear strength. These properties make them susceptible to settlement and deformation during natural disasters [1]. Constructing directly on such foundations can lead to reduced structural bearing capacity and uneven settlement [2]. Composite foundation and drainage consolidation methods are widely used for soft foundation treatment. The composite foundation method involves installing vertical reinforcement elements with high strength to share the upper load, offering the advantage of shorter construction periods [3]. In contrast, the drainage consolidation method establishes drainage channels to accelerate excess pore water pressure dissipation, promoting the consolidation of soft soil foundations. This method is cost-effective but requires a period of extended construction [4]. The bearing mechanism of composite foundations is complex, involving cushion load transfer and pile-soil interaction. The research is mainly carried out through theoretical derivation, numerical simulation, and experimental analysis. [PERSON] [5] proposed and verified the calculation method for settling the cement fly-ash gravel (CFG) pile composite foundation. [PERSON] [6] found that the vertical stress of the pile varies with depth. [PERSON] [7] foundthat the pile side friction resistance increases with the load. He [8] discussed the cushion mechanism of the CFG pile composite foundation in detail through research. They deduced the optimal space between piles, cushion thickness, pile-soil stress ratio, and actual replacement ratio used to guide the design of CFG pile composite foundations. [PERSON] [9] obtained the influence law of the thickness of the cushion layer. Its compression modulus on the pile-soil stress ratio and settlement through finite element analysis and the research results provide a theoretical basis for the appropriate selection of the cushion layer thickness and its materials, which is conducive to the optimized design of composite foundations. Pervious concrete is porous concrete composed of cement, coarse aggregate, or a small amount of fine aggregate, water, and admixtures in specific proportions, providing permeability and air permeability functions. Due to its high porosity and high permeability, permeable concrete is often considered an alternative to traditional hard impermeable pavement, which can control rainwater economically and in an environmentally friendly manner [10]. Currently, pervious concrete is widely used in roads, sidewalks, parking lots, and low-traffic buildings. It is also an environmentally friendly concrete material. The aggregate type, particle size, pore size connection, and pore size of permeable concrete significantly impact the strength and permeability of permeable concrete [11]. The performance of permeable concrete can be improved by optimizing the mix ratio, using additives, and improving the preparation process [12]. For example, permeable concrete made of cyclone aggregate and recycled aggregate has high compressive strength and permeability, respectively [13]. Adding mineral admixtures such as ore powder, fly ash, and silica fume can optimize the interface transition zone of permeable concrete and improve the comprehensive performance of permeable concrete [14]. It is concluded that the main difference between permeable concrete pile composite foundations and traditional piles is soil consolidation around the pile, and its bearing characteristics need to be further studied. This study aims to analyze the bearing characteristics of pervious concrete piles in composite foundations through laboratory experiments and numerical simulations.