# Experimental Study on Scour Resistance Performance Enhancement of Chongqing Red Clay
###### Abstract
[25] conducted physical flume tests on cement-solidified soil-protected pile foundations, concluding the feasibility of this protection method. For small-diameter piles, the optimal protective range diameter was seven times the pile diameter, whereas for large-diameter piles, it was reduced to five times. [PERSON] et al. [26] evaluated the long-term performance of solidified soft soil through immersion, wet-dry cycle, and freeze-thaw cycle tests. Results showed that soft soil modified with curing agent and recycled fine aggregate remained intact after 28-day water immersion, exhibited minimal mass and strength loss under wet-dry cycles, and demonstrated excellent freeze-thaw resistance. [PERSON] et al. [27] utilized alkali-activated steel slag as a curing agent to improve the mechanical properties of saline soil. They found that unconfined compressive strength increased significantly at dosages exceeding 15%, accompanied by denser structures and continuous gel-bonded particle networks, confirming its effectiveness for saline soil modification. [PERSON] et al. [28] demonstrated that seawater significantly weakens the mechanical performance of cement-solidified soil while curing agent addition mitigates this effect. Each 0.5% increase in polyacrylamide (PAM) dosage improved 7-day and 14-day compressive strength by 27.03% and 34.61%, respectively. [PERSON] et al. [29] revealed that the flowability of solidified soil increases with water content but decreases with curing agent dosage, while the slurry retention rate declines with higher flow velocity and flowability. [PERSON] et al. [30] highlighted that strength enhancement in cement-solidified soil primarily stems from interparticle cementation and expansive product filling, where cementation forms the foundation of strength development and filling facilitates its progression. [PERSON] et al. [31] modified five types of soft clay with varying liquid limits using two curing agents, demonstrating that improvement effects depend critically on water content and curing agent dosage. Although previous studies have confirmed the excellent performance of solidified soil, the contradiction between its flowability and anti-dispersion under complex hydrodynamic conditions remains unresolved. Specifically, high-flowability solidified soil exhibits severe dispersion upon water entry, while low-flowability solidified soil fails to meet pumping requirements, a technical bottleneck that severely restricts engineering applications. This study focuses on the scour protection project for pile foundations of Piers 15 and 16 (with a maximum pile foundation exposure of 5.3 m) of the Chongqing Jiangjin Yangtze River Highway Bridge, using local red clay as the research material. Through flowability tests, anti-dispersion tests, scour resistance tests, and microstructural analysis, we reveal the performance evolution of solidified soil under multi-factor coupling effects, clarify the critical thresholds for underwater anti-dispersion and construction flowability, and determine the optimal mix proportion that balances scour resistance and construction feasibility, thereby providing theoretical support and design basis for bridge pier foundation protection engineering.