长江下游三角洲堆积平原地区粉砂土高速路基边坡防护——以s19通锡高速南通段为例

Slope Protection of Silty Sand High-Speed Roadbed in Delta Accumulation Plain Area of Lower Reaches of Yangtze River—Taking the Nantong Section of s19 Tongxi Expressway as an Example

摘要: 粉砂土路基边坡水毁灾害是我国交通基础设施运维的核心难题，年均直接经济损失达85亿元，其中60%以上与粉砂土“三高一低”(高渗透敏感性、高孔隙率、高离散性、低胶结强度)特性相关。本研究以s19通锡高速南通段为典型案例，通过多尺度方法揭示了水毁机理：微观尺度上，同步辐射CT (0.7 μm分辨率)证实含水率超临界值(ω_cr = 18.5% ± 2.3%)时，颗粒接触点减少40%，黏聚力骤降78.2%；宏观尺度上，流固耦合模型显示渗透系数k_s > 4.7 × 10⁻⁵ cm/s且坡度 > 32˚时，边坡失稳概率超85%。针对行业痛点，提出创新防护体系：生态防护方面，狗牙根草皮根系抗拉强度达85 MPa，可降低饱和导水率62%；微生物矿化技术(MICP)使土体强度提升220%，但需解决干湿循环下强度保留率仅61%的缺陷。通过AHP评估，生态–MICP复合技术可降低全寿命成本35.5%。研究进一步构建智慧化发展路径，包括北斗/GNSS监测(预警精度 ± 1.2 mm)和3D-CNN滑坡预测模型(AUC = 0.93)。建议修订现行规范，增设粉砂土动态设计条款(如截水盲沟间距 ≤ 5 m)，并建立分级防护标准。未来需重点突破冻融循环适配性(冻融区损坏率23.5%)和低碳技术集成(生物炭固碳0.8~1.2 kg/m³)，推动行业从“被动抢险”向“主动防控”转型。

Abstract: The water damage disaster of silty sand subgrade slope is the core problem of transportation infrastructure operation and maintenance in China. The average annual direct economic loss is 8.5 billion yuan, of which more than 60% is related to the “three high and one low” (high permeability sensitivity, high porosity, high dispersion, low cementation strength) characteristics of silty sand. In this study, the Nantong section of s19 Tongxi Expressway was taken as a typical case, and the mechanism of water damage was revealed by multi-scale method. At the micro scale, synchrotron radiation CT (0.7 μm resolution) confirmed that when the water content was supercritical (ω_cr = 18.5% ± 2.3%), the particle contact point was reduced by 40%, and the cohesion dropped by 78.2%. On the macro scale, the fluid-solid coupling model shows that when the permeability coefficient k_s > 4.7 × 10⁻⁵ cm/s and the slope > 32˚, the slope instability probability exceeds 85%. Aiming at the pain points of the industry, an innovative protection system is proposed: in terms of ecological protection, the tensile strength of bermudagrass turf root system reaches 85 MPa, which can reduce the saturated hydraulic conductivity by 62%; microbial mineralization technology (MICP) increases the strength of soil by 220%, but it is necessary to solve the defect that the strength retention rate is only 61% under dry-wet cycle. Through AHP evaluation, the ecological-MICP composite technology can reduce the life-cycle cost by 35.5%. The research further constructs a smart development path, including Beidou/GNSS monitoring (early warning accuracy ± 1.2 mm) and 3D-CNN landslide prediction model (AUC = 0.93). It is recommended to revise the current specifications, add dynamic design clauses for silty sand (such as the spacing of blind ditches ≤ 5 m), and establish graded protection standards. In the future, it is necessary to focus on breaking through the adaptability of freeze-thaw cycles (the damage rate of freeze-thaw zone is 23.5%) and the integration of low-carbon technologies (biochar carbon sequestration is 0.8~1.2 kg/m³), so as to promote the transformation of the industry from “passive rescue” to “active prevention and control.”