堆载作用下含炭质软弱地层的变形特征分析

Analysis of Deformation Characteristics of Carbonaceous Soft Strata Under Surcharge Loading

摘要

含炭质的软弱土体通常具有强度低、压缩性高、易产生塑性流动的特性,其地层在堆载作用下极易进入塑性屈服状态,导致地层出现显著侧向变形,可能对其所在地层及周围地基造成不利影响。以湖南某高速公路含炭质深厚淤泥地层条件下的混凝土拌合站建设为工程背景,针对地表堆载可能引发地层侧向变形并危及邻近地基的问题开展了研究。首先,建立了能反映含炭质软土层力学特性的地层数值模型,并利用现场实测数据验证了该模型的合理性;然后,基于验证的计算模型,采用数值模拟方法系统分析了深厚含炭质淤泥地层在堆载作用下的变形与附加应力分布模式;最后,通过参数分析,探讨了地层组合(特别是全风化炭质泥灰岩层厚度)以及堆载大小、堆载方式对地层侧向位移的影响规律。具体结论如下:地层的侧向位移主要由软弱土体进入塑性屈服状态并产生持续侧向流动所致;堆载对侧向位移的影响范围约为2倍填土宽度,且侧向位移对堆载的响应比沉降更为敏感;全风化层越厚,受堆载影响的范围和深度越大;在总填筑高度相同的情况下,分层填筑次数越多,产生的侧向位移越小。研究揭示了堆载作用下含炭质软弱地层的变形机理,以期为含炭质深厚淤泥地区评估堆载填筑影响提供借鉴和参考。

Abstract

Carbonaceous soft soils typically exhibit low strength, high compressibility, and a tendency toward plastic flow. Under surcharge loading, such strata are prone to enter a plastic yield state, leading to significant lateral deformation, which may adversely affect both the stratum itself and the surrounding foundations. Taking the construction of a concrete batching plant under deep carbonaceous silty clay conditions along a highway in Hunan Province as its engineering background, research was conducted to address the potential problem of lateral deformation of the stratum caused by surface surcharge loading that could endanger nearby foundations. First, a numerical model of the soil strata reflecting the mechanical properties of carbonaceous soft soils was established and verified using field measurement data to confirm its validity. Then, based on the validated model, a numerical simulation method was systematically used to analyze the deformation and additional stress distribution patterns of the deep carbonaceous silty clay layer under surcharge loading. Finally, through parameter analysis, the study explored the effects of stratum composition (particularly the thickness of the fully weathered carbonaceous mudstone layer), as well as the surcharge magnitude and method, on lateral displacement of the strata. The specific conclusions are as follows: lateral displacement of the strata is mainly caused by the soft soil entering a plastic yield state and undergoing ongoing lateral flow. The influence range of surcharge loading on lateral displacement is approximately twice the width of the fill, and the lateral displacement is more sensitive to surcharge than settlement. The thicker the fully weathered layer, the greater the range and depth affected by the surcharge loading. Under the same total fill height, more layers of fill result in smaller lateral displacement. This study reveals the deformation mechanisms of carbonaceous soft soil under surcharge loading, aiming to provide reference and guidance for assessing the impact of surcharge fills in areas with deep carbonaceous silty clay.

关键词

路基工程 / 淤泥 / 堆载 / 侧向变形 / 数值模拟

Key words

roadbed engineering / silty clay / surcharge loading / lateral deformation / numerical simulation

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基金资助

国家自然科学基金面上项目(52578503)