土体初始结构强度的表征及其数值确定方法

Characterization of initial structural strength of soils and its numerical determination method

【目的】定量地表征岩土体的结构性,对探明岩土工程性质具有重要意义。为描述岩土体结构性的强弱,【方法】首先通过分析传统先期固结压力与结构性岩土体先期固结压力的内在联系,提出岩土材料的初始结构强度表征;随后对天然含水与饱和状态青海旱台黄土试样进行侧限压缩试验,并基于改进的Casagrande数值确定法获取其初始结构强度;最后构建土体初始结构强度数值确定的计算框架,并通过算例核验该框架的有效性。【结果】结果显示:侧限压缩条件下土体的初始屈服应力为岩土体初始结构强度的表征,非结构性土的初始结构强度仅由物理压密贡献,结构土与沉积岩的初始结构强度是由物理压密与成岩作用共同贡献;提出的压硬性边界条件(在竖向应力P属于0到最后阶荷载的定义域内,孔隙比随着lgP的增加单调递减)可为数值确定法择选出更适用于压缩曲线的拟合模型。【结论】改进的数值确定法具有良好的精确性与适用性,可快速精准地获取岩土体初始结构强度,为岩土工程设计提供理论依据。

[Objective]Quantitative analysis of geotechnical material structures is of great significance for identifying the engineering properties.To describe the structural strength of soils,[Methods]the relationship between traditional pre-consolidation pressure and that of structural geotechnical materials is firstly analyzed,and the initial structural strength characterization of geotechnical materials is presented.Following this,a lateral compression test was conducted on Hantai loess from Qinghai Province,and its initial structural strength was obtained based on a modified version of the Casagrande numerical determination method.Subse-quently,a calculation framework for assessing the initial structural strength of geotechnical material is developed and its validity is confirmed through examples.[Results]The results indicate that,the initial yield stress under confined compression is a representation of the initial structural strength of geotechnical material.The strength of unstructured soil is only contributed by physical compaction.Conversely,the strength of structured soils and sedimentary rocks originates from both physical compaction and diagenesis.The proposed compression-hard boundary condition can be used to select a more suitable fitting model for the compression curve,which is the pore ratio decreases consistently with the logarithmic increase of vertical stress,when this stress lies between 0 and the last order load.[Conclusion]The enhanced numerical determination method proposed in this study exhibits high accuracy and applicability.This research provides a rapid and precise approach for determining the initial structural strength of geotechnical materials,thereby laying a solid theoretical foundation for the design in geotechnical engineering.