现场软土欠固结程度孔压消散试验评价方法

原位测试技术分析软土的应力历史可以避免取样及室内土工试验对土样的扰动，其结果能真实地反映现场土体的工程特性。以往基于孔压静力触探（CPTU）测试技术的超固结比（OCR）计算方法主要是针对超固结土取得的，缺乏对现场处于欠固结状态土体的考虑，具有一定的局限性。在已有研究成果的基础上，提出采用不完全孔压消散曲线的末段及时间平方根倒数外推法计算原位初始孔压，如果初始孔压大于静水压力，表明原位土层中存在固有孔压，为欠固结土。在此基础上，通过计算固结状态参数，可进一步对软土层的欠固结程度进行定量评价。工程应用表明，该方法不受软土性质和地域限制，具有普遍适用性，是合理可行的。在缺乏室内固结试验成果的情况下，可高效快捷地判别软土层的固结状态。研究成果对合理评价欠固结软土的工程特性具有一定的指导意义。

Degree of underconsolidation determination method of in-situ soft soil through pore pressure dissipation test

Stress history of soft soil analyzed by in-situ test technology can avoid the structural disturbance of soils during sampling and laboratory experiments,and better reflect their real property.Traditional overconsolidation ratio(OCR) calculation methods of cone penetration test with pore pressure measurement(CPTU) technology are mainly based on overconsolidated soils and lack consideration of those soils under the condition of underconsolidated state.Therefore,it shows certain limitations in practical application.Based on literature review,a consolidation state evaluation method is introduced in detail.First,the in-situ initial pore pressure is deduced through final part of the incomplete pore pressure dissipation test curve together with the extrapolation method of inverse time square root of time.It means that there exists inherent pore pressure if the initial pore pressure is greater than hydrostatic pressure;and the soil is underconsolidated.Then,the degree of underconsolidation of soft soil can be quantitatively evaluated by calculating the parameter of consolidation state.Engineering application indicates that the method is not only reasonable but feasible,and can be widely used without limitation of soil property and region.The method can effectively determine the consolidation degree of soft soil without any laboratory consolidation test.The research achievement is instructive for reasonable engineering property assessment of underconsolidated soft soils.