Despite recent advances in the procedures for logging rotary borehole core, the Lambeth Group Upper Shelly Beds are often inadequately characterised during ground investigations for underground construction. With no recognised industry guidance, there has been a lack of clarity and detail in many logging records, other than a generic description of “dark grey clay with many shells and (local) hard bands.” Improvements in describing these deposits have been hindered by the relatively limited extent of their subcrop and rarity of surface exposure, allied to a lack of precedent intersection during underground construction excavation.

Geological logging during construction of the Thames Tideway Tunnel has revealed a laterally continuous sequence of strata within the Upper Shelly Beds through central London. This ranges in lithology from strongly indurated shell ‘coquinas’, mudstones and limestones to organic-rich laminated clays, silts and fine sands. Abrupt changes in lithology and fossil fauna are displayed across sharp contacts between beds, indicative of rapid fluctuations in sea level (and so potentially of climate change) during the period of deposition.

Notwithstanding their comparatively limited thickness of between 1.4 and 1.6 m within the area of investigation, the Upper Shelly Beds represent significant challenges for underground construction, most notably a reduction in the rate of excavation through the stronger layers of material. Early identification of the sequence has enabled modification and improvement to the on-site construction cycle and provided valuable assurance for the existing engineering design.

This paper is intended to provide guidance for recognising the sequence of strata within the Upper Shelly Beds during future ground investigations in central London, with similar benefits for early recognition of the stronger layers during engineering design.

尽管最近对旋转钻孔岩心进行测井的程序有所进步，但是Lambeth Group上壳层床在地下施工的地面调查中常常没有足够的特征。在没有公认的行业指导的情况下，除了“带有许多壳和（局部）硬带的深灰色粘土”的一般描述之外，许多伐木记录中都缺乏清晰度和细节。描述这些沉积物的改进因其次作物的相对有限的程度和地表的稀有性而受到阻碍，并且与地下建筑开挖期间缺乏先验的相交有关。

泰晤士河潮道隧道施工期间的地质测井显示，贯穿伦敦市中心的上谢利河床内地层横向连续。岩性范围从坚硬的贝壳“ coquinas”，泥岩和石灰石到富含有机物的层压粘土，粉砂和细砂。床层之间的尖锐接触显示出岩性和化石动物群的突然变化，这表明在沉积期间海平面迅速波动（从而可能引起气候变化）。

尽管在研究区域内其相对有限的厚度在1.4到1.6 m之间，但上部雪层床对地下建筑构成了重大挑战，最显着的是通过更坚固的材料层降低了开挖速度。对顺序的早期识别可以修改和改善现场施工周期，并为现有的工程设计提供了宝贵的保证。

本文旨在为将来在伦敦市中心进行地面调查时识别上雪莱层中的层序提供指导，并为工程设计过程中尽早识别强层提供类似的好处。