Characteristics of shallow underground ancient channels in urban areas: A case study of Quaternary underground palaeochannel in Tonghu Basin, Guangdong Province

Human civilization and urban development are closely related to rivers. Due to its longitudinal and horizontal evolution, the complex distribution of palaeochannel formed in the geological history period and buried underground, the distribution in urban underground is relatively complex. However, in view of the prominent engineering geological problems such as the sensitivity and vulnerability of the distribution area of palaeochannel in the process of space development, it is urgent to find out the spatial characteristics and engineering characteristics of palaeochannel course. The quaternary system of Tonghu basin in Huizhou City, located in the east wing large bay area of Guangdong Province, was taken as an example. Comprehensive use of drilling and geophysical data, combined with surface inherited deposits, this work started from fine stratigraphic division and sedimentary facies identification, through the process of "vertical staging, lateral demarcation, flat profile interaction". A set of methods for analyzing and describing ancient rivers were establish by analyzing the structure of ancient river and sedimentary interior in depth step by step, which can provide reference for the characterization of underground space in other areas of the Greater Bay Area and other cities with similar sedimentary characteristics.