ABSTRACT
Geological uncertainty is common due to complex depositional processes as one layer appears to be randomly embedded in neighbouring layers. The geo-structures could be significantly affected by geological uncertainty, such as tunnels. Borehole data obtained during the geological survey is the most commonly used information to simulate geological uncertainty. However, borehole data is usually sparse and inadequate. With the process of tunnel excavation, a large amount of new formation information will be continuously revealed. How to effectively used this disclosed geological information to update previously modeled formations? In other words, the geological cross-section along the planned tunnel trajectory can be used as additional information to incorporate with the original borehole data to update the simulated stratum dynamically. This study aims to develop a dynamically updating geological simulation framework incorporating the original borehole data and geological cross-section revealed from continuous tunnel excavation. The coupled Markov chain (CMC) model is a popular method to simulate geological uncertainty. Firstly, the initial stratum is obtained using the coupled Markov chain model based on limited borehole data. Then, the geological formation of the tunnel cross-section will be given with the process of tunnel excavation. Next, adding the additional information to the coupled Markov chain model to update the whole stratum simulation. The dynamic update of the whole stratum simulation can be realized along the tunnel trajectory by repeating the above process. The proposed framework can provide a dynamic formation modelling with tunnel excavation. It continuously updates the whole simulated stratum through the formation information revealed by the tunnel cross-section. It can also be used to forecast geological cross-sections ahead of the tunnel face, which will be helpful for tunnel construction. Results show that the proposed method can adequately use the original borehole data and revealed geological information to update the simulated stratum with the tunnel excavation dynamically.
