the mechanism of hysteretic ground settlement caused by shield tunneling in mixed-face conditions

by:Gewinn     2019-09-05
Shield is widely used in coal mine roadway, hydropower tunnel, traffic tunnel, etc.
But tunneling with a tunnel rig (TBM)
It will inevitably cause ground subsidence.
Although a large number of studies have been carried out on the surface settlement caused by tunnel excavation in soft soil, at present, the research on the surface settlement caused by tunnel excavation in sand pebble formation is still very limited, it is not possible to fully study the delayed settlement mechanism caused by tunnel excavation in sand pebble formation.
The ground stability state or surface settlement can be determined according to the actual situation
Monitoring data of surface dynamic sinking time.
Subsequently, the tunnel tunneling parameters can be adjusted according to different geological conditions. A sand-pebble-
The soil matrix is a typical non-uniform material. The macro-
The mechanical properties of this matrix are very different from any material.
In the case of low water level and small interference, the formation can be stable for a long time.
Taking into account the features of the formation, the ground loss can be divided into two stages: immediate settlement and delayed settlement, the former tends to be stable, and the latter tends to occur in the sand.
Cobblestone formation, where the development speed of settlement is much slower than that of a single formationmedium strata.
In the case of settlement lag, the monitoring data is not enough to guide the construction. Cobble-
The soil matrix can be regarded as a spatial structure system composed of single granular soil, granular soil particles and pellets.
Based on two-dimensional particle flow code (PFC2D)
The mechanical properties of the matrix and the shield tunneling process are simulated.
The movement of Pebble particles is tracked and recorded in real time.
This model discusses the mechanism of surface collapse from the perspective of macroscopic mechanics.
According to the model, a matrix forms
The stable arch covering the underground cavity seems to wear out gradually as the cavity expands and eventually penetrates into the ground.
The surface movement rules and the formation mechanism of surface subsidence in the whole rock tunnel are studied.
The main factors affecting the surface settlement are the propulsion speed, the groundwater level and the support period.
In numerical analysis, surface-
The loss lag is reproduced and the on-site monitoring data is verified.
The results of this study provide a new method for the Study of ground subsidence similar to the formation.
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