Ground subsidence due to the backfill pressure in tunnel boring machine

In shield tunnel boring machine constructions, backfill pressure affects surface settlement and the stability of other underground structures nearby. Therefore, it is essential to pre-calculate backfill pressure in the design stage. This study examines and compares the seven internationally known backfill pressure calculation theories and calculates and analyzes the backfill pressures in six virtual ground conditions. The calculated backfill pressure increased as the ground cover increased, but the increase rate decreased. Also, this study performs a numerical analysis to identify the impact on ground settlement and tunnel crown settlement. In the end, settlement was more impacted by face pressure than backfill pressure in the unsaturated and saturated ground conditions. Also, as the ground cover increased, the impact of backfill pressure decreased, and as the applied face pressure decreased, the impact of backfill pressure increased.

Experimental and numerical distribution of pressure on the abutment with backfill from tyre bales

This article describes the tests of the pressure distribution on bridge abutment generated by the backfill made of the recycled car tyres compressed in the form of bales with interfaces of medium sands and a buffer layer with tyre shreds. Backfill pressure distribution was measuring continuously over a period of three months using a pressure sensors. Static and dynamic load tests of abutment were conducted and cyclic horizontal displacements of the abutment wall, as a simulation of thermal elongation / shortening of the bridge span were also performed. The results of pressure field measurements were compared with results of numerical analysis performed using the GEO5 program basing on finite element method. Compatibility results of field measurements and numerical analysis was pretty good, and the maximum difference was about 25%. Based on field measurements and numerical analysis, a 2÷4 times reduction of pressure on bridge abutment was found, if the tyre bales had been used, compared to conventional backfilling of medium sand.

Study on Emergency Monitoring and Deformation Law of Slope

The slope of a project in Guiyang, due to heavy rain and other causes of serious deformation, the arrangement of 40 monitoring points, the slope of the emergency monitoring monitoring shows that the use of rapid and then accurate emergency method is feasible; Backfill pressure can stabilize the slope quickly. The supporting slope is characterized by strong deformation integrity and retrograde sliding. Guizhou is a mountainous area with many engineering slopes, which has reference value for emergency monitoring of similar slopes.