Abstract
Monitoring analysis was performed for the deformation characteristics of a deep roadway in soft rock masses in a certain mine by the convergence instrument. It was indicated that shotcrete and bolt support for the surrounding rock deformation under forces produced a poor effect so that a shotcrete rockbolt mesh coupling support pattern was put forward and four coupling support schemes were designed to carry out field monitoring for surrounding rock deformations on the basis of above schemes. According to the research, we could summarize as follows. Firstly, when load in floor strata reached a certain value, shear failure took place on the edge of floor; then, with the continuous increase of such a load, shear zones were subsequently expanded and connected together into one big region; at that time, as the load on floor strata had been up to its limit, the floor could be settled sharply as long as this load went up slightly so that the uplift of rock mass gave rise to floor heave. Secondly, bearing capacity of floor rocks was dependent on the average binding force, internal friction angle and unit weight of floor rocks as well as the concentrated stress action width of lateral wall and the average pressure value borne by the roadway floor. Thirdly, after the shotcrete rockbolt mesh coupling support was adopted, two-sided displacement dropped 80% and above, roof subsidence decreased more than 70% and the capacity of floor heave falls by over 90%; as a result, stability of the roadway could be significantly improved.
Highlights
Surrounding rocks of tunnels are found to be in a complex mechanical environment after roadway excavation
If the load keeps going up, those zones can be connected together into one big region subsequently; at that time, it is indicated that the load on floor strata has reached its ultimate bearing capacity Pu and it is on the verge of being damaged
With a slight increase in such a load, the floor could be settled sharply so that general shear failure happens to the floor strata and floor heave is generated by the uplift of floor rock mass
Summary
Surrounding rocks of tunnels are found to be in a complex mechanical environment after roadway excavation. Soft rock roadway of No 600 level (depth of 600 m) in an underground mine is taken as an example to study dynamic evolution laws of soft rock roadway stress as well as the surrounding rock stress and displacement features in floor roadway during their exploitation by adopting a method of field monitoring combining numerical simulation On this basis, is a shotcrete rockbolt mesh coupling support pattern presented, but four support schemes are designed direct at the engineering practice. In accordance with measured results, it can be seen that due to impacts of excavation and in situ stress field, high-stress soft rock roadways are significantly deformed with a two-sided displacement of 155 mm, a roof subsidence of 93 mm and a floor heave capacity of being up to 232 mm which is the greatest one among roadway deformation and displacement followed by two-sided displacement and the smallest roof subsidence Those monitoring results indicate that current support pattern is unable to effectively control the deformation of surrounding rocks.
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