Research of optimal floor heave control technology and its engineering application in soft rock roadway

In the soft rock mining area of western China,the floor heave is a kind of common form of soft roadway distortion and failure.The deformation of surrounding rock caused by floor heave has become a major problem that hinders the efficient mine production.It is also an urgent problem in the western mining area.At present,the widely used control scheme is to control the floor heave of roadway by pouring concrete material,inverse arch and bolt support.However,according to the on-site destruction results,the ordinary C20 concrete material with inverted bottom arch has defects such as low strength and poor compaction,and cannot effectively control the floor heave.The large-scale destruction of the bottom corner of roadway and its two walls reveal the shortcomings of the support scheme.Based on this,a scheme of optimizing the pouring material was proposed to improve its initial setting time and strength,the optimal treatment scheme of concrete pouring material was to mix quicklime into concrete slurry in different proportion.The strengths of the test pieces with different quicklime incorporation at different ages were tested,and then the optimal ratio scheme was selected.Scanning electron microscope was used to observe and analyze the structure of pouring material,and the optimized pouring material was determined to meet the performance requirements of the pouring material in the inverted arch structure.The optimized support scheme was optimized for the bottom corner of the roadway and the weak area of the two sides of the support to strengthen the support strength of the roadway,and control the floor heave by combining with the bottom arch.The results show that during the curing period,the maximum uniaxial compressive strength of the test piece is 30.15 MPa,which is 1.39 times the strength of the ordinary C20 concrete material,and the tensile strength is 1.75 MPa,which is 1.41 times the strength of the test piece not mixed with quicklime.Scanning electron microscope observation and analysis show that when the content of quicklime is 10%,the structure of the test piece is dense,the amount of Ca (OH)2,AFt and pores in the slurry is significantly reduced,and the mechanical properties of the casting material are effectively improved.Engineering practice shows that with the optimized pouring material the maximum bottom drum volume is only 101 mm during the 50-day monitoring period,and the roadway bottom heave volume is reduced to 34% of the original supporting scheme.The surrounding rock control effect is obvious.