Functional filling of mine thermal storage has achieved the synergy of deep underground ore deposits and geothermal energy extraction. It is urgent to develop functional filling materials with suitable phase change parameters and excellent physicochemical properties. Aiming at the current situation that microencapsulated phase change materials (MicroPCM) lead to the decrease of compressive strength and thermal conductivity of the backfill

this study carries out pre-experiments to investigate the strength characteristics and thermal properties of the phase change backfill. After determining an optimal MicroPCM additive amount

the study further investigated the effects of various silicon carbide (SiC) additions (ranging from 0% to 8% by mass) on the compressive strength

thermal conductivity

and specific heat capacity of the phase change backfill. The density

water secretion rate

and fluidity of the backfill were also tested. At the same time

scanning electron microscope-energy dispersive spectrometer (SEM-EDS) was used to observe its micro-morphology

and energy spectrum analysis was carried out to explain the macro-experimental phenomena

to explore its thermal energy storage stability under alternating high and low temperature cycles. The following conclusions were obtained that the specific heat capacity of the phase change backfill reached a maximum of 1.75 MJ/(m·K) at 5% MicroPCM addition. The maximum density of the backfill

1.67 g/cm³

occurred at 2% SiC addition. As SiC content increases

both fluidity and water secretion of the backfill gradually rised. The compressive strength and thermal conductivity of the backfill increased continuously with the increase of SiC addition

and the increase was 10.1% and 21.7%

respectively

to 6.64 MPa and 1.12 W/(m·K) at 4% addition

and then the growth trend decelerated. The specific heat capacity of the phase change backfill exhibited a trend of initial growth followed by decay with increasing SiC addition. The fluctuation amplitude remained small. The maximum specific heat capacity of 2.32 MJ/(m³·K) is achieved at 4% SiC addition

making this the recommended SiC content. After 500 cycles of alternating high and low temperatures

the compressive strength of the phase change backfill increased

with a positive correlation to SiC content. Both the coefficient of thermal conductivity and specific heat capacity decreased

with the rate of decline gradually diminishing. This study offers data for reference in practical engineering applications of thermal storage filling.