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In order to study the effect of backpacking containing barite powder on the heat transfer efficiency of buried pipe boreholes in plain and mountainous areas of Beijing, a comparative analysis of laboratory experiments and field thermal response experiments was carried out. The quaternary boreholes in plain areas were backfilled with medium sand and the bedrock boreholes in mountainous areas were backfilled with cement mortar. When the specific gravity of medium sand barite powder was 5%, the thermal conductivity of medium sand backfill samples increased by 14%. When 5% barite powder was added to cement mortar, the thermal conductivity increased 7.3%. According to the field thermal response test results, under summer conditions in the same site, the heat transfer rate of a backfilling borehole containing barite powder increased by 2.4 W/m and 3.5% per meter compared with that of the medium-sand backfilling borehole in plain area. The heat transfer rate of cement mortar backfill containing barite powder increased by 2.7 W/m and 3.9% per meter. The numerical simulation model of the quaternary system and bedrock area was established. It was found that the content of barite powder increased to 10% and the heat transfer rate of boreholes increased by about 6.0%. In general, the heat transfer capacity of buried pipe is improved and its sustainability gets better after adding barite powder.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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