Causes and Countermeasures of freeze-thaw damage o

Causes and Countermeasures of freeze-thaw damage of Shanqian hydropower station channel

Shanqian hydropower station in Luanping county, Hebei Province is located in the middle and upper reaches of Luanhe River. It is a runoff power station with a design head of 16m, a design flow of 16.7m3/s, a total installed capacity of 1.92mw, and an annual power generation of 7gwh. The power station adopts hp-rtm process to produce small composite material parts. The diversion channel is 2km and the tailrace channel is 1km when the temperature impact is large. Due to the cold winter climate in Yanshan Mountain Area in northern Hebei Province, the minimum temperature at night is -21 ~ -29.5 ℃ and the maximum temperature during the power generation shutdown time from the end of December to the beginning of January of the next year is -8 ~ 5 ℃. The channels of the power station are alternately frozen and thawed, which can not reveal their essential damage, so that the cement mortar on the surface of the masonry is denuded, the frozen soil behind the retaining wall expands, so that the straight wall tilts to the inner side of the channel by dozens of centimeters, and many collapses occur, Seriously affect the mastery of waste plastic recycling technology nbsp; The construction of waste plastic recycling economy system has helped the safe operation and economic benefits of power stations

1 reasons for channel freeze-thaw

after years of operation and management practice, the author has a certain understanding of the freeze-thaw problem, and the main reasons are as follows

1.1 poor construction quality reduced the frost resistance of the channel

as the power station was built in the early 1980s, the low level of specialization of the construction team, poor quality of workers, and inadequate management caused the project quality to get out of control. The channel soil foundation is not compacted, the backfill on both sides of the channel wall is not dense, the cement mortar grade is too low, the masonry is not full, and all processes are not constructed according to the process requirements, resulting in strong water permeability and poor anti-seepage and anti freezing capacity of the masonry

1.2 the selection of channel section is unreasonable

the intake channel of the Piedmont power station and most of the sewage channels are of masonry structure, and the section type is rectangular. The advantage of rectangular section compared with ladder section is that the width of the channel top is small, and the occupation of cultivated land can be reduced by 22%. The disadvantage is that the channel walls on both sides need to adopt a larger section due to the high earth pressure, which increases the amount of masonry work and engineering investment. After recent years' operation, it is found that the rectangular section is more suitable for rock foundation, and on the soil foundation, the wall gradually tilts towards the canal due to the expansion of frozen soil behind the straight wall, which becomes an important reason for the collapse of the canal wall

1.3 improper selection and use of building materials

the masonry or concrete works at the winter water level changes and the alternating parts of freezing and thawing are not designed and constructed according to the frost resistance requirements, especially the pozzolan cement and slag cement with poor frost resistance and permeability resistance are used, their grades are low, and the silt content in the sand is large. The cement causes serious freeze-thaw damage of the masonry and mortar falling off