Cracking characteristics and reinforcement measures of the middle outlets in the Xiaowan arch dam.
|Location||Crack number||Depth of cracks (m)||Cracking description||Reinforcement measures|
Number 21 dam monolith (number 1 diversion outlet)||21LF-1 ||1.2||0.3 ||Cracks are distributed at ring shape in the dam monolith from EL 1012 m~1110 m. There are 19 cracks with length less than 3 m in the left side wall of the number 1 middle diversion outlet at the downstream side and 1 microcrack with length smaller than 2.3 m in the right sidewall|| |
Crackings around the diversion middle outlets have been inspected before August 2008. At that time, these cracks did not coalesce with the thermal cracks caused due to temperature gradients, which were not completely identified. The reinforcement measures were cracking filing and surface permeable-resistant coating
It was noted that cracks around the diversion middle outlets have coalesced with the thermal cracks due to temperature gradients till May 2009. The main reinforcement measures include chemical grouting, crack filling, and surface permeable-resistant coating, which are detailed as follows
(1) Cracks are grooved and filled
(2) Surface permeable-resistant coating: the surface of the dam monoliths is coated using impermeable polyurea with a thickness of 4 mm in 2 m around the cracks. For the area with the dense fine cracks, the 2 m is counted from the crack located in the boundary of the area
(3) Chemical grouting is applied in the cracks which coalesce with the thermal cracks due to temperature gradients
|21LF-2 ||1.7 ||0.3 ||In April 2009, a crack with a length of 29 m along the flow direction was found in the floor of the number 1 middle diversion outlet at the upstream side, which perpendicularly intersected with thermal cracks due to temperature gradients. No cracks were found in the roof and side walls|
Number 22 dam monolith (number diversion outlet)||22LF-1||1.1 ||0.3 ||Cracks are distributed in the number 22 dam monolith between ELs 1068 m and 1098 m but above the floor of the number 2 middle diversion outlet whose EL is 1065 m|
|1 ||0.2 ||Cracks coalesce with surface cracks in the number 2 middle diversion outlet. The cracks 22LF-2 are distributed in the number 22 dam monolith at ELs between 1013 m~1050 m. The cracks 22LF-3 are distributed above 5 m~7 m below the cracks 22LF-2 |
Large number of irregular microcracks were observed to distribute in ring shape in the floor, side walls, and roof of the number 2 middle diversion outlet between the thermal cracks 22LF-2 and 22LF-3 in the second-round inspection of the outlets in February 2009.
|22LF-4||1 ||0.3 ||The cracks lie in the downstream side of the number 22 dam monolith between ELs 972 m~1012 m, which are expected to intersect with the surface of the dam monolith|
Number 23 dam monolith (number 3 diversion outlet)||23LF-1||1.7||0.5||The cracks are distributed in the number 23 dam monolith between ELs 1001 m~1108 m and extend through the number 3 middle diversion outlet |
|23LF-2||1.75||0.5||The cracks lie in the number 23 dam monolith between ELs 977 m~1025 m, which extend till 1021 m but have not reached the floor of the number 3 middle diversion outlet.|