The recheck results show that the dam crest elevation and wave wall elevation of Xia Ting Reservoir meet the specification requirements, and the flood discharge capacity of reservoir flood discharge facilities meets the design requirements. The existing flood control capacity reaches 1 10,000-year return period, which conforms to the flood control standard (GB 5020 1-94), and the current flood control safety is "A".
2 engineering quality evaluation
2. 1 topography and geology of the reservoir area
The dam site of Xia Ting Reservoir is located in the middle and low mountainous area at the southern foot of Siming Mountain. The mountains around the reservoir area are wide, and the elevation of the basin is above 400 m. Above the dam site, there is a mountain stream channel with short source and rapid flow. The riverbed is covered with sand and pebbles, and some bedrock is exposed on both banks. The reservoir basin and reservoir bank are composed of impermeable volcanic rocks and a small amount of sedimentary rocks, and the dip angle of strata is generally slow, mostly below 20 degrees. Although there are Macun-Yucun faults leading to the outside of the reservoir, they are on the backwater line, and most of them are filled by the time pulse, which is well cemented and will not cause permanent leakage.
2. 1.2 macun landslide
The Xiashishan landslide in Macun is located on the right bank of the reservoir area, with a linear distance of 2.2km from the dam site, with a total volume of nearly100000 m3, 80% of which is above the flood level, and most of the sliding surfaces are below the natural groundwater level, so the change of groundwater level caused by reservoir impoundment has little influence on it. After the reservoir is filled with water, the stability safety factor K=0.98, which is only reduced by 2%. In order to monitor the development trend of landslides, the Provincial Hydropower Design Institute has set up special displacement monitoring facilities inside and outside the landslides. After 20 years' regular monitoring and inspection by Xia Ting Reservoir Management Bureau, it is confirmed that the Xiashishan landslide in Macun has never occurred since the reservoir impoundment. Add the safety assessment website to your favorites.
2.2 Engineering Geology of Dam Site Area
2.2. 1 lithology and geological structure
The bedrock distributed in the dam area is Moshishan Formation of Upper Jurassic, which is composed of layered altered breccia tuff, conglomerate breccia, spherulite, silicified rhyolite mixed with sericitized crystallized pearl porphyry and tuff lava from bottom to top, and covered with Quaternary alluvial-diluvial sandy pebble layer. There are 29 faults in the dam foundation, most of which are distributed on the right side of 10# dam section, and the dip angle along the river channel is steep. The fracture zone is generally narrow (0.05 m ~ 0.4 m), and individual faults reach1.2 m ~ 2.0 m. The fillings are mainly breccia and mylonite, and some of them contain fault mud. There are mainly two groups of joints, N700E, SEL800, N200W and NEL800, which form an angle of 350 ~ 550 with the dam axis.
Layered altered breccia tuff is most widely distributed in dam foundation (6 # ~ 16 # dam section), with a gentle dip angle (100 ~ 230), with a single layer generally ranging from 0.5 m to 2.0 m, and a thicker one reaching 4.5 m ... 6 # ~12 # dam section. The interlayer is mainly composed of scaly and lenticular cuttings, fragments and stone powder, which is generally sericitized and generally filled with secondary yellow mud within 5 ~ 6 m below the bedrock surface. The anti-sliding stability of riverbed dam section is controlled by this interlayer, and the F value of weak interlayer is designed to be 0.35 ~ 0.45.
hydrogeology
The groundwater in dam foundation is bedrock fissure diving, and its permeability is controlled by fault structure, bedding plane and flow surface.
Ω = 0.055 ~ 0. 17 (L/min m m) for the left abutment, 0.02 ~ 0.05 (L/min m m) for the riverbed and dam foundation, and 0.047 ~ 0.063 L/min m for the unmelted interlayer. Among them, 1 1 ~ 14 dam section with developed faults and bedding, the dam foundation has strong water permeability, and the relative impermeable boundary (ω
2.3 dam foundation and bank slope treatment quality evaluation
The excavation of dam foundation and abutment is carried out according to the design and construction specifications, and the prying treatment is relatively thorough. Pre-splitting blasting is mostly used in dam foundation excavation, and the excavation size is standardized, which has little vibration to bedrock and the excavation of dam foundation and abutment is qualified. The special geological problems existing in the foundation, such as faults and broken interlayers, are treated in engineering.
Two rows of cement grouting curtain are used for dam foundation seepage control (one row for the left and right abutment), and the unit water absorption meets the design requirements. The interlayer in the drainage hole of dam foundation is protected by "combined filter".
2.4 dam concrete engineering quality evaluation
The overall dimensions and smoothness of the dam meet the design requirements. During the dam construction, some temperature control measures were taken, but cracks still appeared in some parts of the dam. After that, low viscosity epoxy grouting was adopted, and the treatment effect was good, and the strength of concrete met the requirements of the specification.
This time, Anjian conducted core drilling, rebound strength measurement and carbonation depth test on dam concrete. The sampling positions are as follows.
See table 2. 1 and table 2.2 for the test results of upstream and downstream dams and pier tops. The compressive strength at the test age and the compressive strength at the converted age of 28d meet the design requirements.
Table 2. 1 Compressive strength and carbonation depth of concrete core sample
sample ore
figure
location
Dam section number
And wheelbase
Pile number
Altitude (m)
carbonize
depth
(mm)
age
specific
design strength
Compressive strength at test age (Mpa)
1#
Upstream surface
3 dam section
Wheelbase 0
0+0 18.0
74.63
five
≥20 years
150#
36.9
2#
Upstream surface
7 dam section
Wheelbase 0
0+097.0
74.63
four
≥20 years
200#
43.7
3#
Upstream surface
13 dam section
Wheelbase 0
0+202.7
74.63
three
≥20 years
150#
36.9
4#
Downstream surface
4 dam section
16.5 downhole
0+46.4
70.80
10
≥20 years
100#
34.6
5#
Zadunding
19.0 downhole
0+83.6
89.00
seven
≥20 years
150#
4 1.2
6#
Zadunding
19.0 downhole
0+ 103.5
89.00
seven
≥20 years
150#
40.8
7#
Downstream surface
13 dam section
Lower shaft 42.3
0+ 195.4
40.60
six
≥20 years
100#
25.2
Table 2.2 Measurement Results of Rebound Strength of Concrete
Inspection location/date
(6 September 2004)
Number of survey areas (unit)
Conversion value of concrete compressive strength (Mpa)
Contemporary concrete
Estimated intensity (MPa)
Average intensity value
Standard deviation
Minimum strength value
▽18.00m
1 1 upstream face in dam section corridor
10
48.9
8.5
37.4
35.0
▽18.00m
Inner face and downstream face of gallery of dam section 8
10
39.4
12.6
25.5
18.6
54.00 meters
12 inner and downstream face of dam section corridor
10
45.0
8.6
33.7
30.9
54.00 meters
1 1 upstream face in dam section corridor
10
32.7
6.3
26.2
22.3
1# downstream face of right pier of hole
eight
37.0
4.8
3 1.5
3 1.5
Side face of left pier of No.3 hole
10
56.9
3.3
5 1.5
5 1.4
Side face of left pier of 4# hole
10
54.6
4.2
47.8
47.8
Side face of right pier of No.5 hole
10
54.4
4.2
48.0
47.5
70.00 meters
Upstream face of dam section 14 corridor
10
42.8
4.2
35. 1
35.9
70.00 meters
Downstream face of corridor of No.7 dam section
10
37.7
5.5
3 1.3
28.7
70.00 meters
Upstream face of corridor in 10 dam section
10
36.0
3.0
32.7
3 1. 1
54.00 meters
15 left side of gallery entrance of dam section
10
29.3
2.9
25.3
24.6