September/October 2022 - 18

designed and installed at both the gates. The outlet was
reopened for water flow in October 2016.
Trevi also managed the maintenance and repair of the
tunnel dewatering systems, and the four main gantry cranes
located at the guard gate tower, at the bottom outlet regulating
structure, at the spillway and at the hydropower intakes.
Another remarkable feature was the inspection and
maintenance of the steel bulkheads. These bulkheads are
lodged in a concrete structure located in the lake at about 40
m (131 ft) depth. With the deployment of a dedicated pontoon
and a specialized crew including six divers, bulkheads were
lifted to the surface and fully inspected. Refurbishment was
successful and bulkheads were returned to their storage
position in the reservoir. This allowed for the dewatering of
the upstream culverts and the inspection of the entire length
of the 700 m (2,297 ft) long twin bottom outlet tunnels. All the
joints and expansion joints were inspected and repaired
where necessary.
Bathymetric surveys and hydraulic computer models
were applied to evaluate the scour potential in the plunge
pool. Based on these models, a structure with dentates (also
known as baffle blocks) was designed and installed at the exit
of the bottom outlets to dissipate the water energy and reduce
future erosion of the stilling/plunge basin during operation.
Drilling and Grouting
Drilling and grouting started in earnest
at the end of October 2016. The goal of
these works was to install a grout
curtain along the full length of the 2,200
m (7,218 ft) grouting gallery, and at the
490 m (1,608 ft) east and 220 m (722 ft)
west abutments, by injecting grout
mixes able to intercept and plug
openings ranging in size from fissures
to voids. Due to the stratigraphy,
previous grouting depths and design
considerations, it was necessary to drill
and inject grout to a depth of 150 m
(492 ft) or greater. The grout curtain was
also extended through the 280 m (919 ft)
length immediately west of the
spillway to grout the rock between the
base of the embankment and the top of
the grouting gallery.
The dam remained operational
during grouting operations. As a result,
especially during periods of higher
water levels in the reservoir, the
grouting activities were further
complicated by significant water-head
of as much as 100 m (328 ft) and
significant artesian conditions.
18 * DEEP FOUNDATIONS * SEPT/OCT 2022
Main mixing plants
Drilling operations in the gallery
The grouting gallery is accessible through two relatively
long and narrow adits located at left and right abutments. The
size of the gallery, with slopes up to 41%, posed significant
challenges in terms of equipment configuration and
maneuvering, entailing the use of small-size rigs and grouting
plants. Soilmec supported Trevi in customizing the machines
with special features.

September/October 2022

Table of Contents for the Digital Edition of September/October 2022

TOC
September/October 2022 - Intro
September/October 2022 - 1
September/October 2022 - 2
September/October 2022 - TOC
September/October 2022 - 4
September/October 2022 - 5
September/October 2022 - 6
September/October 2022 - 7
September/October 2022 - 8
September/October 2022 - 9
September/October 2022 - 10
September/October 2022 - 11
September/October 2022 - 12
September/October 2022 - 13
September/October 2022 - 14
September/October 2022 - 15
September/October 2022 - 16
September/October 2022 - 17
September/October 2022 - 18
September/October 2022 - 19
September/October 2022 - 20
September/October 2022 - 21
September/October 2022 - 22
September/October 2022 - 23
September/October 2022 - 24
September/October 2022 - 25
September/October 2022 - 26
September/October 2022 - 27
September/October 2022 - 28
September/October 2022 - 29
September/October 2022 - 30
September/October 2022 - 31
September/October 2022 - 32
September/October 2022 - 33
September/October 2022 - 34
September/October 2022 - 35
September/October 2022 - 36
September/October 2022 - 37
September/October 2022 - 38
September/October 2022 - 39
September/October 2022 - 40
September/October 2022 - 41
September/October 2022 - 42
September/October 2022 - 43
September/October 2022 - 44
September/October 2022 - 45
September/October 2022 - 46
September/October 2022 - 47
September/October 2022 - 48
September/October 2022 - 49
September/October 2022 - 50
September/October 2022 - 51
September/October 2022 - 52
September/October 2022 - 53
September/October 2022 - 54
September/October 2022 - 55
September/October 2022 - 56
September/October 2022 - 57
September/October 2022 - 58
September/October 2022 - 59
September/October 2022 - 60
September/October 2022 - 61
September/October 2022 - 62
September/October 2022 - 63
September/October 2022 - 64
September/October 2022 - 65
September/October 2022 - 66
September/October 2022 - 67
September/October 2022 - 68
September/October 2022 - 69
September/October 2022 - 70
September/October 2022 - 71
September/October 2022 - 72
September/October 2022 - 73
September/October 2022 - 74
September/October 2022 - 75
September/October 2022 - 76
September/October 2022 - 77
September/October 2022 - 78
September/October 2022 - 79
September/October 2022 - 80
September/October 2022 - 81
September/October 2022 - 82
September/October 2022 - 83
September/October 2022 - 84
September/October 2022 - 85
September/October 2022 - 86
September/October 2022 - 87
September/October 2022 - 88
September/October 2022 - 89
September/October 2022 - 90
September/October 2022 - 91
September/October 2022 - 92
September/October 2022 - 93
September/October 2022 - 94
September/October 2022 - 95
September/October 2022 - 96
September/October 2022 - 97
September/October 2022 - 98
September/October 2022 - 99
September/October 2022 - 100
September/October 2022 - 101
September/October 2022 - 102
September/October 2022 - 103
September/October 2022 - 104
September/October 2022 - 105
September/October 2022 - 106
September/October 2022 - 107
September/October 2022 - 108
September/October 2022 - 109
September/October 2022 - 110
September/October 2022 - 111
September/October 2022 - 112
September/October 2022 - 113
September/October 2022 - 114
September/October 2022 - 115
September/October 2022 - 116
September/October 2022 - 117
September/October 2022 - 118
September/October 2022 - 119
September/October 2022 - 120
September/October 2022 - 121
September/October 2022 - 122
September/October 2022 - 123
September/October 2022 - 124
September/October 2022 - 125
September/October 2022 - 126
September/October 2022 - 127
September/October 2022 - 128
September/October 2022 - 129
September/October 2022 - 130
September/October 2022 - 131
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/march-april-2024
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/january-february-2024
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/november-december-2023
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/september-october-2023
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/july-august-2023
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/may-june-2023
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/Jan-feb-2021_nxtbook
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/july-august-2021
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/march-april-2023
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/january-february-2023
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/november-december-2022
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/september-october-2022
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/july-august-2022
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/may-june-2022
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/march-april-2022
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/january-february-2022
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/november-december-2021
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/sept-oct-2021
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/july-aug-2021
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/may-june-2021
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/march-april-2021
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/january-february-2021
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/november-december-2020
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/September-October-2020
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/may-june-2020
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/march-april-2020
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/january-february-2020
https://www.nxtbook.com/dfi/DEEP-FOUNDATIONS/july-august-2020
https://www.nxtbookmedia.com