INGENIEUR
The infiltration section of a tunnel is the
groundwater collection section, where the
groundwater table is located, so groundwater can
seep into the tunnel to provide a water source for
the system. The vertical shafts in the infiltration
section are also called mother wells and are dug
first to explore the aquifer. The initial digging
of the mother wells is usually at the outcrops of
rich springs, which are locally called the Digging
Springs, the Expanding Springs and the Extending
Springs in sequence.
Vertical wells
Once the mother wells are successfully located, an
array of vertical shafts (locals call them wells) are
constructed along the downslope of the alluvial
fan to align the tunnels, provide ventilation and
facilitate future maintenance (e.g. cleaning silt
sediment). The interval between two adjacent
shafts generally ranges from 60m to 100m in
the upper section, 30m to 60m in the middle
section and 10m to 30m in the lower section. The
diameter of the shafts is about 1–1.5m. The depth
decreases progressively down the slope, generally
ranging from 40m to 70m in the upper section (to
a maximum of 100m), 20m to 40m in the middle
section and 3m to 15m in the lower section.
Water conveying tunnels
The conveyance section of a tunnel is used
to transport collected groundwater to low soil
surfaces adjacent to farmlands. The length of the
tunnel varies from 3km to 5km, and the longest
in Xinjiang is more than 10km. The tunnel has
an appropriate slope gradient to ensure water
transport by gravity. The tunnel gradient mainly
depends on soil conditions, and is normally less
than that of the slope on the ground. The inner size
of a tunnel is large enough so that the tunnel can
accommodate at least one person for excavation
operation. The cross-section of many tunnels is
oviform, about 2m high and 1m wide, but existing
old tunnels have irregular shapes.
Once the vertical shafts are completed, they
are connected by a single tunnel. The excavation
tools are mainly a mattock and a short-handled
spade. A windlass is usually installed at the mouth
of the shaft. Workers on the surface, with the
help of the windlass, raise a bucket loaded with
silt unearthed by an underground worker. A cow is
Figure3: Models at the museum demonstrating
winching method to lower workers into the well
Figure 4: Models at the museum demonstrating
another winching method to transport earth
materials from the tunnels
76 VOL 81 JANUARY-MARCH 2020