10th Asian Regional Conference of IAEG (2015)

Study on the comprehensive logging experiment of the Nibashan Tunnel, China
Yong REN(1), Jun WU(2), Xiyong WU(1)(3), Chunwei SUN(1)(1) Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, China
E-mail: ng_iln@hotmail.com; wuxiyong@126.com(2) Guizhou Expressway Group Co. Ltd., Guizhou Province, China(3) Moe Key Laboratory of High-speed Railway Engineering, Southwest Jiaotong Unviersity, China
Abstract
Nibanshan Tunnel located in the core of the Daxiangling Anticline, Sichuan Province,
China. The strike of the axial line is mainly NW which varies SN at the tunnel section, and thetunnel goes through the anticline which contains 16 structural fracture zones. The bed rocks,
the various petrographic formation and the structural fracture zones constitute a complicatedhydro-geological system. Many field tests were carried out in the purpose of clarifying thehydro-geological framework of the tunnel zone. Taking the ZK No.2 logging as an example,
the use of the comprehensive logging experiment as an investigation method of thehydro-geological framework is introduced in this paper.
Keywords: Comprehensive logging experiment; hydro-geological framework; Nibanshan
Tunnel; solution resistivity; longitudinal wave velocity; lateral resistivity
1.

Introduction

comprehensive logging experiment to understand theunderground water reservoir characteristic of theigneous rocks and the permeability of the fault zones in
the purpose of safety construction (e.g., Li, 2003).

As a kind of linear underground building, thetunnel will inevitably pass through different hydrology
geology in the construction process. Water inflow is acommon geological disaster and the main inducement
cause of other disasters (e.g., Kong, 2011).
The Nibashan tunnel is located in the edge ofLongmeshan fault. The maximum depth of the tunnel is1701 m, and about 5 km length of the tunnel is deeper
than 1600 m. As a result, a large number ofunderground water is stored in the igneous rockfissures and joints in mountain. The formation of water
inrush passages is mostly the geological flaws,
including fault, fracture, joints and unfavorable sectionin the surrounding rock over a tunnel (Shi and Singh,2001). Some scholars have researched the microscopic
pore characteristics in acidic volcanic reservoir fromthe oil and gas exploration (Pang et al., 2007). The
water reservoir space has characteristics of complexity,
instability and heterogeneity, because of thenonuniformity of the igneous compositions, thecondensation environmental differences and the uneven
degree of porosity and fissures (Holmøy and Nilsen,2014). The water inrush is likely to occur in the fault
zone and joint fissures developing zone, but the fault
seal capacity is not yet discussed (e.g., Lv and Ma,
2003). Therefore, it is essential to carry out

2.

Engineering geological conditions

Nibanshan Tunnel located in the core of the
Daxiangling Anticline, Sichuan Province, China, and itis the dominant project of the Yaan-Lugu expressway.
As the watershed of the Daduhe water system and the
Qingyijiang water system, Daxiangling Mountain is an
important climatic boundary, the north section (Ya-an
direction) is humid and rainy while the south section(Lu-gu direction) is dry.
The lithology of the tunnel is mainly composed ofrhyolite (69%), andesite (21%) and granite in the lower
series of Proterozoic, Sinian System, clastic rock in
Sinian System, Cambrian System, Ordovician System
and Permian System, and Quaternary overburden layer.
The structure of the Nibashan Mountain isconsidered as a diapir structure which displays the “Ω”
form (Fig.1; Ling et al., 2015). The reverse fault (F2and F7) located in the sides of the anticline, making the
anticline into a symmetrical form. The No.2 logging(ZK2) which goes through the Fx2 fault located in thenorth part of the tunnel and has the elevation and depthof about 1953 m and 450.5 m respectively and the1

10th Asian Regional Conference of IAEG (2015)

elevation and depth of the tunnel in the logging’s
position is 1527m. The anticline profile, geologicalstructure and boreholes’ positions are shown in Fig.1.

Fig. 1 The anticline profile and geological structure diagram of the Nibashan tunnel. (a) The structuralcharacteristics of the Nibashan tunnel; (b) The sketch map of the relative position of the faults and the boreholes
3.

Comprehensive logging experiment

solution resistivity was measured every 2 hours and thesampling interval and speed were the same as above.
One original curve ρ0 was gained in the firstmeasurement, after the water was salinized, 4 otherrecovery curves were measured (ρ1~ρ4), and the last
recovery curve (ρ4) was very close to the original curve(ρ0). The curves gained in the experiment are shown in
Fig.2.
As is shown in the diagram: the resistivity in the
0~253 m section of the well recovered very fast to theoriginal status, indicating that the liquid was diluted,
which meant that there were productive aquifers in thesection; the productive aquifers were deduced to hostin at the depth of 36 m, 96 m and 146 m, because of theabnormal resistivity changes at the positions (ρ0, ρ2).
All the curves changed abnormally at the depth of
146m, which indicated that there was serious water
inflow at that depth. The resistivity catastrophe
appeared at the depth of 253 ~ 260 m and the curves
below got recovered slowly (almost 10 h), whichshown that there was no aquifer below.

Borehole logging is a very robust tool toaccurately locate transitions between weathered layers
and fractures in hard rock settings; therefore, it canhelp substantially in the construction of regional andlocal hydrogeological models (e.g., Chandra et al.,2008, 2014; Chatelier et al., 2011; Dewandel et al.,2010; Chen et al., 2008).
3.1 Salt solution resistivity method
In this single logging method, the JGS-1
comprehensive logging instrument made by Chongqing
Geological Instrument Factory was applied.
After the instrument was assembled, the salt
solution resistivity probe was put down into theborehole to measure the resistivity. Sampling interval
was set at 1.0 m, the downward speed was set at 4m/min. And after the first curve was acquired, the fluidof the borehole was salinized by salt. The salt bags
were fixed on the cable every 0.1 m and opened almost
at the same time to make sure that the fluid of theborehole was salinized uniformly. Then the salt

2

10th Asian Regional Conference of IAEG (2015)section owns the lowest resistivity, with an averagevalue of 443.6 Ω·m; the 149.5 ~ 267.5 m section has
the average value of 875.5 Ω·m. The two lowest
resistivity sections refer to the surface weathered zone
and the fault fracture zone respectively, which aresupposed to be the productive aquifer. Other sections
with lower resistivity value are 268.0 ~ 347.0 m and
384.0 ~ 414.0 m, and the average value is 2077.8 Ω·m
and 2563.1 Ω·m respectively, which refer to thefracture development surrounding rock mass. The
segmentation and the qualitative assessment of thesurrounding rock are shown in Table 1.

Fig. 2 The salt solution resistivity recovery curve
3.2 Longitudinal wave velocity and lateral resistivity
methodAfter the resistivity was measured, X411 3-lateralresistivity probe and S523 acoustic wave probe were
installed to measure the lateral resistivity andlongitudinal wave velocity respectively.
First of all, the probe was put down to the bottomof the well, and then the measurement began from thebottom to the top. Sampling interval was set at 0.5 m,
and the downward speed was set at 10 m/min.

Fig. 3 The 3-lateral resistivity curve

3.2.1 3-lateral resistivity
As is shown in Fig.3, the result of the lateralresistivity measurement is quite clearly: the 1.5~21.5 m
Table1. Segmentation and the qualitative assessment of the surrounding rock
Depth (m)NumberRange value (Ω·m)

Average value (Ω·m)

Assessment

1.5~21.5

41

214.3~1190.2

443.6

Strongly~ weakly weathered zone

22.0~149.0

255

1552.1~4288.1

3274.66

Fracture~Blocky rock mass

149.5~267.5

237

367.3~1904.7

875.5

Fault fracture zone

268.0~347.0

159

1211.4~3501.9

2077.8Fracture development rock mass

347.5~383.5

73

3062.2~4386.9

4002.4Intact rock mass

384.0~414.0

61

1991.3~3419.57

2563.1

Fracture development rock mass

414.5~450.0

722929.2~5020.0

4102.1Intact rock mass

3

10th Asian Regional Conference of IAEG (2015)

Table 2. Segmentation and the qualitative assessment of the surrounding rock
Depth
(m)

NumberRange value

Average value(km/s)(km/s)

Assessment

1.5~34.5

67

1.18~3.91

2.87

Strongly~ weakly weathered zone

35.0~143.0

217

3.67~4.43

4.08

Blocky rock mass

143.5~176.5

67

3.28~3.98

3.54

Fault fracture zone

177.0~395.0

437

3.55~4.70

4.21

Blocky rock mass

395.5~407.5

25

3.41~3.93

3.56

Fracture development rock mass

408.0~450.085

3.86~4.75

4.48

Intact rock mass

3.2.2 Longitudinal wave velocity
The borehole can be divided into 6 parts according
to the longitudinal wave velocity: 1.5 ~ 34.5 m section
belongs to the strongly~ weakly weathered zone which
has the minimum velocity value of 2.87 km/s inaverage; 35.0 ~ 143.0 m and 177.0 ~ 395.0 m sections
belongs to the blocky rock mass and the velocity value
are 4.08 km/s and 4.21 km/s respectively; the fault
fracture zone identified in this method is not that thickthan the method above which only hosts in the 143.5 ~
176.5 m section; the 395.5 ~ 407.5 m section has thesecond lowest average value of 3.56 km/s which refers
to the fracture development rock mass and the 408.0 ~450.0 m section has the maximum average value of
4.48 and is considered as the intact rock mass. The
segmentation and the qualitative assessment of thesurrounding rock are shown in Table 2.

4.

Discussion and result

The distinguishability of the longitudinal wave
velocity method is not that good as the 3-lateralresistivity method, the fracture development rock massin the depth of about 268.0~347.0m is not beenrecognized, but the segmentation and the qualitative
assessment of the surrounding rock match well in
general.
According to the comprehensive logging
experiment, the thickness of the weather zone is about
30m, and the fault fracture zone hosts in the depth ofabout 140 ~ 270 m. The hanging wall of the Fx2 fault
has lower 3-lateral resistivity and longitudinal wave
velocity values which indicated that the fracturedeveloped better in the hanging wall of the Fx2 fault,
and based on the salt solution resistivity recovery curve,
the hanging wall is much productive an aquifer than the
footwall, so that water inflow may easily occur in the
hanging wall during construction.
According to the 3-lateral resistivity andlongitudinal wave velocity experiment, there is afracture development rock mass section in the depth ofabout 380~420m, which owns lower 3-lateralresistivity and longitudinal wave velocity values,
though the facture is always thought to be tightly
closed in such a depth. So there might be a rhythmic
layering in the depth of about 380 ~ 420 m with anelevation of 1513m, which is close to the elevation of
the tunnel (1527m), but we are not sure about that
because of the lack of the borehole (there are only 4borehole in the whole length of the tunnel). Yet the
influence of the rhythmic layering should be taken into
account during construction, and the comprehensive
logging experiment can still be an effective method in
the investigation of the hydro-geological framework.
5.

Conclusion

The investigation of the hydro-geologicalframework of Nibashan tunnel in Sichuan Province,
China is quite difficult because of the steep topography.
Three types of curves are gained in comprehensive

Fig.4 The longitudinal wave velocity curve410th Asian Regional Conference of IAEG (2015)

logging experiment during the field investigation andthe conclusion obtained from the present study can be
drawn as follows:(1) The thickness of the weather zone is about
30m, and the fault fracture zone hosts in the depth ofabout 140 ~ 270 m.
(2) The fracture developed better in the hanging
wall of the Fx2 fault, and water inflow may easily occur
in the hanging wall during construction.
(3) There might be a rhythmic layering in thedepth of about 380 ~ 420 m which is very close to thedepth of the tunnel and the influence of the rhythmic
layering should be taken into account during
construction.

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Single-borehole measuring method for broken rockzone in gently inclined thin layer weakness structure,
Journal of Coal Science and Engineering (China), Vol.
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Dewandel, B., Perrin, J., Ahmed, S., Aulong, S., Hrkal,
Z., Lachassagne, P., Samad, M. and Massuel, S.
(2010): Development of a tool for managing
groundwater resources in semi-arid hard rock regions:application to a rural watershed in South India,
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Characteristics of microscopic pore structure andphysical property parameter in acidic volcanic
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Acknowledgements
The authors would like to acknowledge Limao
Qin and Chengwu Wei for field investigation. This
work was supported by research funds awarded by
National Natural Science Foundation of China (Nos.
41172261, 41472256), National Railway Ministry
Technology R&D Program, China (No. 2010G016-B)
and Project for Top-notch Innovation of Southwest
Jiaotong University (SWJTU 2014-033).
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