10th Asian Regional Conference of IAEG (2015)

Rockfall Hazard Assessment for a Railway Line in Western Shanxi Province, China
Sixiang LING(1), Xiaoning LI(1)(2), Xiyong WU(1)(3), Yong REN(1), Chunwei SUN(1)and Siyuan ZHAO(1)(1) Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, China
E-mail: lingyou1104@163.com; swustlxn@126.com(2) School of Civil Engineering and Architecture, Southwest University of Science and Technology, China(3) Moe key Laboratory of High-speed Railway Engineering, Southwest Jiaotong University, China
Abstract
Rockfalls can cause serious damage to people, property, facilities and transportation
corridors. Therefore, the detachment of large size boulders and their fall track represent issues
that should be evaluated for the construction of lifelines or transportation corridors. In thispaper, we illustrate the assessment of the rockfall hazard along a small area of the railway line
(Yinghuo railway) and three profiles selected in different rockfall models. In the area, we havecarried out detailed field surveys and software simulations that allow generating simple
rockfall hazard trajectories at each profile. From the fieldwork, location and size of detachedblocks having potential to fall were described. The aim of this study was a preliminary
assessment of rockfall hazard for this railway site. We evaluate this hazard potential andperform a series of rockfall analyses and discuss the results. RocFall V.4.0 software has beenused to calculate bounce heights, total and translational kinetic energies, and translational
velocities of the falling blocks of different masses. The results were exploited to evaluate therockfall hazard along the threatened element at risk. Finally, to reduce the rockfall hazard,
remedial measures including rock bolts and placement of flexible restraining nets aresuggested.
Keywords: Rockfall hazard, Assessment, RocFall, Trajectories, Kinetic energies
1. Introduction
Rockfall is one of the major concerns along
different urban areas and transportation routes all over
the world (Bunce et al., 1997; Huang, 2011; Topal et al.,2012). And also, the rockfall can cause injuries anddeath to roadway users, traffic delays and diversions,
damage of road surface in transportation corridors(Hungr et al., 1999; Budetta, 2004). A rockfall is a
fragment of rock detached by sliding, toppling or
falling that falls along a vertical or sub-vertical cliff,
proceeds down slope by bouncing and flying along
ballistic trajectories (Ansari et al., 2012). The
occurrence and magnitude of rockfall depends on many
influencing factors, which include chemical weathering,
freezing-thawing, earthquake effects, train vibration,
and anthropogenic effect or a combination(Krautblatter and Dikau, 2007; Haas et al., 2012). The
behavior of rockfalls is affected by a high degree of
uncertainty. The energy lost by blocks during impact orrolling is a complex function of the geomechanicalproperties, e.g., the shape, the size of the block, and the
local geometry and roughness of the slope (Frattini et1al., 2008). Several researchers made experiments andsimulations to evaluate the kinematic parameters offalling rocks at specific locations and translational
velocities of the unstable rocks (e.g., Giani et al., 2004;
Dorren et al., 2006; Bourrier et al., 2009, 2012; Youssef
et al., 2015). When rockfall promoters have prepared
the cliff for rockfalls, then visible detachments of rockfragments are induced by the rockfall triggers. Finally,
to prevent the rockfall hazard, a prime concern is toassess the possibility of rockfall path, energy, andvelocity associated with it.
In this work, we present the results of an attempt
to evaluate rockfall hazard in a railway line, western
Shanxi province, China. Based on extensive field work
focusing on the characteristics of dominantdiscontinuities controlling the stability of blocks, thelocations of three types of rockfall model wereidentified. Rockfall hazard in this corridor isdetermined through numerical simulations of rockfall
trajectories. More specifically, the study is aimed isdelineating different rockfall model in railway corridor,
tracing of the ballistic trajectory, evaluating therebound height, total and translational kinetic energies,

10th Asian Regional Conference of IAEG (2015)

and translational velocities in different rockfall model,
and proposing protection measures.
2. Regional and site setting
The study area is located on the southern HequCounty, western Shanxi province (Fig. 1). The study
area is part of the Loess Plateau with loess tableland,loess hill and loess gully landforms, with 850 ~ 1250 m
above sea level. The terrain lowered gradually from the
Shaquan Town (southeast) to the Yellow River(northwest). The study area has a temperate continental
monsoon climate. The mean annual temperature isapproximately 8.8 °C and average annual rainfall is
460 mm. The Yellow River flows from the norththrough the south in the western boundary of study area.
A railway constructed from Yingta Village (ShaquanTown) to Huoshan Village in study area (Fig. 1). The

strata are covered in study area can be divided into fivegeological ages, as follow:(i) Quaternary in age, covered by yellowish loess.
(ii) Baode Formation, Pliocene in age, consistingof sandstone and conglomerate.
(iii) Shihezi Formation, Lower Permian in age,consist of sandstone, siltstone, shale, mudstone andthin coal. The color of Shihezi Formation in the study
area is purplish red, grayish yellow and yellowish
green.
(iv) Taiyuan Formation, Upper Carboniferous inage, including clay rock, mudstone, sandstone,
limestone and mineable coal. The color of this member
is grayish white to purplish red.
(v) Majiagou Formation, Middle Ordovician inage, consist of limestone, argillaceous limestone,
dolomite and dolomite limestone. The color of thisstratum is gray to grayish white.

Fig. 1 Location and Geological map of the study area.

Fig. 2 Two-dimensional model profile of three typical rockfalls; (a) profile A, (b) profile B, (c) profile C.

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10th Asian Regional Conference of IAEG (2015)

Table 1 The physical parameters of rock blocks and parameters of slope at each profile
ProfileUnstable RockA
Sandy conglomerateBsandstoneCsandstone
UCS: uniaxial compressive strength

Bulk Density(g/cm3)
2.47
2.62
2.62

UCS
(MPa)
42
55
63

The rockfalls have been experiencing in steep andvertical slopes of this railway corridor during recent
year, and frequently represent the main threat to theembankment, track, subgrade, train equipment, etc.
Rockfalls occur in the strata of Pliocene and Permian
age at this railway. We selected three different rockfall
profiles and divided into toppling, falling, and sliding
model at profile A, B, and C, respectively (Fig. 1 andFig. 2). The profile A, B, and C are located at
39°09′33″N and 111°14′23″E, 39°09′30″N and
111°10′01″E, and 39°11′01″N and 111°11′04″E,
respectively (Fig. 1). The petrography characters ofeach profile are also illustrated in Fig. 2. The strikemeasured on the bedrock at A, B, and C profiles are
103°, 340°, 335°, respectively, and the dips are 11°, 17°,21°, respectively (Fig. 2a, b, c).
3. Rockfall modeling methodology
Rockfall hazard depends not only on the
discontinuities but also on the lithology of the rock, thetopography, inclination of the slope, size/shape of theboulder and the slope surface properties (Schweigl etal., 2003). During the last decade, various two or
three-dimensional programs have been developed andtested to simulate fall of a boulder down from profileand to compute rockfall trajectories (e.g., Guzzetti etal., 2002; Frattini et al., 2008; Bourrier et al., 2009;
Tunusluoglu and Zorlu, 2009; Leine et al., 2014). In
this study, two-dimensional rockfall simulation was
carried out using the Rocscience’s analysis package
RocFall V. 4.0 program from Rocscience Inc. RocFall
is a program designed specifically to statistically assess
the risk caused due to toppling, falling, and sliding
rocks. The program determines energy, velocity,
number of blocks, and bounce height for the entire
slope as well as for location of rock end points. In thisprogram, the rock block is considered to be a simple
point with rockmass concentrated at the center ofgravity. The rock block collides with the slope surface
should consider the coefficient of normal restitution(Rn) and coefficient of tangential restitution (Rt).
Theses coefficients of restitution are importantparameters for obtaining the loss of energy in rockfall
simulation at every impact along the slope. The values
are dependent on the rock type of each profile and canbe measured according to different methods including
in situ tests, back analysis and laboratory studies(Azzoni et al., 1995; Giacomini et al., 2009; Asteriou etDiameter(m)
0.2~0.8
0.3~1.0
0.4~1.5

Slope Gradient
(º)
65~85
60~90
50~90

Slope Height
(m)
15
22
30

al., 2012). And also, the RocFall program should
consider the angular velocity of the rock block and theroughness of slope surface. The slope forming material
mainly is bedrock outcrop (sandstone, shale, mudstone,
thin coal, etc.) and colluvium at the slope toe in thisstudy area (Fig. 2). The coefficient of normal
restitution (Rn) for bedrock and colluvium (Talus
without vegetation) is 0.35 and 0.32 respectively, andthe coefficient of tangential restitution (Rt) for bedrockand colluvium is 0.85 and 0.82 respectively taken fromthe RocFall program. The RocFall program takes into
account the angle of each slope for the modeling ofslope roughness, therefore, the natural friction angle (U)was considered as 30º. The outlines of the three
profiles were determined according to the field
investigation. A concave position occurred under theunstable rock in profile B (Fig. 2b) and some soft rockhas the scarp in profile C (Fig. 2c). In the current study,
for all seeder points, an initial velocity of 0.0 m/s in
profile A and B, but 0.1m/s in profile C was assumed tosimulate rockfall motion. The physical properties andother parameters of historical rockfalls at each profile
are shown in Table 1.
4. Results and discussion
The rockfalls occurred at profile A, B and C along
the railway was analyzed. We calculated the masses offalling rock as cube, and different rock masses ranging
between 100 kg and 5000 kg based on the field
investigation of three profiles and the rockfall historical
records of the study area. Most incompetent rocks tend
to break during the first impact of the falling rocks on
the slope surface and about 75 ~ 85% of energy is lost
during that impact (e.g., Evans and Hungr, 1993). The
trajectories of falling blocks from RocFall program areshown in Fig. 3. The trajectories indicate that all theblocks will reach or cross the subgrade of railway andwill impact on the railway line.
Four different parameters were observed in thecurrent study including bounce heights, total kinetic
energies, translational kinetic energies, andtranslational velocities during free fall of rocks alongeach profile and at middle line of railway were
determined (Table 2 and Fig.4) and the results of thesimulation are summarized below. Bouncing behavior
is not only governed by the geometry and themechanical characteristics of the slope and the falling
block but also depends on the kinematics at impact

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10th Asian Regional Conference of IAEG (2015)

Fig. 3 Rockfall trajectories for the falling blocks in each profile; (a) 500kg blocks of profile A, (b) 1000kg blocks ofprofile B, (c) 2000kg blocks of profile C.
Table 2 The simulation results extracted from RocFall simulation program in different masses for each profile.
ProfileMass (kg)
BH (m)TV (m/s)
TKE (kJ)
TrKE (kJ)A
100
0~1.12 (0.16)
0~13.71 (7.10)
0~11.78 (3.26)
0~9.40 (2.52)
500
0~0.96 (0.27)
0~13.66 (6.95)
0~57.66 (15.56)
0~46.66 (12.07)
1000
0~0.93 (0.37)
0~13.45 (7.00)
0~112.68 (32.08)
0~90.44 (24.49)
B
100
0~4.27 (1.00)
0~16.39 (7.87)
0~15.64 (4.34)
0~13.43 (3.10)
500
0~4.23 (1.15)
0~15.66 (7.22)
0~71.84 (18.23)
0~61.28 (13.05)
1000
0~4.18 (1.12)
0~15.49 (7.45)
0~119.00 (38.80)
0~90.69 (27.74)
2000
0~4.22 (1.00)
0~15.87 (7.35)
0~297.55 (75.83)
0~179.05 (54.17)
C100
0~6.26 (2.22)
0~20.65 (10.22)
0~26.12 (7.22)
0~21.33 (5.22)
500
0~6.27 (2.43)
0~20.64 (10.34)
0~105.37 (36.83)
0~130.49 (26.71)
2000
0~6.24 (2.00)
0~20.66 (10.06)
0~522.39 (140.19)
0~426.80 (101.11)
5000
0~6.30 (2.37)
0~20.76 (10.27)
0~1316.00 (363.55)
0~1077.52 (264.08)
The values of parentheses are at 0 m location of the middle line of railway in each profile. BH = Bounce height (m);TV = Translational velocity (m/s); TKE = Total kinetic energy (kJ); TrKE = Translational kinetic energy (kJ).
angle. The bounce height values for different blocks
were determined in Table 2 and Fig. 4. In profile A, thebounce height reached 0.16 ~ 0.37 m at mass of 100 ~1000 kg in middle line of railway (location of 0 m) (Fig.
4a). And also, the bounce heights were range of 1.00 ~1.15 m and 2.00 ~ 2.43 m at middle line of railway inprofile B and C, respectively (Fig. 4d, g).
The kinetic energy of fallen blocks has a direct
relationship with their masses and the square of thevelocity of these blocks. Larger the block size willproduce more energy causing more destructive rockfall.
The vegetation cover has an effective impact indecreasing falling rocks. The three profiles in thisrailway all covered with outcrop and talus without
vegetation. The total and translational kinetic energies
and translational velocities further decrease after
continuous impacts along the slope, but these energies
and velocities continue to be increased until reaching
the maximum limit at each profile (Fig. 4). The
maximum total and translational kinetic energies and4translational velocities are found as 11.78 ~ 112.68 kJ,
9.40 ~ 90.44 kJ, and 13.45 ~ 13.71 m/s for profile A of
100 ~ 1000 kg blocks respectively; 15.64 ~ 297.55 kJ,
13.43 ~ 179.05 kJ, and 15.49 ~ 16.39 m/s for profile Bof 100 ~ 2000 kg blocks; and 26.12 ~ 1316.00 kJ,
21.33 ~ 1077.52 kJ, and 10.06 ~ 10.34 m/s for profile
C of 100 ~ 5000 kg blocks. And also, these values arerange of 3.26 ~ 32.08 kJ, 2.52 ~ 24.49 kJ, and 6.95 ~7.10 m/s of 100 ~ 1000 kg blocks for profile A at
middle line of railway respectively (Fig. 4b, c); 4.34 ~
75.83 kJ, 3.10 ~ 54.17 kJ, and 7. 22 ~ 7.87 m/s of 100~ 2000 kg blocks for profile B (Fig. 4e, f); 7.22 ~363.55 kJ, 5.22 ~ 264.08 kJ, and 10.06 ~ 10.34 m/s of
100 ~ 5000 kg blocks for profile C at middle line ofrailway (Fig. 4h, i). Perret et al. (2004) mentioned thatkinetic energy could be divided into three intensity
zones. First zone has a value more than 300 kJ are ofhighest intensity and cause major damage to theinfrastructure. Medium intensity energies range of 30 ~300 kJ, which may leave infrastructures impaired and10th Asian Regional Conference of IAEG (2015)

Fig. 4 Graph between bounce height (height above slope), total kinetic energy, translational kinetic energy andtranslational velocity versus distance for different masses of falling rock in each profile; (a), (b) and (c) profile
A; (d), (e) and (f) profile B; (g), (h) and (i) profile C.
disrupt transportation means for considerable period oftime. As demonstrated by the maximum parameters
values in middle line of railway, most of mass falling
blocks along each profile in the current study have
fitted in medium intensity range of the kinetic energy.
Therefore, most of falling blocks threatened the safetyof trains and users, and broken the track and subgradeof railway.
It is essential to take precautionary measuresagainst rockfall hazards. To face the risk posed by
rockfall, there are several types of technical measures
based on protective structures, such as rockfall
constructing barrier fences and restraining nets (Peila etal., 1998). In the current study different techniques
were used in different profile, including (i) restraining
nets should use in profile A to retain the little unstable
block, (ii) most of unstable blocks need to be removed
in profile B and then use the nets covered the slope
surface, and (iii) most of unstable rock should use rockbolts and anchoring to prevent the cracks or joints inporifle C to slide and fall on the railway.

corridor, western Shanxi province, have been
investigated and analyzed by rockfall simulation. Field
investigation indicated that there are many unstable
blocks and areas that are belong to sandy conglomeratein age of Pliocene and sandstone in age of Lower
Permian. The present study of three profiles in railway
provides useful information about rockfall simulation
investigations. Two-dimensional rockfall analyses are
performed using the data collected from the study area.
The conlusions obtained from the present study can be
drawn as follows:(1) To describe the rockfall hazard along theYinghuo railway, an extensive field survey of rockmass properties, potential critical blocks and slope
profile geometry. Three typical rockfall modelingprofiles (toppling, falling, and sliding) are observed
and the weight of the falling blocks varies between 100
kg and 5000 kg.
(2) The rockfall simulation provides information
about the trajectory path and the rockfall bounce heightwith distance for the rockfall site. For middle line ofrailway (Location = 0 m), the bounce heights are of
0.16 ~ 0.37 m, 1.00 ~ 1.15 m, and 2.00 ~ 2.43 m forprofile A, B, and C, respectively. The rockfall analyses
results also revealed that the detached blocks will have

5. Conclusion
Three typical rockfall profiles in Yinghuo railway

510th Asian Regional Conference of IAEG (2015)very high velocity and kinetic energy. The total andtranslational kinetic energies and translational
velocities values are of 3.26 ~ 32.0 kJ, 2.52 ~ 24.49 kJ,
and 6.95 ~ 7.00 m/s for profile A; 4.34 ~ 75.83 kJ, 3.10
~ 54.17 kJ, 7.22 ~7.87 m/s for profile B; 7.22 ~ 363.55
kJ, 5.22 ~ 264.08 kJ, and 10.06 ~ 10.34 m/s for profile
C in middle line of railway. These values indicate ahighly dangerous phenomenon in Yinghuo railway
corridor.
(3) To prevent possible loss of Yinghuo railway
corridor, considering the remove the little unstable
blocks, cover the slope surface by restraining nets, andanchoring the large unstable rocks.
Acknowledgment
The authors would like to acknowledge Yuxiang
Zhou and Ganggang Wang for field investigation. This
work was supported by research funds awarded by the
National Natural Science Foundation of China (Nos.
41472256, 51348003), National Railway Ministry
Technology R&D Program, China (No. 2010G016-B),
Program for Excellent Innovation of PhD candidate inSouthwest Jiaotong University (SWJTU 2015-40), andProject for Top-notch Innovation of Rail-transit
Industry in Southwest Jiaotong University (SWJTU
2012-19).
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