Landslide risk managementin the coastal zoneof the Kuibyshev reservoir
in connection with designingof the high-speed line
"Moscow-Kazan"

Nikolai Petrov, Chuvash State University,
Inna Nikonorova, Chuvash State University,
Vladimir Mashin, JSC "Institute Giprostroymost”

2. Introduction.
High-speed Railway (HSR-2) "Moscow-Kazan-Yekaterinburg", which is planning to start building in 2017, will
create the necessary incentives for the development of the economies of many subjects of the RussianFederation. By the project HSR-2 will cross the Volga in the Kuibyshev Reservoir area. The length of thebridge will be more than 4.5 km. As the intersection is considered land in Mariinsky Posad district on theterritory of the Chuvash Republic.

3. This site is located on the right elevated landslide bank of the river Volga to 1.5 km above therecreation center "Belye kamny" or 500 meters below the village of New Kushnikovo. It is highly
relevant the definition of sustainability the section of the route HSR-2 under the conditions ofexistence of landslide risk on the coast and the development of recommendations to improve its
resistance to the required variables from the normative documents.

4. The research task was to assess the overall and local stability of the river Volga valley slopes

between the marks 120 m (edge ​of the plateau) and 52 m (Shoreline, Kuibyshev reservoir, Volgariverbed) in the zone of HSR-2 location; determine the stability of the edge of the plateau on total
length by 25 m at the site of the road crossing the Volga River valley; evaluate the role of erosion andabrasion processes on the Kuibyshev reservoir coast in the general stability of the slope and its parts;
clarify hydrogeological features of the array and their role in the overall and local stability of slope.

5. Materials and methods of research. To solve the problems it was necessary to evaluate the hydrologicalconditions of the reservoir; analysis of hydrogeological and geomorphological conditions of the coastal zone
by performing the engineering and geological survey (EGS); prepare a consolidated geological section of
fundamental bases of the array on materials the reference wells and outcrop studies; study of structure of
the old landslide system (blocks, tiers, stories) in the strip passing HSR-2, connections between elements of
the landslide system (blocks in tiers, between tiers of different generations, their subordination in stories) inaccordance with the methodological workings [1-5,7-10]; identifying the main factors and causes oflandslides, with particular attention to the role of the Volga in the management of sustainability theconsidered slope and landslide processes within it in the past and at present.

6. Three geological and geomorphological profile of the landslide slope were drawn up according to theEGS, materials mining and drilling works of the "Giprostroymost" Institute and route observations. Then,based on them were made the structural and kinematic calculation models. On the profiles shown
retrospectively various positions of landslide bodies in the area of the considering Volga hillside: in its past
(before the landslide) and present (after a landslide) states.

7. Results of the research.
Viewed plot widths up to 320 m along theshore of the Volga and an average lengthof 240 m and a height of 68 meters is an
old landslide system which presented bylandslide tiers of 2 generations associatedby method of conjugation. Slope array iscomposed of terrigenous-carbonate strata
the Urzhum tier of middle Permian and it
submitted by alternation of reddish-brown
clay with variegated marl and light graylimestone, sometimes - with varying
degrees of weathering silt and siltstone.

8. Engineering and geological conditions that has been determined the stability of slopes.
Taking into account the specificity of the geological structure of area (irregular alternation of a wide variety of terrigenous
and carbonate rocks layers), in the office processing of materials it was decided to allocate not separated traditionalvarieties of Tatarian stage rocks of the Permian system in the sections (clay, silt, limestone, etc.) but rock strata presented byvarious combinations of these varieties with the consolidated physical and mechanical properties (IGE):
Stratum 1 (IGE-1). Clay is a reddish-brown, light, with weakly calcareous portions, with interlayers of siltstone and marl (inthe range of 5.6-5.9 m and 6.9-7.4 m respectively); to a depth of 2.0 m - hardly plastic, below - mainly semi-solid
consistency. Thickness of the stratum is 10.5 m, the lower mark - 111.3 m. It is a local aquitard (AT-1). By the weathering
crust is timed perched water, which is unloaded within the main failure wall and provocative earth flows.
Stratum 2 (IGE -2). Marl (55%) is interbedded with limestone (45%): clayey marl is fractured, with nests of silt. Fractured
limestone is destroyed to the state of broken stone and flour, it is slightly cavernous, with aquifer (AF-1). Thickness of thestratum is 3.7 m, the lower mark - 107.6 m.
Stratum 3 (IGE-3). The clay is light, dense and solid, slightly fractured, marly and with a few layers and nests of silt. It iswith rock debris of limestone and siltstone at the bottom. Thickness of the stratum is 6.2 m, the lower mark - 101.4 m. It
is a local aquitard (AT-2) for the AF-1.
Stratum 4 (IGE-4). Limestone is white, destroyed to rubble state, mainly clay, with interlayers of strong limestone, slightly
cavernous, at the base – with gravel marl. It is aquifer (AF-2). Thickness of the stratum is 10.5 m, the lower mark - 90.9 m.
Stratum 5 (IGE-5). Clays (60%) are interlayered with marl (40%): clay is reddish-brown, light, hard, fractured, sites by sites
is like mudstone, with lenses and interlayers of silt solid. Marl is hard, fractured, with an admixture of silt. Thickness ofthe stratum is 13.8 m, the lower mark - 77.1 m. It is a local aquitard (AT-3) for the AF-2.
Stratum 6 (IGE-6). Limestone (71%) is grayish-white and white, strong, cavernous, with interlayers of marl, silt,interbedded with thick, solid, slightly calcareous clay. It is aquifer (AF-3). Thickness of the stratum is 17.1 m, the lower
mark - 60.0 m.
Stratum 7 (IGE-7). It is limestone (70%) with interlayers of marl (30%). Limestone is light gray, strong, cavernous,fractured, sometimes destroyed to the state of broken stone and flour. A layer is aquiferous (AF-4). Marl is light pink,thick, solid and slightly fractured, with nests of silt. Thickness of the stratum is 10.7 m, the lower mark of 49.3 m.
Stratum 8 (IGE-8). It is limestone (70%) and marl (30%) with interlayers of siltstone and mudstone. The rocks crushed torubble state. Marl is multicolored, solid, fractured, clayey with lenses and layers of argillite (0.4-0.7 m), very strong,fractured, calcareous. A layer is aquiferous (AF-5). Thickness of the stratum is 10.5 m, the lower mark - 38.4 m.

9. Geomorphological features.
The surface of the plateau is inclined at
a 4-5 degree angle to the Volga; runoff
promotes erosion dismemberment of
the plateau edge and wall disruption,
gully formation, drainage of the slope
array. Low-water mark level of theVolga (reservoir) is 52.0 m, in flood
55.3 m and before filling of thereservoir is about 49.0 m. The Volga
bed is separated from the shore byridge of islands, so the processes ofthe bottom and side erosion arealmost stopped; indications of abrasion
processes are not noticeable.

Old landslide 2-3-stepping slope consistsof a number of genetically interrelated
elements: lower denudation plateau – isa disruption wall of 1st order 2ndgeneration old landslide, old landslide
terrace of the same generation, landslide
scarp and landslide terrace of the 1stgeneration, landslide block of planar
displacement (PD), the front block ofthrusting-bulging, coastal erosion-talus
scarp (ancient cliff), towpath. Theaverage slope steepness is 15,5degree on
its edge to the shoreline of the Volgariverbed. Total slope length is 220 m anda height of 68-70 m.

11. These genetic elements are described in more detail below:
1. Denudation plateaus almost without cover formations, inclined at an angle about 4-5o to the Volga River.
His part adjacent to the brow is complicated by a variety of gullies and ravines with constant streams in thebottoms. It is covered by deciduous forests with occasional oaks older than 150-200 years. Brow plateau
jagged, with the circus shaped ledges. They are tops of small landslides, earth flows. Marks surface is 120122 m and it increase in the SW direction.
2. Failure wall of the old landslide the 1st order, 2nd generation of 20-22 m in height (between markers 95and 102 m) and steepness 20-25o is complicated by five ravines and many small landslides in the ravine andin the slope. It is under planning denudation by runoff and sliding saturated soils, it is turf-covered by forestof various age (from 20-30 to 60-70 years) and has no signs of violation of general stability.

3. Old landslide terrace (2nd generation) up to 40 m and a width of 100 m, is complicated by branchedravines 1 and 2, diverging to the failure wall and converging at the front edge of the terrace. Ravines
adjacent to the brow of denudation slopes, that testify ravines ancient age. Therefore, landslide terraces
are even older. The right side of the terrace with a mark of 97-100 m surface and steepness of to 5o is best
preserved then left steeper (up to 7°) apart. The rear terrace seam pit №3 opened crushed landslide soils.
The front edge of the terrace sharply cut by scarp, the fourth element of the slope. This terrace is the edgeof the plateau, dropped nearly 20 m along a circular surface (radius of about 160-170 m).
4. Landslide scarp height 5-8 m (the height increases in a northerly direction) is the front face of the block
2nd generation, or a fragment of a failure wall slip landslide 1st generation without evidence of tongue
units (thrusting, bulging, etc.). The ledge is cut of ravines, gullies on both sides, but behind ravines it goingagain in both directions in no less vivid form, despite the significant planning. These gullies are muchyounger then quite deep landslides.
5. Landslide terrace length of 35-40 m is the surface of the head rotation block of landslide tier 1stgeneration. The front edge of the block is in the compression zone and on the border with the planar
displacement block is complicated by the shaft and the extrusion bumps.
6. Landslide block of up to 40-45 m is a fragment of the primary slope of the Volga river displaced in the 1sttier almost on a plane surface. Block is almost structural, with no signs of plastic deformation. At the frontedge there are dome-shaped uplifts - plastic compression signs (by type of "barrel") in the area of tongue
block.
7. Front thrusting-bulging block with a surface having a reverse gradient. There are signs of squeezing anduplift on the day surface of the block.
8. Coastal erosion and talus ledge or ancient cliff with no signs of avalanches and landslides. Slope isstabilities, turf-covered, up to 12-15 m between the average marks of 70 and 56 m.
9. Shoreline, at elevation 56-52 m is presented by bedrock outcrops and boulders fall apart (colluvium) oflimestone and dolomite is between the low-water (52-53 m) and high water (56-57 m) level, width up to 10
m without signs of coastal erosion. This is the front part of the landslide system with thrusting signs ofinterbedded marl, limestone and partly of clay strata.

13. Analysis of hydrogeologicalcharacteristics of the array

The survey data and the drilling confirmed
the presence here of only two aquifers(AF): 1st type of perched water - on theedge of the plateau (118-115 marks) and2nd AF interstratal type - lower marks 7779 m in the fundamental array on plateau,
and the landslide slope. Power both AF
are atmospheric, infiltration and by
overflowing through fractures from theupper to the lower horizon.
Upper AF with of perched water regime
discharged from the upper edge of thefailure wall, is now not play a significant
role in the stability of deep landslides, but
provokes small, localized landslides,earth
flows within the failure walls, and on thesides of the ravine. This horizon will play asignificant role in the future of landslide
deformation deep recess beads, and it
should be intercepted by trapping drains
before excavation construction.

15. Dangerous geological and engineering-geological phenomena and processes.
Two landslide tiers (upper and lower) is well manifested in geomorphological profile, with two failurewalls, with two head blocks with rotation features (the reverse slope of the surface, drainage basins at
the rear seam), with mounds of extrusion on the border of the head and medium blocks and signs ofbulging in the front of the lower tier. These and many other features clearly indicate that there wasformed a deep multi-block sliding landslide (cutoff).

•According to the description, landslide tiers of
two generations are connected by theinterfacing way (upper more younger tier divesunder the first). They have undergone toconsiderable slope denudation. The head failure
wall, as the area of the upper unloading AF ofperched water type, is moistened at the edge. It
is much planned with the participation of local
flow landslides, including solifluction type.

•Existing data indicate about the involvement oflandslides 1st order to the group of slip
landslides with head rotation-dumping blocks
and tongues within the riverbed. The
underwater tongues part was, perhaps longer.
However, to determine the eroded by the Volgapart of landslide accumulations is now
impossible.

•Now erosion and abrasion Volga role inlandslide deformation is insignificant, as themainstream of the Volga in study site is closest
to the left bank and a bay was formed at theright bank and was separated by a chain ofislands from the mainstream.

18. Landslide slopes and landslide pressures stability calculations.
For the forecast the stability of our slope used practice has tested the geological similarity method(analogies), based on a comparative analysis of all the relevant factors of the geological array environment,
combined with the structural and functional analysis of existing landslides, compiling calculation models thatsimulate the state of the slope at moments "to displacement" and "after displacement" landslide.

19. Calculation models, compiled by the historical and geological and palaeogeomorphological analysis the landslide survey
materials taking into account the experience of performing such works since 1985 in many regions of the former USSR. They
reflect the 4 stages of evolution of the slope during the Late Pleistocene and Holocene: 1) the initial erosion-talus stage (the"before the displacement" state of the slope); 2-3) then the steps of forming two landslide tiers with its failure walls, headand other blocks including front (state "after displacement"); 4) the final stage of the modern denudation - smoothing thelandslide system elements (planning of the failure walls, filling cracks and turfing surface, formation of gullies, etc.). We areput in the basis of the structural and kinematic analysis of the models an established correlation between the elements oflandslides and their presence in relief (diagnostic signs) in the form of landslide terraces with different slopes surfaces,shafts and extrusion hillocks between the blocks, fragments the primary surface of the slope, and others.

20. Conclusion.
•••

The stability calculations of 3 profiles
includes at 6-7 models have shown thatthe system is in a very stable state (Cs =1.05-1.07). This parameter should be atleast 1.3 taking into account building
codes for the normal operation.
The erosion and abrasion Volga role inlandslide deformation is insignificant, as
the mainstream of the Volga in study site
is closest to the left bank and a bay wasformed at the right bank and wasseparated by a chain of islands from themainstream.
The authors recommend to improve slope
stability (Cs 1.3) to carry out anti-landslide
events. They should include the verticalplanning of the slope (truncation of thehead active landslide blocks that lead to
unloading head parts of landslide tiers),
regulation of surface runoff andgroundwater interception of the top AF
and loading the front of the landslide by
concrete dam (if necessary).

Thank you for your attention!