Rockslides

Falling Boulders

Local Slope failure

Complete Slope Failure

Identify the geotechnical factors

Conduct a stability analysis

Review Possible Solutions

Discuss Selected solution

Erosion has lead to

poor contact

between base and

limestone formations.

As a result, there is a

multitude of loose

blocks with high

potential of tumbling

downhill. The issue was

exasperated by a

devastating fire in the

area that accelerated

the erosion process.

In the lower region of the

slope there is clay inter-

bedded with shale with a

50 ° dip. The orientation of

these layers can generate

local slope failure.

Flooded areas can be seen behind the low

wall of the inner lane of the road indicating

that there is an issue with drainage.

The poor drainage has resulted in longitudinal

cracks along the route. In addition, poor

drainage can affect the stability of the slope.

• Identified the potentially unstable slopes or sections

• Mapping springs, sinks and wet or flooded areas

• Hydrological conditions• Characteristics and distribution of major soil

deposits• Nature and geotechnical rock formations • Behavior of the slope• Measuring possible movements on the

slope

The highest concentrations of gypsum and gypsum clays is in the highest regions of the mountain road, and lower in proportion at the bottom before crossing the ravine.

From the junction with the ravine until Gestalgar it is predominately clay and gypsum plaster mass

The areas with the highest proportion of gypsum has inter-bedded wall formation predominantly with silty clays and sandstone

In outcrop, siltstone layers represent a really low ratio to the clay fractions. Regarding the deterioration of materials, are presented moderately weathered, with sections of greater weathering.

They have a medium to high plasticity and a consistency ranging from very firm and hard.

Material is easily eroded by rain generating gullies and washouts at the foot of the slopes

Two fracture planes were identified from the geological data collected in the field along with readings from inclinometers that were installed.

Boring samples were taken to perform a series of test:

Triaxial Stress TestUnconfined Compression TestCasagrandeSieve AnalysisAtterberg’s LimitsDirect Shear Test

Test results were used to determine:Principal stressesPlasticity Soil ClassificationCohesionFriction Angle

Probe Prof. (m) SUCSSimple Compression Triaxial Direct Cut

RCS (kPa) ε (%) c’ (kPa) ϕ’(º) c’ (kPa) ϕ’(º)

S-1proy

4,05 CL 385 2,79,20 ML 294 35,0º

13,50 SC 400 1,816,00 SC 855 2,220,00 CL 475 5,1

S-2proy

1,80 CH 29 24,0º 24 21º4,70 ML 22 38º7,00 CL 430 2,68,70 CH 44 21,0º

11,70 CL 58 32,0º12,60 Lutita 539019,30 Lutita 960 4,3

S-1com 15,60 Yesos 17800

S-2com

1,50 SC 64 32º10,50 GC 250 3,7 118 43º16,60 ML 823 1,420,10 CL 93 37º

7,1%

14,3%

21,4%

42,9%

14,3%

0,0%5,0%

10,0%15,0%20,0%25,0%30,0%35,0%40,0%45,0%

SM SC ML CL CH

Clasificación USCS - Formación K (14 muestras)• USCS: CL and ML (silty clays) (64.3%)

• PG-3: Marginal (53.8%) and Tolerable (46.2%)

• AASHTO: type A-7-6 (61.5%) The group A-7-6 is a medium plasticity clayey soil -high.

7,7%

15,4%

7,7% 7,7%

61,5%

0,0%

10,0%

20,0%

30,0%

40,0%

50,0%

60,0%

70,0%

A-2-7 A-4 A-6 A-7-5 A-7-6

Clasificación AASHTO - Formación K (13 muestras)

The GEO-SLOPE stability program enables the use any of the following methods: Fellenius, Bishop Simplified Janbu, Spencer, Morgenstern-Price, Corps of Engineers, Lowe-Karafiath, Balance and Finite Element Generalized Limit.

GEO-SLOPE program is used to determine the safety coefficient "FS" for each sliding surface defined. This definition is done automatically in the case of circular surfaces, for which determines the minimum value "FS" in each center and the global minimum of all surfaces defined.

In this profile a historical slide was identified, which covered the entire hillside where the current road is embedded. The slip ring is located in the contact between different permeability soils, soils and impermeable Keuper clays.

Inclinometers were installed to measure any possible movements within the slip ring. The results of the measurements taken indicated this slide is not active.

Recent landslides have been detected in the in the upper part of the slope along with accumulation of potentially unstable blocks.

Section B-B’

High levels of gypsum within the clay, along with an unfavorable

inclination of the slope is causing collapse of materials. As a result,

the lower portions of the slope are being weakened.

At this part of the road headed towards the town of Gestalgar, the slope has a higher grade than the rest of the route. As a result, there is a higher concern with the slope failing and greater risk of falling rocks. In addition, the accumulation of water under the road impacts the stability of the slope.

Imagen 53. Perfil geológico-geotécnico. Sección I-I’

In this profile the problem detected is a continuation of the issue in H-H‘ profile. The historic slip covers a length along the road about 50 m away.

Imagen 55. Perfil geológico-geotécnico. Sección K-K’ Imagen 56. Perfil geológico-geotécnico. Sección L-L’

Imagen 57. Perfil geológico-geotécnico. Sección M-M’Imagen 58. Perfil geológico-geotécnico. Sección N-N’

Could lead the amplify problems detected in this area causing collapsed areas and longitudinal cracks in the road surface. Monitoring of the field inclinometers no motion is observed in the road at this time.

Local slip failure caused by erosion of clays in the side of the roadCrossbreeding of a fault zone and therefore a more tectonizedgeological structure

Local section B-B’

Two Different Slip Planes

Global Stability; Safety factor: 1,001

Local Stability: Safety factor: 1,13

Drainage Improvement

Re-vegetation

Reinforced Hanging Mesh

Dynamic Barriers

Slope Stabilization Optionsa. Installing Micropilesb. Alternating Slope Geometryc. Combination of both

Longitudinal Drainage System

Placing embankment with the drain serves a dual purpose:•Retaining fine soils from runoff, soil creep, etc. •Improved local slope stability

Advantages of vegetation is it reduces soil erosion and improves the local slope stability:

Intercept (avoids direct impact with the ground, reduces the volume of precipitation reaching the ground and delays the arrival of rain to the ground).

Protection against splash erosion Intervention in surface runoff: limits

the disintegration of soil particles and transport.

Modify the mechanical properties of the soil (soil reinforcement by roots).

The micropiles improve stability by increasing the normal stress and reducing the shearing stress on the sliding plane

Micropiles will increase the safety factor of the slope from 1.0 to 1.128

Local stability is increased with the addition of micro-piles to 1.5

The implementation of micro-piles can not achieve stability of the entire slope due the naturally steep slope and does not provide the desired safety factor.

By removing soil from the head of the slope and reducing over all slope angles with the use of benches along the mountain side the safety factor is increased and the stability is improved.

Changing slope geometry of Section B-B increases overall Safety Factor

to 1.12.

In section B-B: The local stability of the slope is improved with a safety factor 1.52.

Mic

rop

iles

Alte

red

Slo

pes

Local stability improves with increases of Safety Factor to 1.5

Overall stability increases to 1.12

1.200.00 € Investment

Global stability Safety Factor increases for each profile ranged 1.3 - 2.2

300.000 € Investment

Dynamic Barriers Installed

Slope Geometry at section B-B altered to stabilize the slope and increase the safety factor

Small retaining wall added to toe of slope to further increase the safety factory

The city will consider drainage improvements in future proposals for road improvements

The city will also consider re-vegetation of the hillside in future budget plans

Giani, G. P. Rock Slope Stability Analysis. Rotterdam: A.A. Balkema, 1992. Print.

Smith, I. M. Smith's Elements of Soil Mechanics. 8th ed. Oxford: Blackwell Pub., 2006. Print.

Walker, Bruce, and Robin Fell, eds. Soil Slope Instability and Stabilisation. Rotterdam: A.A. Balkema, 1987. Print.

Government, U. S. Landslide Handbook: A Guide to Understanding Landslides. Place of Publication Not Identified: Llc, 2012. Print.

Sanz, Ricardo Valiente. ESTUDIO ESTABILIDAD LADERA SITUADA ENTRE PK 11 500 A 11 800 DE LA CV-377 ACCESO GESTALGAR. Tech. no. 15-010. DEPARTAMENTO DE INGENIERÍA DEL TERRENO. Valencia: n.p., n.d. 0-46. Print.