Road Cut Slopes Research Articles

Assessment of Rockfall Hazard along the Road Cut Slopes of State Highway-72, Maharashtra, India

Rockfall is a major problem in high hill slopes and rocky mountainous regions and construction of highways at these rockfall prone areas often require stable slopes. The causes of rockfall are presence of discontinuities, high angle cut slopes, heavy rainfall, and unplanned slope geometry etc. Slope geometry is one of the most triggering parameters for rockfall, when there are variations in slope angle along the profile of slope. The Present study involves rockfall hazard assessment of road cut slopes for 15 km distance starting from Mahabaleshwar town along State Highway-72 (SH-72). The vertical to subvertical cut slopes are prone to instability due to unfavorable orientation of discontinuities in slope face of weathered and altered basaltic rockmass. The predominant type of instability has been found as wedge type failure involving medium to large size blocks. In order to investigate the existing stability conditions, analyses were carried out at two locations under different slope conditions. The kinematic analysis was performed using stereographic projection method. RockFall 4.0 numerical simulator software was used to calculate the maximum bounce heights, total kinetic energies and translational velocities of the falling rockmass blocks, and a comparative analysis is presented with increasing the mass of blocks and height of the slope. The result of numerical analysis shows that varying slope angle geometry creates more problems as compared to the mass of blocks in the scenario of rockfall.

Rock Mass Classification and Slope Stability Assessment of Road Cut Slopes in Garhwal Himalaya, India

There are many rock mass classification schemes which are frequently used for different purposes such as estimation of strength and deformability of rock masses, stability assessment of rock slopes, tunneling and underground mining operations etc. The rock mass classification includes some inputs obtained from intact rock and discontinuity properties which have major influence on assessment of engineering behaviour of rock mass. In the present study, detail measurements were employed on road cuts slope faces in Garhwal Himalayas to collect required data to be used for rock mass classification of Rock Mass Rating (RMR) and Geological Strength Index (GSI). The stability assessment of rock slopes were also done by using Slope Mass Rating. In addition the relation between RMR and GSI were also evaluated using 50 data pairs.

전라남도 ◯◯우회도로 비탈면 붕괴발생원인 및 토사지반특성 사례 연구

2007년 9월 태풍 "나리"의 영향으로 전라남도 지역에서 많은 붕괴비탈면이 발생되었으며, <TEX>${\bigcirc}{\bigcirc}$</TEX>우회도로에 위치한 도로비탈면에서 붕괴가 발생되어 도로시설물을 파손시켰다. 본 연구의 목적은 붕괴비탈면의 현장특성과 구성 토사의 공학적 특성 및 점토광물의 분포, 정량분석 결과 등을 바탕으로 붕괴발생원인을 고찰하는 것이다. 대상비탈면은 화산암 기원의 풍화토사로 이루어져 있으며 붕괴부에서는 소규모 단층과 염기성암맥이 발견된다. 상부자연비탈면 내 진입로는 포장이 되지 않았고, 배수로의 설치 미흡으로 인하여 많은 유수가 붕괴부 쪽으로 집중되는 환경이었다. 붕괴부 토사는 저소성실트와 고소성점토로 분류되며, X선회절분석에서는 스멕타이트와 버미큘라이트와 같은 팽윤성 점토광물이 다량 함유되어 있음이 확인되었다. 대상비탈면은 배수시설의 설치 불량, 지질학적 약대 존재, 활성도가 큰 점토광물의 함유 등으로 붕괴가 발생되었던 것으로 판단된다. On September 2007, numerous slopes at Jeonranam-Do collapsed as a result of rainfall related to Typhoon Nari. Failure occurred at a road cut-slope on the <TEX>${\bigcirc}{\bigcirc}$</TEX> detour road, damaging transport infrastructure. This study aims to determine the cause of failure based on field investigations, the geotechnical properties of soil, clay mineral composition, and quantitative analysis. The studied cut slope consists of weathered soil that originated from volcanic rocks, and minor faults and a mafic dyke. Surface water tends to seep into the soil because the roadway is not sealed and because of poorly installed drainage. Sieve and XRD analyses indicate that soils in the failure zone are ML and CH, which are prone to swelling due to the presence of clay minerals such as smectite and vermiculite. The slope failed due to the improper construction of drainage facilities, the presence of geological weak zones, and high soil contents of swelling clay.

Reply to the discussion by F. Gutiérrez, P. Lucha, J. Guerrero, M. Gutiérrez and D. Carbonel on the article ‘Paleoseismological analysis of an intraplate extensional structure: the Concud fault (Iberian Chain, eastern Spain)’

This reply tackles the three main points of discussion of the comment, carefully distinguishing those constructive contributions from the potentially confusing ones. (1) We accept that we should have utilised previously published datings of the middle terrace, even if we consider them to be less reliable than the used ones, so broadening the slip-rate range from 0.23–0.33 mm/y to 0.16–0.33 mm/y. Nevertheless, their revision of the post-middle terrace slip rate charges us two contradictory imputations: that we underestimate the throw in a 25% (36 m vs. 47 m) and that this results in ‘anomalously high slip rates’. We analyse the adduced error, and we confirm our initial estimate based on our more reliable stratigraphic marker, so rejecting both criticisms. (2) About the paleoseismological interpretation at Los Banos trench, we appreciate the hint about displacement partitioning on the master fault and in our hypothetical blind normal fault during the last three events; however, such partitioning was already considered in our retrodeformation analysis. We believe that there is enough evidence for the two events questioned by the commenters, as well as for the interpretation of the colluvial wedge that evidences one of them. (3) With respect to the fault affecting the youngest terrace: (a) both traces exposed on orthogonal road-cut slopes belong to the same normal fault, and we prove it by means of basic structural constructions, and (b) it does not exhibit any feature suggesting a non-tectonic origin, as the commenters state.

Road Slide Detection Algorithm Using CCD Camera

In this paper, we proposed the vision-based efficient algorithm for road slide detection like as destruction of road cut slope. The proposed algorithm defines the image region as non surveillance and surveillance which is further divided by road, boundary and non road region. After that, it find the moving block, remember the history of movement using the TTL(Time To Live) table, determine the road slide by checking the existence of moving blocks from non road region to road region together. We confirmed the proposed algorithm detected the road slide effectively through experiments.

Stability Analysis of Cut Slopes Using Continuous Slope Mass Rating and Kinematic Analysis in Rudraprayag District, Uttarakhand

In mountain terrains of Himalaya, road and highway networks play a vital role in remote areas for transportation, public network and all kind of socio-economic activities. The stability of rock slopes along the roads and highways is a major concern in these hilly regions. Any kind of slope failure may lead to disruption in traffic, loss of properties and lives/injuries as well as environmental degradation. The unplanned excavations of rock slopes for construction or widening purposes may undermine the stability of the slopes. The present study incorporates the stability analysis of road cut slopes along NH-109 which goes to holy shrine of Kedarnath. Slope failure is not only a phenomenon of rainy season but it has also been encountered even in dry season. The study area experiences high vehicular traffic especially from March to August due to pilgrims since it is the only road to Kedarnath. The distance of about 20 km between Rudraprayag and Agastmuni has been investigated. The continuous slope mass rating (CSMR) technique has been used for slope stability analysis at five different locations. CSMR is modification of original slope mass rating (SMR) proposed by Romana which is based on well established rock mass rating (RMR) technique. Kinematic analysis was also carried out to evaluate these sites for types of failure and its potential failure directions. The potentially vulnerable sites were identified. The results indicate that the CSMR technique may be exploited to assess the stability of rock slopes in the Himalayan territory.

The implementing of some plant species in erosion control on slopes

With the need to conserve and improve the environment, it is recommended to employ plant materials in the erosion control of torrents and slopes alongside roads. Considering the well-known properties of some willow species regarding their power of vegetative reproduction, survival in poor soils and often flooded alluvium, we researched into the potentials of the following species: Salix triandra L., Salix purpurea L. and Salix incana Schrk. in the catchment of the warehouse 'Gvozdac', Experimental Estate Goc, Serbia. The research started in 2004 and has continued till the present day. The above-mentioned willow species showed significant efficiency in the bank protection of torrential watercourses and on the moist slopes of embankments and cuts of roads. Some of them can even stand a certain degree of aridity, while other species, on poor, eroded soil exposed to long and extreme drought, could not survive and did not show the expected effect, which is also the consequence of the absence of maintenance and adequate attention to such erosion-control works. In spite of the above, one of the willow species survived even in the most severe conditions, checking the erosion of the road cut slope and the road construction itself, and prevented the impacts of aggressive atmospheric waters, thus halting the erosion ridges and the removal of the asphalt road surface. The above facts prove that, with adequate measures of maintenance, plant materials can be very successfully applied for both longitudinal structures and to check dams in torrent control, as well as in erosion control on the slopes in catchments, both in civil engineering works and in forest exploitation. The research requires closer attention, extending the interests to some grass and shrub species, with the aim of ecological erosion control and reclamation of endangered watercourses, slopes and, in general, environmental protection and nature conservation. .

Evaluating cut slope failure by numerical analysis—a case study

Slope failure is very common phenomenon in hilly regions, especially in young techno active mountainous like Himalayas. It is hazardous because of the accompanying progressive movement of the slope-forming material. In order to minimize the landslide effects, slope failure analysis and stabilization requires in depth understanding of the process that governs the behavior of the slope. The present article mainly deals with the analysis of the stability of road cut slopes of Rudraprayag Area, Uttarakhand, India. The area experiences local as well as regional slides every year. Extensive field study was carried out along the road cut slopes. Laboratory experiments were conducted to determine the various Physio-mechanical properties of rock mass. These properties have been used as input parameters for the numerical simulation of slope using FLAC3D (Fast Lagrangian Analysis of Continua) including geological discontinuities. The computed deformations and the stress distribution along the failure surface are compared with the field observations. The study indicates that the overall slope is unstable except at the location E where slope is critically stable. The effects of instability have been thoroughly considered and remedial measures have been recommended.

Measurement and prediction of natural and anthropogenic sediment sources, St. John, U.S. Virgin Islands

A quantitative understanding of both natural and anthropogenic sediment sources is needed to accurately assess and predict the potentially adverse effects of land development on aquatic ecosystems. The main objective of this study was to quantify sediment production and delivery rates in a dry tropical environment on the island of St. John in the eastern Caribbean. One to three years of measurements were used to determine values and empirical functions for estimating sediment production from streambanks, treethrow, undisturbed hillslopes, zero-order sub-catchments, unpaved road surfaces, and road cutslopes. Sediment production also was measured from both undisturbed and roaded first-order sub-catchments. Among natural sources of sediment, streambanks had the highest mean erosion rate at 100 Mg ha − 1 yr − 1 . The uprooting of trees along stream margins is estimated to generate approximately of 0.2 Mg of sediment per kilometer of stream per year, or about 0.1 Mg ha − 1 yr − 1 for a stream corridor that consists of a 9-m wide channel and a 3-m wide buffer zone. Undisturbed 40 m 2 hillslope plots generated 0.01 to 0.27 Mg ha − 1 yr − 1 . Mean sediment yields from undisturbed zero- and first-order catchments were only 0.01 and 0.08 Mg ha − 1 yr − 1 , respectively. Unpaved roads that were graded at least every other year had sediment production rates ranging from 57 Mg ha − 1 yr − 1 for a road with a 2% slope to 580 Mg ha − 1 yr − 1 for a road with a 21% slope. Sediment production rates from ungraded roads were about 40% lower than those from recently graded roads, while production rates from steep abandoned roads were only 12 Mg ha − 1 yr − 1 . Cutslope sediment production rates ranged from 20 to 170 Mg ha − 1 yr − 1 , but their contribution to sediment yields at the road segment scale was relatively small. Since unpaved roads increase hillslope-scale sediment production rates by several orders of magnitude, the first-order catchments with unpaved roads had sediment yields that were at least five times higher than undisturbed catchments. The relative importance of each sediment source varies from catchment to catchment as a result of the abundance and spatial distribution of landscape types. The values and predictive functions developed in this study have been incorporated into a GIS-based model to predict catchment-scale sediment yields. Application of this model to three basins in St. John suggest that unpaved roads are currently the dominant sediment source, and that they are responsible for increasing watershed-scale sediment yields by 3–9 times relative to undisturbed conditions. Both the data from the present study and the GIS model can help estimate sediment production and catchment-scale sediment yields in similar environments.

Development and application of a GIS-based sediment budget model

Accelerated erosion and increased sediment yields resulting from changes in land use are a critical environmental problem. Resource managers and decision makers need spatially explicit tools to help them predict the changes in sediment production and delivery due to unpaved roads and other types of land disturbance. This is a particularly important issue in much of the Caribbean because of the rapid pace of development and potential damage to nearshore coral reef communities. The specific objectives of this study were to: (1) develop a GIS-based sediment budget model; (2) use the model to evaluate the effects of unpaved roads on sediment delivery rates in three watersheds on St. John in the US Virgin Islands; and (3) compare the predicted sediment yields to pre-existing data. The St. John Erosion Model (STJ-EROS) is an ArcInfo-based program that uses empirical sediment production functions and delivery ratios to quantify watershed-scale sediment yields. The program consists of six input routines and five routines to calculate sediment production and delivery. The input routines have interfaces that allow the user to adjust the key variables that control sediment production and delivery. The other five routines use pre-set erosion rate constants, user-defined variables, and values from nine data layers to calculate watershed-scale sediment yields from unpaved road travelways, road cutslopes, streambanks, treethrow, and undisturbed hillslopes. STJ-EROS was applied to three basins on St. John with varying levels of development. Predicted sediment yields under natural conditions ranged from 2 to 7 Mg km −2 yr −1, while yield rates for current conditions ranged from 8 to 46 Mg km −2 yr −1. Unpaved roads are estimated to be increasing sediment delivery rates by 3–6 times for Lameshur Bay, 5–9 times for Fish Bay, and 4–8 times for Cinnamon Bay. Predicted basin-scale sediment yields for both undisturbed and current conditions are within the range of measured sediment yields and bay sedimentation rates. The structure and user interfaces in STJ-EROS mean that the model can be readily adapted to other areas and used to assess the impact of unpaved roads and other land uses sediment production and delivery.

Simulated rainfall evaluation of revegetation/mulch erosion control in the Lake Tahoe basin: 2. Bare soil assessment

AbstractSlopes that have been disturbed through roadway, ski slope or other construction often produce more sediment than less disturbed sites. Reduction or elimination of sediment loading from such disturbed slopes to adjacent streams is critical in the Lake Tahoe basin. Here, use of a portable rainfall simulator (RS), described in the first paper of this series, is used to evaluate slope effects on erosion from bare volcanic and granitic soils (road cut and ski run sites) common in the basin in order to establish a basis upon which revegetation treatment comparisons can be made. Rainfall simulations (60 mm h−1, approximating a 100‐year, 15‐minute storm) at each site included multiple replications of bare soil plots as well as some adjacent ‘native’, or relatively undisturbed soils below trees where available. Field measurements of time to runoff, infiltration, runoff, sediment discharge rates, and average sediment concentration were obtained. Laboratory measurements of particle‐size distributions using sieve and laser counting methods indicated that the granitic soils had larger grain sizes than the volcanic soils and that road cut soils of either type also had larger grain sizes than their ski run counterparts. Particle‐size‐distribution‐based estimates of saturated hydraulic conductivity were 5–10 times greater than RS‐determined steady infiltration rates. RS‐measured infiltration rates were similar, ranging from 33–50 mm h−1 for disturbed volcanic soils and 33–60 mm h−1 for disturbed granitic soils. RS‐measured runoff rates and sediment yields from the bare soils were significantly correlated with plot slope with the exception of volcanic road cuts due to the narrow range of road cut slopes encountered. Sediment yields from bare granitic soils at slopes of 28 to 78 per cent ranged from ∼1 to 12 g m−2 mm−1, respectively, while from bare volcanic soils at slopes of 22 to 61 per cent they ranged from ∼3 to 31 g m−2 mm−1, respectively. Surface roughness did not correlate with runoff or erosion parameters, perhaps also as a result of a relatively narrow range of roughness values. The volcanic ski run soils and both types of road cut soils exhibited nearly an order of magnitude greater sediment yield than that from the corresponding native, relatively undisturbed, sites. Similarly, the granitic ski run soils produced nearly four‐times greater sediment concentration than the undisturbed areas. A possible goal of restoration/erosion control efforts could be recreation of ‘native’‐like soil conditions. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Study on introducting a vegetation colony on roadcut slopes of the Siwalik region in Nepal-An experimental study at the Churiya Pass-

Although Nepal has been implementing conventional soil bioengineering measures to protect and stabilize bare roadcut slopes, it is still seeking a perennial strategy to combat the instability and destabilization of slopes. A case study was carried out at a Churiya Pass roadcut slope, which had been a serious issue for the Department of Roads(DOR), to protect and stabilize the slope from severe deterioration. The study area lies in the Siwalik region, which is very fragile and has a high erosion capacity. The DOR was unable to solve the problem through conventional soil bioengineering measures, as evidenced by the results of a revegetation project in 1993. This case study was carried out to investigate the adaptability and feasibility of a Rapid Afforestation Seeding(RAS)method by a soil seeder in Nepal. With the use of Japan’s hydro-seeder, soil-seeder technology was implemented to protect and stabilize roadcut slopes perpetually, principally by establishing a woody vegetation colony. Most of the basic materials used in the study were imported from Japan. Only half of the soil and organic matter used for preparing the carrying soil was locally prepared and arranged; it was mixed with carrying soil imported from Japan a 1:1 ratio. Local and imported plant species were used in the study. A year after the vegetation was introduced, the entire degraded study area was covered by the introduced Nepalese as well as Japanese species, showing excellent growth of more than 2 m in height. The established vegetation colony successfully prevented the development and formation of ephemeral gullies that would have resulted from concentrated flows, and protected the roadcut slope from further deterioration from severe erosion. The findings of the study show that a 3-cm growth-foundation layer is ample for growing both native and introduced vegetation in the Siwalik region.

Stability of Cut Slopes Against Shallow Failure: Evaluation by Neural Network Model

The discrimination model for road cut slope stability was used to assess 216 cut slope locations on the Chuo Expressway. This model ranks the failure probability of slopes by the rainfall threshold (cumulative precipitation that causes the slope to fail) to identify slopes highly prone to collapse. Because of the complexity (nonlinearity) of the relationship between the factors relating to the cut slope failure and the precipitation that triggers a failure, it has been difficult to correctly evaluate the likelihood of failure for cut slopes. The developed model has overcome that difficulty by involving the neural network as the discrimination technique. The input data included the different factors (topography, soil properties and geology, surface layer status, change in state) in the stability investigation table prepared at the time of road slope inspection, with additional information such as catchment topography. The cut slope data were prepared, referring to a variety of information encompassing the failure history for 30 years after the commencement of service, the rainfall record at the time of failure, the maximum rainfall amount ever recorded, and the data on the status of slope protection around the time of failure. As shown by the discrimination results, the model accuracy (ratio of correct answers to number of slopes evaluated) was as high as approximately 80%, which allowed accurate determination of the amounts of rainfall inducing the failure of different slopes.

Local topoclimate effect on short-term cutslope reclamation success

Cutslopes created by earthworks are a challenge for restoration practitioners. A clear and ecological understanding of environmental constraints is a requirement for successful revegetation. This study was conducted to evaluate the effects of solar radiation exposure (SRE) on short-term plant establishment on road cutslopes after hydroseeding herbaceous plants. The study site is located in gneissic hills (Vigo, Northwest Spain) that were excavated by roadworks. Cutslope steepness is higher than 50° and three aspects (SW, S and SE) were used as SRE treatments. Neither hardness nor surface roughness were significantly different among aspects. There were small significant differences in irradiance among aspects, however, the daily peak had a delay from SE to SW. This irradiance pattern probably accounts for a trend in temperature increase and moisture decrease along the gradient SE–SW–S. Water availability for plants is likely to decrease along this gradient, S being the driest topoclimate. A significant coincident trend of decrease in plant density, plant biomass, total plant cover and seedling development was observed along the SE–SW–S gradient. Moreover, seedling density was extremely low in all aspects, demonstrating the prevailing strong environmental constraints of the site. SRE may affect the early establishment and development of herbaceous plants at cutslopes. Therefore, a good project design for cutslope reclamation should adequately consider local topoclimatic conditions.

The effects of vegetative cover in the erosion prevention of a road slope

Presents the studies performed to evaluate the performance of rolled erosion control products (RECPs) in the prevention of sheet erosion in a road cut slope, under simulated rain conditions. The four different covers used were: ARP 430 – vegetative screen, ARP‐440 – biotextil screen, grass mulch geotextil, control 1 (no rolled product and no vegetation), and control 2 (only grass vegetation and no rolled product). A road slope with dimensions of 47.20m in length, an average height of 7.68m and slope angle of 45° in red podzolic soil was chosen to perform this experiment, due to its edaphics and climatic similarity to most existing Brazilian road slopes found in south and south‐east regions. The erosion parameters were evaluated along the experiment for 360 days. Two simulated rains were performed at 330 days and at 360 days of the experiment. A rain intensity of 65mm/h was chosen to simulate the actual rain conditions in the area. Physical and chemical characterization, fertilization testing and erosion studies were performed to better evaluate the most appropriate conditions for vegetative growth and erosion prevention udner tropical climate conditions.

Effects of forest roads on flood flows in the Deschutes River, Washington

The effects of forest roads on peak flows were examined through a combination of field data collection and modelling in the extensively logged 149 km2 catchment of the Deschutes River, Washington, USA. Based on a field survey, the connectivity of culverts to the channel network was related primarily to hillslope curvature and distance to the natural stream channel. Culvert crest stage recorders operated during winters 1996/97 and 1997/98 demonstrated that higher flows occurred in ditches draining clearcuts compared to forested areas. Contrary to expectation, road cutslope height did not seem to affect culvert peak runoff. A distributed hydrologic model was used to evaluate road effects on peak flows in nine subcatchments (2·2 to 21 km2) of the Deschutes River as well as the Deschutes main stem. The model-predicted increases in the mean annual flood due to forest roads alone ranged from 2·2 to 9·5 per cent, and from 2·9 to 12·2 per cent for the 10 year event. These increases are roughly equivalent to slightly smaller than those predicted for harvest effects alone. Simulated road effects on peak flows were independent of forest harvest state. However, at the hillslope scale, modelled as well as field-monitored road ditch response was dependent on harvest state. Modelled road effects generally increased with flood return period, while vegetation effects decreased. Copyright © 2001 John Wiley & Sons, Ltd.

Revegetation of Roadcut Slopes in Mesa Verde National Park, U.S.A.

AbstractThe geology of Mesa Verde National Park (MVNP) poses unique problems to road construction and maintenance. Major geologic formations of the Park consist of an overlying resistant sandstone cap underlain by highly erodable shales. Once this sandstone cap is removed, the shales are easily eroded away, creating the notable mesas of the region. In many places, road construction has removed the sandstone layer and vegetation resulting in unaesthetic barren slopes that require continual maintenance and have proven difficult to revegetate. An experiment was conducted to evaluate the effectiveness of several cultural techniques combined with seeding and transplanting indigenous plants for revegetation of these roadcut slopes. Techniques evaluated were fertilization, mulching, soil pitting, and polyacrylamide amendments. Replicated test plots were established at three roadcut sites in MVNP to evaluate these techniques by measuring percent plant cover by species over a 4‐year period. A combination of seeding grasses and transplanting forbs and shrubs appeared to be the optimal way to maintain species diversity and structure on the roadcuts while accomplishing the goal of revegetating these difficult sites. The perennial forb Aster glaucodes and the shrub Artemisia ludoviciana showed high survival when transplanted in the experimental roadcut sites. These species, as well as the perennial grass Pascopyrum smithii, also established well from seed. The addition of an organic fertilizer, in combination with mulch, proved to be the most effective method of improving vegetation cover for these and other transplanted species.

Erosion Control Techniques on Forest Road Cutslopes and Fillslopes in North Alabama

Road cutslopes and fillslopes account for approximately 50 percent of the total road disturbance area on steep terrain and contribute as much as 60 percent of sediment from forest roads. The significance of erosion control techniques on these vulnerable components of the road prism has become evident in recent years. A study to gain a better understanding of erosion control techniques on road cutslopes and fillslopes is detailed. Sediment and runoff yield from three erosion control treatments and a control were investigated on west-facing 2:1 and 1.5:1 cutslopes and fillslopes, respectively, on a newly constructed road during a 30-month study. The treatments evaluated were a wood excelsior erosion mat, native species grass, and exotic species grass. Factors detected to significantly affect sediment yield from road sideslopes were treatment, time, and treatment-time interaction based on analysis of variance. Significant reductions in sediment yield and runoff were found on all treatments on both the cutslope and fillslope. The erosion mat most effectively controlled erosion losses on both slopes for all study periods.

A Soil Identification Method for Potential Road Construction Problem Sites on the Olympic Peninsula, Washington

Several logging road subgrades and cut slopes failed under wet construction conditions in the 1980's on the Olympic Peninsula in Washington. Although standard laboratory soil test results did not indicate this would occur, field tests showed possible soil failure. A majority of these soils were coarse-grained with significant amounts of fines (silt and clay). Field soil identification methods indicated that these soils had a moisture content above the plastic limit; the laboratory test results were mostly non-plastic. During construction, the soils performed like plastic soils with low strength values, although in the laboratory the soils had suitable strength values for normal road construction methods. An hypothesis that standard laboratory tests for soil strength values do not detect organic and/or clay minerals that lead to failure under wet road construction conditions on the Olympic Peninsula was proven correct. A combined field and laboratory testing procedure was developed for identifying these soils. (A)

Estimation of the colluvial soil volume on road-cut slopes along forest road

Estimation of the colluvial soil volume on road-cut slopes along forest road