HAZARD ASSESSMENT OF SLOPE FAILURES IN CONGLOMERET AT TIKRIT, NORTHERN IRAQ

The degree and nature of slope failure hazards reflected the rock properties of unstable slopes, effective characteristics as slope high, slope angle, rock discontinuities, weathering, presence of water, and the consequence level depend on several parameters. Ditch (width, shape, volume), traffic, shoulder width to decide slopes mode and rest rock properties. Applying the Missouri Rock Fall Hazard Rating System Failure types happened and probably in the research area (Rock Fall, Toppling, Rolling). Nature parameters control hazard cases, station 7 represented alone the Tikrit bridge, water contact along a year, western shoulder of the bridge near the cliff, traffic problems, man-made, and buildings above slope apex, stations 4 and 5 people using Al-Bilaj area for swimming, fishery, and tourism, stations 1, 2, 3 and 6. Human activities are less than at stations 4 and 5. Consequently, the study area is sufferings hazard, and so should include warning suddenly failures. Stations1, 6 and 7 were classified as High-Risk High Consequence, while 2, 3, 4 and 5 were classified as High-Risk Low Consequence


INTRODUCTION
The study area is located at the western bank of the Tigris River in Tikrit city.It located at a cliff with an elevation of about 135 m above the sea level.It determined by a coordinate of longitudes (43°41¢00"-43°41¢23" E) and latitudes (34°36¢00"-34°40¢50"N) as shown in Figure (1).Seven stations nominated as 1, 2, 3, 4, 5, 6 and 7 were selected for studying according to the procedure of Anon (1972 and1977) and Al-Saddi (1981) for the slopes high 23.33-46.662ft (7-14 m), above ground surface represented by Pleistocene alluvial fans, in addition to a cliff.The study area shows NW-SE valleys that transport the rain fall to the

Alhadad
Vol.53, No.1C, 2020 122 Tigris River (Fig. 2).The study area includes a horizontal and inclined bedding plane, with 5 ᴏ inclination southwestward.The beds include fractures as vertical tension joints or cracks, some surfaces of these joints are parallel to the surface slope, while the others are perpendicular (Alhadad and Ward, 2019).The climate of the area is arid to semiarid with an annual average rain fall of about 160 mm and summer temperature 49 ᴏ and 13 ᴏ in Winter.
Mostly, the climate used as an indication to the influence on the rock weathering (I.M. O., 1990-2017), slope, failure happened and probably happened according conditions of weathering, as well as other factors.Occurrence and history.The previous studies were done in Tikrit area.Abdulrazzag (2011)

MATERIALS AND METHODS
This study deals with the hazard assessment for slope stability of the conglomerate that has been evaluated.Different tools (geological compass, hammer, global position system (GPS), camera, Tape measurement, and Nylon bag for sample collection).The unstable rock at area studied creates serious safety hazards to traffic (Plates 1, 2, 3, 4, 5, 6 and 7).The diagrams shown in Figures (3&4) were drown according to Hoek and Bray (1981) and Al-Saddi (1981).
The description of rocks in all selected stations in the area of interest in terms of engineering geology has been done based on the report suggested by the working party of the engineering group of the Geological Society of London (Alhadad and Ward, 2019).Seven Stations were selected to be studied and described according to Anon (1972 and1977).Color described in terms of three parameters, basic color, a mixture to basic colors, and the value or the lightness of color (Anon, 1972) The grain size was applied to all rocks and the size ranges used for soils would appear to be suitable for this purpose, (Anon, 1972).Bedding planes are described.Joints were described according to Anon (1972) including orientation of joints, dip and their characteristics such as spacing, their persistence on bedding plane, and if they are opened or closed.Weathered state described according to the effect of weathering on the resistance of rocks and other characteristics such as loss of strength, opening in joints and discoloration.There are six grades of weathering based on Anon (1972).The mechanical strength of the rock sample and indirectly measured compressive strength from point load test showed the terms and a scale of strength (Anon, 1972).Rock Name, should be written in capital letters.Then, rock name followed by suffixes which include, the compressive strength.
Permeability, based on discontinuity spacing.provides generalized values for jointed rocks (Anon,1972).some of them had determined the engineering properties of rock and rock masses (Hoek, 1977;ISRM, 1981&1985;and Farmer, 1992), but others had studied the effect of rolling and toppling rocks from the rock slopes on the high ways using different simulation programs for example, CRSB (Jones et al., 2000).Recently there are many authors describing rock fall hazard rating systems that have been implemented by several states in USA and Canada including Oregon (Pierson, 1992); Utah (Pack and Boie, 2002); New Hampshire (Fish and Lane, 2002); New York (Hadjin, 2002); Washington (Ho and Norton, 1991); Tennessee (Bateman, 2002;Bellamy et al., 2003;Van dewater et al., 20050, (Maerz, et al, 2004;Maerz, et al., 2005) in Youssef and Maerz (2009).MORFH RS Classified the rock cuts in two classes, risk and consequence failure.Risk consists 11 factors and consequences 12 factor as shown in Table 1.The values of the risk and the consequence parameters were summed and normalized to produce a risk or consequence rating on a scale of 0-100 for each.The adjustment factors of each rock class (if not equal to zero) are added separately to the risk side (scale of 0 to 12) or the consequence side (scale of 0 to 15).The maximum risk or consequence rating is 100 (Maerz et al., 2005) (Tables 1 and 2).

Results
The studied stations (1, 2, 3, 4, 5, 6 and 7) showed variation evaluation according to their results in both of the field surveying, and laboratory tests as well (Table 3 and Plates 1, characteristics of the rock discontinuities, the height of the rock slope, rock weathering style, presence of water, man-made and adequacy of the catchment ditch (Table 4).The level of consequence depends on the amount and speed of traffic, the decision site distance and other factors shown in The field investigation and measurements for 7 stations across the cliff on the western side of the Tigris River at the study area indicate that these cut stations have 60.5 -86.5% high risk, and 37.5 -67.25% low-high consequence rating values (Table 4 and 5).

CONCLUSIONS
Some important points can be concluded from this study as below: 1-Rock compressive strength played an important parameter in stability of rocks in addition to water, slope high, slope angle, traffic, etc.

Fig. 2 .
Fig.1.Location map of the study area

Table 3 . Results of Surveying and laboratory test of research area for 7 stations
Table 5 represent risk values and consequence values (Figs.5&6).