‘y- 351 I I I I I V ETH/88/013 Government of Ethiopia Water Resources Development Authority BALE GADULA IRRIGATION PROJECT Annex D Geological and Geotechnical Report of weib Diversion Weir by Anania Abay Theodros G/Egziabher United Nations Development Food and Agriculture Organization cf F rogramne the United Nations Addis Ababa June 1992CONTENTS 1. INTRODUCTION 2. GEOLOGY AND GEOMORPHOLOGY 2.1 Geomorphology 2.2 Geology 2.2.1 Basaltic Formation 2.2.2 Soil Formation 3 . GEOTECHNICAL FEATURES OF THE FOUNDATION 4 . CONSTRUCTION MATERIALS 4.1 4.2 4.3 Coarse Aggregates Sand for Concrete Earth Lining Material for Canal 5 CONCLUSIONS ANNEXES Geological Section of the Foundation Eoreholes logs Test pits logs Laboratory results. Location mapI. INTRODUCTION Th» Bale Gadula Tiiigat ton project la located about 9 5 km f i om Goba in Gore Awtata (Bale Region), about 520 km aouth-eaat ot Addie Ababa between v b' O' latitude and 40" l«' to 40" longitude 57* The irrigation aiea (flint phase) Is situated on the left bank ot Weyib I ivei bounded by the i ivei from South-West, Kuban village from the west and the Assendabo dry stiuam from north and north east. For this phase only a diversion weir will be needed. The height of the Diversion weir is about 1.5m, with the purpose to irrigate about 550 ha. Geological and geotechnical investigations were carried on the weyib river basin from Dec. 31, 1991 to Jan 24, 1992. At the weir axis three boreholes were drilled to the following depths: BH-1 12m EH-2 9.20m BH-3 7.20 making a total of 28.40m. In the command area four boreholes were drilled to determine the thickness of soil formation, the shallowest borehole is about 3.23m and the deepest is 8.35m. In addition ten hand dug pits have been excavated along the mam canal to a depth of 3m. This helps in adopting proper methods if excavation and determining the engineering properties of the excavated materials which will be used as construction material. Samples have been collected from the hand dug pits for the following laboratory tests: Grain size Analysis Atterberg limit Proctor compaction2. GEOLOGY AND GKQMORPHOlogy 2 •1 GEOMORPHOLOGY The project area is surrounded by hard formati located on the Weyib river valley Basaltic rock, outcroppin on of the Trap series of lava of the river stream. 9 on both sides of the valley and Starting from the bottom of the sides of the rh.m mountains there is a thick layer of colluvial deposit of Bllck cotton soil dips with a gentle slope to the river stream. Generally Weyib river follows along a fault line which has a general direction N100°W or S80°E Since most of the catchment area is covered with forest there is no high sediment transportation into the reservoir. 2.2 GEOLOGY 2.2.1 Basaltic Formation The Easaltic rock is formed in Tertiary period, as a Trap-series of lava. This dense Black rock with vesicular texture, is outcropping on both sides of the valley and river stream. On the surface of the rock appears a joint, which has beer, formed due to shrinkage on the cooling of the magma. In- addition the appearance and disappearance of vesicles every few meters in depth, shows the flow of the lava was a repeated process. Generally, the similarity of rocks outcropping on the river stream and few places of the command area on both the left and right sides of the valley, in-addition to the topography of the area shows there was displacement due to faulting. But there is no indication of active faulting at present. 2.2.2 Soil Formation A thick soil formation covered a valley. The soil can L- ---------------------- on the mode of formation. brown, the Blackish sc-- - dries up with small cracks. large area of the be" classified as a Residual soil, based tion. The color varies from black to oil swells enormously when wetted and 23 ’ GZOTECHNICAL FEATURES OF THE foundation means^of drVlV’h i f d*111 ^oles, and the l0n9 the ax*s were carried out by data collected fror th= boreholes assisted in preparation of the Geological Section o. the foundation and in evaluation of the engme=rinc properties of the foundation. From top to the bottom of the Geological section is: ^yiae-rmg a. Dark brown, clay with abundant grass roots, 1.1 64 and Pi 36, imperivous soil, classified as Highly plastic clay (CH) . b. Fine to coarse clayey sand with Gravels classified as GC, permeability coefficient K=1.45xl0'4 cm/s. Vesicular Basalt, highly jointed, vesicles filled with calcite, permeability coefficient evaluated in the bore holes by means of packer test, the value K=10’‘ to 10‘ m/s 7 4. CONSTRUCTION MATERIALS 4 .1 Coarse Aggregates The bottom of the hill is covered with cobbles and boulders which have been transported from the hill due to gravity. It is possible to use them as a source for aggregates. In-addition, both sides of the valley, which are very near to the weir site can be used as a quarry sites. 4 . 2 Sand for Concrete As mentioned on the report prepared by the Korean team, the only source for sand in Toggona river 74km from the weir site just near Robe town. According to the laboratory results, there is 35% fine to coarse sand and 65% fine to medium Gravel (poorly graded sandy Gravel). 4.3 Earth Lining Material for Canal Section Along the main canal ten hand dug pits were excavated to a depth of three meters, to evaluate the sub-surface-of the main canal. At Test pit No 1, No 2, No 3, No 4, No 7, bed rock was encountered at depths, from 2.00 to 2.90m. According to the laboratory results, the soil taken from test pits is classified as impervious highly plastic clay, with L.L ranging from 64 to 130 and P.I ranging from 24 to 100. 3Six modified compaction tests were carried out, and the value of MDD are between 1.2 and 1.47 g/cc with the corresponding value of OMC between 27% and 39%. On the same, sample strength tests have been carried out to determine the effective angle of internal friction and cohesion. The results are: PHI cohesion ranges from 0.78 kg/cm’ ranges from 3.37s to 1.82 kg/cm . to 15.83s, 2 5. CONCLUSIONS According to the data collected from the bore holes,laboratory results and Geological surveying it is possible to give the following conclusions: The selected weir site is suitable from the geological point of view, and since the bed rock is at a suitable depth, the weir can be founded on strong bed rock. Since the joints decrease with depth there is no major risk on the weir foundation. The nearness of the quarry site to the project area with unlimited quantity of stones is one of the advantages. Since the workability is poor and volume change is critical of the material excavated from the canal, some design consideration must be given to use as earth lining material (if necessary). 4n LOCATION: BORING LOG PROJECT: WEYIB DIVERSION WEIR UORTNC N°: b.H.1 C,XS INC: NW ELEVATION (mtn.) CORE I1ARREI. TYl’E: DOUBLE (NQ.BQ) WATER DEPTH (mts.) 6.00m BIT TYPE: DIAMY £ I RECOVERY ROD t r DESCRIPTION SPT IN SITU M Lfi -tt- y u y TEST Dark brown clay, Medium 1- plastic, abundant roots. 1.80m * K= 1.45xl0"4 cm/s- * & & * & * 8 , 9 - 10 - 1 1 - 1 2 - 1 3 - 1 4 . 1 5 - 16 - 1 7 . 18 . 1 9 - 20 • 31 - 2 2 - 2 3 - 24 - Fine to coarse clayey sand with Gravells 3.70m From 3.70 to 4.65 Highly vesicular Basalt, with vertical to sub-vertical joints, filled with fine materials. From 4.65 to 9.40m vesicular Basalt, vesicles filled with calcite, sib-vertical joints, spacing 7 to 30cm, filled with fine materials. From 9.40m to 12.00m Highly vesicular Basalt, and vericles are not filled, sub-vertical joint, spacing 20 to 50cm K=3xl0~6 m /s K=3.3xlC' m/s K=8.78xlC **I boring log PROJECT: WEYIB LOCATION:1 PROJECT: WEYIB LOCATION: BORING LOG UORINC N°: B.H.3 ELEVATION (inl».) WATER DEPTH (mts.) 1.55 CASING: NW (0=7 6mm) COIIF. IIAJUIEI. TYPE: DOUBLE (NQ,BQ) BIT TYPE: DI AMYWEYIB IRRIGATION PROJECT SITE: AXqos .Vis .W! LOGGED BY: ............ TEST PIT NO. .1-............................ APPROX. COORD... ./................ I^PTH DESCRIPTION SAMPLES 0:5 Black, plastic clay with abundant grass 1 —■ Light grey, silty cl^y, with Concretions. CW 1.50 2------- -ight grey, sandysilty caly With concretions 2.80 3---- Bed Rock 4____ cttt. Al°n8 C^e Main Canal LOGGED MV • TEST PIT NO...2........................................... APPROX. COORD....................................... /............... DEPTH DESCRIPTION SAMPLES Black, plastic clay with abundant grass roots » 1— 1.76m 2------ 3----- Brown silty clay with Concretions 3.163 Bed RockWEYjB IRRIGATION PROJECT SITE: . A°. A A . . A n h e Main Canal TFCT PTT Un 3 LOGGED BY: ............................................................... APPROX COORD -• /..................... DEPTH DESCRIPTION SAMPLES Black, plastic clay with Abundant grass roots 1_ 1.50 ^rg^jn clay with concretion 7 Bed rock 3_____ CTTT- Along the, Main Canal _ ytct »tt an..................... 4 ______ APPROX. COORD... DEPTH DESCRIPTION SAMPLES Black, plastic clay with abundant grass roots « 1----- 1.26m Brown, plastic clay with abundant concretions 2____ 2.40m Bed Rock 3------ AWEYIB IRRIGATION PROJECT SITE: .Alm. MAIN. CpppI.... TEST PIT NO. ... .5.1.................................... LOGGED BY: APPROX. COORD... /..................... 'depth DESCRIPTION SAMPLES — 1 ------- Block, plastic clay with abundunt grass roots 1.32m ar own clay with concretions 1.75 Bed Rock SITE* LOGGED BI: .V1.® .Canal TEST PIT NO APPROX. COORD DEPTH DESCRIPTION SAMPLES Black, plastic clay with grass roots » Brown clay with few concretions Bed Rock go ro I1I1I1I11■WEYIB IRRIGATION PROJECT SITE: . Along. ;he. £ana.l.... TEST PIT NO. ... I . . J................................ LOGGED BY: APPROX. COORT)...................... • / •Ji . u DEPTH DESCRIPTION SAMPLES 1 — Black, plastic clay, with abundant grass roots 2 ------- 2.30m — Brown clay, with few concretions 2.95m 3 Bed rock SITE:.. LOGGED BY: tbs .caudl TEST PIT HO APPROX. COORD DEPTH DESCRIPTION SAMPLES » Black, plastic clay, with abundant grass roots. Brown clay with rew concretionsWEYIB SITE: Alon^ the Main canal IRRIGATION PROJECT TEST PIT NO. 9 LOGGED BY: APPROX. COORD / DEPTH DESCRIPTION SAMPLES Black, plastic clay, with abundant grass roots. ----- 2.30m Brown clay with few concretions 3 ____ 3.00m____________________________________________ ___ SITE:. .AtoS .the Main .Canal LOGGED BY: e. DEPTH DESCRIPTION TEST PIT BO.....Ay APPROX. COORD/................................................................. SAMPLES - - ■ Block, plastic clay, with abundant grass roots and few gravels — X00 bed rockW.R.D.A..SOIL-MECHANICS,LABORATORY PROJECT,ETHIOPIA SHEET NO.1 .A80RAT0RY TEST RESULTS.bale.gaiwla — — — 15/APKlL/yz nnAru C17C nTCTDTDIITinM t PASSING ___________ —--------------------- A Jierberg.limits. BELOW 0.002 to 0.075 tol 0.425 t| 2 to 0.425 mm] 2 mm • .4.75 4.75t0 | 19.1 t u ABOVE LL PI SL LAB. NO 19.1mm 1 76.2mm 76.2mm -J % % UNIFIED SOIL CLASS IFICATION ) FIEL IDENTIFICAf TION ) DEPTH (m) CLAY SILT Sand GRAVEL CPBBtE GS f Im 1 c F C 1 39b TPi 0.5 - 1.5 34 33 33 64 36 2.77 CH 3*6 TP j 1.5 - 2.9 2 ( 41 57 64 37 2.71 CH 397 TP 2 0 - 1.76 70.2 25.67 4.13 91 56 2.75 CH 397 tp2 1.76-3.16 70 16 14 82 56 2.76 CH > 398 tp3 1.5 - 2.0 32 30 38 43.4 24.3 2.69 CL ■ 399 tp4 1.26-2.4 50 42 8 74 52 2.71 CH 400 tp6 1.62-2.7 60.5 29.9 9.6 124.5 87.5 2.64 CH 401 tp7 2.3 -2.95 80.2 15.68 4.12 133 89 2.62 CH-ABORATORY TEST RESULTS.^ .U4QUU......................... W.R.D.A. SOIL MECHANICS LABORATORY PROJECT,ETHIOPIA 15/APRIL /92 REF MO.00002/92 SHEET M0.1 GRAIN SIZE DISTRIBUTION I PASSING ........... ...............................A Kerberg limits UNIFIED J LAB. NO FI ELI IDENTIFICA' TION )1 DEPTH (m) BELOW 0.002 0.002 to 0.075 mm 0.075 to 0.425 mm 0.425 tf 2 to 2 mm 1 4.75 4.75to 19.1mm 19.1 t 76.2mm i ABOVE 76.231a LL % PI X SOIL Ci-ASS IFICATION CLAY SILT !>and F M 1C GRAVEL F i C CPBBtE SL % GS 402 tp3 0.95-2.45 70.5 25.19 4.31 127 87 2.7 CH 402 TPg 2.45-3.0 80. 'l 17.9 2.0 150 107 2.72 CH i 403 TP9 0.45-2.3 70.9 27.98 1.12 102.‘ 61.3 2.69 CH 403 tp9 2.3- 3.0 85 12.5 2.5 131 97 2.70 CH ILASUkjlORY TEST RESDlTS^bale.gadula UihoistjruEu/juturjed cample W.R.D.A SOIL MECHANICS PROJECT,ETHIOPIA 15/APRIL /92 SHEET NO.t 00002/92 Er. NO. Laj NO. SOIL CuASSir iCATIt’ 1 (m) iWC IiMSITUF STRtN,’H TEST 01 R/TRI SP.gr OMC z MOD g/cc TOTAu stress ErrECTIi'l ■ STRESS c, Kg/cmz 0o C‘ p” CONSOLIDATION \ DATA REMAIK 1 390 TP! (0.5-2.9) I 29 1 1.46 1.67 9.59° _______ 2 391 tp2 (0-3.16) ______ 31 1.32 0.70 15.83° i 3 392 tp4 (0-2.4) 27 1.47 1.82 8.21 4 393 tp6 (0.8-2.7) 38 1.2 1.15 3.37 5 394 TP 7 (0.85-2.95) 39 1.22 1.15 4.35 j 6 395 tp9 (0.99-3.0) 37 1.21 1.56 7.5per; passing .075 1 -LAY SIEVE N°/SIZE Medium SAMPLE N* DEPTH-M CLASSIFICATION poorly graded Gravelly sand I. GRADATION CURVES Plotted Checked PROJECT Saoi£le_DQfB_ Sadmitted by Report Na Date of Report ^hief of^U^hTab^fofySUD AN FIGURE I PROJECT LOCATION Z■\ 1 • Notitnoi Boundary 1 \ I \ + vT ) Rood \ '• Rdilrwd SOMALIA BALE GADULA PROJECT STTE MOGAD6H0 UGANDA
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