Attachment 6_AID-696-A-16-00008 Isuku Iwacu Soil test report.pdf

DISCLAIMER

The opinions and contents of this report are the sole responsibility of SNV and do not necessarily reflect the views of the United States Agency for International Development or the United States Government

SOIL PRE-TEST REPORT

RWANDA RURAL SANITATION –

ISUKU IWACU ACTIVITY

May 2018

Photo: Isuku Iwacu

TABLE OF CONTENTS

1. Introduction……………………………………………………………………………………………..4

2. Scope of the work……………………………………………………………………………………….4

3. Soil identification……………………….………………………………………………………………9

4. Soil description in different Districts…………………………….……………………………………….10

.Kicukiro District………………………………………………………………………………………….10

Nyarugenge District………………………………………………………………………………………20

Rwamagana District………………………………………………………………………………………28

Kayonza District…………………………………………………………………………………………..36

Ngoma District…………………………………………………………………………………………….49

Ruhango District…………………………………………………………………………………………..61

Nyanza District……………………………………………………………………………………………72

Nyabihu District…………………………………………………………………………………………..79

LIST OF TABLES AND FIGURES

FIGURES

- Figure 1:Soil resistance test with penetrometer………………………………………………..4

- Figure 2:Pit excavation in Rwamagana District………………………………………………..5

TABLES

- Table 1:Soil classification based on grain size …………………………………………………8

- Table 2: Technical specifications……………………………………………………………….11

- Table 3: Kicukiro soil profile and lithology presentation………………………………………12

- Table 4: Soil characteristics in Kicukiro District……………………………………………….13

- Table 5: Gishikiri village/Kanombe sector soil resistance……………………………………...14

- Table 6: Kabuye village/Gikondo sector soil resistance………………………………………..15

- Table 7: Ruhanga village/Masaka sector soil resistance………………………………………..16

- Table 8: Nyarugenge soil profile and lithology presentation…………………………………...20

- Table 9: Soil characteristics in Nyarugenge District……………………………………………20

- Table 10: Inyambo village/Nyarugenge sector soil resistance…………………………………..21

- Table 11: Kagunga village/Nyamirambo sector soil resistance…………………………………23

- Table 12: Rwamagana soil profile and lithology presentation…………………………………..28

- Table 13: Soil characteristics in Rwamagana District…………………………………………...28

- Table 14: Nyirabiteri village/Fumbwe sector soil resistance…………………………………….29

- Table 15 : Rwamibungo village/Nyakariro sector soil resistance………………………………..32

- Table 16: Kayonza soil profile and lithology presentation………………………………………36

- Table 17: Soil characteristics in Kayonza District……………………………………………….37

- Table 18: Bwiza village/Nyamirama sector soil resistance………………………………………37

- Table 19: Mbarara village/Rwinkwavu sector soil resistance……………………………………39

- Table 20: Nyamata village/Ndego sector soil resistance…………………………………………42

- Table 21: Rugunga village/Murundi sector soil resistance……………………………………….45

- Table 22: Ngoma soil profile and lithology presentation………………………………………...49

- Table 23: Soil characteristics in Ngoma District…………………………………………………50

- Table 24: Kibimba village/Kibungo sector soil resistance……………………………………….50

- Table 25: Nyamabuye village/Mugesera sector soil resistance…………………………………..52

- Table 26: Nyamirindi village/Mutenderi sector soil resistance…………………………………..54

- Table 27: Rugarama village/Gashanda sector soil resistance…………………………………….56

- Table 28: Ruhango soil profile and lithology presentation……………………………………….59

- Table 29: Soil characteristics in Ruhango District………………………………………………..61

- Table 30: Kajevuba village/Mwendo sector soil resistance……………………………………….62

- Table 31: Karama village/Ntongwe sector soil resistance…………………………………………64

- Table 32: Kidoma village/Mbuye sector soil resistance……………………………………………66

- Table 33: Bugarama village/Bweramana sector soil resistance…………………………………….68

- Table 34: Nyanza soil profile and lithology presentation…………………………………………..72

- Table 35: Gahogo village/Busogo sector soil resistance……………………………………………73

- Table 36: Rugarama village/Busasamana sector soil resistance…………………………………….75

- Table 37: Nyabihu soil profile and lithology presentation………………………………………….79

- Table 38: Soil characteristics in Nyabihu District…………………………………………………...79

- Table 39: Kadatemwa village/Kintobo sector soil resistance………………………………………. 80

- Table 40: Muturirwa village/Rambura sector soil resistance…………………………………………82

1 INTRODUCTION

Under the USAID-funded Isuku Iwacu – Rwanda Rural Sanitation Activity (RRSA) implemented SNV, and including World Vision International and Water for People in the following eight districts: Kayonza, Kicukiro, Ngoma, Nyabihu, Nyanza, Nyarugenge, Ruhango, and Rwamagana, SNV hired Eng. Dominique HITAYEZU, expert in geotechnical, to carry out additional geotechnical studies across the eight districts.

The geotechnical investigations have been realized based on technical specifications and terms of reference submitted by the client.

The content of this report will be based mainly on in situ soil investigations, laboratory test analysis in terms of defining the site conditions and characteristics of the existing ground in different districts investigated.

2 SCOPE OF THE WORK.

Before starting the site investigation, a site visit has been organized for visual inspection of the project. A reconnaissance visit was done in each District for making identification of the site locations in different cells for each District.

The second phase of our mission was devoted to conduct Geotechnical Investigations divided into two tranches:

- The first tranche consisted of conducting the penetration test using a light dynamic penetrometer in order to determine the allowable stress of soil in each area identified, and to provide the necessary information on the nature and behaviour of the soil or rock layers in place.

Figure1: Soil resistance test with Penetrometer.

- The second tranche consisted of conducting soil reconnaissance by making pits 2 m deep each followed by soil sampling. All samples collected were conducted in the laboratory for identification.

Figure 2: 2m deep Pit excavation in Rwamagana

Our geotechnical study has been conducted in terms of making soil investigations on existing natural ground, making deep investigations on all locations where construction of latrines will be made for determining and defining the soil stability of the materials in place; carrying out all problems encountered and finding the sustainable solutions for each problem.

All activities realized are presented in the table below:

DISTRICT SECTOR/VILLAGE N0 PITS N0 DCP SOIL SAMPLES

KICUKIRO

GIKONDO/KABUYE 1 1 1

KANOMBE/GISHIKIRI 1 1 1

GAHANGA/RUKORE 1 0 1

MASAKA/RUHANGA 1 1 1

NYARUGENGE NYAMIRAMBO/KAGUNGA 1 1 1

NYARUGENGE/INYAMBO 1 1 1

RWAMAGANA FUMBWE/NYIRABITERI 1 1 1

NYAKARIRO/RWAMIBUNGO 1 1 1

KAYONZA

MURINDI/RUGUNGA

RWINKWAVU/MBARARA

NDEGO/NYAMATA

NYAMIRAMA/BWIZA

NGOMA

MUTENDERI/NYAMIRINDI

KIBUNGO/KABIMBA

GASHANDA/RUGARAMA

MUGESERA/NYAMABUYE

RUHANGO

MWENDO/KAJEVUBA

BWERAMA/RUGARAMA

MBUYE/KIDOMA

NTONGWE/KARAMA

NYANZA BUSORO/GAHOGO

BUSASAMANA/RUGARAMA

NYABIHU RAMBURA/KAMIRO

KINTOBO/KADATERURWA

3. DYNAMIC CONE PENETRATION TESTS REALIZATION

The testing was carried out at the existing ground with a TRL Dynamic Cone Penetration (DCP) which is an instrument designed for the rapid in situ measurement of the structural properties of existing ground with unbound granular materials . The underlying principle of the DCP is that the rate of penetration of the cone, when driven by a standard force, is inversely related to the strength of the material as measured by, for example, the California Bearing Ratio (CBR) test. Where the soil layers have different strengths, the boundaries between the layers can be identified and the thickness of the layers determined.

During our DCP testing, we followed TRL instructions stipulating that « penetration rates as low as 0.5 mm/blow are acceptable but if there is no measurable penetration after 20 consecutive blows it can be assumed that the DCP will not penetrate the material. Under these circumstances a hole can be drilled through the layer using either an electric or pneumatic drill or by coring. The lower layers of the ground can then be tested in the normal way ». DCP results have been processed in appendix No.1.

The test was conducted by means of a standard TRL DCP device having the following features:

- Drop weight: 8 kg

- Drop height: 575 mm

- Cone diameter: 20 mm

- Apex angle of cone: 60°

DCP testing were conducted at nine (8) points as follow:

- Rwamagana District: 2points

- Nyanza District: 2 points

- Nyabihu District: 2 points

- Nyarugenge District: 2points

4. LABORATORY TESTING

The trial pit research was followed by sampling and collection of all samples to the laboratory for identification and analysis.

The following laboratory tests have been made on each sample

- Sieve analysis

- Natural moisture content

- Atterberg limits

4.1 Geotechnical investigations

This section highlights the detailed subsoil investigation of identified areas . This is based on the field and laboratory tests conducted on all trial pits made. Description of subsoil condition, soil characteristics and details of different parameters will be based on the following tests:

4.2. Index properties and soil classification

Index properties refer to those properties of a soil that indicate the type and conditions of the soil, and provide parameters for the classification. They are also referred as classification properties and classification or index tests are performed in laboratory for determination of these properties.

Basically, two types of tests are performed to identify the type and conditions of the soil. These include:

· Particle size distribution

· Consistency Limit (Atterberg Limits)

4.3. Particle size distribution analysis

Particle size distribution analysis or simply sieve analysis is a screening process in which coarse fractions of soil are separated by means of series of sieves. Particle sizes larger than 0.075 mm are usually analyzed by means of mechanical sieving and Soil materials finer than 0.075 mm are analyzed by means of sedimentation or hydrometer analysis.

For the mechanical sieving, the soil is passed through a series of sieves with the mesh size reducing progressively, and the proportions by weight of the soil retained on each sieve are measured. There are a range of sieve sizes that can be used, and the finest is usually a 75 mm sieve. Sieving can be performed either wet or dry.

To determine the grain size distribution of material passing the 75mm sieve the hydrometer method is commonly used. The soil is mixed with water and a dispersing agent, stirred vigorously, and allowed to settle to the bottom of a measuring cylinder. As the soil particles settle out of suspension the specific gravity of the mixture reduces. A hydrometer is used to record the variation of specific gravity with time. By making use of

Stoke’s Law, which relates the velocity of a free falling sphere to its diameter, the test data is reduced to provide particle diameters and the % by weight of the sample finer than a particular particle size.

The end product of the sieve analysis is the particle-size distribution curve, whereby the percentage passing a specific sieve is plotted against the sieve sizes.

Out of the particle size distribution analysis curve, the following parameters can be determined and be used for the soil classification:

(i). Effective size (D10): This parameter is the diameter in the particle-size distribution curve corresponding to 10% finer. The effective size of a granular soil is a good measure to estimate the hydraulic conductivity and drainage through soil.

(ii). Uniformity coefficient (Cu): This parameter is defined as

C D Du = 60

Where D60: diameter corresponding to 60% finer.

(iii). Coefficient of gradation (Cc): This parameter is defined as

C D

D Dc =

60 10( )

Additionally, from the particle size distribution curve, the percentage of fines, sand and gravel sizes can be calculated as shown in table 1. This is done according to the classification system in use.

Table 1: soil classification based on the grained size

5. SOIL IDENTIFICATION

From the various pits realized at each location, we carried out a sampling of soils to determine the characteristics of soil bearing for each location. The identification tests were performed to complete the laboratory results obtained from these tests, we conducted a classification of these soils to allow for a Team who will be tasked with the design of structures to decide whether the soils in place are able to support the foundation or whether they should be eliminated forever if their resistance is not sufficient.

Interpretation of the results

Table2: Technical Specifications

Prescriptions for materials tested Tests Specifications Procedure

Organic matter <= 1% NF P 18 - 586

Water content <Wopm NF P94 - 050

Sieve analysis Dmax< 100 mm NF P 18 - 560 % Fines < 35

Atterberg limits

LL<50 NF P 94 -

IP < 25

6.SOIL DESCRIPTION IN DIFERENT DISTRICTS.

6.1.KICUKIRO DISTRICT

6.1.1 GEOTECHNICAL MAP OF SAMPLED AREA IN KICUKIRO DISTRICT

6.1.2 SOIL PROFILE AND LITHOLOGY IN KICUKIRO DISTRICT

The geotechnical investigations have been conducted in Gikondo sector, Kabuye village; Kanombe sector, Gishikiri village, in Gahanga sector, Rukore village and Masaka sector, Ruhanga village. The following observations have been made during our site investigation.

Table 3: Kicukiro soil profile and lithology presentation Location Soil lithology Soil Profile Observations

Gikondo/Kabuye

-10cm of organic top soil followed by a soft layer of silt coarse materials 80cm thick. From 1m to 2m deep, the soil become compact with more coarse elements.

Kanombe/Gishikiri

-15 cm of organic top soil followed by a layer of gravelly lateritic materials 85 cm thick. The under ground soil from 1m deep is strongly compacted and very hard.

Gahanga/Rukore

-10 cm of organic top soil, followed by a layer of gravelly lateritic materials 1m thick. The under ground layer is hard rocky.

Masaka/Ruhanga

-20 cm of organic top soil followed by a lateritic materials more than 2m thick.

6.1.3 SOIL IDENTIFICATION IN KICUKIRO DISTRICT

Table 4 : Soil characteristics in Kicukiro District

6.2 DCP TEST RESULTS IN KICUKIRO DISTRICT

Table 5: Gishikiri village/Kanombe sector soil resistance Depth (cm)

Number of blows (N)

Resistance at the point

(N/m2)

Resistance at the point

(Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 4.00 1.9 19 0.94 20 7.00 3.3 33 1.64 30 20.00 9.4 94 4.68 40 20.00 9.4 94 4.68 50 21.00 9.8 98 4.92 60 27.00 12.6 126 6.32 70 29.00 13.6 136 6.79 80 41.00 19.2 192 9.60 90 50.00 23.4 234 11.71

Sample N° Kanombe/Gishi kiri

KabuyeI/Gikon do

Masaka/Ruha nga

Gahanga/Ruk ore

Sieve Analysis

Sieves (mm) 40 100.00 100.00 100.00 100.00

31.5 100.00 100.00 100.00 100.00 25 100.00 100.00 100.00 100.00 20 98.39 100.00 100.00 100.00 16 96.43 100.00 100.00 100.00 14 93.62 100.00 100.00 100.00 12 90.20 100.00 100.00 99.10 10 86.09 100.00 100.00 97.64 8 79.68 100.00 100.00 92.37

6.3 73.68 100.00 100.00 85.30 5 66.08 100.00 100.00 80.46 4 58.13 100.00 100.00 75.15

3.15 49.14 100.00 100.00 69.02

2.50 39.42 100.00 100.00 61.01

2 28.47 100.00 99.95 51.80 1 22.36 98.47 98.30 41.30

0.32 18.40 94.28 94.34 35.09

0.16 15.60 82.31 84.21 31.02

0.08 13.98 78.51 78.70 29.22

0.75 13.98 78.51 78.70 29.22

Natural water content

Atterberg Limits WL 30.6 30.2 39.8 24.4

PI 9.7 10 9.9 0

Classification HRB A-2-4 A-2-4 A-2-4 A-3 I.G. (0) (0) (0) (0)

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240250

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Resistance at the Point (MPA)

Series1

Table 6: Kabuye village/Gikondo Sector soil resistance Depth (cm)

Number of blows (N)

Resistance at the point

(N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 6.00 2.8 28 1.41 20 4.00 1.9 19 0.94 30 2.00 0.9 9 0.47 40 2.00 0.9 9 0.47 50 2.00 0.9 9 0.47 60 1.00 0.5 5 0.23 70 1.00 0.5 5 0.23 80 10.00 4.7 47 2.34 90 11.00 5.2 52 2.58 100 12.00 5.6 56 2.81 110 14.00 6.5 65 3.24 120 16.00 7.4 74 3.70 130 20.00 9.3 93 4.63 140 20.00 9.3 93 4.63 150 21.00 9.7 97 4.86 160 22.00 10.2 102 5.09 170 24.00 11.1 111 5.55 180 27.00 12.5 125 6.25 190 25.00 11.6 116 5.78 200 26.00 12.0 120 6.02 210 27.00 12.3 123 6.17 220 26.00 11.9 119 5.94 230 24.00 11.0 110 5.49 240 24.00 11.0 110 5.49 250 27.00 12.3 123 6.17 260 28.00 12.8 128 6.40 270 26.00 11.9 119 5.94 280 27.00 12.3 123 6.17 290 26.00 11.9 119 5.94 300 28.00 12.8 128 6.40 310 27.00 12.2 122 6.10 320 29.00 13.1 131 6.55 330 31.00 14.0 140 7.00 340 30.00 13.6 136 6.78 350 41.00 18.5 185 9.26 360 50.00 22.6 226 11.30

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240

De pt h in c m

Table 7: Ruhanga village/Masaka sector soil resistance

(cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point

(Bars) Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 4.00 1.9 19 0.94 20 5.00 2.3 23 1.17 30 5.00 2.3 23 1.17 40 5.00 2.3 23 1.17 50 5.00 2.3 23 1.17 60 4.00 1.9 19 0.94 70 4.00 1.9 19 0.94 80 6.00 2.8 28 1.41 90 7.00 3.3 33 1.64 100 7.00 3.3 33 1.64 110 6.00 2.8 28 1.41 120 10.00 4.7 47 2.34 130 10.00 4.7 47 2.34 140 9.00 4.2 42 2.11 150 8.00 3.7 37 1.87 160 8.00 3.7 37 1.87 170 10.00 4.7 47 2.34 180 11.00 5.2 52 2.58 190 14.00 6.6 66 3.28 200 12.00 5.6 56 2.81 210 10.00 4.6 46 2.31 220 11.00 5.1 51 2.54 230 14.00 6.5 65 3.24 240 17.00 7.9 79 3.93 250 18.00 8.3 83 4.16 260 20.00 9.3 93 4.63 270 19.00 8.8 88 4.40 280 19.00 8.8 88 4.40 290 18.00 8.3 83 4.16 300 20.00 9.3 93 4.63 310 21.00 9.6 96 4.80 320 23.00 10.5 105 5.26 330 22.00 10.1 101 5.03 340 21.00 9.6 96 4.80 350 24.00 11.0 110 5.49 360 30.00 13.7 137 6.86 370 34.00 15.5 155 7.77

380 50.00 22.9 229 11.43

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90100110120130140150160170180190200210220230240250

De pt h in c m

GENERAL COMMENT:

Based on laboratory test results and considering soil resistances results from the DCP test done, the behavior of the existing soil in Kicukiro District is presented as follow:

- The soil presented good characteristics from the top soil to 2m deep, the excavation works from the surface to more than 4m deep should be conducted without any soil sliding or collapse.

- The soil is stable enough and cohesive, the excavation works should be conducted in normal conditions

- It is possible to make manual excavations works from the surface to 4m deep, after this depth, the soil become strongly hard and rocky.

- Considering the stability of the soil in place and its resistance, we propose construction of natural latrines in Kicukiro District.

We recommend the use of masonry foundations where the top soil will be protected by a small circular wall

40cm thick with masonry. The cement/sand mixing ratio should be 1/3

6.3 NYARUGENGE DISTRICT

6.3.1 GEOTECHNICAL MAP OF SAMPLED AREA IN NYARUGENGE DISTRICT

6.3.2 SOIL PROFILE AND LITHOLOGY IN NYARUGENGE DISTRICT

The geotechnical investigations have been conducted in Nyamirambo sector, Kagunga village; and in Nyarugenge sector, Inyambo village. The following observations have been made during our site investigation.

Table 8: Nyarugenge soil profile and lithology presentation

Nyamirambo/Kagunga

-From the top to 1m deep, the soil in place is silt sandy brown colored, less consistent and cohesionless

Nyarugenge/Inyambo

30cm of organic top soil followed by a compact gravel materials.

6.3.3. SOIL IDENTIFICATION IN NYARUGENGE DISTRICT

Table 9: Soil characteristics in Nyarugenge District

Sample N° Nyarugenge/ Inyambo

Nyamirambo /Kagunga

Sieve Analysis

Sieves (mm) 40 100.00 100.00

31.5 100.00 100.00 25 100.00 100.00 20 99.63 100.00 16 98.76 100.00 14 97.35 100.00 12 94.57 100.00 10 92.79 100.00 8 89.72 99.95

6.3 84.62 99.85 5 79.27 99.85 4 73.71 99.80

3.15 68.91 99.70

2.50 63.93 99.29

2 59.41 97.33 1 53.40 93.85

0.32 48.18 92.94

0.16 41.54 90.52

0.08 40.01 89.01

0.75 39.97 89.01

6.4 DCP TEST RESULTS IN NYARUGENGE DISTRICT

Table 10: Inyambo village/Nyarugenge sector soil resistance

Depth (cm)

Number of blows (N)

Resistance at the point

(N/m2)

Resistance at the point

(Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 4.00 1.9 19 0.94 20 3.00 1.4 14 0.70 30 2.00 0.9 9 0.47 40 2.00 0.9 9 0.47 50 2.00 0.9 9 0.47 60 2.00 0.9 9 0.47 70 5.00 2.3 23 1.17 80 6.00 2.8 28 1.41 90 10.00 4.7 47 2.34 100 7.00 3.3 33 1.64 110 8.00 3.7 37 1.85 120 20.00 9.3 93 4.63 130 24.00 11.1 111 5.55 140 38.00 17.6 176 8.79 150 41.00 19.0 190 9.49 160 50.00 23.1 231 11.57

Natural water content

Atterberg Limits WL 32.5 43.3

PI 12.7 11

Classification HRB A-2-4 A-2-4 I.G. (0) (0)

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240250

De pt h in c m

Table 11: Kagunga Village/Nyamirambo Sector soil resistance

(cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 1.00 0.5 5 0.23 20 1.00 0.5 5 0.23 30 2.00 0.9 9 0.47 40 2.00 0.9 9 0.47 50 1.00 0.5 5 0.23 60 1.00 0.5 5 0.23 70 2.00 0.9 9 0.47 80 2.00 0.9 9 0.47 90 2.00 0.9 9 0.47 100 4.00 1.9 19 0.94 110 1.00 0.5 5 0.23 120 1.00 0.5 5 0.23 130 2.00 0.9 9 0.46 140 3.00 1.4 14 0.69 150 4.00 1.9 19 0.93 160 4.00 1.9 19 0.93 170 5.00 2.3 23 1.16 180 6.00 2.8 28 1.39 190 6.00 2.8 28 1.39 200 6.00 2.8 28 1.39 210 6.00 2.7 27 1.37 220 7.00 3.2 32 1.60 230 7.00 3.2 32 1.60 240 7.00 3.2 32 1.60 250 8.00 3.7 37 1.83 260 8.00 3.7 37 1.83 270 8.00 3.7 37 1.83 280 10.00 4.6 46 2.29 290 11.00 5.0 50 2.51 300 9.00 4.1 41 2.06 310 9.00 4.1 41 2.03 320 11.00 5.0 50 2.49 330 12.00 5.4 54 2.71 340 14.00 6.3 63 3.16 350 15.00 6.8 68 3.39 360 14.00 6.3 63 3.16

(cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

370 12.00 5.4 54 2.71 380 13.00 5.9 59 2.94 390 16.00 7.2 72 3.62 400 17.00 7.7 77 3.84 410 18.00 8.0 80 4.02 420 16.00 7.1 71 3.57 430 18.00 8.0 80 4.02 440 19.00 8.5 85 4.24 450 20.00 8.9 89 4.47 460 21.00 9.4 94 4.69 470 20.00 8.9 89 4.47 480 21.00 9.4 94 4.69 490 21.00 9.4 94 4.69 500 25.00 11.2 112 5.58 510 32.00 14.1 141 7.06 520 50.00 22.1 221 11.04

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240

De pt h in c m

GENERAL COMMENTS:

- Subsurface conditions characterized by silt sandy soil brown colored followed by lateritic soil with good cohesion and enough stable.

- The excavations works should be conducted naturally from the surface to 5m deep mainly in

Nyamirambo sector where the soil is less cohesive and present low resistance.

- The DCP test results of Nyarugenge sector present high soil resistance at 1.60m deep

We recommend the construction of two types of latrines in Nyarugenge District; Natural latrines should be constructed in North Western zones of the District where the soil present low resistance like in

Nyamirambo sector, and Safi latrines should be constructed in Eastern zones like in Nyarugenge District where the refusa lis reached at 1.60m deep.

We recommend the use of masonry foundations where the top soil will be protected by a small circular wall 40cm thick with masonry. The cement/sand mixing ratio should be 1/3

6.5 RWAMAGANA DISTRICT.

6.5.1 GEOTECHNICAL MAP OF SAMPLED AREA IN RWAMAGANA DISTRICT

6.5.2 SOIL PROFILE AND LITHOLOGY IN RWAMAGANA DISTRICT

The sub surface investigations have been conducted in Fumbwe sector, Nyirabiteri village ;and Nyakariro sector, Rwamibungo village. The following observations have been made during our site investigation.

Table 12: Rwamagana soil profile and lithology presentation

Fumbwe/Nyirabiteri

-From the surface to 1.5m deep, the soil in place is soft limon less consistant and cohesionless.

Nyakariro/Rwamibungo

20cm of organic top soil followed by a gravelly compacted lateritic soil more than 1.5 m thick.

6.5.3. SOIL IDENTIFICATION IN RWAMAGANA DISTRICT

Table 13 Soil characteristics in Rwamagana District

Sample N° Fumbwe/Nyirab iteri

Nyakariro/Rwa mibumgo

40 100.00 100.00

31.5 100.00 100.00 25 100.00 99.16 20 100.00 96.80 16 100.00 90.21 14 99.01 85.22 12 99.01 80.46 10 99.01 73.39 8 98.80 65.86

6.3 98.50 58.89 5 98.11 53.61 4 97.64 48.05

3.15 96.32 42.73

2.50 92.20 36.04

2 83.89 29.71 1 75.19 24.67

0.32 62.17 23.27

0.16 53.21 19.85

0.08 45.54 17.18

0.75 45.50 17.04

Atterberg Limits WL 36.5 29.2

6.6 DCP TESTS RESULTS IN RWAMAGANA DISTRICT

Table 14 Nyirabiteri village/Fumbwe soil resistance Depth (cm)

Number of blows (N) Resistance at the point (MN/m2)

Resistance at the point

(Bars) Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 1.00 0.5 5 0.23 20 2.00 0.9 9 0.47 30 2.00 0.9 9 0.47 40 1.00 0.5 5 0.23 50 1.00 0.5 5 0.23 60 2.00 0.9 9 0.47 70 5.00 2.3 23 1.17 80 4.00 1.9 19 0.94 90 6.00 2.8 28 1.41 100 6.00 2.8 28 1.41 110 5.00 2.3 23 1.16 120 4.00 1.9 19 0.93 130 4.00 1.9 19 0.93 140 4.00 1.9 19 0.93 150 5.00 2.3 23 1.16 160 5.00 2.3 23 1.16 170 10.00 4.6 46 2.31 180 11.00 5.1 51 2.54 190 14.00 6.5 65 3.24 200 13.00 6.0 60 3.01 210 12.00 5.5 55 2.74 220 13.00 5.9 59 2.97 230 13.00 5.9 59 2.97 240 14.00 6.4 64 3.20 250 15.00 6.9 69 3.43 260 16.00 7.3 73 3.66 270 17.00 7.8 78 3.89 280 17.00 7.8 78 3.89 290 16.00 7.3 73 3.66 300 17.00 7.8 78 3.89 310 16.00 7.2 72 3.62 320 17.00 7.7 77 3.84 330 17.00 7.7 77 3.84

PI 13.8 8

Number of blows (N) Resistance at the point (MN/m2)

Resistance at the point

(Bars) Bearing capacity (Bars)

340 18.00 8.1 81 4.07 350 16.00 7.2 72 3.62 360 16.00 7.2 72 3.62 370 17.00 7.7 77 3.84 380 17.00 7.7 77 3.84 390 18.00 8.1 81 4.07 400 16.00 7.2 72 3.62 410 17.00 7.6 76 3.80 420 19.00 8.5 85 4.24 430 20.00 8.9 89 4.47 440 21.00 9.4 94 4.69 450 22.00 9.8 98 4.91 460 23.00 10.3 103 5.14 470 24.00 10.7 107 5.36 480 27.00 12.1 121 6.03 490 24.00 10.7 107 5.36 500 26.00 11.6 116 5.81 510 27.00 11.9 119 5.96 520 35.00 15.5 155 7.73 530 50.00 22.1 221 11.04

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240

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Table 15: Rwamibungo village/Nyakariro sector soil resistance

(cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point

(Bars) Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 10.00 4.7 47 2.34 20 18.00 8.4 84 4.22 30 20.00 9.4 94 4.68 40 27.00 12.6 126 6.32 50 34.00 15.9 159 7.96 60 50.00 23.4 234 11.71

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240250

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- In general, the soil encountered during our geotechnical investigations in Rwamagana present good characteristics but not enough cohesive like in Fumbwe sector, Nyirabiteri village where the soil resistance is low with the refusal at 5.30m deep. The excavation works should be conducted manually from the surface to 6m deep in this zone located in North of the District. Some soil protection will be necessary during the excavation works due to the cohesionless of the soil in place.

- The strong soil resistance is encountered in south region of the District where the refusal is obtained at 0.60m deep. The soil in place is a well compacted gravel lateritic followed by a rocky soil. The construction of Safi latrines should be considered in that area.

We recommend the use of masonry foundations where the top soil will be protected by a small circular wall

40cm thick with masonry. The cement/sand mixing ratio should be 1/3

6.7 KAYONZA DISTRICT

6.7.1 GEOTECHNICAL MAP OF SAMPLED AREA IN KAYONZA DISTRICT

6.7.2 SOIL PROFILE AND LITHOLOGY IN KAYONZA DISTRICT

The subsurface investigations have been conducted in Murundi sector, Rugunga village; Rwinkwavu sector, Mbarara village; Ndego sector, Nyamata village and in Nyamirama sector, Bwiza village. The following observations have been made during our site investigation.

Table 16: Kayonza soil profile and lithology presentation

Murundi/Rugunga

10cm of organic top soil compacted lateritic soil more than 1m thick Under which a hard rock is reached.

Rwinkwavu/Mbarara

20 cm of organic top soil compacted lateritic soil more than 1mthick.The presence of water is due to the rain during subsoil investigations.

Ndego/Nyamata followed by a soft layer of limon soil more than 2m thick.

Nyamirama/Bwiza

50cm of organic top soil followed by well compacted gravely lateritic materials reddish colored.

6.7.3 SOIL IDENTIFICATION IN KAYONZA DISTRICT

Table 17: Soil characteristics in Kayonza District

6.8 DCP TESTS RESULTS INKAYONZA DISTRICT

Table 18: Bwiza Village/Nyamirama sector soil resistance Depth (cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 4.00 1.9 19 0.94 20 4.00 1.9 19 0.94 30 10.00 4.7 47 2.34 40 16.00 7.5 75 3.75 50 41.00 19.2 192 9.60 60 50.00 23.4 234 11.71

Sample N° Nyamirama/ Bwiza

Murundi/Ru gunga

Ndego/Nyam ata

Mbarara/Rw inkwavu

Sieve Analysis

Sieves (mm) 40 100.00 100.00 100.00 100.00

31.5 100.00 100.00 100.00 100.00 25 100.00 100.00 100.00 100.00 20 100.00 100.00 100.00 100.00 16 99.10 100.00 100.00 100.00 14 97.24 99.67 100.00 100.00 12 94.44 98.49 100.00 100.00 10 89.02 96.03 100.00 100.00 8 85.40 92.39 100.00 99.96

6.3 83.15 86.67 100.00 99.83 5 77.99 79.92 100.00 98.83 4 73.43 72.56 99.95 96.50

3.15 70.72 63.35 99.90 93.08

2.50 68.64 56.97 99.35 89.32

2 64.21 52.15 97.07 85.16 1 58.92 43.89 90.96 78.42

0.32 49.21 36.11 80.43 69.12

0.16 41.53 26.30 71.93 58.95

0.08 34.30 25.24 69.80 51.73

0.75 34.16 25.24 69.65 51.60

Natural water content

Atterberg Limits WL 40.3 32.6 40.5 36.6

PI 14.9 10.8 12.6 12.3

Classification HRB A-2-6 A-2-4 A-2-4 A-2-6 I.G. (4) (0) (0) (4)

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240250

De pt h in c m

Table 19: Mbarara Village/Rwinkwavu Sector soil resistance

(cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 1.00 0.5 5 0.23 20 1.00 0.5 5 0.23 30 1.00 0.5 5 0.23 40 1.00 0.5 5 0.23 50 1.00 0.5 5 0.23 60 2.00 0.9 9 0.47 70 2.00 0.9 9 0.47 80 2.00 0.9 9 0.47 90 2.00 0.9 9 0.47 100 2.00 0.9 9 0.47 110 2.00 0.9 9 0.46 120 2.00 0.9 9 0.46 130 3.00 1.4 14 0.69 140 4.00 1.9 19 0.93 150 5.00 2.3 23 1.16 160 6.00 2.8 28 1.39 170 6.00 2.8 28 1.39 180 7.00 3.2 32 1.62 190 9.00 4.2 42 2.08 200 6.00 2.8 28 1.39 210 6.00 2.7 27 1.37 220 7.00 3.2 32 1.60 230 7.00 3.2 32 1.60 240 8.00 3.7 37 1.83 250 9.00 4.1 41 2.06 260 9.00 4.1 41 2.06 270 10.00 4.6 46 2.29 280 10.00 4.6 46 2.29 290 10.00 4.6 46 2.29 300 12.00 5.5 55 2.74 310 14.00 6.3 63 3.16 320 12.00 5.4 54 2.71 330 14.00 6.3 63 3.16 340 12.00 5.4 54 2.71 350 10.00 4.5 45 2.26 360 10.00 4.5 45 2.26

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

370 10.00 4.5 45 2.26 380 10.00 4.5 45 2.26 390 11.00 5.0 50 2.49 400 11.00 5.0 50 2.49 410 10.00 4.5 45 2.23 420 12.00 5.4 54 2.68 430 11.00 4.9 49 2.46 440 14.00 6.3 63 3.13 450 21.00 9.4 94 4.69 460 20.00 8.9 89 4.47 470 19.00 8.5 85 4.24 480 19.00 8.5 85 4.24 490 19.00 8.5 85 4.24 500 18.00 8.0 80 4.02 510 17.00 7.5 75 3.75 520 17.00 7.5 75 3.75 530 18.00 7.9 79 3.97 540 19.00 8.4 84 4.19 550 17.00 7.5 75 3.75 560 20.00 8.8 88 4.42 570 19.00 8.4 84 4.19 580 20.00 8.8 88 4.42 590 22.00 9.7 97 4.86 600 21.00 9.3 93 5

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100 110

De pt h in c m

Table 20: Nyamata Village/Ndego Sector soil resistance

(cm)

Number of blows (N) Resistance at the point (MN/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 1.00 0.5 5 0.23 20 1.00 0.5 5 0.23 30 2.00 0.9 9 0.47 40 2.00 0.9 9 0.47 50 2.00 0.9 9 0.47 60 4.00 1.9 19 0.94 70 3.00 1.4 14 0.70 80 2.00 0.9 9 0.47 90 2.00 0.9 9 0.47 100 3.00 1.4 14 0.70 110 2.00 0.9 9 0.46 120 2.00 0.9 9 0.46 130 3.00 1.4 14 0.69 140 4.00 1.9 19 0.93 150 5.00 2.3 23 1.16 160 5.00 2.3 23 1.16 170 5.00 2.3 23 1.16 180 4.00 1.9 19 0.93 190 4.00 1.9 19 0.93 200 2.00 0.9 9 0.46 210 3.00 1.4 14 0.69 220 2.00 0.9 9 0.46 230 2.00 0.9 9 0.46 240 4.00 1.8 18 0.91 250 4.00 1.8 18 0.91 260 4.00 1.8 18 0.91 270 5.00 2.3 23 1.14 280 6.00 2.7 27 1.37 290 7.00 3.2 32 1.60 300 7.00 3.2 32 1.60 310 7.00 3.2 32 1.58 320 8.00 3.6 36 1.81 330 8.00 3.6 36 1.81 340 8.00 3.6 36 1.81 350 8.00 3.6 36 1.81 360 9.00 4.1 41 2.03

Number of blows (N) Resistance at the point (MN/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

370 10.00 4.5 45 2.26 380 11.00 5.0 50 2.49 390 11.00 5.0 50 2.49 400 12.00 5.4 54 2.71 410 13.00 5.8 58 2.90 420 14.00 6.3 63 3.13 430 16.00 7.1 71 3.57 440 17.00 7.6 76 3.80 450 17.00 7.6 76 3.80 460 18.00 8.0 80 4.02 470 19.00 8.5 85 4.24 480 20.00 8.9 89 4.47 490 18.00 8.0 80 4.02 500 19.00 8.5 85 4.24 510 17.00 7.5 75 3.75 520 17.00 7.5 75 3.75 530 17.00 7.5 75 3.75 540 18.00 7.9 79 3.97 550 25.00 11.0 110 5.52 560 28.00 12.4 124 6.18 570 35.00 15.5 155 7.73 580 38.00 16.8 168 8.39 590 50.00 22.1 221 11.04

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240

De pt h in c m

Table 21: Rugunga Village/Murundi Sector soil resistance

(cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 16.00 7.5 75 3.75 20 24.00 11.2 112 5.62 30 27.00 12.6 126 6.32 40 28.00 13.1 131 6.56 50 30.00 14.1 141 7.03 60 34.00 15.9 159 7.96 70 47.00 22.0 220 11.01 80 50.00 23.4 234 11.71

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240250

De pt h in c m

- The existing soil in Kayonza district show many varieties where the soft soil with important thickness is encountered in south and West of the District, and the hard soils followed by rocks from 1m deep are generally encountered on North and Est of the District

- In North and Est where the hard soil and rocky soils are dominant,t he excavations works should be complicated. The high soil resistance is observed in Murundi and Nyamirama sectors and should be extended in the rest of Northern and Estern sectors like Rukara, and Gahini sectors where the underground soil is rocky. The Safi toilets should be applicable in that area.

- In south and East, the manual excavations works should be done from the surface to more than 5m deep. The natural latrines should be constructed easily.

wall 40cm thick with masonry. The cement/sand mixing ratio should be 1/3

6.9 NGOMA DISTRICT

6.9.1 GEOTECHNICAL MAP OF SAMPLED AREA IN NGOMA DISTRICT

6.9.2 SOIL PROFILE AND LITHOLOGY IN NGOMA DISTRICT

The sub surface investigations have been conducted in Mutenderi sector, Nyamirindi village; Kibungo sector, Kabimba village; Gashanda sector, Rugarama village and Mugesera sector, Nyamabuye village.

The following observations have been made during our site investigation.

Table 22: Ngoma soil profile and lithology presentation

Mutenderi/Nyamirindi followed by a soft gravelly lateritic soil more than 1.5m thick.

Kibungo/Kabimba

From the surface to 1m deep, soft gravel lateritic soil is dominant, followed by a gravel compacted lateritic material more than 2m

Gashanda/Rugarama followed by a black gravelly lateritic soil well compacted more than 2m thick.

Mugesera/Nyamabuye

15 cm of organic top soil followed by a fine soft limon soil more than 2m

6.9.3 SOIL IDENTIFICATION IN NGOMA DISTRICT

Table 23: Soil characteristics in Ngoma District

6.10 DCP TESTS RESULTS IN NGOMA DISTRICT

Table 24: Kibimba Village/Kibungo Sector soil resistance Depth (cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 4.00 1.9 19 0.94 20 8.00 3.7 37 1.87 30 12.00 5.6 56 2.81 40 14.00 6.6 66 3.28 50 17.00 8.0 80 3.98 60 24.00 11.2 112 5.62 70 29.00 13.6 136 6.79 80 31.00 14.5 145 7.26 90 34.00 15.9 159 7.96 100 50.00 23.4 234 11.71

Sample N° Kibungo/Kab imba

Mugesera/ Nyamabuye

Mutenderi/N yamirindi

Gashanda/R ugarama

Sieve Analysis

Sieves (mm) 40 100.00 100.00 100.00 100.00

31.5 100.00 100.00 100.00 100.00 25 100.00 99.47 97.40 99.24 20 99.00 99.26 94.07 97.77 16 97.65 96.64 89.47 97.24 14 94.98 95.56 85.60 95.30 12 92.87 93.02 82.07 91.59 10 89.41 87.04 74.20 85.42 8 85.34 79.67 66.33 78.52

6.3 80.44 68.76 55.77 66.21 5 75.19 60.75 49.53 57.18 4 68.98 52.72 44.23 48.01

3.15 61.53 44.27 39.97 39.34

2.50 54.53 32.55 35.63 29.89

2 48.32 27.51 32.73 27.22 1 40.59 24.38 29.57 24.89

0.32 35.54 23.18 28.47 23.68

0.16 25.78 20.05 24.70 20.26

0.08 24.07 17.66 22.83 18.92

0.75 23.95 17.59 22.77 18.92

Natural water content

Atterberg Limits WL 32.1 30.6 27.9 35.6

PI 11.6 9.7 9.4 9.8

Classification HRB A-2-4 A-2-4 A-2-4 A-2-4

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240250

De pt h in c m

Table 25: Nyamabuye Village/Mugesera Sector soil resistance

(cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 2.00 0.9 9 0.47 20 2.00 0.9 9 0.47 30 4.00 1.9 19 0.94 40 4.00 1.9 19 0.94 50 7.00 3.3 33 1.64 60 20.00 9.4 94 4.68 70 27.00 12.6 126 6.32 80 40.00 18.7 187 9.37 90 41.00 19.2 192 9.60 100 43.00 20.1 201 10.07 110 45.00 20.8 208 10.41 120 50.00 23.1 231 11.57

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240250

De pt h in c m

Table 26: Nyamirindi Village/Mutenderi Sector soil resistance

(cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 6.00 2.8 28 1.41 20 20.00 9.4 94 4.68 30 20.00 9.4 94 4.68 40 19.00 8.9 89 4.45 50 18.00 8.4 84 4.22 60 19.00 8.9 89 4.45 70 16.00 7.5 75 3.75 80 17.00 8.0 80 3.98 90 16.00 7.5 75 3.75 100 20.00 9.4 94 4.68 110 21.00 9.7 97 4.86 120 20.00 9.3 93 4.63 130 24.00 11.1 111 5.55 140 27.00 12.5 125 6.25 150 28.00 13.0 130 6.48 160 50.00 23.1 231 11.57

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250

De pt h in c m

Table 27: Rugaranma Village/Gashanda Sector soil resistance

(cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 10.00 4.7 47 2.34 20 14.00 6.6 66 3.28 30 18.00 8.4 84 4.22 40 21.00 9.8 98 4.92 50 22.00 10.3 103 5.15 60 30.00 14.1 141 7.03 70 31.00 14.5 145 7.26 80 50.00 23.4 234 11.71

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240250

De pt h in c m

The existing soil in Ngoma District present good characteristics and is well cohesive.

- The excavation works should be done naturally from the surface to 2.5m deep where the soil is soft, from this depth, the lateritic hard soil is encountered followed by a rocky soil.

- The excavation works should be done without land slide or soil collapse.

- Considering the high soil resistance encountered (Refusal in all zones tested is between 1 and 2m deep) we propose the construction of Safi latrines in Ngoma District.

We recommend also the use of masonry foundations where the top soil will be protected by a small circular wall 30cm thick with masonry. The cement/sand mixing ratio should be 1/3

6.11 RUHANGO DISTRICT

6.11.1 GEOTECHNICAL MAP OF SAMPLED AREA IN RUHANGO DISTRICT

6.11.2 SOIL IDENTIFICATION IN RUHANGO DISTRICT

The sub surface investigations have been conducted in Mwendo sector, Kajevuba village; Bweramana sector, Rugarama village; Mbuye sector, Kidoma village ; and Ntongwe sector, Karama village

The following observations have been made during our site investigation.

Table 28: Ruhango Soil profile and lithology presentation

Mwendo/Kajevuba followed by a soft gravel soil less compacted more than 2m deep.

Bweramana/Rugarama followed by a compacted gravel soil more than 1m deep

Mbuye/Kidoma followed by a sandy gravel materials well compacted more than 2m deep.

Ntongwe/Karama

20 cm of soft organic top soil followed by a coarse sandy gravel soil well compacted more than 2m deep.

Table 29: Soil characteristics in Ruhango District

Sample N° Bweramana/ Bugarama

Mbuye/Kida ma

Mwendo/Kaj evuba

Ntongwe/Kar ama

Sieve Analysis

Sieves (mm) 40 100.00 100.00 100.00 100.00

31.5 100.00 100.00 99.35 100.00 25 100.00 100.00 97.95 98.92 20 100.00 100.00 95.83 96.90 16 100.00 98.78 93.40 94.46 14 100.00 96.35 88.55 91.52 12 99.20 93.22 83.23 87.72 10 97.60 88.48 75.95 83.54 8 94.68 82.17 68.73 78.61

6.3 91.12 75.17 60.21 71.01 5 87.44 67.78 49.41 61.42 4 83.32 60.52 40.04 52.25

3.15 78.48 53.74 33.73 44.56

2.50 73.44 44.74 28.53 36.52

2 67.88 35.22 25.82 30.25 1 58.68 28.91 23.74 24.97

0.32 46.64 24.65 22.00 19.18

0.16 39.08 21.22 21.06 15.73

0.08 33.24 18.26 20.32 13.80

0.75 33.20 18.22 20.32 13.80

Natural water content

Atterberg Limits WL 30.1 25 32.1 26.1

PI 10.3 8.3 11.5 9.4

Classification HRB A-2-4 A-2-4 A-2-4 A-2-4

6.12. DCP TESTS RESULTS IN RUHANGO DISTRICT

Table 30: Kajevuba Village/Mwendo Sector soil resistance

Depth (cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 5.00 2.3 23 1.17 20 12.00 5.6 56 2.81 30 17.00 8.0 80 3.98 40 29.00 13.6 136 6.79 50 36.00 16.9 169 8.43 60 35.00 16.4 164 8.20 70 41.00 19.2 192 9.60 80 50.00 23.4 234 11.71

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240250 De pt h in c m

Table 31: Karama village/Ntongwe Sector soil resistance

(cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 14.00 6.6 66 3.28 20 16.00 7.5 75 3.75 30 26.00 12.2 122 6.09 40 30.00 14.1 141 7.03 50 30.00 14.1 141 7.03 60 40.00 18.7 187 9.37 70 38.00 17.8 178 8.90 80 38.00 17.8 178 8.90 90 37.00 17.3 173 8.67 100 36.00 16.9 169 8.43 110 37.00 17.1 171 8.56 120 40.00 18.5 185 9.25 130 41.00 19.0 190 9.49 140 42.00 19.4 194 9.72 150 45.00 20.8 208 10.41 160 50.00 23.1 231 11.57

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240250 De pt h in c m

Table 31 Kidoma village/Mbuye Sector soil resistance

(cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 4.00 1.9 19 0.94 20 8.00 3.7 37 1.87 30 16.00 7.5 75 3.75 40 18.00 8.4 84 4.22 50 21.00 9.8 98 4.92 60 21.00 9.8 98 4.92 70 24.00 11.2 112 5.62 80 30.00 14.1 141 7.03 90 31.00 14.5 145 7.26 100 34.00 15.9 159 7.96 110 35.00 16.2 162 8.10 120 33.00 15.3 153 7.63 130 41.00 19.0 190 9.49 140 50.00 23.1 231 11.57

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240250

De pt h in c m

Table 33: Bugarama Village/Bweramana soil resistance

(cm)

Number of blows (N) Resistance at the point (N/m2)

Resistance at the point (Bars)

Bearing capacity (Bars)

0 0.00 0.0 0.00 0.00 10 9.00 4.2 42 2.11 20 19.00 8.9 89 4.45 30 27.00 12.6 126 6.32 40 31.00 14.5 145 7.26 50 30.00 14.1 141 7.03 60 38.00 17.8 178 8.90 70 40.00 18.7 187 9.37 80 41.00 19.2 192 9.60 90 42.00 19.7 197 9.84 100 43.00 20.1 201 10.07 110 47.00 21.7 217 10.87 120 50.00 23.1 231 11.57

20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

100.00 110.00 120.00 130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00 210.00 220.00 230.00 240.00 250.00 260.00 270.00 280.00 290.00 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 380.00 390.00 400.00 410.00 420.00 430.00 440.00 450.00 460.00 470.00 480.00 490.00 500.00 510.00 520.00 530.00 540.00 550.00 560.00 570.00 580.00 590.00 600.00

0 10 20 30 40 50 60 70 80 90 100110120130140150160170180190200210220230240250

De pt h in c m

- The existing soil in Ruhango District present good characteristics and is well compacted from the surface to 2m deep.

- The excavation works should be done naturally from the surface to 3m deep where the soil is soft, from this depth, the lateritic hard soil is encountered…