Project No.: R01

Transcription

1 Report to Voigts Construction on a Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Project No.: R01 Date Issued: November 2018

2 Report to Voigts Construction on a Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal TABLE OF CONTENTS 1. INTRODUCTION INFORMATION SUPPLIED SITE DESCRIPTION FIELDWORK Test Pits Dynamic Cone Penetrometer (Light) or DPL Tests SITE GEOLOGY GROUNDWATER LABORATORY TESTING Materials Usage and Classification Transported Soils Residual Shale Material Weathered Shale Material Residual Dolerite Material GENERAL STABILITY OF THE SITE DEVELOPMENT RECOMMENDATIONS Proposed Development Excavatability Earthworks Site Area south of Drainage Line Site Area north of Drainage Line Drainage Surface Water Drainage Groundwater Drainage Foundations Lodge / Hotel Building Subgrade Improvement beneath Roads, Paving and Parking Areas CONCLUSIONS Appendix A : Appendix B : Appendix C : Test Pit Logs DPL Test Results Laboratory Test Results Figures 1 to 4 PREPARED: DATE: November 2018 NAME: Mark Richter SIGNATURE: Contents Page 1 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

3 Report to Voigts Construction on a Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal 1. INTRODUCTION Gondwana Geo Solutions (Pty) Ltd were requested by Mr Jannie Cronje of Umsunguli Project Management (UPM), on behalf of the Client, Voigts Construction (Pty) Ltd, to provide a cost estimate for a geotechnical investigation for the proposed new development of Royal Albert Lodge at Albert Falls Dam, KwaZulu-Natal. A cost estimate was submitted on 26 October The appointment to proceed with the geotechnical investigation was provided by Voigts Construction on 28 October This report contains the results of the geotechnical investigation. Recommendations are provided for earthworks, foundations, materials usage and subgrade preparation, groundwater and drainage. 2. INFORMATION SUPPLIED A copy of a drawing referenced UPM (Sewer layout) -ALTERNATE RevB, showing the general layout of the site was made available by UPM for the geotechnical investigation. 3. SITE DESCRIPTION The site for the proposed Royal Albert Lodge development is located on the western shore of Albert Falls Dam near Ottos Bluff, Pietermaritzburg (Figure 1). It is bounded on the east by Albert Falls Dam, on the west by existing houses, on the south and north by game fences. The northern game fence also marks the property (Figure 2). Topographically, the site slopes downwards to the east at about 1V to between 5 and 8 Horizontal. The slope steepens noticeably near the western boundary as this coincides with band of rocky outcrop marking a dolerite intrusion. The slope is relatively planar but increases in gradient north of a significant drainage line which effectively subdivides the site into a southern 2/3 and the remainder on the north. A small dam is located in the prominent drainage line towards the lower eastern part of the site. Some erosion gullies traverse the site from west to east, running roughly parallel to the drainage line in an easterly direction, i.e. towards the dam in general. A gravel road runs along the eastern and western boundaries of the site. The site is well stocked with wildlife. The site has scattered acacia trees and generally short grass. The following plates provide a more detailed perspective of the site. Plate 1: Dam on central drainage line Plate 2: Drainage line downslope of dam Page 1 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

4 Plate 3: Drainage line in foreground with northern boundary fence behind Plate 4: Perspective towards the dam Plate 5: Elevated ridge caused by dolerite intrusion Plate 6: Perspective of site to the east 4. FIELDWORK The fieldwork for the investigation was carried out on the 9 th October 2018 and comprised the following: Test pits, and Dynamic Cone Penetrometer (Light) Tests 4.1 Test Pits Twenty four test pits, designated RA1 through RA22, and RA24 & RA25, were dug using a Cat 426 Tractor Loader Backhoe (TLB) supplied by a Voigts Construction, at the approximate positions shown in Figure 2. The test pits were terminated either in residual soils due to the maximum achievable excavation depth of the TLB, or earlier refusal on bedrock. The refusal depths and depth to bedrock (where applicable) are shown in Figure 2. The test pits were profiled 1 by an engineering geologist and representative soil samples recovered for later laboratory testing at SGS Matrolab in Durban. The detailed logs are given in Appendix A. 1 Geoterminology Workshop (2002) Guidelines for Soil and Rock Logging - SAIEG-AEG-SAICE (Geotech Div) pp47 Page 2 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

5 4.2 Dynamic Cone Penetrometer (Light) or DPL Tests Dynamic Cone Penetrometer Light, or DPL tests, designated DPL1 to DPL22 were carried out adjacent to the test pits of the same number at the approximate positions shown in Figure 1. The DPL test comprises a 20mm diameter solid steel retractable cone driven vertically into the ground using a 10 kg hammer dropped through a height of 550mm. The resistance to penetration is measured in terms of number of blowcounts per 300mm advance. It should be noted that material on which DPL tests refuse cannot be accurately determined since the test does not allow any samples to be recovered for identification. Therefore, refusal may occur on very dense, cemented or gravelly horizons, as well as on bedrock. The results of the DPL test, comprising plots of blow count per 300mm advance and inferred consistency against depth are provided in Appendix B. 5. SITE GEOLOGY As shown by an extract of the 1: geological map, 2930 Durban, presented in Figure 3, the site is underlain by the rocks of Pietermaritzburg Formation of the Ecca Group, Karoo Supergroup. These rocks are intruded by dolerite of Jurassic age, evident on the western boundary of the general site. The site itself is underlain by a mantle of transported (colluvial) and residual soils overlying the shale bedrock. The thickness of this soil mantle varies across the site. The colluvial soils, comprising dark brown to black, shattered and fissured, soft to firm, silty sandy clay, are on average 0.6m thick, in the range 0.4 to 0.8m. Occasionally the base of the colluvial layer is characterised by a gravelly, partially ferruginised horizon. The gravel in this layer comprises rounded shale fragments and nodular ferricrete. The colluvial soils are underlain by residual soils derived from the insitu weathering of the shale bedrock. The thickness and character of the residual shale soils varies across the site significantly; in the area to the south of the drainage line, representing the southern two-thirds of the site, the residual shale is characterised by a yellowish grey to olive, intensely shattered and slickensided, soft becoming stiff with depth, silty clay. The residual soil shows occasional ferricrete gravel and calcrete nodules some 50 to 10mm in size but which are soft and friable. The residual shale grades into weathered shale below an average depth of 1.8m, in the range 1.5 to in excess of 3m. The shale can be described as brown to olive, completely to highly weathered, very closely laminated and bedded, intensely to very closely jointed, and very stiff to very soft rock in strength. The shale is general sub-horizontally bedded. North of the drainage line the ground conditions vary significantly from those underlying the southern area. The colluvial soils are similarly present but generally but much thinner; only about 0.3m in average thickness. Residual soil development is also markedly thinner and comprises yellowish brown to yellow, silty gravelly clayey sand. As a result, the shale bedrock occurs much closer to surface and is more accessible for foundations and roadworks. The shale bedrock is similar to that described above, however, the effects of the dolerite intrusion on the western margin of the site become evident with some shale altered by thermal metamorphism. The dolerite intrusion on the western margin of the site, running north-south and marked by a sudden increase in slope and elevation in this area, is represented by deeply weathered residual soil comprising a yellowish to reddish brown, firm to stiff slightly sandy clayey silt to silty clayey sand. Dolerite core-stones or boulders are found to occur in a matrix of this residual material. Page 3 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

6 Plate 7: Typical soil profile : transported and structure residual soils overlying shale; note black hillwash soils Plate 8: Residual shale: shattered and slickensided Plates 9 & 10: Residual dolerite consisting of a slightly clayey sandy silt with hard dolerite corestones 6. GROUNDWATER No groundwater seepage was encountered in any of the test pits that were excavated. However, it can be assumed that groundwater seepage will occur at the soil/ rock interface or boundary and would be most prevalent during or after rainfall events, and most certainly, the rainy season. 7. LABORATORY TESTING Laboratory testing was scheduled on selected samples that were obtained from selected layers in the test pits. The following tests were conducted: Indicator Testing (Particle Size Analysis, Atterberg Limit Determinations) Foundation indicator (as above but including Hydrometer Analysis) on selected samples Modified AASHTO compaction and California Bearing Ratio tests on selected samples The laboratory test results are summarised in Table 1 below, and the full results are contained in Appendix C. Page 4 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

7 Table 1 Summary of Results of Particle Size Distribution Analysis, Atterberg Limit Determinations and CBR tests TP No. Depth (m) Description Particle Size % Atterberg Limits Clay Silt Sand Gravel LL PI LS% GM Modified AASHTO MDD (kg/m³) OMC % CBR Values (%) Compaction MDD (%) Swell (%) Classification & Activity RA Dark grey medium to highly weathered very soft to soft rock SHALE. Pietermaritzburg Formation A-6(6); CL; Low; Type D Gravel Wearing Course (slippery) RA Dark brown medium to highly weathered intensely laminated very closely jointed very soft to soft rock SHALE. Pietermaritzburg Formation A-2-6(0); G8/G9; Type D Gravel Wearing Course (slippery) RA Yellowish brown streaked grey and black intensely laminated very soft to soft rock SHALE. Pietermaritzburg Formation A-2-6(1); G10; Type D Gravel Wearing Course (slippery) RA Slightly moist dark brown mottled grey loose clayey gravelly SAND. Hillwash A-7-6(13); CL; <G10; Type D Gravel Wearing Course (slippery) RA Slightly moist dark grey loose to medium dense sandy clayey GRAVEL. Hillwash A-7-6(10); CL; <G10; Type D Gravel Wearing Course (slippery) RA Dry to slightly moist yellowish brown stiff fissured shattered and slickensided sandy clayey SILT. Residual Shale A-6(13); CL; Low RA Slightly moist yellow to brown mottled grey and olive stiff intensely shattered and slickensided slightly sandy silty CLAY. Residual Shale A-6(10); CL; Low Page 5 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

8 TP No. RA8 RA9 RA12 RA19 RA20 RA25 Depth (m) Description Slightly moist dark brown mottled grey loose clayey gravelly SAND. Hillwash. Slightly moist yellow to brown mottled grey speckled black micro-shattered and slickensided sandy silty CLAY. Residual Shale. Slightly moist dark brown silty clayey SAND to sandy CLAY. Hillwash (Colluvium). Slightly moist dark brown shattered silty sandy CLAY. Hillwash. Slightly moist yellowish brown firm to stiff shattered and slickensided sandy silty CLAY. Residual Shale. Slightly moist yellowish brown medium dense gravelly clayey SAND. Residual Dolerite. Dry to slightly moist light brown speckled yellowish brown medium dense gravelly sandy SILT. Residual Dolerite. Slightly moist yellowish brown firm slightly sandy clayey SILT becoming more sandy with depth. Residual Dolerite. Particle Size % Atterberg Limits Clay Silt Sand Gravel LL PI LS% GM Modified AASHTO MDD (kg/m³) OMC % CBR Values (%) Compaction MDD (%) Swell (%) Classification & Activity A-6(13); CL; Low A-6(9); CL; Low A-6(12); CL; Medium A-2-6(3); SC; Low; Type D Gravel Wearing Course (slippery) A-2-7(2); SM; Low <G10; Type D Gravel Wearing Course (slippery) A-2-6(1); SC; Low; G8/G10; Type E Gravel Wearing Course (ideal) A-2-7(1); SC; Low G8/G10; Type E Gravel Wearing Course (ideal) A-2-6(1); SC; Anticipate G10; Low; Type E Gravel Wearing Course (ideal) LL - Liquid Limit GM - Grading Modulus Classification in Terms of: USPRA 2 PI - Plasticity Index MDD - Maximum Dry Density Unified Soil Classification System 3 LS - Linear Shrinkage OMC - Optimum Moisture Content D.H. Van Der Merwe (1964) 4 ; TRH 14(1985) 5 TRH 20 (1990) 6 2 US Public Roads Administration Classification (Modified from Allen 1945) 3 ASTM D Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System). June D.H. Van Der Merwe (1964). The Prediction of Heave from the Plasticity Index and Percentage Clay Fraction of Soils. The Civil Engineer, pp TRH 14 (1985) - Guidelines for Road Construction Materials; Technical Recommendations for Highways, South African National Institute for Transport and Road Research 6 TRH 20 (1990) Draft The Structural Design, Construction, and Maintenance of Unpaved Roads: Technical Recommendations for Highways, Committee of State Roads Authorities, South African National Institute for Transport and Road Research Page 6 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

9 7.1 Materials Usage and Classification The insitu materials sampled from the site have been classified in terms of their suitability for use in road construction on the basis of field observations and laboratory testing Transported Soils The colluvial soils, ranging from silty clay to sandy clay in composition, classify in the range A-6(12) to A-7(13) in terms of the USPRA classification system and CL in terms of the USCS system. The soils are relatively highly plastic, i.e. with a Plasticity Index (PI) in the range 20 to 23, and grading modulus (GM) values from 0.38 to Clay contents range between 41 and 53%; combined silt and clay values range from 56 to 85%. The California Bearing Ratio (CBR) tests yielded less than 3 at both 90% and 93% maximum and extremely high CBR swells between 6 and 7% at 100% MDD. The colluvial soil materials thus tested do not meet G10 quality in terms of TRH14:1985. As a result, they are generally considered to be extremely poor subgrade materials Residual Shale Material The residual shale material also ranges in composition from silty clay to gravelly sandy clay in composition with completely to highly weathered shale fragments making up the gravel. These soils classify in the range A-2-7(2) to A-6(9), and CL. The soils are relatively highly plastic, i.e. with PI in the range 17 to 28 and GM from 0.15 to Clay contents range between 26 and 85%; combined silt and clay values range from 56 to 85%. Full materials strength tests were done on a single sample; a CBR value of less than 3 was obtained throughout for all compaction ranges, with very high CBR swells of 3.5% at 100% MDD. The residual shale materials thus tested do not meet G10 quality in terms of TRH14:1985. As a result, they are generally considered to be extremely poor subgrade materials Weathered Shale Material The weathered shale material ranges in composition from gravelly clayey silty sand to gravelly sandy clay in composition, with highly weathered shale fragments making up the gravel. These soils classify in the range A-2-6(0) to A-6(6) and CL. The PI ranges from 14 to 20, and GM from 1.23 to Combined silt and clay values range from 18 to 49%. CBR values range between 5 and 7, and 6 and 11, at 90% and 93% MDD respectively, with low CBR swells of less than 0.8% at 100% MDD. This material ranges in quality between G10 and G8 but should be assumed to be G10 on average, allowing for variability in composition. Under no circumstances should the weathered shale be used as a rockfill or dump-rock material. It should pulverised into soil-sized particles and properly compacted when used in the construction of fills, subgrades or road layer works. It may can be used for the wearing course of unsurfaced roads, but will be slippery when wet and should not be used on steep grades Residual Dolerite Material The residual dolerite occurring beneath the brow on the western margin is described as a sandy silt to silty sand with occasional fine gravel and weathered dolerite boulders in a matrix of the finer material. These soils classify in the range A-2-6(1) to A-27(1) and SC. The PI ranges from 15 to 20, and GM from 1.54 to Combined silt and clay value are of the order of 25%. CBR values range between 5 and 6, and 10 and 11, at 90% and 93% MDD respectively, with CBR swell in the range 0.5 to 1.2% at 100% MDD. Page 7 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

10 This material ranges in quality between G10 and G8 but should be assumed to be G10 on average, allowing for variability in composition. It will be suitable as a gravel wearing course material for unsurfaced roads, however, may be slippery when wet. 8. GENERAL STABILITY OF THE SITE A visual assessment of the site indicates that there have been no problems related to general site and slope stability. There is no evidence of the following signs which may indicate ground instability problems: Tension cracks in slopes associated with groundwater emissions Hummocky land patterns Tension cracks in existing buildings, paving or swimming pool structures Palaeo slip features such as old slip scars or slip debris The site is thus considered stable with very low risk of earthflow and translational slope failure problems and that conditions prevailing at the site are favourable for the proposed development, provided the recommendations given in this report are adhered to. The dip of the shale beds is generally towards the east not exceeding 5 degrees to the horizontal. A problem to be noted is the generally clayey composition of the soils underlying the majority of the site. In particular, the expansive nature of the relatively deeply formed, residual shale soils south of the drainage line, must be taken into account for the design of foundations. 9. DEVELOPMENT RECOMMENDATIONS 9.1 Proposed Development The development will comprise the construction of the main lodge or hotel building near the shore of the dam with 44 smaller accommodation units extending upslope to the western boundary. The accommodation units will be double storey while the hotel building will be single storey with some double volume rooms. The development will be served by roads and paved areas. 9.2 Excavatability A general indication of the depth to which Soft Excavation material (SABS 1200) occurs is obtained from the final depths of the excavated inspection pits dug for the geotechnical investigation, shown in Figure 2. These depths range from about 1.75 to greater than 3.00m below existing ground level, with an average of 2.5m below existing ground level. With depth it is anticipated that weathered bedrock, becoming increasingly hard in strength, will be encountered below these refusal depths. These materials can be expected to require Intermediate to Hard Excavation. 9.3 Earthworks Earthworks on this site is likely to comprise the formation of levelled building platforms for the lodge building and associated accommodation housing units. However, the site is generally gently to moderately sloping towards the east and it is expected that minimal earthworks, with cuts and fills to maximum 1.5m height, will be required. It is recommended that all earthworks be carried out in accordance with SABS 1200DM. Notwithstanding the extremely poor subgrade materials beneath the majority of the site, the following general earthworks may be considered applicable: Page 8 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

11 Topsoil, generally forming the upper 100mm of the soil profile should be removed and stockpiled for later use as topsoil and landscaping. In general, it is recommended that cut slopes in soil and fill embankments have a slope not steeper than 1 vertical to 1.5 horizontal to promote stability. Cuts in shale bedrock may be constructed to 1 vertical to 0.5 horizontal provided there are no unfavourably dipping joints in the cutting face which may combine with the cut angle to produce potentially unstable slopes. Fills should be placed in layers not exceeding 200mm loose thickness, and compacted to a minimum of 95% Modified AASHTO maximum dry density. Boulders larger in size that 2 /3 of the layer thickness should not be included in the fill material. Both during and after construction, the site should be well graded to permit water to drain readily away and to prevent ponding of water anywhere on the ground surface. All terraces and earthworks in general should be sloped to a gradient of not less than 1 vertical in 50 horizontal to prevent ponding and ingress of water into the subsoils. Surface drainage should be directed away from the crests of fill embankments to prevent over-topping and erosion of fill slopes. Cut and fill slopes should be top-soiled and planted with grass. This will limit erosion of these slopes and the problems associated with wash-aways of fill embankments. Ideally grass sodding should be carried out to provide immediate protection to the embankments. Subgrade materials of unacceptably high clay content will need to be cut to spoil or stockpiled for landscaping purposes Site Area south of Drainage Line This area is compromised by the existence of relatively deep, active, clayey subgrade materials in the form of the following: Hillwash soils (gravelly sandy silty clay) to an average depth of 0.6m; <G10 in quality Residual shale material below the hillwash to to an average depth of 2.5m: <G10 in quality These soils range from low to medium expansiveness, are extremely poor subgrade soils, and will be problematic for use in construction of earthworks. They will be highly moisture sensitive and difficult to compact; most likely it will be necessary to stabilise them by blending them with more inert materials to render them more workable, although this in itself will present practical difficulties. They will be prone to formation of extensive shrinkage cracks arising from swelling and contracting with seasonal moisture changes. These materials are best used for landscaping or otherwise spoiled. A solution that may be considered is to utilise the shale and residual dolerite materials from the northern parts of the site, and which present better quality fill materials, for the construction of platforms and road subgrades Site Area north of Drainage Line This area is underlain by relatively shallow shale bedrock which is relatively easy to excavate (being Soft Excavation to at least 2m depth). No major problems are expected with earthworks in this area. This area may be used to supply better quality materials for fills and road construction to the rest of the site. In that this part of the site will yield abundant shale of reasonable quality (at least G10), the earthworks could be planned to supply borrow materials for the rest of the site. This also applies to the residual dolerite which underlies the north- western part of the site 9.4 Drainage Surface Water Drainage A most important factor in the promotion of a stable site is the control and removal of both surface and ground water from the site. It is important that the design of the stormwater management system allow for the drainage of accumulated surface water. Such water should be directed towards the roads within or around the site which will ultimately drain to the east (i.e. the Albert Falls Dam). Disposal of stormwater should in any case conform to the Local Authority s requirements. Page 9 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

12 Surface drainage of building platforms should be designed to direct water away from fill edges to prevent overtopping of the fill crest and erosion of the fill embankment slopes. It is important that grassing of fill embankments be carried out as soon as possible after construction Groundwater Drainage While no groundwater seepage was encountered in any of the test pits dug, it is very likely that groundwater seepage will occur at the interface between the soil and shale bedrock during or after heavy rains, and most certainly, during the wet season. However, if groundwater seepage is encountered during construction, these zones will need to be controlled with effective subsoil drains, particularly where water is likely to gain ingress into the structural layers of roads or into house platforms. 9.5 Foundations The ground conditions beneath the site are clearly characterised by soils of expansive or active nature. In terms of the foundation class system guidelines provided by the NHBRC 7, it is considered that the foundation classes H1/R are applicable to the area north of the drainage line and H2/H3 to the on the remainder of the site to the south of the drainage line, respectively. These foundation classes are based on the calculation of potential heave that may occur beneath buildings, using the Van der Merwe method. The following information has been used: Estimate of insitu moisture content of expansive layer Heave classification of the foundation soils Average depth of expansive layer beneath foundation, and Depth to groundwater seepage From the laboratory test results the residual shale soils classify as Low and Low to Medium in some areas. Given that the thickness of the founding layer extends from below the foundation to the shale bedrock (i.e. no groundwater seepage was observed in any of the test pits dug), anticipated heave movements beneath foundation could be expected to be in the range 20 to 30mm in the area south of the drainage line and between 5 and 12mm in the area north of the drainage line, taking into account at least partial saturation of the soils at the time of investigation. Differential heave should be taken as 50% of these values. The recommended foundation design for the accommodation units is provided in detail in Table 2 below. 7 NHBRC House Building Manual Parts 1 & 2; Revision No. 1, February 1999 Page 10 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

13 Table 2 Foundation design, building procedures and precautionary measures for single storey residential structures founded on soil horizons subject to heave Site Class Estimated Total Heave (mm) Construction Type H <7.5 Normal Modified normal Foundation Design and Building Procedures (Expected damage limited to Category 1) Normal construction (strip footing or slab-on-the-ground foundations). Site drainage and service/plumbing precautions recommended. Lightly reinforced strip footings. Articulation joints at all internal/external doors and openings. Light reinforcement in masonry. Site drainage and service/plumbing precautions. H Soil raft Stiffened or cellular raft Remove all or part of expansive horizon to 1.0m beyond the perimeter of the structure and replace with inert backfill, compacted to 93% MOD AASHTO density at -1% to +2% of optimum moisture content. Normal construction with lightly reinforced strip footings and light reinforcement in masonry if residual movements are <7.5mm or construction type appropriate to residual movements. Site drainage and service/plumbing precautions. Stiffened or cellular raft with articulation joints or lightly reinforced masonry. Site drainage and service/plumbing precautions. H Piled construction Split construction Piled foundations with suspended floor slabs with or without ground beams. Site drainage and service/plumbing precautions. Combination of reinforced brickwork/block work and full movement joints. Suspended floors of fabric-reinforced ground slabs acting independently from the structure. Site drainage and service/plumbing precautions. Soil Raft Stiffened or cellular raft As for H1. As for H2. H3 >30 Piled construction As for H2. Soil raft As for H1. Notes: Differential heave assumed to equal 50% of total heave. The relaxation of some of these requirements, e.g. the reduction or omission of steel or articulation joints, may result in a Category 2 level of expected damage. It is recommended that the foundations for all structures be designed by a competent structural engineer. In addition, it is further recommended that the precautions are taken in the construction of the block/brickwork, drainage and plumbing as outlined in Table 2 above. In the area north of the drainage line it is recommended that the buildings be founded in in the shale bedrock where a maximum allowable bearing pressure of 80kPa is considered applicable. For single storey structures, footing widths of 600mm must be used, founded at a depth of at least 0.6m below ground surface. In the area south of the drainage line the most suitable and economical type of house foundation is likely to be the reinforced concrete raft. No foundations should be founded on, or in fill unless the fill is specifically engineered for this purpose. If a building is located over the fill part of a platform then the footings will need to be taken down through the fill and into the insitu material where the above bearing pressure recommendation applies for fills no thicker than 1.0m. To optimise shallow founding, it is recommended that the buildings are positioned in areas of cut of building platforms as far as possible. It is recommended that GGS inspect and approve all foundation excavations to confirm depth of founding and bearing pressure. Page 11 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

14 9.5.1 Lodge / Hotel Building No details have been provided of the Lodge building, other than it will generally be single storey with double volume rooms in some parts. Below the location of the lodge building the residual soils are fairly deep, in excess of 3m in places. Heave forces are likely to be at their maximum. A stiffened raft foundation solution may well not be applicable for this structure because of the following: Footprint of the building may be too large for the design of an efficient raft Footprint may not be of regular outline, such as square or rectangular, which is most suitable for the design of rafts Variable loading conditions across its width / area may also make the use of a raft not feasible It is anticipated that the building will need to be supported on piles designed to resist the uplift forces which will be caused by the heave of the foundation soils when wetting up. The heave forces on the piles can be expected to be fairly significant, requiring that piles be reinforced for their full length as well as socketed into the shale bedrock to prevent their being uplifted. The building will need to be suspended above the active subgrade using suspended floors and beams. All piles should be designed by a competent geotechnical engineer. 9.6 Subgrade Improvement beneath Roads, Paving and Parking Areas The insitu materials, as discussed above, are generally of very poor subgrade quality (<G10) and unsuitable for use in the construction of roads, parking and paved areas. Subgrade treatment on this site will be essential. This will consist of the undercutting of the insitu clayey materials to a depth of at least 300mm below the top of road subgrade level and replaced with a good quality selected subgrade material imported from shale or dolerite borrow areas established on site or from elsewhere. The actual depth of undercut required should be confirmed by the Engineer, as determined from the traffic loads, volumes and design life in mind. The clayey materials removed from the undercuts should be spoiled unless they can be used for landscaping, etc 10. CONCLUSIONS This report contains the preliminary results of a geotechnical investigation carried out for the Royal Albert Lodge development on the western shore of Albert Falls Dam near Ottos Bluff, Pietermaritzburg. The site is underlain by a mantle of transported and residual soils overlying the shale bedrock of the Pietermaritzburg Formation. It is considered that conditions prevailing at the site are generally favourable for the proposed development, provided the recommendations given in this report are adhere to. Recommendations for earthworks and drainage to promote the stable development are given. The founding conditions beneath the site point to expansive or active soil conditions which will need to be taken into account in the design of foundations. The site has been classified as H1/R (north of the drainage line) and H2/H3 (south of the drainage line) according to the NHBRC guidelines. The lodge building is likely to require founding on piles designed to withstand uplift and the building itself suspended above the active subgrade. The insitu subgrade materials beneath the area to the south of the drainage line which dissects the site are of extremely poor quality and subgrade treatment beneath roads, parking and paved areas will need to be carried out. This would require the boxing out or undercutting of the soils below top of subgrade and replacement with a suitable selected material taken from identified borrow pit areas. Therefore, borrow areas within the shale area on the northern side of the drainage line and residual dolerite on the western margin of the site should be identified for this purpose. Page 12 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

15 Finally, the ground conditions described in this report refer specifically to those encountered in the inspection pits, DPL tests and exposures logged on site. It is therefore quite possible that conditions at variance with those discussed above can be encountered elsewhere. It is therefore important GGS carry out periodic inspections of the earthworks and open foundation excavations. Any change from the anticipated ground conditions could then be taken into account to avoid unnecessary expense. In this regard it is important that the construction phase of the project be treated as an augmentation of the geotechnical investigation. Page 13 Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\18-156R01 (report only).doc

16 APPENDIX A Geotechnical Investigation carried out for the Royal Albert Lodge, Albert Falls Dam, KwaZulu-Natal Path : C:\Users\Merrill\Desktop\Job Folders\ Royal Albert Lodge\Report\App A cover page.docx

17 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA1 Sheet 1 of 1 JOB NUMBER: Scale S1 1: Topsoil with roots. Dry dark brown sandy clayey shale GRAVEL. Residual Shale. Dark grey medium to highly weathered very soft to soft rock SHALE. Pietermaritzburg Formation. NOTES 1) Final depth at 1.20m. Refusal on soft rock shale. 2) No groundwater seepage. 3) No sidewall collapse. 4) Samples taken : S m (1 x Small) CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA1 dotplot 7022 PBpH67

18 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA2 Sheet 1 of 1 JOB NUMBER: S1 Scale 1: Topsoil. Dry dark brown sandy clayey shale GRAVEL. Residual Shale. Dark brown medium to highly weathered intensely laminated very closely jointed very soft to soft rock SHALE. Pietermaritzburg Formation. Note: J1 = 0-5 degrees. NOTES 1) Final depth at 1.50m. Refusal on soft rock shale. 2) No groundwater seepage. 3) No sidewall collapse. 4) Samples taken : S m (3 x Bulk) CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA2 dotplot 7022 PBpH67

19 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA3 Sheet 1 of 1 JOB NUMBER: S1 Scale 1: Topsoil with roots. Slightly moist dark brown silty clayey SAND to sandy CLAY. Hillwash (Colluvium). Slightly moist olive brown shattered and slickensided silty sandy CLAY. Residual Shale. Yellowish brown streaked grey and black intensely laminated very soft to soft rock SHALE. Pietermaritzburg Formation. NOTES 1) Final depth at 1.80m. Refusal on soft rock shale. 2) No groundwater seepage. 3) No sidewall collapse. 4) Samples taken : S m (3 x Bulk) CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA3 dotplot 7022 PBpH67

20 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA4 Sheet 1 of 1 JOB NUMBER: Scale 1:50 S Topsoil with roots. Slightly moist dark brown mottled grey loose clayey gravelly SAND. Hillwash. Dark grey to brown moderately to highly weathered intensely laminated very soft to soft rock SHALE. Pietermaritzburg Formation. NOTES 1) Final depth at 1.50m. Refusal on soft rock shale. 2) No groundwater seepage. 3) No sidewall collapse. 4) Samples taken : S m (3 x Bulk) CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA4 dotplot 7022 PBpH67

21 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA5 Sheet 1 of 1 JOB NUMBER: Scale 1:50 S Topsoil. Slightly moist dark grey loose to medium dense sandy clayey GRAVEL. Hillwash. Dark grey to olive highly to completely weathered very soft rock SHALE. Pietermaritzburg Formation. Dark grey to olive medium to highly weathered very soft to soft rock SHALE. Pietermaritzburg Formation. NOTES 1) Final depth at 1.50m. Refusal on soft rock shale. 2) No groundwater seepage. 3) No sidewall collapse. 4) Samples taken : S m (3 x Bulk) CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA5 dotplot 7022 PBpH67

22 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA6 Sheet 1 of 1 JOB NUMBER: Scale 1: Topsoil. Slightly moist dark grey loose to medium dense sandy clayey GRAVEL. Hillwash. Slightly moist dark brown loose to medium dense sandy clayey GRAVEL with large indurated shale blocks ( mm diameter). Dry to slightly moist yellowish brown stiff fissured shattered and slickensided sandy clayey SILT. Residual Shale. Yellowish brown completely to highly weathered intensely laminated very closely jointed very soft rock SHALE. Pietermaritzburg Formation. NOTES 1) Final depth at 2.50m. Refusal on very soft to soft rock shale. 2) No groundwater seepage. 3) No sidewall collapse. 4) No samples taken. CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA6 dotplot 7022 PBpH67

23 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA7 Sheet 1 of 1 S1 Scale 1: Topsoil with roots. JOB NUMBER: Slightly moist dark brown silty clayey SAND to sandy CLAY. Hillwash (Colluvium). Slightly moist yellow to brown mottled grey and olive stiff intensely shattered and slickensided slightly sandy silty CLAY. Reworked Residual Shale NOTES 1) Final depth at 3.00m. No refusal. 2) No groundwater seepage. 3) No sidewall collapse. 4) Samples taken : S m (1 x Small) CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA7 dotplot 7022 PBpH67

24 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA8 Sheet 1 of 1 Scale 1: Topsoil with roots. JOB NUMBER: Slightly moist dark brown silty clayey SAND to sandy CLAY. Hillwash (Colluvium). Slightly moist yellow to brown mottled grey speckled black firm becoming stiff with depth micro-shattered and slickensided sandy silty CLAY with occasional small rounded ferricrete nodules and rounded shale gravel pieces. Residual Shale NOTES 1) Final depth at 2.70m. No refusal. 2) No groundwater seepage. 3) No sidewall collapse. 4) No samples taken. CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA8 dotplot 7022 PBpH67

25 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA9 Sheet 1 of 1 S1 Scale 1: Topsoil with roots. JOB NUMBER: Slightly moist dark brown silty clayey SAND to sandy CLAY. Hillwash (Colluvium). Slightly moist yellow to brown mottled grey and olive stiff intensely shattered and slickensided slightly sandy silty CLAY. Residual Shale NOTES 1) Final depth at 2.80m. No refusal. 2) No groundwater seepage. 3) No sidewall collapse. 4) Samples taken : S m (1 x Small) CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA9 dotplot 7022 PBpH67

26 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA10 Sheet 1 of 1 S1 Scale 1: Topsoil with roots. JOB NUMBER: Slightly moist dark brown silty clayey SAND to sandy CLAY. Hillwash (Colluvium). Slightly moist yellow to brown mottled grey speckled black firm becoming stiff with depth micro-shattered and slickensided sandy silty CLAY with occasional small rounded ferricrete nodules and rounded shale gravel pieces. Residual Shale NOTES 1) Final depth at 2.70m. No refusal. 2) No groundwater seepage. 3) No sidewall collapse. 4) Samples taken : S m (1 x Small) CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA10 dotplot 7022 PBpH67

27 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA11 Sheet 1 of 1 JOB NUMBER: Scale 1: Topsoil. Slightly moist to moist dark brown firm to stiff shattered silty sandy CLAY with fine gravel. Colluvium. Slightly moist olive grey to yellowish brown stiff shattered and slickensided sandy silty CLAY with nodules of ferricrete and calcrete. Residual Shale. Dark brown completely to highly weathered very soft rock SHALE. Pietermaritzburg Formation. NOTES 1) Final depth at 2.30m. Refusal on very soft to soft rock shale. 2) No groundwater seepage. 3) No sidewall collapse. 4) No samples taken. CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA11 dotplot 7022 PBpH67

28 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA12 Sheet 1 of 1 JOB NUMBER: Scale 1: Slightly moist dark brown silty clayey SAND with numerous roots. Topsoil. Slightly moist dark brown shattered silty sandy CLAY with numerous ferricrete nodular gravel and calcrete nodules. Slightly moist yellowish brown firm to stiff shattered and slickensided sandy silty CLAY. Residual Shale. Yellowish brown to grey completely to highly weathered very closely to closely jointed very thinly bedded very soft rock SHALE. Pietermaritzburg Formation. NOTES 1) Final depth at 2.50m. Refusal on very soft to soft rock shale. 2) No groundwater seepage. 3) No sidewall collapse. 4) No samples taken. CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA12 dotplot 7022 PBpH67

29 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA13 Sheet 1 of 1 JOB NUMBER: Scale 1: Topsoil. Slightly moist to moist dark brown firm to stiff shattered silty sandy CLAY with fine gravel. Colluvium. Slightly moist yellowish brown to olive shattered and slickensided sandy silty CLAY. Residual Shale. Dark grey completely to highly weathered very closely to closely laminated intensely jointed very soft rock SHALE. Pietermaritzburg Formation. NOTES 1) Final depth at 2.20m. No refusal. 2) No groundwater seepage. 3) No sidewall collapse. 4) No samples taken. CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA13 dotplot 7022 PBpH67

30 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA14 Sheet 1 of 1 Scale 1: Topsoil. JOB NUMBER: Slightly moist to moist dark brown firm to stiff shattered silty sandy CLAY with fine gravel. Colluvium. Slightly moist yellow to orange brown stiff shattered and slickensided sandy silty CLAY with nodules of ferricrete and calcrete. Residual Shale NOTES 1) Final depth at 2.70m. No refusal. 2) No groundwater seepage. 3) No sidewall collapse. 4) No samples taken. CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA14 dotplot 7022 PBpH67

31 VOIGTS CONSTRUCTION Royal Albert Lodge HOLE No: RA15 Sheet 1 of 1 Scale 1: Topsoil. JOB NUMBER: Slightly moist to moist dark brown firm to stiff shattered silty sandy CLAY with fine gravel. Colluvium. Slightly moist olive grey to yellowish brown stiff shattered and slickensided sandy silty CLAY with nodules of ferricrete and calcrete. Residual Shale. Slightly moist yellow to orange brown stiff shattered and slickensided sandy silty CLAY with nodules of ferricrete and calcrete. Residual Shale NOTES 1) Final depth at 2.70m. No refusal. 2) No groundwater seepage. 3) No sidewall collapse. 4) No samples taken. CONTRACTOR : MACHINE : DRILLED BY : PROFILED BY : CAT 428E MVR TYPE SET BY : MC SETUP FILE : STANDARD.SET D0CD Gondwana Geo Solutions INCLINATION : DIAM : 12/11/ :44 TEXT :..rtlodge\logs\ra1ra25.doc ELEVATION : X-COORD : Y-COORD : HOLE No: RA15 dotplot 7022 PBpH67