Document Number SANS 1936-1 - Geotechnical Division
DRAFT SOUTH AFRICAN STANDARD (DSS):PUBLIC ENQUIRY STAGEDocument numberSANS 1936-1Reference7135/1936-1/SPDate of circulation2011-12-20Closing date2012-02-21Number and title:SANS 1936-1: DEVELOPMENT OF DOLOMITE LAND — PART 1: GENERAL PRINCIPLES ANDREQUIREMENTSRemarks:PLEASE NOTE: The technical committee, SABS SC 59P: Construction standards – Geotechnical standardsresponsible for the preparation of this standard has reached consensus that the attached documentshould become a South African standard. It is now made available by way of public enquiry to allinterested and affected parties for public comment, and to the technical committee members forrecord purposes. Any comments should be sent by the indicated closing date, either by mail, or by fax,or by e-mail toSABS Standards DivisionAttention: Compliance and Development departmentPrivate Bag X191Pretoria0001Fax No.: (012) 344-1568 (for attention: dsscomments)E-mail: dsscomments@sabs.co.zaAny comment on the draft must contain in its heading the number of the clause/subclause to which itrefers. A comment shall be well motivated and, where applicable, contain the proposed amended text. The public enquiry stage will be repeated if the technical committee agrees to significant technicalchanges to the document as a result of public comment. Less urgent technical comments will beconsidered at the time of the next amendment.THIS DOCUMENT IS A DRAFT CIRCULATED FOR PUBLIC COMMENT. IT MAY NOT BE REFERRED TO AS ASOUTH AFRICAN STANDARD UNTIL PUBLISHED AS SUCH.IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL,COMMERCIAL AND USER PURPOSES, DRAFT SOUTH AFRICAN STANDARDS MAY ON OCCASION HAVE TO BECONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO WHICH REFERENCE MAY BEMADE IN LAW.AZ96.10 2008/08/08 sabs pta
ISBN 978-0-626-SANS 1936-1:2012Edition 1SOUTH AFRICAN NATIONAL STANDARDDevelopment of dolomite landPart 1: General principles and requirementsPublished by SABS Standards Division1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001Tel: 27 12 428 7911 Fax: 27 12 344 1568www.sabs.co.za SABS
SANS 1936-1:2012Edition 1Table of changesChange No.DateScopeAcknowledgementThe SABS Standards Division wishes to acknowledge the work of the National Department ofPublic Works and the National Dolomite Risk Management Working Committee established oninstruction of the Cabinet Committee on Governance and Administration in developing thisdocument.ForewordThis South African standard was approved by National Committee SABS SC 59P, Constructionstandards – Geotechnical standards, in accordance with procedures of the SABS StandardsDivision, in compliance with annex 3 of the WTO/TBT agreement.This document was published in xxxxxx 2012.Reference is made in 3.10 to the "relevant national legislation". In South Africa this means theEngineering Profession Act, 2000 (Act No. 46 of 2000) or the Natural Scientific Professions Act,2003 (Act No. 27 of 2003).SANS 1936 consists of the following parts, under the general title Development of dolomite land:Part 1: General principles and requirements.Part 2: Geotechnical investigations and determinations.Part 3: Design and construction of buildings, structures and infrastructure.Part 4: Risk management.Annex A forms an integral part of this document. Annexes B and C are for information only.
SANS 1936-1:2012Edition 1IntroductionThe development of dolomite land continues to present a challenge in South Africa. Whileopportunities exist in the development of such land, the adverse effects relating to the formation ofsinkholes and subsidences, whether naturally or as a result of the development, cannot be ignored.In the absence of risk mitigation measures, sinkhole formation can result in loss of life. In addition,sinkholes and subsidences can cause severe damage to buildings and infrastructure and affect theirserviceability.Avoiding the hazard associated with dolomite land by prohibiting development of any kind on suchland is not practical as between four and five million South Africans currently reside or work on suchland. Twenty-five per cent of Gauteng, the commercial, mining and manufacturing centre of SouthAfrica, is located on dolomite land. At the other end of the spectrum, undue acceptance of risk is notan option given the potential severity of the consequences and the Government’s obligations interms of the Bill of Rights. Systematic risk mitigation measures are therefore required.South African research shows that 96 % of sinkholes and subsidences that have occurred to datewere man-induced, generated by ingress of water from leaking water-bearing infrastructure, poorstormwater management, etc. or due to artificial lowering of the groundwater level. Consequently,intervention through an integrated, comprehensive and pro-active dolomite risk managementstrategy has the potential to reduce the incidences of ground instability events (sinkhole andsubsidence formation) by reducing the likelihood of water gaining entry into the subsurface profile,or controlling de-watering/recharging of the dolomite aquifer.The objective of SANS 1936 is to set requirements for the development of dolomite land in order toensure that people live and work in an environment that is seen by society to be acceptably safe,where loss of assets is within tolerable limits, and where cost-effective and sustainable land usageis achieved.1
SANS 1936-1:2012Edition 1ContentsPageAcknowledgementForewordIntroduction .11 Scope .32 Normative references .33 Definitions .44 Requirements for land safety and usage .74.14.24.34.4General . 7Qualitative performance requirements . 7Quantitative performance requirements . 7Repair of sinkholes. 125 Compliance with the requirements . 12Annex A (normative)Required competence levels for geo-professionals. 13Annex B (informative) Dolomite land in South Africa. 15Annex C (informative) Mechanisms associated with sinkhole and subsidence formation . 19Bibliography . 232
SANS 1936-1:2012Edition 1Development of dolomite landPart 1:General principles and requirements1 Scope1.1 This part of SANS 1936 establishes qualitative and quantitative performance requirements forthe development of dolomite land with respect to land safety and land usage, to ensurea) a tolerable hazard; andb) that the current land usage does not compromise the future use of such land.NOTE 1 The qualitative requirements are framed around the current body of knowledge and a standardapproach to investigating and evaluating dolomite land, as set out in SANS 1936-2, which has enabled atolerable hazard rating to be established in South Africa.NOTE 2 This part of SANS 1936 provides a performance-based framework within which dolomite land maybe developed. It is based on a similar four-level performance-based system that is used in SANS 10400.1.2 This part of SANS 1936 also provides the means by which compliance with the performancerequirements may be established.1.3 This part of SANS 1936 applies to dolomites of the Malmani and Campbell Rand subgroups.NOTE This part of SANS 1936 may, however, be used for guidance on good practice on other dolomite andlimestone formations.1.4 This part of SANS 1936 does not apply to recent calcretes.2 Normative referencesThe following referenced documents are indispensable for the application of this document. Fordated references, only the edition cited applies. For undated references, the latest edition of thereferenced document (including any amendments) applies. Information on currently valid nationaland international standards can be obtained from the SABS Standards Division.SANS 1936-2, Development of dolomite land – Part 2: Geotechnical investigations anddeterminations.SANS 1936-3, Development of dolomite land – Part 3: Design and construction of buildings,structures and infrastructure.3
SANS 1936-1:2012Edition 1SANS 1936-4, Development of dolomite land – Part 4: Risk management.SANS 2001-BE3, Construction works – Part BE3: Repair of sinkholes and subsidences.3 DefinitionsFor the purposes of this document, the following definitions apply.3.1acceptableacceptable to the authority administering this part of SANS 1936, or to the parties concluding thepurchase contract, as relevant3.2competence levellevel of competencemeasure of proficiency for professionals engaged in work on dolomite land determined in terms ofeducation, category of professional registration, experience, knowledge and recognition by theprofessionNOTE The competence levels (1 to 4) are defined in annex A.3.3competent personperson who is qualified by virtue of his experience, qualifications, training and in-depth contextualknowledge of development on dolomite land toa) plan and conduct geotechnical site investigations for the development of dolomite land, evaluatefactual data, develop a geological model, derive interpretative data and formulate an opinionrelating to the outcomes of such investigations;b) develop and inspect for compliance the necessary precautionary measures required on dolomiteland to enable safe and sustainable developments to take place;c) develop dolomite risk management strategies; ord) investigate the cause of an event and participate in the development of the remedial measuresrequired3.4dolomite area designationclassification of dolomite areas in terms of the extent of mitigation required to achieve and maintain atolerable hazard3.5dolomite landland underlain by dolomite or limestone residuum or bedrock (or both), within the MalmaniSubgroup and Campbell Rand Subgroup, typically at depths of no more thana) 60 m in areas where no de-watering has taken place and the local authority has jurisdiction, ismonitoring and has control over the groundwater levels in the areas under consideration; orb) 100 m in areas where de-watering has taken place or where the local authority has no jurisdictionor control over groundwater levelsNOTE For more information on dolomite land in South Africa, see annex B.4
SANS 1936-1:2012Edition 13.6dolomite risk management strategyprocess of using scientific, planning, engineering and social processes, procedures and measuresto manage an environmental hazard, and encompasses policies and procedures set in place toreduce the likelihood of events (sinkholes and subsidences) occurring on dolomite land3.7dwelling housesingle dwelling unit and any garage and other domestic outbuildings thereto, situated on its ownproperty3.8dwelling unitunit containing one or more habitable rooms and provided with sanitation and cooking facilities3.9eventoccurrence of a sinkhole or subsidence3.10geo-professionalpractitioner of geotechnical engineering or engineering geology who is registered in anycategory of registration provided for in the relevant national legislation (see foreword)3.11hazardsource of potential harmNOTE A hazard can be a risk source, i.e. an element which alone or in combination has the intrinsic potentialto give rise to risk3.12hazard ratingnumber of events that can potentially occur per hectare over a 20-year period due to developmentNOTE A tolerable hazard rating is one that complies with the requirements for a tolerable hazard (see 3.26).3.13infrastructureroads, railway lines, runways, liquid-retaining structures, stormwater systems, power lines, pipelinesand associated structures; including water, sewer, fuel and gas lines, reservoirs, public swimmingpools, attenuation and retention ponds for stormwater management, pump stations, dams,reservoirs and artificial lakes or similar constructed works.3.14inherent hazardpotential for an event (sinkhole or subsidence) to develop in a particular ground profile on dolomiteland3.15inherent hazard classIHCclassification system whereby a site is characterized in terms of eight standard inherent hazardclasses, denoting the likelihood of an event (sinkhole or subsidence) occurring, as well as its predictedsize (diameter)NOTE Inherent hazard classes are defined in SANS 1936-2.5
SANS 1936-1:2012Edition 13.16parcel of landtract of land, comprising one or more farm portions or properties registered in a deeds registry, andidentified for the purpose of development3.17potential loss of supportpotential removal of support below the foundation due to a nominal sinkhole or subsidence event3.18qualitative performance requirementperformance requirement stated in qualitative terms3.19quantitative performance requirementsperformance criteria which enable qualitative requirements for a nominated level or performance tobe complied with3.20return periodrecurrence intervalestimate of the average interval of time between events of a certain size3.21riskeffect of uncertainty on objectivesNOTE Risk is often expressed in terms of a combination of the consequences of an event and the associatedlikelihood of occurrence.3.22sinkholefeature that occurs suddenly and manifests itself as a hole in the ground3.23standsingle piece of land registered, or in the process of being registered, in a deeds registry3.24subsidenceshallow, enclosed depressionNOTE Most South African literature previously used the term “doline” when referring to a subsidence asdefined above. The use of the term “subsidence” is in line with international literature and practice.3.25suitablecapable of fulfilling or having fulfilled the intended function, or fit for its intended purpose3.26tolerable hazardwhere the number of events experienced is less than 0,1 events per hectare per 20 years(preferably tending to 0 per hectare), i.e. a return period of an event occurring on 1 ha of more than200 years.NOTE Mitigating measures might need to be implemented in order to achieve a tolerable hazard.6
SANS 1936-1:2012Edition 14 Requirements for land safety and usage4.1 GeneralRisk management is commonly understood to be the culture, processes and structures used toeffectively manage potential opportunities and adverse effects. In the context of dolomite land, theopportunities include the development potential of the land. The adverse effects include the hazardpresented by the formation of sinkholes and subsidences, which result in potential harm or loss (orboth).Broadly speaking, risk on dolomite land can be managed bya) placing restrictions on land use;b) ensuring appropriate development is allowed in relation to the inherent hazard;c) establishing requirements for the management and monitoring of surface drainage and dewatering;d) establishing requirements for the installation of below-ground infrastructure, particularly waterbearing services;e) establishing requirements for the construction and maintenance of above-ground and belowground water-bearing structures; andf) establishing design requirements and procedures for buildings and infrastructure to allow, as aminimum, the safe evacuation of occupants and users in the event of a hazard occurring.4.2 Qualitative performance requirementsThe use of dolomite land and land underlain by the Black Reef Formation shall present a tolerablehazard over time.NOTE 1 The Black Reef Formation, where present, is included as part of dolomite land due to the presence ofthe weathering products of dolomite within this formation and the possibility that the position of the contactbetween the Black Reef Formation and overlying Malmani Subgroup dolomite is not accurately mapped.NOTE 2 A tolerable hazard is implied in the quantitative requirements contained in 4.3.NOTE 3 For more information on sinkhole and subsidence formation, see annex C.4.3 Quantitative performance requirements4.3.1 The inherent hazard class (IHC) of parcels of dolomite land shall be determined by means ofa geotechnical site investigation conducted in accordance with the requirements of SANS 1936-2.NOTE Inherent hazards are expressed in terms of three broad categories, namely low, medium and high,typically, but not exclusively, denoting the anticipated number of events per area over time.4.3.2 Based on the outcomes of such an investigation, the appropriate dolomite area designation(D1 to D4, see table 1) and design level investigation requirements shall be determined inaccordance with tables 2 and 3. Parcels of dolomite land shall be described in terms of their landuse category, followed in brackets by their dolomite area designation e.g. C3(D2) so that theappropriate precautionary measures can be readily communicated.NOTE 1 The aim of dolomite area designations D2 to D4 is to introduce precautionary and mitigatingmeasures that strive to reduce the frequency of events per hectare to what equates to a tolerable hazard.NOTE 2 Dolomite area designation D1 applies only to those instances where the development of the landpresents a tolerable hazard.7
SANS 1936-1:2012Edition 14.3.3 On land categorized as D2 and D3, in terms of table 1, appropriate precautionary measuresin accordance with the principles and requirements of SANS 1936-3 shall be implemented tomitigate the risks associated with the development of such land.4.3.4 On land designated as D4, in terms of table 1, the following site-specific measures shall beimplemented:a) site characterization, analysis and design, specification of precautionary measures, supervisionof implementation and formulation of a dolomite risk management plan shall be undertaken by aCompetence Level 4 geo-professional (see annex A);b) the foundation design, design of the structure, precautionary measures and dolomite riskmanagement plan shall specifically address and effectively mitigate the dolomite risks present onthe site;c) the site characterization, foundation design and design of the structure, precautionary measuresand dolomite risk management requirements shall be reviewed and approved by an independentCompetence Level 4 geo-professional (see annex A) and, where relevant, by a structuralengineer with a similar level of competence; andd) all aspects of the development proposal shall be reviewed and approved by the local authority,who may request a further review by an authority-designated Competence Level 4 peer (seeannex A), if required.4.3.5 The owners of developments located on dolomite land shall establish and implementappropriate dolomite risk management strategies in accordance with the principles andrequirements of SANS 1936-4 to mitigate the risks associated with developments on such land.4.3.6 The local authorities in whose jurisdiction the developments in 4.3.2 to 4.3.5 fall shallestablish, implement and maintain a dolomite risk management strategy in accordance with theprinciples and requirements of SANS 1936-4 to mitigate the risks associated with developments onsuch land.4.3.7 Parcels of land underlain by the Black Reef Formation shall comply with the requirements of4.3.1 to 4.3.6 unless such formation has been assessed as p
NOTE 2 This part of SANS 1936 provides a performance-based framework within which dolomite land may be developed. It is based on a similar four-level performance-based system that is used in SANS 10400. 1.2 This part of SANS 1936 also provides the means by which complia
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