bs 5930 a2 dpc feb 2010

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a

Date: 3 February 2010

Origin: National

Latest date for receipt of comments: 31 March 2010 Project no.: 2008/03046

Responsible committee: B/526/3 Site investigation and ground testing

Interested committees: B/526

Title: Draft BS BS 5930+A2 Code of practice for site investigations

Supersession information: If this document is published as a standard, the UK implementation of it will supersede

AMD1 TO BS5930 : 1999 and partially supersede. NONE If you are aware of a current national standard whichmay be affected, please notify the content developer (contact details below).

WARNING: THIS IS A DRAFT AND MUST NOT BE REGARDED OR USED AS A BRITISH STANDARD.THIS DRAFT IS NOT CURRENT BEYOND 31 March 2010.

This draft is issued to allow comments from interested parties; all comments will be given consideration prior topublication.No acknowledgement will normally be sent.See overleaf for information on commenting.

No copying is allowed, in any form, without prior written permission from BSI except as permitted under theCopyright, Designs and Patent Act 1988 or for circulation within a nominating organization for briefing purposes.Electronic circulation is limited to dissemination by e-mail within such an organization by committee members.

Further copies of this draft may be purchased from BSI Customer Services, Tel: +44(0) 20 8996 9001 or email

[email protected]. British, International and foreign standards are also available from BSI Customer Services.Information on the co-operating organizations represented on the committees referenced above may be obtainedfrom the responsible committee secretary.

Cross-references

The British Standards which implement International or European publications referred to in this draft may be foundvia the British Standards Online Service on the BSI web site http://www.bsigroup.com.

Direct tel: 020 8996 6434Responsible Content Developer: John Devaney

E-mail: [email protected]

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DPC: 10/30190274 DC

Draft for Public Comment

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b

IntroductionYour comments on this draft are invited and will assist in the preparation of the resulting British Standard. If nocomments are received to the contrary, this draft may be implemented unchanged as a British Standard.

Please note that this is a draft and not a typeset document. Editorial comments are welcome, but you are advised notto comment on detailed matters of typography and layout.

Submission of CommentsThe guidance given below is intended to ensure that all comments receive efficient and appropriate attention by theresponsible BSI committee.

This draft British Standard is available for review and comment online via the BSI British Standards Draft Reviewsystem (DRS) as http://drafts.bsigroup.com. Registration is free and takes less than a minute.

Once you have registered on the DRS you will be able to review all current draft British Standards of nationalorigin and submit comments on them. You will also be able to see comments made on current draft standards byother interested parties.

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BS 5930, Code of practice for site investigations

Amendment 2

The amendment only affects the following subclauses shown.

Foreword

Insert new third paragraph:

Amendment 2 to this standard removes text superseded by BS EN 22475-1:2006, and

makes reference to the relevant standard for each affected subclause.

2.1 soil and rock

Change to read:

have the meanings ascribed to them by common usage in UK civil engineering and

construction and, as yet, there are no universally accepted definitions. An indication

of the scope of these terms is found in section 6.Soil is defined in BS EN ISO 14688-

1:2002, 3.1and rock is defined in BS EN ISO 14689-1:2003, 3.1.

3 Normative references

Add the following references:

BS EN 1997-2:2007,Eurocode 7 Geotechnical design Part 2: Ground

investigation and testing.BS EN ISO 22475-1:2006, Geotechnical investigation and testing Sampling

methods and groundwater measurements Part 1: Technical principles for

execution.

BS EN ISO 22476-3, Geotechnical investigation and testing Field testing

Part 3: Standard penetration test.

13.3 Sampling considerations (NEW SUBCLAUSE)

The criteria for selection of techniques and methods for sampling and groundwater

measurements should be selected following BS EN ISO 22475-1:2006, 5.2.

14.1 Introduction

Revise first paragraph to read:

The factors involved in the choice of the most suitable procedures for boring

(including drilling), sampling, probing, tests in boreholes and field tests, as

determined by the character of the ground, are considered in 14.2to 14.10. Further

detailed information may be found in BS EN 1997-2:2007, Section 3and BS EN ISO

22475-1:2006, Clause 5. Frequent reference is made to classes of sample quality;

these are defined in 21.222.2.

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14.6 Overconsolidated clays

Revise second paragraph to read:

Samples of clays in the firm to stiff strength range taken with a 100 mm open-tube

sampler usually suffer only a small amount ofa degree of materialdisturbance, and are

generally accepted aswill not produce samples better thanclasses 1 or2. With very

stiff and hard clays, however, there is significant disturbance. Thin-wall samplers

jacked into the ground can howeverproducebetter qualityclass 1samples. Where the

nature of the problem

14.7 Clay containing gravel, cobbles or boulders

Revise third paragraph to read:

driven past the coarser particles. Therefore, quite often, the samplesrecoveredGenerally, the samplesare of limited length, have been disturbed by coarse

particles, and are only class 4 or 5.

14.10 Discontinuities

Revise final paragraph to read:

The extent of the excavations is governed by the spacing between discontinuities

and the size of the works (see 41.2.344.4.3).

17.4 The logging of excavations and boreholes and the describing of

soils and rock


The lead driller should normally be responsible for recording the information obtained

from the borehole as it arises

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17.8.1 Driller

Revise subclause, including title to read:

17.8.1 DLead driller

The lead driller in charge of an individual drilling rig should be skilled in the practiceof exploration of the ground by means of boreholes, simple sampling and testing,

making groundwater observations in boreholes, and properly recording the

information obtained. Where available they should also have appropriate

accreditation.In the UK, all boring and drilling operatives, including lead drillers and

drillers (drilling support operatives) employed on the contract should hold a valid and

current audit card of competence applicable to the work and the specific drilling

operation on which they are engaged, as issued by the British Drilling Association Ltd

under its BDA Audit, or an equivalent body in a state of the European Union. They

should also hold CSCS blue skilled (Land Drilling) cards.

NOTE In the UK, the British Drilling Association operates an accreditation scheme

for drillers.

20.7.1 Introduction

Revise last paragraph and add a note to read:

Drilling is in part an art, and its success is dependent upon good practice and the skill

of the lead driller, particularly when coring partially cemented, fractured, weathered

and weak rocks or superficial deposits. Good drillers have had adequate training,

together with considerable experience.

NOTE Further guidance on drillers is given in 17.8.1and in BS EN ISO 22475-1:2006.

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20.7.3 Rotary core drilling

Revise first paragraph and add a note to read:

This is normally carried out using conventional or wireline double or triple tube core

barrels (a triple tube system may be simulated by a double barrel fitted with a semi-

rigid plastic liner) fitted with diamond or tungsten tipped core bits. Specifications ofall the major components found in core barrels, rods and casings may be found in BS

4019BS EN ISO 22475-1:2006. The objective of core drilling is to achieve optimum

core recovery and core quality consistent with cost. The choice of drill and compatible

in-hole and surface equipment, their condition and suitability for the work anticipated,

are all most important if the objective is to be achieved. Detailed guidance on the

selection of core bits for particular formations or the suitability of various techniques

in different types of soil and rock are beyond the scope of this document and advice

should be sought from a drilling specialist.

NOTE General guidance on the available techniques and their suitability to various groundconditions is however given in BS EN ISO 22475-1:2006.

Delete Table 1 Sizes of rotary core barrels

Revise fifth paragraph to read:

Some standardDetailed information relating tocore barrel sizes and the core sizes

they produce are listed in Table 1BS EN 22475-1:2006, Annex C. When a double

core barrel is fitted

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20.7.4 Core extrusion and preservation


The core should preferably be extruded in the same direction as it entered the barrel.

The core should be extruded into a half-round rigid receiving tray (e.g. plastic

guttering) in such a manner that it is completely supported. When it is required topreserve the core such that it does not dry out, a convenient method is to extrude it

into thin gauge polythene sheet or tube (layflat) placed within the half-round tray,

which can then be wrapped and sealed with plastic tape. Where selected lengths of

core are to be preserved at their natural moisture content for laboratory testing, any

drilling mud contamination and softened materials should first be removed and the

sample should then be wrapped in foil and coated with successive layers of waxed

cheese cloth and labelled. The difficulties of extrusion and preservation can be

overcome by the use of triple-tube core barrels or double tube core barrels with plastic

liners. Split liner tubes are another method of examining the recovered core without

further damage after the drilling process. Seamless metal or plastic liners are

particularly useful where core is to be removed from site for logging, or whereconfined undisturbed samples are required for sample observation and subsequent

laboratory testing, although care should be taken to ensure that any retained drilling

fluid is drained off as quickly as possible.

It is recognized that core may be recovered from a variety of material types. The

majority of core may however be obtained within cohesive soils of variable strength

and in rocks in various states of weathering and also having variable strength. Some

core may be obtained by using double tube core drilling and some by triple tube core

drilling. Either of these systems may include the use of a semi rigid plastic liner.

Irrespective of the material type or presence of a core liner system, the core should be

extruded from the core barrel in the same direction as it entered the barrel. Core

should be carefully extruded into core boxes having receiving channels appropriate to

the diameter of the core.

It is important to note that the sampling category cannot be improved once coring has

taken place.

Unless stated to the contrary for individual investigations, it should be assumed that

all core obtained will be required to comply with sampling category A as defined in

BS EN 22475-1. This may be achieved by the use of appropriate core bit, core barrel

and flushing medium. Cores recovered may be divided into:

a) Cores not sensitive to moisture content change: Category A status may bemaintained by either the use of sealed core liner or by immediately wrapping all

extruded core with suitable impermeable material e.g. cling film, plastic sheeting.

b) Cores sensitive to moisture change: Category A status should be maintained by

sealing the core immediately with the use of moisture sealing material e.g.

cheesecloth soaked in wax, waxed sealed tubes.

Where the core is to be sub-sampled for specific laboratory testing, this should be

done immediately after the core has been extruded into the core box. When core liner

has been used this may be done by cutting both the liner and core in two places in

order to remove the sample.

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The sub-samples category A status should be maintained as described in b). Each

sample should be clearly labelled. The sample should be placed in an appropriate

container that will protect the sample during transport.

20.9 Backfilling excavations and boreholesRevise first paragraph to read:

The need and specification for the grout is project dependent. The backfill material

should be of lower permeability than the surrounding ground (see BS EN ISO 22475-

1:2006, 5.5).

22.1 General principles


There are four mainthe followingtechniques for obtaining samples (see [40]):

a) taking disturbed

22.2 Sample quality


The sampling procedure should be selected on the basis of the quality of the sample

that is required, and is assessed largely by the suitability of the sample for appropriate

laboratory tests(see also BS EN 1997-2:2007, Section 3 and BS EN ISO 22475-

1:2006). Table 2 shows a classification for soil samples developed in Germany. Auseful basis for classifying samples in terms of quality is provided in [41].

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22.4 Open-tube samples

Revise subclause to read:

22.4.1 Principles of design

NOTE BS EN ISO 22475-1, 6.4.2.1, 6.4.2.5 and particularly 6.4.2.6 identify two categories of opentube (OS) samples. These are thin-wall (type OS-T/W) and thick-wall (type OS-TK/W) open tube

samples. Details of dimensions, applicability, and sample categories and quality are given in BS ENISO 22475-1, Table 3 and Table 4.

22.4.1.1 General

Open-tube samplers consist essentially of a tube that is open and made sharp at one

end and fitted at the other end with means for attachment to the drill rods. A non-

return valve permits the escape of air or water as the sample enters the tube, and

assists in retaining the sample when the tool is withdrawn from the ground. Figure 1

shows the basic details of a sampleran open tube sampler (OS-TK/W)suitable for

general use, which has a single sample tube and simple cutting shoe. The use of

sockets and core catcher is discussed in 22.4.4. An alternative sampler incorporates adetachable inner liner.

The fundamental requirement of a sampling tool is that it should cause as little

remoulding and disturbance as possible when forced into the ground. Three features

of the design control the degree of disturbance: the cutting shoe, the inside wall

friction and the non-return valve. The sampling procedure (see 22.4.2), is also an

important factor in controlling sample disturbance.

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2 22 1

21

Area ratio 100%D D

D

=

Figure 1 Basic details of open-tube sampler(UK)

22.4.1.2 The cutting shoe

The cutting shoe should normally be of a design similar to that shown in Figure 1 and

should embody the following features:

a) Inside clearance.The internal diameter of the cutting shoe,DCD1, should beslightly less than that of the sample tube,DSD3; to give inside clearance this is

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typically 1 % of the diameter. This allows for slight elastic expansion of the

sample as it enters the tube, reduces frictional drag from the inside wall of the tube

and helps to retain the sample. A large inside clearance should be avoided since it

would permit the sample to expand, thereby increasing the disturbance.

b) Outside clearance.The outside diameter of the cutting shoe,DWD2, should be

slightly greater than the outside diameter of the tube, DTD4, to give outside

clearance and facilitate the withdrawal of the sampler from the ground. The

outside clearance should not be much greater than the inside clearance.

c) Area ratio.The area ratio represents the volume of soil displaced by the sampler

in proportion to the volume of the sample (see Figure 1). It should be kept as

small as possible consistent with the strength requirements of the sample tube.

The area ratio is about 30 %from about 30 % to 50 %for the general purpose 100

mm diameter sampler(OS-TK/W), and about 10 %up to about 15 %for a thin-

walled sampler(OS-T/W). Some special samplers have a large outside diameter

DTD4, relative to the internal diameterDCD1, e.g. in order to accommodate a loose

inner liner. The sampling disturbance is reduced by using a cutting shoe that has along outside taper and is considerably less than that which would be expected

from the calculated area ratio(see Figure 2).

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Figure 2 Delft continuous sampler 66 mm

22.4.1.3 Wall friction

This can be reduced by a suitable inside clearance and by a clean, smooth finish to the

inside of the tube.

22.4.1.4 Non-return valveThe non-return valve should have a large orifice to allow air and water to escape

quickly and easily when driving the sampler, and to assist in retention of the sample

when removing the sampler from the borehole.

22.4.2 Sampling procedure

Before a sample is taken, the bottom of the borehole or surface of the excavation or

heading should be cleared of loose or disturbed material as far as possible. Some or all

of any such loose or disturbed material that is left normally passes into the overdrive

space of the sampler.

Below the water table, certain types of laminated soils occurring below the bottom ofthe borehole or excavation may be disturbed if the natural water pressure in the

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laminations exceeds the pressure imposed by the water within the borehole or

excavation. To reduce this effect, it is necessary to keep the level of the borehole

water above the groundwater level appropriate to the location of the sample.

The sampler can be driven into the ground by dynamic means, using a drop weight or

sliding hammer, or by a continuous static thrust, using an hydraulic jack or pulley

block and tackle. There is little published evidence to indicate whether dynamic or

static driving produces less sample disturbance, and for most ground conditions it is

probable that there is no significant difference. The driving effort for each sample

may be recorded as an indication of the consistency of the ground.

The distance that the tool is driven should be checked and recorded because, if driven

too far, the soil is compressed in the sampler. A sampling head with an overdrive

space (see Figure 1) allows the sample tube to be completely filled without risk of

damaging the sample. After driving, the sampler is steadily withdrawn. The length of

sample that is recovered should be recorded, compared with the distance that the tool

was driven, and any discrepancy investigated. For example, if the length of the sample

is less than the distance driven, the sample may have experienced some compressionor, alternatively, the sample tool may have permitted the sample to slip out as the tool

was being withdrawn.

22.4.3 Thin-walled samplers(Type OS-T/W)

Thin-walled samplers are used for soils that are particularly sensitive to sampling

disturbance, and consist of a thin-walled steel tube whose lower end is shaped to form

a cutting edge, with or without a small inside clearance. The area ratio should be

about 10 % or lessless than 15 %, although area ratios up to 25 % and taper angles of

between 5 and 15 may be acceptable if it can be demonstrated that the sample

quality is not affected. They are pushed into the soil by continuous static thrust from

hydraulic jacks or pulley block and tackle. These samplers are usually only suitable

for fine soils up to a firm to stiff consistency, and free from large particles, although

samples have been successfully obtained from very stiff soils. They normally give

class 1 samples of all fine cohesive soils, including sensitive clays, provided that

sinking the borehole has not disturbed the soil. Samples between 75 70 mm and 100

120 mm in diameter are usually obtained and samples up to 250 mm in diameter are

sometimes obtained for special purposes. It is to be noted that disturbance at the base

of the borehole occurs in weak soil below a certain depth because of stress relief.

Piston samples penetrating well below the base of the borehole are therefore

preferable (see 22.5). A typical thin-walled sampler is illustrated in Figure 32.

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Figure 3 2 A typical thin-walled sampler

22.4.4 General purpose 100 mm diameter (U100) open-tube sampler

(type OS-TK/W)

The 100 mm diameter open-tube sampler is the standard sampler for routine use with

cable percussion boring and is usually driven into the ground using a sliding hammer

or drop weight. It can be used in all cohesive soils and in weak rock, such as chalk

and weathered Keuper marl. In non-sensitive fine cohesive soils of stiff or lower

consistency, the standard open tube sampler (see Figure 1) may sometimes give class

1 2 samples but, more often, class 2 3 samples. In sensitive clay, class 2 samples may

be obtained. In brittle or closely fissured materials, such as certain weak rocks and

hard clays, and also in stony materials, the sampler gives class 3 samples; this is

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because sampling disturbs these materials, reducing the sample quality to class 3, or

class 4 if water has been added to the borehole.

The sampler is illustrated in Figure 1 and Figure 3, and consists of a rigid steel or

alloy sample barrel, about 450 mm in length, with a screw-on cutting shoe and drive

head. The area ratio should not normally exceed 30 %, but . Tthe use of a liner system

increases the area ratio above 30 %up to 50 % andreduces the sample qualities

referred to above by one or more classes. Sample barrels can be coupled together with

screw sockets to form a longer sampler. Two or three standard barrels coupled

together are often used for sampling soft clays, although the increased length of the

sample tube may lead to some disturbance.

In soils of low cohesion, such as silt and silty fine sand, the sample may fall out when

the tool is withdrawn from the ground. Sample recovery can be improved by inserting

a core catcher between the cutting edge and the sample barrel, as shown in Figure 1

and Figure 3.

Smaller samplers of about 50 mm or 75 mm diameter can be used if use of the 100

mm sampler is precluded by the borehole size. The smaller samplers are of similar

design, except that the cutting edge may not be detachable.

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A) Standard system B) Plastic liner system

Key

1 sample tube (cadmium-plated steel or aluminium)

2 core catcher (optional)

3 cutting shoe (plain or serrated edge)

4 steel body tube (enclosing plastic liner)

5 core catcher (optional)

6 spacing ring

7 cutting shoe (plain or serrated edge)

8 U100 drive head (bell housing)

Figure 3 U100 sampler (NEW FIGURE)

22.4.5 Split-barrel standard penetration test sampler(type S-SPT)

The split-barrel sampler is used in the standard penetration test and is described in test

19 of BS 1377:1990BS EN ISO 22476-3. It takes samples 35 mm in diameter and has

an area ratio of about 100 %. It is used to recover small samples, particularly under

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conditions which prevent the use of the general purpose 100 mm sampler, and gives

class 3 or class 4 samples (see also 25.2).

22.5 Stationary piston sampler

Insert note after title:

NOTE BS EN ISO 22475-1:2006, 6.4.2.1, 6.4.2.5and particularly 6.4.2.7identify two categories of

piston (PS) samples. These are thin-wall (type PS-T/W) and thick-wall (type PS-TK/W) piston samples.Details of dimensions, applicability, and sample categories and quality are given in BS EN ISO 22475-1:2006, Table 3 and Table 4.

22.5.1 Thin-walled stationary piston sampler

Change title and first two paragraphs to read:

22.5.1 Thin-walled stationary piston sampler(type PS-T/W)

The thin-walled stationary piston sampler consists of a thin-walled sharpened sample

tube containing a close-fitting sliding piston, which is slightly coned at its lower face.

The sample tube is fitted to the drive head, which is connected to hollow drill rods.

The piston is fixed to separate rods, which pass through a sliding joint in the drive

head and up inside the hollow rods. Clamping devices, operated at ground level,

enable the piston and sample tube to be locked together or the piston to be held

stationary while the sample tube is driven down. Figure 4 shows the basic details of a

stationary piston sampler. The sample diameter is normally 75 mm or 100 mm, but

samplers up to 250 mm diameter are used for special soil conditions. Typically , for

the smaller diameter holes,samples up to 1 m long can be taken.

Initially, the piston is locked to the lower end of the sample tube to prevent water or

slurry from entering the sampler. In soft clay, with the piston in this position, the

sampler can be pushed below the bottom of the borehole. When the sample depth is

reached, the piston is held stationary and the sample tube is pushed or pulled down by

a static thrust until the drive head encounters the upper face of the piston. An

automatic clamp in the drive head prevents the piston from dropping down and

extruding the sample while the sampler is withdrawn. The application of air under

slight pressure via an air line fastened to the outside of the sample tube can relieve

suctions at the base of the sample tube during withdrawal. Hydraulically operated

piston samplers are also available.

22.6.2 The Delft continuous sampler

Change first paragraph to read:

The Delft continuous sampler, developed by Delft Geotechnics [44] is available in

two sizes to take continuous samples 29 mm and 66 mm in diameter. The 66 mm

sampler shown in Figure 2 is pushed into the ground with a conventional Dutch deep

sounding machine having a thrust of 200 kN. The sampler is

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22.8 Rotary core sampler

Insert note after title:

NOTE Details of rock sampling materials and sampling by various methods of rotary core drillingare given in BS EN ISO 22475-1:2006, 7.1, 7.3and Table 5.

22.9 Window sampler

Change second paragraph to read:

The system uses sample tubes, normally 1 m long, which can be screw-coupled

together or coupled to extension rods and fitted with a screw-on cutting shoe suitable

for hard driving. The sample tubes and accessories are available in a range of

diameters, a typical suite being 100 mm, 80 mm, 60 mm, 50 mm and 36 mm.

Change fifth paragraph to read:

The system produces samples of quality class 5, but in certain circumstances classes3or 4are obtainable,and is often used for investigations in contaminated ground.

22.10 Block samples

Add final item to list:

d) Remoulded soil should be carefully removed from the sampling location.

22.11.1 General

Add new last paragraph:

Handling, transport and storage of samples should conform to BS EN ISO 22475-

1:2006, Clause11.

23.1 General


Groundwater measurement installations and groundwater measurement methods

should conform to BS EN ISO 22475-1:2006, Clause 9and Clause 10respectively.

23.2.2 Observations in boreholes and excavation


In the case of piezometers measuring absolute pore pressure, the atmospheric pressure

should also be recorded at the same time as the piezometer reading.

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23.3 Groundwater samples


Sample containers should be made from an inert material, be clean and completely

filled with the water sample so as to minimize contact with oxygen. The samples

should be transported and stored in the dark, at low temperatures and tested as soon aspossible after sampling.

24 Introduction

Revise second-last paragraph to read:

Field tests described in this section 4usually exclude theincludetests in boreholes

described in section 3.

25.1 General

Revise to read:

The various forms of test that are commonly conducted as complementary or

supplementary to a ground investigation carried out by borings are described in 25.2

to 25.7. Inevitably, there is some overlap with other clauses within section 4. For

example, pumping tests are described in clause 27because in that instance the borings

are incidental to the test. In the same way, vertical loading tests may be carried out

near the surface or at the bottom of a borehole, so the main details of these tests are

described in 31.1and 25.5covers only those aspects particular to boreholes. Clause

25and other clauses within section 4are in a sense complementary to each other, and

where a particular test is not described in one, it should be sought in the other.

25.2.1 General

Change references from BS 1377-9:1990, 3.3 to BS EN ISO 22476-3, BS EN

1997-2 and NA to BS EN 1997-2 (three of).

Correct typo:

gravel of or coarser

Delete: The test description in BS 1377-9:1990, 3.3is in close agreement with the

international reference test procedure of the ISSMFE (International Society of Soil

Mechanics and Foundation Engineering) [53].

25.2.2 Advantages and limitations

Change reference from BS 1377-9:1990, 3.3 to BS EN ISO 22476-3, BS EN 1997-

2 and NA to BS EN 1997-2.

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25.2.3 Interpretation

Replace first sentence with: Interpretation of the test results into

derived/geotechnical parameters is important but great care has to be taken when

selecting correlations for this purpose. BS EN 1997-2 does give some examples of

interpretation in Annex F; any correlations used should be reported in the GroundInvestigation report.

Change third sentence to read: outside the UK can meanhas meantthat SPT results

and soil parameters derived from data from other countries may not correlate with

results from SPTs derived in accordance withprevious UK standards. However, with

the adoption of BS EN ISO 22476-3, this situation is less likely to be the case in

futureBS 1377-9.

Figure 7 Relationship between dimensionless intake factorF/Dand length to diameter ratio of piezometerL/D

Revise formula in to read:

( )

( ) ( )2

2.32 /

log 1.1 / 1 1.1 / e

L DF

DL D L D

=

+ +

(see [60])

26.2.1 General principles

Change reference from BS 1377-9:1990, 3.2 to BS EN ISO 22476-2, BS EN 1997-2 and NA to BS EN 1997-2

Delete: Table 4 gives specifications for a range of configurations, including those

from BS 1377 and the International Reference Test Procedure of the ISSMFE [53],

though other configurations may be more appropriate in some circumstances [80].

26.2.2 Uses and limitations

Change the fourth sentence (adding a fifth) to read: The main limitation of dynamic

probing is that the soil being tested cannot be identified, although samplingtechniques using the machine operated equipment are have being been developed.

Some examples of the use and interpretation of dynamic probing results are given in

BS EN 1997-2, Annex G and NA to BS EN 1997-2, but these correlations have not

been proven in UK conditions.

Table 4 Details of dynamic probing test specifications

Delete Table 4.

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26.3.1 General

Insert new second sentence in third paragraph, to read: The older type of mechanical

penetrometer measures the cone and friction resistance by means of a system of

internal rods, which thrust against a hydraulic load capsule set at ground surface. The

older type of mechanical penetrometer measures the cone and friction resistance bymeans of a system of internal rods, which thrust against a hydraulic load capsule set at

ground surface. Mechanical penetrometers are occasionally used

26.3.4 Mechanical static cone penetrometer

Insert new sentence at the end of the first paragraph, to read: For both probes the

cone and the friction sleeve can slide along the body of the probe and thrust against

pressure rods located inside the hollow penetrometer rods. The older type of

mechanical penetrometer measures the cone and friction resistance by means of a

system of internal rods, which thrust against a hydraulic load capsule set at ground

surface.

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Table 12 General identification and description of soils

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41.3.2 A scale of consistency, strength and relative density

Revise fourth paragraph to read:

Where measurements of the undrained shear strength are made in the field using a

field or hand vane, or in the laboratory by triaxial test, an undrained strength can also

be given on the field recordonly in the reportwhere required or appropriate using thescale below:

In second-last paragraph, delete: (see BS 1377:1990).

41.4.4.1 Introduction


The soil name is based on particle size distribution of the coarse fraction and/or the

plasticity of the fine fraction as determined by the Atterberg Limits. Thesecharacteristics are used because they can be measured readily with reasonable

precision, and estimated with sufficient accuracy for descriptive purposes. They give

a general indication of the probable engineering characteristics of the soil at any

particular moisture content. Table 13 is a key to the naming and description of soils

by hand and eye. It will be seen that where a soil (omitting any boulders or cobbles)

sticks together when wetand remoulds it often contains about 35 % or more of

fine material, and it is described as a fine soil (CLAY or SILT dependent on its

plasticity). With less than about 35 % of fine material (when it does not stick together

and remould), it is usually described as a coarse soil (SAND or GRAVEL

dependent on its particle size grading). The description of soil containing boulders or

cobbles is discussed in 41.4.4.2.

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41.4.4.2 Deposits containing boulder-size and cobble-size particles

Revise to read:

When the sample is considered representative, such as may be the case in very

large bulk samples from excavations or in excavated or exposed faces, then these

deposits are described as follows:

Main name Estimated boulder or

cobble content of very

coarse fraction

BOULDERS Over 50 % is of boulder size

(>200 mm)

Over 50 % of material is very

coarse (> 63 mm)

COBBLES Over 50 % is of cobble size

(200 mm to 63 mm))

The term large boulder does not have an upper size limit, so dimensions should be

given wherever available.The proportion of cobbles in a boulder deposit (or vice versa) may be quantified using

the terms with a little, with some, or with much as shown in the following table.

Term Secondary constituent by weight

BOULDERS with occasional cobbles Up to 5 % cobbles

BOULDERS with some cobbles 5 % to 20 % cobbles

BOULDERS with many cobbles 20 % to 50 % cobbles

COBBLES with many boulders 20 % to 50 % boulders

COBBLES with some boulders 5 % to 20 % bouldersCOBBLES with occasional boulders Up to 5 % boulders

Very coarse soils with secondary finer material (coarse and fine soil) should alsobe

described as follows.

Term Composition

BOULDERS (or COBBLES) with a little

finer materiala)

Up to 5 % finer material

BOULDERS (or COBBLES) with some finer

materiala)

5 % to 20 % finer material

BOULDERS (or COBBLES) with much

finer materiala)

20 % to 50 % finer material

Rows deleted

a)The description of finer material is made in accordance with 41.4.2to 41.4.6, ignoring

the very coarse fraction; the principal soil type name of the finer material may also be given

in capital letters, e.g. COBBLES with some sandy CLAY.

Finer material (coarse and fine soil) with a secondary very coarse fraction should be

described in accordance with BS EN ISO 14688-2:2004 Table 1. Percentages are

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approximate visual estimates in a field description and should only be taken as a

subjective guide.

Representative sampling of soil mixtures containing very coarse soils is not possible

in normal boreholes, and is very difficult even in conventional trial pits; a

representative sample of a soil including boulders would need to weigh more than a

tonne (BS 1377:1990). Cobbles or boulders are often noted only in passing on the

drillers records, but frequently have a much greater significance to the engineering

works (particularly piling or excavation). The location of individual cobbles and

boulders should be noted on the log, even when it is considered appropriate to include

the very coarse soil as part of the main description. Where possible, the characteristics

of such cobbles and boulders should be described using the terms in Clause 44.

41.4.4.5 Deposits containing mixtures of fine soil and coarse soil


The following terms may be used to describe those common soils that include a

mixture of soil types. The appropriate quantified terms should be used before the

principal soil type. It is recommended that the dominant secondary fraction comes

immediately before the principal soil termword order for secondary fractions before

the principal soil term should be increasing proportion when there are two coarse soil

secondary features, or coarse and then fine if one of each. To avoid ambiguity, if any

of the constituent sizes require separate sentences after the main description; this

commonly applies to the gravel or, less frequently, the sand fractions. Additional

detail can be added in these sentences as appropriate, such as the estimated percentage

proportion or consistency, e.g. Gravelly very clayey SAND. Gravel (10 %) is fine of

rounded quartz. Clay is firm.

Revise third paragraph to read:

Soils that exhibit cohesion but have a high proportion of coarse particles, such as

many glacial deposits, are difficult to describe. Descriptions with cumulative

proportions of the various fractions, excluding cobbles and boulders, exceeding

100 % are incorrect. The inclusion of very coarse particles with finer material gives a

description with more than 100 % fractions.

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41.4.6 Organic soils and peats


Small quantities of dispersed organic matter can have a marked effect on plasticity

and hence the engineering properties and produce a distinctive odour and dark colour

tints; increasing quantities of organic matter heighten these effects [176178]. Iforganic matter is present as a secondary constituent, the following qualifying terms

may be appropriate [178179].

Revise fifth paragraph to read:

Peat is classified according to the degree of decomposition and condition, as given in

Table 13 (see the penultimate rows, Organic soils). Inorganic soils may occur as

secondary constituents of a peat, and should be described for example as slightly

clayey or very sandy, these terms being used qualitatively here. If the peat forms a

horizon of major engineering significance, a fuller description using the scheme ofvon Post may be appropriate [178]and [180].

43.2 Field assessment of grading


Coarse and fine soils are distinguished by whether they stick together when wet and

remould; the water content may need to be adjusted to correctly assess this. The

coarse silt/fine sand boundary (0.063 mm) can be assessed by eye, the coarse silt

particles only being visible with the aid of a hand lens.

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43.3 Field assessment of plasticity

Revise title and text to read:

43.3 Field assessment of plasticity

NOTE The Dry Strength test is described in BS EN ISO 14688-1:2002, 5.6.

43.3.1 Methods

In the laboratory, the effect of the finer particles on the properties of a soil is assessed

from measurements of the plasticity (Atterberg Limits) of the fraction finer than 0.425

mm. The distinction between clay and silt is then made using the plasticity chart, on

which the A-line is an empirical boundary. This chart should be used with caution as

the presence of different clay minerals, fine and medium sand or organic matter, for

example, can affect the measured plasticity. For instance, increasing sand content

decreases plasticity, whereas, conversely, increasing organic content increases

plasticity. This effect on the measured plasticity is different when hand tests are used

for a field assessment. In the field the extent to which the soil shows cohesion andplasticity may be used for the assessment of the fine fraction of coarse soils and dry

strength, toughness and dilatancy may be used for the assessment of fine soils. The

terms silty CLAY and clayey SILT should normally only be used when the secondary

fraction is important, such as when it significantly modifies the appearance and/or

behaviour of the principal.

43.3.2 Cohesion and plasticity of the fine fraction of coarse soils

To examine a soil sample for these characteristics it should first be loosened; this

could necessitate, for instance, crushing the soil with the foot or a mallet, and then

moulding and pressing a handful of the material in the hands. It may be necessary to

add water and to pick out the larger pieces of gravel. A soil shows cohesion when,with a certain moisture content, its particles stick together to give a relatively firm

mass. A soil shows plasticity when, with a certain moisture content, it can be

deformed without rupture, i.e. without losing cohesion. Clays, silts and some peats are

cohesive and plastic; sands may cohere when wet but are neither cohesive nor plastic.

It should normally be possible to distinguish between the presence of silt and the

presence of clay. Soils plotting near the A-line on a plasticity chart (see Figure 18)

tend to be classified as clays.

43.3.3 Toughness of fine soil

Toughness refers to the character of a thread of moist soil rolled on the palm of the

hand, moulded together, and rolled again until it has dried sufficiently to break at adiameter of about 3 mm, as in the plastic limit test. In this condition, inorganic clays

of high plasticity are fairly stiff and tough; those of low plasticity are softer and more

crumbly. Inorganic silts give a weak and often soft thread that breaks up, crumbles

readily, and may be difficult to form. Organic soils and peat have a very weak, spongy

or fibrous thread, which may be difficult to form at all, and their lumps crumble

readily.

43.3.4 The dilatancy test

A pat of soil moistened to be soft, but not sticky, is held on the open horizontal palm

of the hand. The side of the hand is then jarred against the other hand several times.

Dilatancy is shown by the appearance of a shiny film of water on the surface of the

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pat. When the pat is squeezed or pressed with the fingers, the surface dulls as the pat

stiffens and finally crumbles. These reactions are marked only for predominantly silt-

size material and fine sand, and normally indicate the presence of these materials.

43.3 Field assessment of fine soil

The description of fine soils, that is the distinction between CLAY and SILT as aprincipal soil type, is made on the basis of a series of hand tests described as follows.

First, a representative sample of the material for examination is selected and all

particles larger than medium sand until a specimen are removed. This soil is moulded

into a ball about 25 mm diameter until it has the consistency of putty; water should be

added or the ball allowed to dry out as necessary in order to achieve the correct

consistency.

Dilatancy.

Mould the ball, adding water if necessary, until it has a soft, but not sticky,

consistency.

Smooth the soil ball in the palm of one hand with the thumb, the blade of a knife

or a small spatula.

Shake horizontally, striking the side of the hand vigorously against the other hand

several times. Alternatively the pat can be manipulated between the fingers of both

hands.

Record the speed with which water appears while shaking, and disappears while

squeezing as none, slow, or rapid.

Toughness.

Shape the test pat into an elongated pat and roll by hand on a smooth surface orbetween the palms into a thread about 3 mm in diameter. If the sample is too wet to

roll easily, it should be allowed to dry. Fold the sample threads and reroll repeatedly

until the thread crumbles at a diameter of about 3 mm when the soil is near the plastic

limit. Record the pressure required to roll the thread. Also, record the strength of the

thread. After the thread crumbles, the pieces ought to be lumped together and kneaded

until the lump crumbles. Record the toughness of the material during this kneading.

Describe the toughness of the thread and lump as low, medium, or high.

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Plasticity.

On the basis of observations made during the toughness test describe the plasticity of

the material in accordance with the following criteria.

Description Criteria

Non plastic A 3-mm thread cannot be rolled at any watercontent

Low The thread can barely be rolled and the lump

cannot be formed when drier than the plastic

limit

Medium The thread is easy to roll and not much time

is required to reach the plastic limit. The

thread cannot be rerolled after reaching the

plastic limit. The lump crumbles when drier

than the plastic limit

High It takes considerable time rolling andkneading to reach the plastic limit. The thread

can be rerolled several times after reaching

the plastic limit. The lump can be formed

without crumbling when drier than the plastic

limit

Dry strength.

From the moulded material, make a ball of material about 12 mm in diameter and

allow to dry in air.

Test the strength of the dry balls or lumps by crushing between the fingers. Note

the strength as none, low, medium, high, or very high.

The presence of high-strength water-soluble cementing materials, such as calcium

carbonate, may cause high dry strengths. The presence of calcium carbonate can be

detected from the intensity of the reaction with dilute hydrochloric acid.

Feel.

The feel of the fine soils is different and the sensitivity of the fingertips in making

this distinction should not be underestimated.

o Clays feel smooth and readily take a polish when smeared with a blade or

thumb. As the silt content increases, this propensity to polish decreases.

o Silts feel silky with that lovely soft feel.

o If there is an organic content, this imparts a more soapy feel to the soil.

Behaviour in air and water.

Prepare a ball of soil and place it in a bucket or tub of clean water. Silt will

disintegrate within a few minutes, whereas plastic clay will remain unchanged for

much longer.

Smear some soil over a smooth surface (glass or plastic) or even better the back

of your hand. Clay will remain wet whereas silt will dry within a few minutes. Once

the soil is dry, it will not be possible to brush the clay off, because the smaller

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particles have settled into the pores of you skin, whereas the silt will brush off,

leaving your hands clean.

Cohesion.

Prepare a 25mm ball or pat of soil and compress it between your fingers. A clay

will deform in a plastic manner without rupture. A silt on the other hand will tend tocrumble rather than deform.

While carrying out all these tests, water will have been added to the soil. The coarser

is the soil, the more you will have had to keep adding water to keep it in prime

condition for the tests.

The naming of the soil as CLAY or as SILT is then based on the results of these hand

tests as follows.

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Soil description CLAY Silty CLAY Clayey SILT SILT

Dilatancy None None to slow Slow Slow to rapid

Toughness High Medium Low to medium Low or thread

cannot be

formed

Plasticity High Medium Low Non-plastic

Dry strength High to very

high

Medium to high Low to medium None to low

Feel Smooth, sticky

(when wet)

Smooth Silky Silky, gritty

Behaviour in

water

Disintegrates

slowly if at all

Disintegrates

slowly

Disintegrates in

water

Disintegrates

rapidly in water

Behaviour in air Dries slowly

with shrinkage

Dries slowly

with shrinkage

Dries quickly,

brushes off

Dries quickly,

brushes off

Cohesion Deforms

without rupture.

Maintains shape

and moisture

during handling

Deforms

without rupture.

Maintains shape

and moisture

during handling.

Moisture drains Slumps,

moisture drains

In the situation that all the hand tests point to the same conclusion of CLAY or SILT

the decision is straightforward. The more usual case is that the various hand tests give

conflicting results. In this case one of the hybrid terms of silty CLAY or clayey SILT

should be used.43.3.5 Organic soil and peat

Small quantities of dispersed organic matter

44.4.4 Fracture state

Revise un-numbered table to read:

TCR (%) Ratio of core recovered (solid and non intact) to length of core run

SCR (%) Ratio of solid core recovered to length of core run

RQD (%) Ratio of solid core pieces longer than 100 mm to length of core run

Fracture index Count of the number of spacing of fractures over an arbitrary length of

core of similar intensity of fracturing. Commonly reported as Fracture

Index (FI, number of fractures per metre) or as Fracture Spacing (If, mm).

Sometimes reported as minimum/meanmode/maximum (see Figure 20).

Where core is non-intact in the ground, the abbreviation NI may be used.

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Table 15 Terminology and checklist for rock discontinuity

description

Revise first and last columns to read:

Orientation No. of sets

Dip amount only

in cores

Cannotbe described

or summarized in

coreswhere sets of

different dip are

present

Take number of

readings of dip

direction/dip, e.g.

015/018

Report as ranges

and on stereo netif appropriate

Record orientation

and spacing of sets

to each other and all

details for each set

Bibliography

Footnote to all ISRM references:

8) See also: ISRM Commission on Testing Methods. The Blue Book:The Complete

ISRM Suggested Methods for Rock Characterization, Testing and Monitoring:1974-

2006. Ulusay R. and Hudson J.A. (Eds.). International Society for Rock Mechanics.

2007.

bs 5930 a2 dpc feb 2010

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