1、BRITISH STANDARD BS 3680-10E: 1993 ISO 9195:1992 Measurement of liquid flow in open channels Part 10: Sediment transport Part 10E: Sampling and analysis of gravel bed materialBS3680-10E:1993 This British Standard, having been prepared under the directionof the Industrial-process Measurement and Cont
2、rol Standards Policy Committee, waspublished underthe authorityof the Standards Board and comes into effect on 15 January 1993 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference PCL/3 Draft for comment 89/28058 DC ISBN 0 580 21564 4 Committees responsib
3、le for this British Standard The preparation of this British Standard was entrusted by the Industrial-process Measurement and Control Standards Policy Committee (PCL/-) to Technical Committee PCL/3, upon which the following bodies were represented: Clyde River Purification Board Department of the En
4、vironment Institute of Measurement and Control Institution of Water and Environmental Management National Rivers Authority Water Services Association of England and Wales Welsh Office The following bodies were also represented in the drafting of the standard, through subcommittees and panels: Instit
5、ute of Freshwater Ecology Institute of Hydrology Institution of Civil Engineers University of Newcastle Upon Tyne Amendments issued since publication Amd. No. Date CommentsBS3680-10E:1993 BSI 08-1999 i Contents Page Committees responsible Inside front cover National foreword ii Introduction 1 1 Scop
6、e 1 2 Normative references 1 3 Definitions 1 4 Sampling equipment and procedures 1 5 Assignment of grain sizes 2 6 Frequency 2 7 Grain size/frequency distributions 3 8 Selection of sampling procedure 4 9 Determination of sample size 6 10 Errors 8 Figure 1 Pipe sampler 2 Figure 2 Gravel-cutter sample
7、r 3 Figure 3 Sampling site selection hierarchy 5 Table 1 Weighting factors for conversion of sampling procedures 6 Table 2 Students t values at 95% confidence level for various initial samplesizes 6 List of references Inside back coverBS3680-10E:1993 ii BSI 08-1999 National foreword This Part of BS3
8、680 has been prepared under the direction of the Industrial-process Measurement and Control Standards Policy Committee. It is identical with ISO9195:1992 Liquid flow measurement in open channels Sampling and analysis of gravel-bed material, published by the International Organization for Standardiza
9、tion (ISO). This standard is one of a series of Parts of BS3680-10on sediment transport. The other Parts are as follows. Part10B: Measurement of suspended sediment; Part 10C: Bed material sampling; Part 10D: Methods for determination of concentration, particle size distribution and relative density
10、of sediment in streams and canals. The Technical Committee has reviewed the provisions of ISO772:1988to which reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. A British Standard does not purport to include all the necessary provisions
11、 of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International Standard Corresponding British Standard ISO 4364:1977 BS 3680 Measurement of liquid f
12、low in open channels Part 10C:1980 Bed material sampling (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1to10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incor
13、porated. This will be indicated in the amendment table on the inside front cover.BS3680-10E:1993 BSI 08-1999 1 Introduction Bed material sampling techniques are used to obtain samples of sediment from the bed of a water course. Information with respect to sediment sizes is required for estimating re
14、sistance to flow in open channels and, together with hydraulic data, for calculating bed material load and in making morphological forecasts. 1 Scope 1.1 This International Standard specifies methods for sampling surface and subsurface gravel-bed material and the analytical procedures to determine t
15、he size distribution of gravel-bed material in open channels. 1.2 This International Standard applies to material having diameters of2mm and over. 1.3 In practice, gravel-bed material may consist of two components: a coarser layer on the surface and finer subsurface material. Surface material is par
16、ticularly relevant to investigations of the initiation of bed material movement and flow resistance, while subsurface material is mainly relevant to investigations of bed material transport. This International Standard does not attempt to correlate these two distinct populations. 1.4 There are two s
17、ampling techniques applicable to graded gravel-bed material. One method is to collect a definable in situ volume of material which is subsequently dealt with as a bulk sample. The second method is to sample material from the surface using one of several procedures. These two methods are discussed se
18、parately in this International Standard, and conversion factors are presented which are derived from idealized homogeneous material. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the t
19、ime of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO mai
20、ntain registers of currently valid International Standards. ISO 772:1988, Liquid flow measurement in open channels Vocabulary and symbols. ISO 4364:1977, Liquid flow measurement in open channels Bed material sampling. 3 Definitions For the purposes of this International Standard, the definitions giv
21、en in ISO772apply. 4 Sampling equipment and procedures 4.1 Surface samples 4.1.1 Grid sampling A grid is established over the surface of the gravel deposit and the pebbles immediately below the grid intersection points constitute the sample. Variants on this method include the use of a set of regula
22、rly spaced points, for example footsteps, as grid points and collecting the stone immediately underfoot after one or more steps, by reaching down with eyes closed and collecting the stone first touched by an outstretched finger. For small square grid samples, less than1m 2 , a vertical photograph ca
23、n be taken of the grid-covered area or a scaled photograph can be taken and a grid applied to the photograph. 4.1.2 Areal sampling All the surface pebbles within a selected area constitute the sample. If the gravel is exposed above water, it can be marked with spray paint to facilitate collection of
24、 the surface material. 4.1.3 Transect sampling All the stones exposed under a straight line (wire or string) across the sampling area are collected. 4.2 Bulk samples The samplers described in4.2.1 to4.2.4 are illustrative of the type that has been successfully used for bulk sampling. Actual dimensio
25、ns of the pipe and gravel-cutter samplers may be modified to suit the size of material being sampled. 4.2.1 Pipe sampler The sampler consists of a0,4m long 0,15m diameter open pipe fixed into the bottom of a 0,5m high 0,36m diameter open-topped barrel (seeFigure 1). The pipe, which protrudes0,26m be
26、low the base of the barrel, is worked into the gravel until the bottom of the barrel is flush with the surface of the bed. The material in the pipe can be removed by hand or by scoop into the base of the barrel. This prevents the fines in the sample from being washed away. On completion of sampling,
27、 the pipe sampler is removed by hand from the bed of the river. The sampler, which can be used in up to0,4m of water, enables the surface and subsurface material to be sampled separately.BS3680-10E:1993 2 BSI 08-1999 4.2.2 Freeze-core sampler A 20 mm internal diameter pipe with a fitted point is dri
28、ven into the gravel bed. A tube connected to a carbon dioxide gas tank which has exhaust orifices is inserted into the pipe and carbon dioxide is injected for a few minutes. As it escapes, the expanding gas chills the pipe which causes the pore water near the pipe to freeze. The pipe is removed from
29、 the bed using a hoist attached to a portable tripod. This produces a relatively undisturbed sample of bed material about100mm to150mm in diameter. However, at high stream velocities the size of the core is reduced due to heat transfer from the flowing water. 4.2.3 Gravel-cutter sampler The sampler
30、is made from an open drum0,4m long and0,5m diameter. A series of teeth are cut around the bottom perimeter and handles are added near the top. A rectangular metal sample box, 0,69m long, 0,31m deep and0,41m wide, with one end open and with handles on the narrow sides is placed on the downstream side
31、 of the sampler. The open end is curved along one of the0,41m sides to match the shape of the sampler and has an attached curved lip to hook on to it when in position. The opposite side of the box has a0,16m 0,25m opening with a200mesh screen across it (see Figure 2). One or two people work the samp
32、ler several centimetres into the bed. Samples of surface and subsurface material can then be collected by hand or with scoops. Divers are needed if the sampling depth exceeds0,5m. If the top of the sampler is submerged, the sample box is used for temporary storage to minimize the risk of losing fine
33、s. The screened opening permits a slight current to enter and move through the box, so that fines suspended during sampling are carried into and retained by the sample box together with the scooped material. On completion of sampling, the box is lifted out of the water by hand or with a boat winch.
34、4.2.4 Gravel excavators In boulder-bed channels, large samples are required and this necessitates the use of earth excavators or similar equipment to obtain the requisite volume of sample. 5 Assignment of grain sizes Once the sample has been collected or photographed, it is necessary to assign a lin
35、ear measure of the size of each stone. Generally, the intermediate or b-axis of the stone is used for this purpose and it can be measured with square mesh sieves, calipers or, in the case of surface samples, from photographs, assuming that the b-axis corresponds to the smaller visible axis. 6 Freque
36、ncy After the sampled gravel has been measured, it is divided into size classes, each class containing a percentage of the original sample. Approximately twenty classes are required although it is not necessary for them to have a fixed class interval. The percentages in each class can also be regard
37、ed as frequencies of occurrence. There are essentially two ways of establishing grain size/frequencies. Figure 1 Pipe samplerBS3680-10E:1993 BSI 08-1999 3 6.1 Frequency by mass The frequency of each size interval is expressed as the percentage by mass of the original sample falling into the interval
38、. Bulk samples are normally analysed in this manner. Surface samples can be expressed in this way, although calculations from photographs are based on estimates of particle volumes from size measurements, assuming a constant density. 6.2 Frequency by number The frequency of each size interval is exp
39、ressed as the percentage by number of the total number of particles in the original sample that fall in the interval. Surface samples, especially of coarse gravel and cobbles, are often analysed in this manner. 7 Grain size/frequency distributions 7.1 Surface samples Surface gravel samples, irrespec
40、tive of the type of sampling procedure and frequency determination, are characteristically log-normally distributed. The mean and standard deviation of the logarithmic distribution define the frequency distribution and they can be obtained by standard statistical procedures after transforming all th
41、e measurements to log 10values. The simplest way of determining the characteristics of the logarithmic distribution is to construct a cumulative size distribution (percentage finer than specified size) and plot this on logarithmic (base10)/normal probability paper. The median sample size is equal to
42、 the lg D 50 , where D 50is the median grain size (in millimetres). Figure 2 Gravel-cutter samplerBS3680-10E:1993 4 BSI 08-1999 The sample geometrical standard deviation (s) is estimated by or by where84%, 50%, and16% of the bed material are finer than or equal to D 84(in millimetres), D 50(in milli
43、metres), and D 16(in millimetres) respectively. The cumulative curve can also be used to establish the percentage (n) of the bed material finer than or equal to any specified grain diameter (D n millimetres). D 90 , D 84and D 65are commonly used for flow resistance investigations. 7.2 Bulk samples B
44、ulk samples, irrespective of the type of frequency classification, are approximately log-normally distributed and often modal. Although there are no simple statistical procedures for defining such distributions, values of grain diameter (D nmillimetres), which are less than or equal to n per cent of
45、 the sample can be obtained from a cumulative grain size curve. Typical values used in sediment transport investigations are D 35 , D 50and D 65 . 8 Selection of sampling procedure The following clauses are intended to give general guidance only. Specific investigations may require particular siting
46、. 8.1 Selection of site The first step in site selection is to delineate a homogeneous reach. This reach is defined by morphologic characteristics and is usually at least one meander wavelength, two pools and riffles, or50channel widths in length. Within a homogeneous reach, specific sites should be
47、 located for sampling of the coarser material, as this is associated with the channel-forming processes and sediment transport. In order of priority (see Figure 3) such sites are: a) near the upstream end of centrally located features such as mid-channel bars, diamond bars, and diagonal bars; b) nea
48、r the upstream end of a point bar; c) near the upstream end of a channel side bar; d) at the head of a riffle (normally for smaller streams). Consistency of sampling procedures and sampled sedimentary environments is essential. 8.2 Sampling The choice of sampling procedure is dependent on the charac
49、teristics of the bed material, the flow depth, the requirements of the survey, and the time available. 8.2.1 Surface samples 8.2.1.1 Grid sampling can be carried out on exposed gravel-bars and, using pacing techniques, for collecting stones in water up to about1m deep. Use of photographic techniques enables the size of the surface material larger than20mm to be estimated without disturbing its structure, allows rapid field survey, and can be used in clear water to a depth of0,5m. 8.2.1.2 Areal sampling procedures can be used underwater, to a max
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