The cutting of densely compacted sand under water - Dredging ...

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.The cutting of densely compacted sand under waterDr.ir. S.A. MiedemaAbstractThe use of dredgers to work at sea is strongly dependent upon the ability to work in waves ofvarious heights and lengths. As soon as the critical wave height is reached for a particularvessel, work ceases, so there is general interest in an improved performance with aconsequent reduction in down time. In order to extend the possibility of using floatingdredgers as opposed to semi-submersibles or fixed platforms, the application of swellcompensators for the excavating element, for example, cutter heads, is being attempted. Thisis not so simple as it might appear. In order to design swell compensators for the excavatingelement of dredgers, it is essential to have some understanding of the interactions such asthose between cutter head and soil when cutter suction dredgers are working at sea. Bothqualitative and quantitative predictions relating to this iteration must be made. This articledescribes an empirical, physical cutting model of the cutting forces and gives some results ofmodel tests with a cutter head in densely compacted sand.Pore Water, Shear Stress and CuttingTo optimize the dredging process it is important to understand the cutting process. This willenable predictions to be made in relation to the cutting forces that will be encountered whendifferent types of excavation elements are being used.The literature on this subject indicates that much is already known about the cutting of drysand. The models of Reece 1, 9 and Osman 8 are well known, but is doubtful whether thesemodels are also valid for densely packed sand which is cut under water. When investigatingthis, it was assumed that the rate at which the sand is deformed during the cutting process,was many times greater than the permeability of the sand (the k value).In addition, it was assumed that the deformation rate was so small that the inertial forcescould be neglected.The influence of the deformation rate upon the cutting forces is caused by the presence of avarying amount of pore water, the volume of which is related to the changes in the porevolume in consequence of changes in the shear stress in the sand.The phenomenon of dilatancy is especially important in this respect. In sand that is notcompletely saturated with water, the amount of air in the pores can easily follow the volumechanges because of the compressibility of the air (law of Pascal). This hardly influences thepore pressures. If cutting takes place under water, the inflowing water (which iscompressible) will encounter some resistance, resulting in the creation of a decrease inpressure in the pore water in the shear zone, compared to the hydrostatic pressure in thelocation of the shear zone.For a two-dimensional cutting process (blade length>>thickness of the layer cut) thefollowing can now be derived:Author: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.Figure 1: The two-dimensional cutting processIf a blade moves a distance of Δx in the sand (Figure 1), then for the sand element in theshear zone:Δ V = Δh⋅ Δx⋅ Δn⋅ L(1)In which:ΔV Volume increase in the sand element m 3Δl Length of the sand element mΔh Δl · sin (β) mβ Angle of the shear zone in relation to the direction of cutting degΔn Increase of pore volume in the shear zone, two-dimensional %Δx Movement of the blade in a period of time Δt mL Length of the blade mThe volume of the water that must flow into the sand element now equals:Author: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.Δ Q = ΔV / Δt= Δh⋅ Δn⋅ Δx / Δt⋅ L = vc ⋅ Δh⋅ Δn⋅ L(2)In which:ΔQ Flow rate m 3 /sv c Cutting velocity m/sThis is equivalent to:Δ = v ⋅ Δl⋅ L + v ⋅ Δl⋅ L(3)Q w1w2Hence:vw1+ v = v ⋅ Δn⋅sin(β)(4)w2cFrom the theory of soil mechanics 10 and the groundwater mechanic 11 , it is known that:v w *= k ⋅ i (law of Darcy) (5)In which:v w Total specific flow rate m/sk * Effective permeability coefficient m/si Gradient of water pressure -With:i = Δp /( ρ⋅ g ⋅ δ)(6)In which:ΔpPressure drop in the sand element in relation to the prevailing hydrostaticpressurePaρ The specific mass of water kg/m 3Author: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.g The gravitational constant m/s 2δThe actual path which the water must travel from the free, sand surface tothe shear zonemThus:Δ p = v ⋅ρ⋅g ⋅ δ /(7)w k *And:vww1 w2⋅ L = (v + v ) ⋅ L(8)Substituting this in equation (4) gives:Δ p = ρ⋅ g ⋅ v ⋅ Δn⋅ sin( β)⋅ δ /(9)c k *The average pressure drop in the shear zone can be found by integrating equation (9) over theshear zone, this gives:Δ p = a ⋅ρ⋅ g ⋅ v ⋅ Δn⋅h / k(10)av1c*In which:h The thickness of the layer cut ma 1 The proportionality constant -The fall in pressure is governed by a limiting factor. For a specific product of cutting velocityand cut layer thickness, the drop in pressure will be so great that the absolute pressure in thepores of the sand element may reach saturated water vapor pressure, dependent upon theprevailing environmental conditions. With an environmental temperature of 10° C, this watervapor pressure is about 12cm water column and can thus be disregarded in comparison to theatmospheric pressure. If the saturated water vapor pressure in the pores is reached, cavitationwill occur. The pressure in the pores cannot decrease further and the pressure drop Δpremains constant with an increasing cutting velocity (in the sand element in question).Author: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.Figure 2: Dilatancy during the cutting processFrom Figure 2 it can be seen that the distance between a sand element in the shear zone andthe free sand surface depends upon the location of the sand element in the dilatancy zone.This means that cavitation begins where the effective path of the water is the longest. Thiswill be in an area just in front of the edge of the blade (not at the edge of the blade). With anincrease in cutting velocity, the cavitation zone will extend until it includes almost the entiredilatancy zone.In the development of cavitation in the shear zone, three phases can now be distinguished.Phase 1: The cutting velocity is low and/or the cut layer is thin. Pressure decreases in thepores, but there is still no cavitation. There is a linear decrease in the average pressure withincreasing cutting velocity and the increasing layer thickness.Δ p = a ⋅ρ⋅ g ⋅ v ⋅ Δn⋅h / k(11)av1c*Phase 2: A transitional stage. The cutting velocity increases further and/or the cut layerbecomes thicker. Local cavitation develops in the dilatancy zone. With a further increase incutting velocity and/or in layer thickness, the cavitation zone continues to extend. Thepressure no longer decreases in a linear relation to the cutting velocity and the cut layerthickness, but in accordance with the following equation.[ a ⋅ρ⋅ g ⋅ Δn⋅ v ⋅h / k + a ⋅ρ⋅ g ⋅(y10) ]Δ pav = a2⋅ 3c * 4 +(12)Author: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.Phase 3: Cavitation occurring throughout almost the entire dilatancy zone. With increasedcutting velocity and/or cut layer thickness, the decrease in pressure remains more or lessconstant. At very high cutting velocities, cavitation can even occur behind the edge of thecutting blade.Δ p av = ρ⋅ g ⋅(y+ 10)(13)In which:y Water depth at the cutting position ma 2 , a 3 , a 4 Proportionality constants -Figure 3: Under pressure in the pores as a function of cutting velocity, cut layerthickness and the water depthThese three phases are shown in Figure 3 and can be approximated by the followingequation:avα 1cα2Δ p = ρ ⋅ g ⋅ Δn⋅ v ⋅ h / k(14)*Author: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.This approximation is also evident from Figure 3.The exponents α 1 and α 2 can vary between 0 and 1. When the cohesion and the initial grainstress are neglected, the average shear stress in the dilatancy zone can be demonstrated by:τav= Δp⋅ tan( ϕ)Thus:F c:: Δ p ⋅h⋅ L(15)In which:ϕ Angle of internal friction of the sand in the shear zone degLLength of the blade involved in cuttingmτ avThe average shear stress N/m 2For the cutting force in phase 1, the following is valid:Fc5c2= a ⋅ ρ ⋅ g ⋅ v ⋅ Δn⋅ h ⋅ L / k(16)*If localized cavitation occurs (phase 2) the following is valid:2[ a ⋅ρ⋅ g ⋅ v ⋅ Δn⋅ h ⋅ L / k + a ⋅ρ⋅ g ⋅ (y + 10) ⋅ h ⋅ L]Fc= a6⋅ 3 c* 4(17)With fully developed cavitation throughout the dilatancy zone (phase 3), the followingequation is valid:Fc7= a ⋅ρ⋅g ⋅(y+ 10) ⋅h⋅ L(18)The three phases can be approximated by the following equation:Fcα 1cα2+1= a ⋅ ρ⋅ g ⋅ Δn⋅ L ⋅ v ⋅ h / k(19)*In which:Author: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.a 5 , a 6 , a 7 , a Proportionality constants -F c Cutting force NThis equation forms the basis for the method of calculating the cutting forces required for theexcavation of densely compacted sand with a cutter head.Application of the Cutting Force Model to a CutterheadWhen using this model to make an estimate of the cutting forces, which are obtained inpractice, it is necessary to know the cutting velocity, the cutting direction, the cut layerthickness, the length of the blade involved in cutting and the permeability coefficient of thesand upon which the blades are acting.As the cut layer thickness and the cutting velocity are a function, amongst others, of theposition of the blade in the breach, the shape of the cutter head and of time, and as thepermeability coefficient is not necessarily constant, it is not easy to make an exact calculationof the forces acting on the cutter head. For example, the permeability after shear is greaterthan the permeability before shear. But it is possible by a good choice of characteristic layerthickness, length of the blade involved in cutting and the cutting velocity, to obtain a goodapproximation of the loads on the cutter head by substituting the characteristic values inequation (19). The relation which is found, however, is not purely theoretical.Photo 1: A view of the laboratory test standAuthor: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.Selection of the Characteristic ParametersIn selecting the characteristic cut layer thickness, cutting velocity and length of the bladeinvolved in cutting, it is important that these three parameters can be easily derived from anumber of known values. The cutting velocity is determined by the number of revolutions ofthe cutter head, the swing speed of the cutter suction dredger and the diameter of the cutterhead. In fact, the velocity at any one time is the sum of the vectors of the momentarycircumferential velocity of a blade and the swing velocity. The circumferential velocitychanges direction continually so the velocity of a blade is not constant in time, with respect todirection or speed (Figure 4). As the swing velocity is 6 to 10 times smaller than thecircumferential velocity, it will have little influence upon the cutting velocity. Thecircumferential velocity of the cutter head is selected for the characteristic cutting velocity.vc= 2⋅π ⋅ R ⋅n/ 60(20)ccIn which:n c the number of revolutions of the cutter head rpmR c The average radius of the cutter head mv c =v cf The characteristic cutting velocity m/sFigure 4: The variation of the cutting velocityAuthor: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.The cut layer thickness is also determined by the number of revolutions, the cutter diameter,the swing velocity and the number of blades on the cutter head. Figure 5 illustrates how thecut layer thickness varies as a function of time and the position of the blade. This figure alsoshows the epicyclic path of the blades for undercutting and overcutting. The figure illustrateshow the cut layer thickness decreases for the overcut, from a maximum value, when the bladeenters a breach, to almost 0 at the moment that a blade leaves the breach. For undercutting,the reverse is true. When undercutting, the shape of the cut layer is clearly different from theshape formed when overcutting (Figure 6), which is of consequence with regard to the cuttingforces.The area of the cross section cut, however, is characteristic for each blade. This is shown inFigure 7. This area can be determined by:A = v ⋅ 60⋅B /(n ⋅ z)(21)scIn which:v s The swing velocity m/sz The number of blades -B The height of the breach mFigure 5: The epicyclic path of the bladesThe path followed by the blade in the breach, if the effect of the swing speed is discounted,is:[(Rc − B) / Rc] ⋅ Rcs = arccos(22)Author: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.Thus the average cut layer thickness is:s[ n ⋅ z ⋅ R ⋅ arccos[ (R − B) / R]h = A / s = v ⋅ 60⋅B /(23)ccccIn which:h The characteristic cut layer thickness mSince, with a particular ratio between swing velocity and number of revolutions, the shape ofthe cut layer is fixed (Figure 6), equation (23) can be used for a characteristic cut layerthickness, Figure 6 also shows that as the ratio between the circumferential velocity and theswing velocity increases, the shapes of the cut layers formed during overcutting graduallybecome more similar.The part of the blade involved in cutting depends on size and shape of the blades and on thecross section of the cutter head in the breach (the theoretical cut surface as in Figure 8).Apparently, the theoretical cut surface in the working area increases almost linearly with theheight of the breach and the size of the step. A reasonable assumption would be that there is alinear increase in the cutting blade length in relation to the theoretical cut surface. For thecharacteristic cutting length of the blade, the following equation is given:L = 0.25⋅A ⋅ z /(24)th R cIn which:L The characteristic cutting blade length mA th The theoretical cut surface m 2For a disc-bottom cutter head with vertical blades it can be shown that the actual cuttingblade length is the same as the characteristic cutting blade length. For all other cutter headsthe actual cutting blade length is greater.With the calculated characteristic cutting velocity (eqn. 20), cut layer thickness (eqn. 23) andcutting blade length (eqn. 24) substituted in equation 19, a provisional cutting force modelcan be set up. The only unknown parameter in this model is the permeability coefficient.Other soil mechanical parameters are included in the proportionality constants, such as angleof internal friction and dilatancy angle. If it is assumed that localized cavitation occurs in thecut layers and across the length of the blade, then equation 25 is valid.α1ci = ai⋅[ 2⋅π ⋅ nc⋅ Rc/ 60] ⋅[ vs⋅ 60⋅B /[ nc⋅ z ⋅ Rc⋅arccos[ (Rc− B) / Rc][ 0.25⋅A ⋅ z / R ] ⋅[ 1/ k ]F⋅thc*α2+1(25)In which:Author: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.i=1 gives the radial force perpendicular to the swing directioni=2 gives the radial force in the swing directioni=3 gives the axial forceFor the driving torque, equation 26 is valid:α1c = am⋅ Rc⋅[ 2⋅π ⋅nc⋅ Rc/ 60] ⋅[ vs⋅ 60⋅B /[ nc⋅ z ⋅ Rc⋅ arccos[ (Rc− B) / Rc][ 0.25⋅A ⋅ z / R ] ⋅[ 1/ k ]M⋅thc*α2+1(26)The term (ρ · g · Δn) of equation 19 is included in the proportionality constants.Figure 6: The shape of the cut layerVerification of the Cutting Force ModelTo test the validity of the cutting force model a series of tests was carried out in thelaboratory "The Technology of Soil Movement" of the Delft University of Technology, usingcompacted sand with a d50 of 150 μm and a cone resistance of around 7 MPa. From thesetests the exponents of the characteristic cut layer thickness, cutting velocity and thecoefficient of proportionality were determined for seven cutter heads (scale 1:6, diameter 400mm).Author: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.Table I shows a summary of the overcutting tests and Table II of the undercutting tests.Photos 2 and 3 show two of the cutter heads which were used in the tests.During the laboratory tests it also appeared that for the type of sand used the cutting forcesand the driving torque increased almost linearly with the cone resistance of the sand. It wastherefore decided to make provisional modifications to the model to give:Fi= a ⋅ viα1c⋅ hα2+1⋅ L ⋅ qc(27)AndMc= am⋅ Rc⋅ vα1c⋅ hα2+1⋅ L ⋅ qc(28)In which:q c Cone resistance MPaThe tables I and II refer to these equations.Figure 7: The area of the cross-section of a cut layerAuthor: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.Figure 8: The theoretical cut surfacePhoto 2: A normal crown cutterhead used in the testsAuthor: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.Photo 3: A flattened cutterhead with disc wheel shaped blades used in the testsConclusionsThere was a good correlation between the mathematically derived cutting force model andthe results of the laboratory tests. Although a number of simplifications are applied, it appearsthat the model is reliable and that it can be generally applied to cutter heads, with the provisothat if an accurate prediction of the cutting forces is to be made, the coefficients andexponents for the equations must be determined by model tests for each type of cutter head.These equations lie at the basis of extended equations in which the effect of axial and radialmovements of the cutter head, perpendicular to the swing direction, have been included.These extended equations are implemented in the computer program "DREDMO" with whichthe nonlinear behaviour of a cutter suction dredger in swell can be determined (3, 4, 5 and 6)."DREDMO" can be used to investigate the effectiveness of various types of swellcompensators on cutter suction dredgers. The main issue, however, is the soil cutter headinteraction on which the behaviour of each swell compensator depends. It is thus veryimportant to have a good understanding of the cutting process and to be able to make anestimate of the cutting forces.Table I: Summary of overcutting testswith several types of cutter heads.Table II: Summary of undercutting testswith several types of cutter heads.Variation in swing velocity 7-35cm/sec Variation in swing velocity 4-31cm/secVariation in revolutions 24-180 rpm Variation in revolutions 25-180 rpmTotal number of tests 227 Total number of tests 185Author: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.Correlation coefficients 0.94-0.99 Correlation coefficients 0.91-0.99Bibliography1. Hettiaratchi, D.R.P. & Reece, A.R., "Symmetrical Three-dimensional Soil Failure". J.Terramech. (1964)4, (3), pp45-67.2. Joanknecht, L.W.F., "A Review of Dredge Cutter Head Modelling and Performance".Proc. WODCON VII, San Francisco, Califonia, USA., 1976.3. Keuning, P.J. & Journee, J., "Calculation Method for the Behaviour of a CutterSuction Dredger Oparating in Irregular Waves". Proc. WODCON X, Singapore 1983.4. Koning, J.de & Miedema, S.A. & Zwartbol, A., "Soil/Cutterhead Interaction underWave Conditions". Proc. WODCON X, Singapore, 1983.5. Miedema, S.A., "De interactie tussen snijkop en grond in zeegang". Proc. Baggerdag19/11/1982, T.H. Delft, 1982.6. Miedema, S.A., "Computersimulatie baggerschepen". De Ingenieur, Dec.1983.(Kivi/Misset):7. Os, A.G. van, "Behaviour of Soil when excavated under water". International CourseModern Dredging. June 1977, The Hague, The Netherlands.8. Osman, M.S., "The Mechanics of Soil Cutting Blades". J.A.E.R. 9 (4). Pp.313-328,1964.9. Reece, A.R., "The Fundamental Equation of Earth Moving Machinery". Proc. Symp.On Earth Moving Machinery. Institute of Mechanical Engineering, London, 1965.10. Terzaghi, K. & Peck, R.B., "Soil Mechanics in Engineering Practise". John Wiley &Sons, Inc., 1967.11. Verruijt, A., "Theory of Groundwater Flow". Macmillan, London, 1970.List of Symbols useda 1 ,a 2 ,a 3 ,a 4 The proportionality constants -A th The theoretical cut surface. m 2B The height of the breach. mF c Cutting force. kNg The gravitational constant. m/sec 2h Thickness of the layer cut. mΔh Height of the sand element, Δh = Δl·sin(β). mi Gradient of water pressure. -k * Effective permeability coefficient. m/secΔl Length of the sand element. mL Length of the blade involved in cutting. mn c The number of revolutions of the cutterhead. rpmΔn Increase of pore volume in the shear zone, two dimensional. %ΔpPressure drop in the sand element in relation to the prevailinghydrostatic pressure.kPaR c The average radius of the cutterhead. mAuthor: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.q c Cone resistance. kPaΔQ Flow rate. m 3 /secv c ,v cf Cutting velocity. m/secv s The swing velocity. m/secv w Total specific flow rate. m/secΔV Volume increase in the sand element. m 3Δx Movement of the blade in a period of time Δt. my Water depth at the cutting position. mz The number of blades. -β Angle of the shear zone in relation to the direction of cutting. deg.ϕ Angle of internal friction of the sand in the shear zone. deg.δThe actual path which the water must travel from the free sandsurface to the shear zone.mρ The specific mass of the water. kg/m 3τ av The average shear stress. kPaAuthor: Dr.ir.S.A.MiedemaCopyright: Dr.ir. S.A. Miedema

Bibliography Dr.ir. S.A. Miedema 1980-20101. Koert, P. & Miedema, S.A., "Report on the field excursion to the USA April 1981"(PDF in Dutch 27.2 MB). Delft University of Technology, 1981, 48 pages.2. Miedema, S.A., "The flow of dredged slurry in and out hoppers and the settlementprocess in hoppers" (PDF in Dutch 37 MB). ScO/81/105, Delft University ofTechnology, 1981, 147 pages.3. Miedema, S.A., "The soil reaction forces on a crown cutterhead on a swellcompensated ladder" (PDF in Dutch 19 MB). LaO/81/97, Delft University ofTechnology, 1981, 36 pages.4. Miedema, S.A., "Computer program for the determination of the reaction forces on acutterhead, resulting from the motions of the cutterhead" (PDF in Dutch 11 MB).Delft Hydraulics, 1981, 82 pages.5. Miedema, S.A. "The mathematical modeling of the soil reaction forces on acutterhead and the development of the computer program DREDMO" (PDF in Dutch25 MB). CO/82/125, Delft University of Technology, 1982, with appendices 600pages.6. Miedema, S.A.,"The Interaction between Cutterhead and Soil at Sea" (In Dutch).Proc. Dredging Day November 19th, Delft University of Technology 1982.7. Miedema, S.A., "A comparison of an underwater centrifugal pump and an ejectorpump" (PDF in Dutch 3.2 MB). Delft University of Technology, 1982, 18 pages.8. Miedema, S.A., "Computer simulation of Dredging Vessels" (In Dutch). DeIngenieur, Dec. 1983. (Kivi/Misset).9. Koning, J. de, Miedema, S.A., & Zwartbol, A., "Soil/Cutterhead Interaction underWave Conditions (Adobe Acrobat PDF-File 1 MB)". Proc. WODCON X, Singapore1983.10. Miedema, S.A. "Basic design of a swell compensated cutter suction dredge with axialand radial compensation on the cutterhead" (PDF in Dutch 20 MB). CO/82/134, DelftUniversity of Technology, 1983, 64 pages.11. Miedema, S.A., "Design of a seagoing cutter suction dredge with a swell compensatedladder" (PDF in Dutch 27 MB). IO/83/107, Delft University of Technology, 1983, 51pages.12. Miedema, S.A., "Mathematical Modeling of a Seagoing Cutter Suction Dredge" (InDutch). Published: The Hague, 18-9-1984, KIVI Lectures, Section Under WaterTechnology.13. Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (AdobeAcrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.14. Miedema, S.A., "Longitudinal and Transverse Swell Compensation of a CutterSuction Dredge" (In Dutch). Proc. Dredging Day November 9th 1984, DelftUniversity of Technology 1984.15. Miedema, S.A., "Compensation of Velocity Variations". Patent application no.8403418, Hydromeer B.V. Oosterhout, 1984.16. Miedema, S.A., "Mathematical Modeling of the Cutting of Densely Compacted SandUnder Water". Dredging & Port Construction, July 1985, pp. 22-26.17. Miedema, S.A., "Derivation of the Differential Equation for Sand Pore Pressures".Dredging & Port Construction, September 1985, pp. 35.18. Miedema, S.A., "The Application of a Cutting Theory on a Dredging Wheel (AdobeAcrobat 4.0 PDF-File 745 kB)". Proc. WODCON XI, Brighton 1986.19. Miedema, S.A., "Underwater Soil Cutting: a Study in Continuity". Dredging & PortConstruction, June 1986, pp. 47-53.

37. Miedema, S.A. & Becker, S., "The Use of Modeling and Simulation in the DredgingIndustry, in Particular the Closing Process of Clamshell Dredges", CEDA DredgingDays 1993, Amsterdam, Holland, 1993.38. Miedema, S.A., "On the Snow-Plough Effect when Cutting Water Saturated Sandwith Inclined Straight Blades (Adobe Acrobat 4.0 PDF-File 503 kB)". ASCE Proc.Dredging 94, Orlando, Florida, USA, November 1994.Additional Measurement Graphs. (Adobe Acrobat 4.0 PDF-File 209 kB).39. Riet, E. van, Matousek, V. & Miedema, S.A., "A Reconstruction of and SensitivityAnalysis on the Wilson Model for Hydraulic Particle Transport (Adobe Acrobat 4.0PDF-File 50 kB)". Proc. 8th Int. Conf. on Transport and Sedimentation of SolidParticles, 24-26 January 1995, Prague, Czech Republic.40. Vlasblom, W.J. & Miedema, S.A., "A Theory for Determining Sedimentation andOverflow Losses in Hoppers (Adobe Acrobat 4.0 PDF-File 304 kB)". Proc.WODCON IV, November 1995, Amsterdam, The Netherlands 1995.41. Miedema, S.A., "Production Estimation Based on Cutting Theories for Cutting WaterSaturated Sand (Adobe Acrobat 4.0 PDF-File 423 kB)". Proc. WODCON IV,November 1995, Amsterdam, The Netherlands 1995.Additional Specific Energy and Production Graphs. (Adobe Acrobat 4.0 PDF-File 145kB).42. Riet, E.J. van, Matousek, V. & Miedema, S.A., "A Theoretical Description andNumerical Sensitivity Analysis on Wilson's Model for Hydraulic Transport inPipelines (Adobe Acrobat 4.0 PDF-File 50 kB)". Journal of Hydrology &Hydromechanics, Slovak Ac. of Science, Bratislava, June 1996.43. Miedema, S.A. & Vlasblom, W.J., "Theory for Hopper Sedimentation (AdobeAcrobat 4.0 PDF-File 304 kB)". 29th Annual Texas A&M Dredging Seminar. NewOrleans, June 1996.44. Miedema, S.A., "Modeling and Simulation of the Dynamic Behavior of aPump/Pipeline System (Adobe Acrobat 4.0 PDF-File 318 kB)". 17th Annual Meeting& Technical Conference of the Western Dredging Association. New Orleans, June1996.45. Miedema, S.A., "Education of Mechanical Engineering, an Integral Vision". FacultyO.C.P., Delft University of Technology, 1997 (in Dutch).46. Miedema, S.A., "Educational Policy and Implementation 1998-2003 (versions 1998,1999 and 2000) (Adobe Acrobat 4.0 PDF_File 195 kB)". Faculty O.C.P., DelftUniversity of Technology, 1998, 1999 and 2000 (in Dutch).47. Keulen, H. van & Miedema, S.A. & Werff, K. van der, "Redesigning the curriculumof the first three years of the mechanical engineering curriculum". Proceedings of theInternational Seminar on Design in Engineering Education, SEFI-Document no.21,page 122, ISBN 2-87352-024-8, Editors: V. John & K. Lassithiotakis, Odense, 22-24October 1998.48. Miedema, S.A. & Klein Woud, H.K.W. & van Bemmel, N.J. & Nijveld, D., "SelfAssesment Educational Programme Mechanical Engineering (Adobe Acrobat 4.0PDF-File 400 kB)". Faculty O.C.P., Delft University of Technology, 1999.49. Van Dijk, J.A. & Miedema, S.A. & Bout, G., "Curriculum Development MechanicalEngineering". MHO 5/CTU/DUT/Civil Engineering. Cantho University Vietnam,CICAT Delft, April 1999.50. Miedema, S.A., "Considerations in building and using dredge simulators (AdobeAcrobat 4.0 PDF-File 296 kB)". Texas A&M 31st Annual Dredging Seminar.Louisville Kentucky, May 16-18, 1999.

51. Miedema, S.A., "Considerations on limits of dredging processes (Adobe Acrobat 4.0PDF-File 523 kB)". 19th Annual Meeting & Technical Conference of the WesternDredging Association. Louisville Kentucky, May 16-18, 1999.52. Miedema, S.A. & Ruijtenbeek, M.G. v.d., "Quality management in reality","Kwaliteitszorg in de praktijk". AKO conference on quality management ineducation. Delft University of Technology, November 3rd 1999.53. Miedema, S.A., "Curriculum Development Mechanical Engineering (Adobe Acrobat4.0 PDF-File 4 MB)". MHO 5-6/CTU/DUT. Cantho University Vietnam, CICATDelft, Mission October 1999.54. Vlasblom, W.J., Miedema, S.A., Ni, F., "Course Development on Topic 5: DredgingTechnology, Dredging Equipment and Dredging Processes". Delft University ofTechnology and CICAT, Delft July 2000.55. Miedema, S.A., Vlasblom, W.J., Bian, X., "Course Development on Topic 5:Dredging Technology, Power Drives, Instrumentation and Automation". DelftUniversity of Technology and CICAT, Delft July 2000.56. Randall, R. & Jong, P. de & Miedema, S.A., "Experience with cutter suction dredgesimulator training (Adobe Acrobat 4.0 PDF-File 1.1 MB)". Texas A&M 32nd AnnualDredging Seminar. Warwick, Rhode Island, June 25-28, 2000.57. Miedema, S.A., "The modelling of the swing winches of a cutter dredge in relationwith simulators (Adobe Acrobat 4.0 PDF-File 814 kB)". Texas A&M 32nd AnnualDredging Seminar. Warwick, Rhode Island, June 25-28, 2000.58. Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing theposition of backhoe dredges (Adobe Acrobat 4.0 PDF-File 257 kB)". Texas A&M32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.59. Miedema, S.A., "Automation of a Cutter Dredge, Applied to the Dynamic Behaviourof a Pump/Pipeline System (Adobe Acrobat 4.0 PDF-File 254 kB)". Proc. WODCONVI, April 2001, Kuala Lumpur, Malaysia 2001.60. Heggeler, O.W.J. ten, Vercruysse, P.M., Miedema, S.A., "On the Motions of SuctionPipe Constructions a Dynamic Analysis (Adobe Acrobat 4.0 PDF-File 110 kB)".Proc. WODCON VI, April 2001, Kuala Lumpur, Malaysia 2001.61. Miedema, S.A. & Zhao Yi, "An Analytical Method of Pore Pressure Calculationswhen Cutting Water Saturated Sand (Adobe Acrobat PDF-File 2.2 MB)". TexasA&M 33nd Annual Dredging Seminar, June 2001, Houston, USA 2001.62. Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour ofHydraulic Transport (Adobe Acrobat PDF-File 246 kB)". 21st Annual Meeting &Technical Conference of the Western Dredging Association, June 2001, Houston,USA 2001.63. Zhao Yi, & Miedema, S.A., "Finite Element Calculations To Determine The PorePressures When Cutting Water Saturated Sand At Large Cutting Angles (AdobeAcrobat PDF-File 4.8 MB)". CEDA Dredging Day 2001, November 2001,Amsterdam, The Netherlands.64. Miedema, S.A., "Mission Report Cantho University". MHO5/6, Phase Two, Missionto Vietnam by Dr.ir. S.A. Miedema DUT/OCP Project Supervisor, 27 September-8October 2001, Delft University/CICAT.65. (Zhao Yi), & (Miedema, S.A.),""(Finite Element Calculations To Determine The Pore Pressures When Cutting Water

Saturated Sand At Large Cutting Angles (Adobe Acrobat PDF-File 4.8 MB))". To bepublished in 2002.66. Miedema, S.A., & Riet, E.J. van, & Matousek, V., "Theoretical Description AndNumerical Sensitivity Analysis On Wilson Model For Hydraulic Transport Of SolidsIn Pipelines (Adobe Acrobat PDF-File 147 kB)". WEDA Journal of DredgingEngineering, March 2002.67. Miedema, S.A., & Ma, Y., "The Cutting of Water Saturated Sand at Large CuttingAngles (Adobe Acrobat PDF-File 3.6 MB)". Proc. Dredging02, May 5-8, Orlando,Florida, USA.68. Miedema, S.A., & Lu, Z., "The Dynamic Behavior of a Diesel Engine (AdobeAcrobat PDF-File 363 kB)". Proc. WEDA XXII Technical Conference & 34th TexasA&M Dredging Seminar, June 12-15, Denver, Colorado, USA.69. Miedema, S.A., & He, Y., "The Existance of Kinematic Wedges at Large CuttingAngles (Adobe Acrobat PDF-File 4 MB)". Proc. WEDA XXII Technical Conference& 34th Texas A&M Dredging Seminar, June 12-15, Denver, Colorado, USA.70. Ma, Y., Vlasblom, W.J., Miedema, S.A., Matousek, V., "Measurement of Density andVelocity in Hydraulic Transport using Tomography". Dredging Days 2002, Dredgingwithout boundaries, Casablanca, Morocco, V64-V73, 22-24 October 2002.71. Ma, Y., Miedema, S.A., Vlasblom, W.J., "Theoretical Simulation of theMeasurements Process of Electrical Impedance Tomography". Asian SimulationConference/5th International Conference on System Simulation and ScientificComputing, Shanghai, 3-6 November 2002, p. 261-265, ISBN 7-5062-5571-5/TP.75.72. Thanh, N.Q., & Miedema, S.A., "Automotive Electricity and Electronics". DelftUniversity of Technology and CICAT, Delft December 2002.73. Miedema, S.A., Willemse, H.R., "Report on MHO5/6 Mission to Vietnam". DelftUniversity of Technology and CICAT, Delft Januari 2003.74. Ma, Y., Miedema, S.A., Matousek, V., Vlasblom, W.J., "Tomography as aMeasurement Method for Density and Velocity Distributions". 23rd WEDATechnical Conference & 35th TAMU Dredging Seminar, Chicago, USA, june 2003.75. Miedema, S.A., Lu, Z., Matousek, V., "Numerical Simulation of a Development of aDensity Wave in a Long Slurry Pipeline". 23rd WEDA Technical Conference & 35thTAMU Dredging Seminar, Chicago, USA, june 2003.76. Miedema, S.A., Lu, Z., Matousek, V., "Numerical simulation of the development ofdensity waves in a long pipeline and the dynamic system behavior". Terra et Aqua,No. 93, p. 11-23.77. Miedema, S.A., Frijters, D., "The Mechanism of Kinematic Wedges at Large CuttingAngles - Velocity and Friction Measurements". 23rd WEDA Technical Conference& 35th TAMU Dredging Seminar, Chicago, USA, june 2003.78. Tri, Nguyen Van, Miedema, S.A., Heijer, J. den, "Machine ManufacturingTechnology". Lecture notes, Delft University of Technology, Cicat and CanthoUniversity Vietnam, August 2003.79. Miedema, S.A., "MHO5/6 Phase Two Mission Report". Report on a mission toCantho University Vietnam October 2003. Delft University of Technology andCICAT, November 2003.80. Zwanenburg, M., Holstein, J.D., Miedema, S.A., Vlasblom, W.J., "The Exploitationof Cockle Shells". CEDA Dredging Days 2003, Amsterdam, The Netherlands,November 2003.81. Zhi, L., Miedema, S.A., Vlasblom, W.J., Verheul, C.H., "Modeling and Simulation ofthe Dynamic Behaviour of TSHD's Suction Pipe System by using Adams". CHIDADredging Days, Shanghai, China, november 2003.

82. Miedema, S.A., "The Existence of Kinematic Wedges at Large Cutting Angles".CHIDA Dredging Days, Shanghai, China, november 2003.83. Miedema, S.A., Lu, Z., Matousek, V., "Numerical Simulation of the Development ofDensity Waves in a Long Pipeline and the Dynamic System Behaviour". Terra etAqua 93, December 2003.84. Miedema, S.A. & Frijters, D.D.J., "The wedge mechanism for cutting of watersaturated sand at large cutting angles". WODCON XVII, September 2004, HamburgGermany.85. Verheul, O. & Vercruijsse, P.M. & Miedema, S.A., "The development of a conceptfor accurate and efficient dredging at great water depths". WODCON XVII,September 2004, Hamburg Germany.86. Miedema, S.A., "THE CUTTING MECHANISMS OF WATER SATURATEDSAND AT SMALL AND LARGE CUTTING ANGLES". International Conferenceon Coastal Infrastructure Development - Challenges in the 21st Century. HongKong,november 2004.87. Ir. M. Zwanenburg , Dr. Ir. S.A. Miedema , Ir J.D. Holstein , Prof.ir. W.J.Vlasblom,"REDUCING THE DAMAGE TO THE SEA FLOOR WHEN DREDGINGCOCKLE SHELLS". WEDAXXIV & TAMU36, Orlando, Florida, USA, July 2004.88. Verheul, O. & Vercruijsse, P.M. & Miedema, S.A., "A new concept for accurate andefficient dredging in deep water". Ports & Dredging, IHC, 2005, E163.89. Miedema, S.A., "Scrapped?". Dredging & Port Construction, September 2005.90. Miedema, S.A. & Vlasblom, W.J., " Bureaustudie Overvloeiverliezen". In opdrachtvan Havenbedrijf Rotterdam, September 2005, Confidential.91. He, J., Miedema, S.A. & Vlasblom, W.J., "FEM Analyses Of Cutting Of AnisotropicDensely Compacted and Saturated Sand", WEDAXXV & TAMU37, New Orleans,USA, June 2005.92. Miedema, S.A., "The Cutting of Water Saturated Sand, the FINAL Solution".WEDAXXV & TAMU37, New Orleans, USA, June 2005.93. Miedema, S.A. & Massie, W., "Selfassesment MSc Offshore Engineering", DelftUniversity of Technology, October 2005.94. Miedema, S.A., "THE CUTTING OF WATER SATURATED SAND, THESOLUTION". CEDA African Section: Dredging Days 2006 - Protection of thecoastline, dredging sustainable development, Nov. 1-3, Tangiers, Morocco.95. Miedema, S.A., "La solution de prélèvement par désagrégation du sable saturé eneau". CEDA African Section: Dredging Days 2006 - Protection of the coastline,dredging sustainable development, Nov. 1-3, Tangiers, Morocco.96. Miedema, S.A. & Vlasblom, W.J., "THE CLOSING PROCESS OF CLAMSHELLDREDGES IN WATER-SATURATED SAND". CEDA African Section: DredgingDays 2006 - Protection of the coastline, dredging sustainable development, Nov. 1-3,Tangiers, Morocco.97. Miedema, S.A. & Vlasblom, W.J., "Le processus de fermeture des dragues à bennepreneuse en sable saturé". CEDA African Section: Dredging Days 2006 - Protectionof the coastline, dredging sustainable development, Nov. 1-3, Tangiers, Morocco.98. Miedema, S.A. "THE CUTTING OF WATER SATURATED SAND, THESOLUTION". The 2nd China Dredging Association International Conference &Exhibition, themed 'Dredging and Sustainable Development' and in Guangzhou,China, May 17-18 2006.99. Ma, Y, Ni, F. & Miedema, S.A., "Calculation of the Blade Cutting Force for smallCutting Angles based on MATLAB". The 2nd China Dredging Association

International Conference & Exhibition, themed 'Dredging and SustainableDevelopment' and in Guangzhou, China, May 17-18 2006.100. ,"" (download). The 2nd China DredgingAssociation International Conference & Exhibition, themed 'Dredging andSustainable Development' and in Guangzhou, China, May 17-18 2006.101. Miedema, S.A. , Kerkvliet, J., Strijbis, D., Jonkman, B., Hatert, M. v/d, "THEDIGGING AND HOLDING CAPACITY OF ANCHORS". WEDA XXVI ANDTAMU 38, San Diego, California, June 25-28, 2006.102. Schols, V., Klaver, Th., Pettitt, M., Ubuan, Chr., Miedema, S.A., Hemmes, K.& Vlasblom, W.J., "A FEASIBILITY STUDY ON THE APPLICATION OF FUELCELLS IN OIL AND GAS SURFACE PRODUCTION FACILITIES". Proceedingsof FUELCELL2006, The 4th International Conference on FUEL CELL SCIENCE,ENGINEERING and TECHNOLOGY, June 19-21, 2006, Irvine, CA.103. Miedema, S.A., "Polytechnisch Zakboek 51 ste druk, Hoofdstuk G:Werktuigbouwkunde", pG1-G88, Reed Business Information, ISBN-10:90.6228.613.5, ISBN-13: 978.90.6228.613.3. Redactie: Fortuin, J.B., van Herwijnen,F., Leijendeckers, P.H.H., de Roeck, G. & Schwippert, G.A.104. MA Ya-sheng, NI Fu-sheng, S.A. Miedema, "Mechanical Model of WaterSaturated Sand Cutting at Blade Large Cutting Angles", Journal of Hohai UniversityChangzhou, ISSN 1009-1130, CN 32-1591, 2006.绞 刀 片 大 角 度 切 削 水 饱 和 沙 的 力 学 模 型 , 马 亚 生 [1] 倪 福 生 [1] S.A.Miedema[2],《 河 海 大 学 常 州 分 校 学 报 》-2006 年 20 卷 3 期 -59-61 页105. Miedema, S.A., Lager, G.H.G., Kerkvliet, J., “An Overview of DragEmbedded Anchor Holding Capacity for Dredging and Offshore Applications”.WODCON, Orlando, USA, 2007.106. Miedema, S.A., Rhee, C. van, “A SENSITIVITY ANALYSIS ON THEEFFECTS OF DIMENSIONS AND GEOMETRY OF TRAILING SUCTIONHOPPER DREDGES”. WODCON ORLANDO, USA, 2007.107. Miedema, S.A., Bookreview: Useless arithmetic, why environmental scientistscan't predict the future, by Orrin H. Pilkey & Linda Pilkey-Jarvis. Terra et Aqua 108,September 2007, IADC, The Hague, Netherlands.108. Miedema, S.A., Bookreview: The rock manual: The use of rock in hydraulicengineering, by CIRIA, CUR, CETMEF. Terra et Aqua 110, March 2008, IADC, TheHague, Netherlands.109. Miedema, S.A., "An Analytical Method To Determine Scour". WEDAXXVIII & Texas A&M 39. St. Louis, USA, June 8-11, 2008.110. Miedema, S.A., "A Sensitivity Analysis Of The Production Of Clamshells".WEDA XXVIII & Texas A&M 39. St. Louis, USA, June 8-11, 2008.111. Miedema, S.A., "An Analytical Approach To The Sedimentation Process InTrailing Suction Hopper Dredgers". Terra et Aqua 112, September 2008, IADC, TheHague, Netherlands.112. Hofstra, C.F., & Rhee, C. van, & Miedema, S.A. & Talmon, A.M., "On TheParticle Trajectories In Dredge Pump Impellers". 14th International ConferenceTransport & Sedimentation Of Solid Particles. June 23-27 2008, St. Petersburg,Russia.113. Miedema, S.A., "A Sensitivity Analysis Of The Production Of Clamshells".WEDA Journal of Dredging Engineering, December 2008.

114. Miedema, S.A., "New Developments Of Cutting Theories With Respect ToDredging, The Cutting Of Clay And Rock". WEDA XXIX & Texas A&M 40.Phoenix Arizona, USA, June 14-17 2009.115. Miedema, S.A., "A Sensitivity Analysis Of The Scaling Of TSHD's". WEDAXXIX & Texas A&M 40. Phoenix Arizona, USA, June 14-17 2009.116. Liu, Z., Ni, F., Miedema, S.A., “Optimized design method for TSHD’s swellcompensator, basing on modelling and simulation”. International Conference onIndustrial Mechatronics and Automation, pp. 48-52. Chengdu, China, May 15-16,2009.117. Miedema, S.A., "The effect of the bed rise velocity on the sedimentationprocess in hopper dredges". Journal of Dredging Engineering, Vol. 10, No. 1 , 10-31,2009.118. Miedema, S.A., “New developments of cutting theories with respect tooffshore applications, the cutting of sand, clay and rock”. ISOPE 2010, Beijing China,June 2010.119. Miedema, S.A., “The influence of the strain rate on cutting processes”. ISOPE2010, Beijing China, June 2010.120. Ramsdell, R.C., Miedema, S.A., “Hydraulic transport of sand/shell mixtures”.WODCON XIX, Beijing China, September 2010.121. Abdeli, M., Miedema, S.A., Schott, D., Alvarez Grima, M., “The applicationof discrete element modeling in dredging”. WODCON XIX, Beijing China,September 2010.122. Hofstra, C.F., Miedema, S.A., Rhee, C. van, “Particle trajectories nearimpeller blades in centrifugal pumps. WODCON XIX, Beijing China, September2010.123. Miedema, S.A., “Constructing the Shields curve, a new theoretical approachand its applications”. WODCON XIX, Beijing China, September 2010.124. Miedema, S.A., “The effect of the bed rise velocity on the sedimentationprocess in hopper dredges”. WODCON XIX, Beijing China, September 2010.