CN101798821A - Local scouring forecast method of coastwise wind-electricity tower footing of muddy coast - Google Patents

Abstract

The invention discloses a local scouring forecast method of a coastwise wind-electricity tower footing of a muddy coast, which comprises the following steps of: constructing a two-dimensional tidal current mathematical model and a two-dimensional wave mathematical model of an engineering sea area respectively, analyzing the hydrodynamic condition of the engineering sea area by the two-dimensional tidal current mathematical model and the two-dimensional wave mathematical model and providing oceanic kinetic parameters for determining the maximum depth of the local scouring of the wind-electricity tower footing; selecting Jones and Sheppard formulae which are suitable for bed load which is silver sand particles and an Hanhaiqian formula as a fundamental formula for estimating the local scouring depth of the wind-electricity tower footing of a coastwise wind farm of the muddy coast; and forecasting the maximum depth of the local scouring of the wind-electricity tower footing of the coastwise wind farm of the muddy coast by adopting the modified formula. The invention can better reflect the motion rules of the tidal current and the wave of a prototype, can provide the reliable oceanic kinetic parameters for the calculation of the local scouring depth of the wind-electricity tower footing and has a reasonable and credible calculation result.

Description

Local scouring forecast method of coastwise wind-electricity tower footing of muddy coast

Technical field

The present invention relates to a kind of local scouring forecast method of coastwise wind-electricity tower footing of muddy coast.

Background technology

For the coastal waters wind energy turbine set,, may have influence on the stability of wind-electricity tower because the acting in conjunction of wave and trend will produce local scour around wind-electricity tower.Research and analyse the local scour problem of wind-electricity tower under the wave current acting in conjunction,, have important theory and practice significance for the basic engineering of coastal waters wind electric field blower column foot.

At present, China's offshore wind farm ground zero, domesticly also do not calculate the formula that marine pile foundation is washed away this respect, and the wind-electricity tower scour depth plays crucial effects to the design of wind-electricity tower, and scour depth need be taken all factors into consideration from aspects such as technology, economy, safety, and the scour depth design is little, influence the stable of blower fan column foot, scour depth is big, and engineering quantity strengthens, and investment increases.Therefore, determine that rationally the scour depth of blower fan column foot not only has theory significance, and have important economic implications.

Mainly undertaken for the research of pile foundation local scour at present by field observation and model testing, and based on the latter.

Building substrate on every side generation local scour is hydrodynamic condition and geological characteristics type results of interaction in fact under the wave current acting in conjunction.Building is strengthened near the building some areas current for the reaction of wave current or produces whirlpool, this local strengthening or the current that whirlpool occurs have changed undercutting stress field and the flow field around the cylinder, make originally static sediment incipient motion and defeatedly move that (wave lifts sand, sediment tide transport), promptly produce local scour, formed scour hole.Under the effect of wave and current, generally should come to be discussed respectively according to the size of body diameter D and wavelength L ratio.When D/L＜0.1-0.15 is the minor diameter situation, and cylinder is to almost not influence of wave field, and the reason that causes local scour is the whirlpool that the wave current occur during through cylinder.When D/L＞0.1-0.15, be the major diameter situation, at this moment refraction and diffraction can take place in wave, and the reason that causes local scour is the kinetic undercutting power of the water particle of various composite waves.The basis of offshore wind generating group is when belonging to minor diameter one class, and the reason that causes local scour is the whirlpool that occurs around the cylinder.Because the degree of depth of scour hole is to the stability influence maximum of building, thereby be the key of local scour problem

From the elaboration of front as can be seen, the local scour of small diameter cylinders research obtained many achievements, but because the pile local scour relates to multiple factors such as water, sand, stake footpath, problem is extremely complicated, and still there is certain problem in present achievement in research:

At first, the pile local scour achievement in research on the river is more, and because the effect of trend, wave etc. many than flow action complexity in the river course in the ocean, so the pile local scour achievement in research in the ocean is less;

Secondly, the situation of coarse sand is only considered in most scale-model investigation, because less to mud matter flour sand seashore pile local scour research, neither one is fit to the pile local scour computation schema of this type of seashore fully.

The 3rd, the influence of trend to the pile local scour degree of depth only considered in many researchs, often wave action do not embodied in the formula, ignored the effect of wave, and formula is not carried out this correction on the one hand, therefore make the result of calculation of formula and actual conditions that bigger gap be arranged.

Summary of the invention

The objective of the invention is to forecast the maximum local scour degree of depth of silt coast coastal waters wind energy turbine set wind-electricity tower, have computation schema at this type of seashore than strong adaptability in the hope of seeking.

The present invention adopts following technical scheme for achieving the above object:

Local scouring forecast method of coastwise wind-electricity tower footing of muddy coast of the present invention comprises the steps:

(1) sets up Mathematical Modeling

Set up the two-dimentional tidal current mathematical model and the two-dimentional wave mathematical model in engineering marine site respectively, and come the hydrodynamic condition in analysis project marine site with two-dimentional tidal current mathematical model and two-dimentional wave mathematical model, for the depth capacity of determining the wind-electricity tower local scour provides the drive marine parameter;

(2) determine fundamental formular

Jones and Sheppard formula:

$\frac{D_s}{d_p}=c_1\left(\frac{V_m\left(1\right)-V_d\left(1\right)}{V_{\mathrm{cr}}\left(1\right)}\right)+c_2---\left(1\right)$

${\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HSA00000047810500022.png,HSA00000047810500031.png"\; state="\{\{state\}\}">c</figure-callout>}}_1=(c_3-c_2){(\frac{V_m\left(1\right)}{V_{\mathrm{cr}}\left(1\right)}-1)}^{-1}---\left(2\right)$

${\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HSA00000047810500022.png"\; state="\{\{state\}\}">c</figure-callout>}}_2=2.4\tanh \left[2.18{\left(\frac{D}{d_p}\right)}^{2/3}\right]---\left(3\right)$

${\mathrm{<figure-callout\; id="3"\; label="c"\; filenames="HSA00000047810500022.png,HSA00000047810500031.png"\; state="\{\{state\}\}">c</figure-callout>}}_3=\tanh \left[2.18{\left(\frac{D}{d_p}\right)}^{2/3}\right]{[-0.279+0.049\exp \left(\lg \frac{d_p}{d_{50}}\right)+0.78{\left(\lg \frac{d_p}{d_{50}}\right)}^{-1}]}^{-1}---\left(4\right)$

The Han Hai formula of holding high up:

D _s＝8.48k ₁k ₂B ^0.326V _d(1) ^0.628D ^0.193d ₅₀ ^0.167(5)

The mean flow rate formula of wave water particle:

$V_i\left(2\right)=0.2\frac{H}{D}C---\left(6\right)$

$C=\frac{\mathrm{<figure-callout\; id="2"\; label="gT"\; filenames="HSA00000047810500022.png"\; state="\{\{state\}\}">gT</figure-callout>}}{2\mathrm{\&pi;}}\mathrm{thkD}---\left(7\right)$

$k=\frac{2\mathrm{\&pi;}}{L}---\left(8\right)$

Wave current mixture velocity formula:

V _i(3)＝V _i(1)+V _i(2) (9)

Jones and Sheppard formula after the consideration wave action:

$\frac{D_s}{d_p}=c_1\left[\frac{V_m\left(3\right)-V_d\left(3\right)}{V_{\mathrm{cr}3}}\right]+c_2---\left(10\right)$

${\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HSA00000047810500022.png,HSA00000047810500031.png"\; state="\{\{state\}\}">c</figure-callout>}}_1=(c_3-c_2){(\frac{V_m\left(3\right)}{V_{\mathrm{cr}}\left(3\right)}-1)}^{-1}---\left(11\right)$

${\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HSA00000047810500022.png"\; state="\{\{state\}\}">c</figure-callout>}}_2=2.4\tanh \left[2.18{\left(\frac{D}{d_p}\right)}^{2/3}\right]---\left(3\right)$

${\mathrm{<figure-callout\; id="3"\; label="c"\; filenames="HSA00000047810500022.png,HSA00000047810500031.png"\; state="\{\{state\}\}">c</figure-callout>}}_3=\tanh \left[2.18{\left(\frac{D}{d_p}\right)}^{2/3}\right]{[-0.279+0.049\exp \left(\lg \frac{d_p}{d_{50}}\right)+0.78{\left(\lg \frac{d_p}{d_{50}}\right)}^{-1}]}^{-1}---\left(4\right)$

Consider Han Hai after the wave action formula of holding high up:

D _s＝8.48k ₁k ₂B ^0.326V _d(3) ^0.628D ^0.193d ₅₀ ^0.167(12)

More than the implication of each symbol representative be:

D _sBe pile foundation limit scour depth; d _pBe the stake footpath; D is a maximum water depth; V _i(1) is flow velocity under the pure trend; V _i(2) be the mean flow rate of wave water particle; V _i(3) be the wave current mixture velocity; V _d(j) be the bottom average largest speed of current; V _Cr(j) be the critical initial velocity of silt; V _m(j) be mean velocity in vertical; d ₅₀Be the sand grain median particle diameter; k ₁Be foundation pile layout coefficient, bar shaped gets 1.0, quincunxly gets 0.862; k ₂For foundation pile is arranged vertically coefficient, straight stake gets 1.0, and taper pile gets 1.176; B is the width that on average blocks water under the maximum water depth condition; H is a wave height; C is a velocity of wave; K is a wave number; L is a wavelength;

(3) formula correction

According to " harbour hydrology standard " (JTJ213-98) in the mean flow rate formula of wave water particle, try to achieve the mean flow rate of water particle under the wave action, then the flow velocity under itself and the pure trend is superposeed, obtain the wave current mixture velocity, and replace the flow velocity V under the pure trend in the step (2) with this wave current mixture velocity _i(1), obtains suitable computation schema;

(4) analytical calculation

Choose the described suitable computation schema of step (3), the depth capacity of forecast silt coast coastal waters wind energy turbine set wind-electricity tower local scour.

The present invention can forecast the maximum local scour degree of depth of silt coast coastal waters wind energy turbine set wind-electricity tower.It has following advantage:

(1) because the local scour degree of depth and the bed-sit particle diameter of pile have confidential relation, and many formula all are to be based upon on the basis of coarse sand, to mud matter flour sand seashore and inapplicable.The present invention has chosen and has been applicable to that bed-sit is the Jones of fine sand particle and Sheppard formula and the Han Hai fundamental formular of formula as the estimation silt coast coastal waters wind energy turbine set wind-electricity tower local scour degree of depth of holding high up.

(2) the present invention utilizes the flow velocity of water particle under the flow velocity of the water particle that the formula introduced in the standard produces wave action down and the pure trend to superpose, obtain the wave current mixture velocity, and replace flow velocity under the pure trend in the former basic formula with this wave current mixture velocity.The local scour degree of depth and the actual deviation that obtain are less, and be more reasonable.

(3) the two-dimentional tidal current mathematical model and the two-dimentional wave mathematical model scope of the present invention's foundation have covered whole engineering marine site, and model is through the field data checking, result of calculation is rationally credible, the characteristics of motion that can reflect substance trend and wave preferably can provide reliable drive marine parameter for the local scour depth calculation of wind-electricity tower.

Description of drawings

Fig. 1: the two-dimentional tidal current mathematical model in engineering marine site;

Fig. 2: two-dimentional wave mathematical model;

Weather station, Fig. 3-1 Xiangshui County annual average wind speed its annual change histogram 1980-2005;

Annual mean wind speed year over the years border, weather station, Fig. 3-2 Xiangshui County changes histogram;

The preliminary arrangement diagram of coastal waters, Fig. 3-3 Xiangshui County wind energy turbine set first phase demonstration project.

The specific embodiment

Be elaborated below in conjunction with the technical scheme of accompanying drawing to invention:

Natural situation

Wind energy turbine set first phase demonstration project position, coastal waters, Xiangshui County 121 ° 29 of east longitude ', 30 ° 20 of north latitude ', be positioned at and irritate on the south the river mouth, face each other across the river with Xiangshui County's wind energy turbine set that in the total installation of generating capacity of building is 201MW in marine site to the north of the mouth of the middle mountains and rivers.

Present location, weather station, Xiangshui County is positioned at the rural area of 3 groups of export-oriented comprehensive agricultural development district, Xiangshui County port, Xiangshui County communities, 34 ° 12 of north latitude ', 119 ° 34 of east longitude ', observation field height above sea level 3.7m is positioned at the about 30km of southwest place, wind energy turbine set site.The weather station is built in May nineteen sixty-five, and resettlement was to the present location in 1999.Before 2003, the weather station instrument for wind measurement adopts EL type electric wind aerovane, adopts EL type electric wind aerovane and EC9-1 high dynamic performance anemometer merger operation in 2003～2004, rises in 2005 to adopt the observation of EC9-1 high dynamic performance anemometer fully.The weather station basic condition sees Table 2-1:

Table weather station, 2-1 Xiangshui County basic condition list

Table 2-2 Xiangshui County weather station is mean wind speed statistics outcome table (m/s) month by month over the years

Weather station, Xiangshui County 1966～2005 mean wind speed for many years is 2.9m/s, the wind speed situation of change over the years from weather station, Xiangshui County, in generation nineteen sixty, establishes back, station wind speed and changes more steady, the 1970's began to descend to some extent, 1980, in generation nineteen ninety, obviously descend, and just replys to some extent up to change of address back wind speed in 1999.Change histogram as can be seen from wind speed in year, spring, wind speed was bigger, and be the big wind and moon-scene April, and autumn, wind speed was less, and be the little wind and moon-scene 8～October.

Xiangshui County's weather station over the years month by month mean wind speed statistics achievement see Table 2-2.Annual average wind speed its annual change histogram is seen Fig. 3-1, and mean wind speed year over the years border variation histogram is seen Fig. 3-2.

Among the marine anemometer tower in Xiangshui County is under preparation, do not have the field measurement data at present, use for reference the marine analysis of eolian fruit, the offshore 5km of surveying in the similar area of coastline, Jiangsu Province tendency, 70m height wind-resources is than the high 0.3m/s of seashore, and 60m height wind-resources is than the high about 0.4m/s of seashore.Aggregate analysis, marine underlying surface roughness is very little, so the wind speed with altitude variation is very little, and wind shear exponent is less than 0.1, and then about the marine 5km in area, Xiangshui County, 80m and 65m height wind speed are about 7.1m/s and 7.0m/s, see table 2-3 for details.

According to 1980～2005 years observational data statistics of Xiangshui County's weather station, main meteorological element characteristic value sees Table 2-4.

Table 2-4 Xiangshui County weather station main meteorological element characteristic value

Annotate: 1966～2005 years times of statistics

Northern coastal sea area, Jiangsu is subjected to the control of South Yellow Sea rotatory standing wave system, belongs to non-regular semi-diurnal tides type.

At certain measuring point of surrounding waters, Xiangshui County (34 ° of 45 ' east longitudes of north latitude 119 ° 25 '), collected morning and evening tides data on 1 day～May 31 May in 2007, see Table 2-5.

By table 2-5 as can be known, the high 537cm of this measuring point in May, 2007 climax, minimum tidal height 21cm, extreme tide range 516cm.

119 ° of 25 ' tidal data tables of table 34 ° of 45 ' east longitudes of 2-5 in May, 2007 north latitude

Annotate: 1. tidal datum 290cm under mean sea level; 2. when front two was represented in the time of tide, back two representatives divided, as 0046 expression 0: 46.

Though in coastal waters, Xiangshui County wind energy turbine set is built the zone (being positioned at the about 60km in the northwestward of coastal waters, Xiangshui County wind energy turbine set), the measuring point region depth of water is not darker, is about 15～20m for last table measuring point, the data of this measuring point have certain representativeness.

Wind energy turbine set sea area, coastal waters, Xiangshui County is the more weak zone of jiangsu coast trend intensity, and the mean springs flow velocity is about 0.64m/s, and main flow direction is NNW-SSE, and strength of flood can reach 1.3m/s, and strength of ebb can reach 1.4m/s.1h or high water time begin to transfer to ebb current before this sea area climax, and 2h after the climax～3h ebb tide flow field is the strongest, and 5h～6h transfers flood current again to after the climax.

Xiangshui County bank lacks long-term wave observation data, considers that it is nearer apart from Lianyun Harbour oceanographic station, so the long-term field data of Lianyun Harbour oceanographic station has certain reference value.

Wave observation erect-position in Lianyun Harbour is in thing Lian Dao northwest side, and the depth of water of surveying the ripple floating drum is theoretical depth datum-5.6m, and according near sea-floor relief, this station observed result can be represented the ripple key element at 5m depth of water place.This station observed result shows that wave is based on stormy waves, and it is auxilliary surging, and its frequency of occurrences is respectively 63%, 28%, and Chang Lang is to being NE, NNE to, high seas to being NE, N and NNE to, mean wave height (H for many years _1/10) be 0.6m, the actual measurement maximum wave height is 5.0m, the wave height at different levels frequency of occurrences for many years are: H _1/10〉=2.0m frequency is 2.06%, H _1/10〉=3.5m frequency is 0.009%, and be 3s average period, and the actual measurement maximum cycle is 8.3s.

According to the natural background of coastal waters, Xiangshui County seashore and the position of planning to build marine wind electric field, two offshore survey holes have been arranged, ", north latitude 34 ° 33 ' 37.1 " (1# exploratory hole) and 120 ° 07 ' 11.5 of the east longitude " (2# exploratory hole) that lay respectively at east longitude 119 ° 53 ' 03.8.Disclose according to boring, distribution of strata is as follows, sees table 2-6 and table 2-7 for details:

(1) 1# exploratory hole

1. layer silt clay: grey, stream is moulded, folder silt thin layer, top layer 0.8m flour sand, layer end degree of depth 17.60m, thick 17.60m.

2. the layer flour sand: grey, in close, sorting is better, the bottom contains a small amount of gravel, diameter 0.5-1.0cm, inferior circle is main, the layer end degree of depth 21.50m, thick 3.90m.

3. the layer flour sand: grey, closely knit, sorting is better, 23.0-23.5m presss from both sides more silty clay thin layer.Do not expose, thickness is greater than 8.60m.

Table 2-6 1# exploratory hole resistance to compression limit collateral resistance standard value qsik and extreme end resistance standard value qpk

(2) 2# exploratory hole

1. layer mud matter silty clay: grey, stream is moulded, folder silt thin layer, top 0.3m is a flour sand.Layer end degree of depth 12.20m, thickness 12.20m.

2. layer flour sand: grey, in close-closely knit, sorting is general, the folder fine sand contains a small amount of shell fragment, cohesive soil is mixed in soil layer top and bottom, a small amount of gravel in bottom, diameter 1-2cm, inferior circle is main, layer end degree of depth 28.00m, thickness 15.80cm.

3. layer silt clay: grey, stream is moulded, and contains shell fragment, bottom folder silt, the layer end degree of depth 31.80, thickness 3.80m.

4. layer flour sand: grey, in close-closely knit, the sand content shell fragment, bottom local folder lam is not exposed, thickness is greater than 6.35m.

Table 2-7 2# surveys the hole and visits resistance to compression limit collateral resistance standard value qsik and extreme end resistance standard value qpk

According to Jiangsu Earthquake Bureau data in 1994, the jiangsu coast zone is positioned at the middle and lower reach of Yangtze River of earthquake zone, North China to the South Yellow Sea earthquake band, and this band is a macroseism active belt.But the spatial distribution of the seismic activity of this earthquake zone is uneven.Seismic activity has medium level.According to State Seismological Bureau " Chinese earthquake motion response spectrum block plan eigenperiod " (1: 400 ten thousand) and " Chinese ground motion parameter block plan " (1: 400 ten thousand), this zone is following to surmount the earthquake motion peak accelerator of probability 10% in 50 years between the 0.05-0.1g scope, be equivalent to basic earthquake intensity VI～VII degree, earthquake response spectrum eigenperiod is between 0.45～0.55s scope.The Seismology and Geology environmental complex helps building the large-scale wind electricity field.

On the whole, at first the geological conditions of offshore area, Xiangshui County is good, and areal geology is relatively stable, helps the construction of large-scale wind electricity field.

Secondly, wind electric field blower is high-rise structures, and natural ground can not satisfy requirements such as building resistance to compression, resistance to plucking and overturning or slip resistance analysis, should not adopt natural ground, can adopt pile foundation.

Engineering proposal

The blower fan arrangement principle is:

(1) at first should take into full account and to use marine site surrounding enviroment restrictive condition, consider wind regime such as prevailing wind direction, wind speed condition in the site again.

When (2) arranging, should avoid the wake effect between the wind-powered electricity generation unit as far as possible, fully reduce the extra large cable length between the extension set again, to reduce the conveyance system investment.

(3) to different arrangements, be by whole wind electric field electricity-generating amount maximum, the principle of taking into account each unit generated energy is optimized selection.

(4) for the ease of construction, operation maintenance and reduction construction investment, the engineering same period in the same wind energy turbine set is selected the single-machine capacity wind-powered electricity generation unit identical with model for use as far as possible.

With reference to Xiangshui County's land wind energy turbine set correlative measurement wind data, wind energy distributes and comparatively disperses in the zone, N, NNE, NE, ENE, E, ESE, and wind direction such as SW all have larger proportion to distribute, therefore, require the blower fan spacing bigger when blower fan is arranged, move towards according to the coastline, consider that tentatively one arranges puts 6 units with the double layout of wind energy turbine set 11 vertical coastlines of unit direction, another is arranged and puts 5 units, spacing is got 700m in the blower fan row, and row's spacing is got 700m.Blower fan is arranged and is seen Fig. 2-3:

The blower foundation form is selected

Based on the construction experiences of external offshore wind farm, the blower foundation of external offshore wind farm is generally based on single pile, the depth of water and geological conditions preferably marine wind electric field a small amount of employing gravity type foundation is also arranged, suction type foundation is still under test.The base form that can be used for offshore wind turbine under study for action mainly contains at present: types such as single pile basis, many pile foundations, gravity type foundation, suction type foundation, caisson type basis.In conjunction with the actual conditions of this engineering, domestic construction technology level, this engineering high spot reviews pile foundation (comprising single pile basis and many pile foundations), suction type foundation.

(1) pile foundation

Be used widely in the marine wind electric field that has built up at present in the single pile basis, the single pile basis is specially adapted to shallow water and Intermediate Water Depth waters.The advantage on single pile basis is an easy construction, quick, and basic expense is less, and the compliance on basis is strong.In many wind energy turbine set of building up, all adopt this kind base form.Many pile foundations are similar to the single pile basis, adopt the steel pipe pile more than 3, and the steel pipe pile top adopts steel truss to link to each other with section of foundation, and the section of foundation top is managed orchid and linked to each other with the tower tube.The existing abroad a spot of application of many pile foundations is mainly used in that single-machine capacity is big, the darker wind energy turbine set of the depth of water.

The about 5m of this engineering depth of water, the seabed soil property is based on silt clay, flour sand, and topsoil is that stream is moulded or softly moulded, high-compressibility soil, and supporting capacity is low, and distortion is big, and no natural ground condition needs the employing pile foundation.

(2) suction type foundation

Suction type foundation is to make base fixed by water pressure, have sucker on this basic leg, draw water and bleed behind sucker and the ground sealing below it, just produce the atmospheric pressure of a downward water pressure above the sucker, this pressure is in order to horizontal loadings such as steady wind load, unrestrained loads.This basis is owing to save pile foundation, also gravity abutment that need not be heavy, so infrastructure investment is economized, but this basis is higher to technical requirementss such as sealing, sealings, except that be used for test in the Frederikshaven of Denmark wind energy turbine set, also be not used for actual engineering on a large scale at present.Since sucker bottom sealing, sealing difficulty during this engineering suction type foundation, and this basis is still under test, and technology is immature, so this engineering does not adopt suction type foundation.

According to design, Xiangshui County's offshore wind farm experimental project blower foundation form intends adopting pile foundation.

The stake type is selected

According to present Pile Foundations Design, construction level and construction experience, harbour engineering pile foundation generally adopt steel pipe pile, prestressed concrete pipe pile and castinplace pile three classes.

Steel pipe pile is widely-used in the harbour engineering field, and the main stake of domestic bridge spanning the sea type is steel pipe pile, the large-scale pile driving barge of the existing a greater number of state inner harbor boat unit in charge of construction, and steel pipe pile construction equipment and construction technology are comparatively ripe.For the blower foundation of this engineering 3MW, intend adopting the steel pipe pile of 3 2.5m diameters; Prestressed concrete pipe pile has also obtained a large amount of application in harbour engineering, blower foundation for this engineering 3MW, if adopt the pile for prestressed pipe scheme, need to adopt 10 of high-strength prestressed concrete pipe piles, after surfacing, pile tube adopt concrete bearing platform to link to each other with section of foundation; Castinplace pile also has application in harbour engineering, the stake footpath of bored pile mainly is subjected to the restriction of drilling machine, and general present maximum gauge is no more than 3.5m, according to this project geologic condition, intend adopting 4 diameter 2.2m castinplace piles, adopt concrete bearing platform to be connected after stake is surfaced with section of foundation.

Consider from the construction angle, steel pipe pile scheme easy construction, speed is fast, and construction quality is guaranteed, and expense is few, is optimal case.The pile for prestressed pipe scheme adopts pile driving barge piling, the cast-in-situ concrete cushion cap, and construction is complicated, and this scheme is inferior to the steel pipe pile scheme.The castinplace pile scheme need be built the offshore construction platform, cast-in-situ concrete, and device therefor is more, complex procedures, expense is more, and this scheme is the poorest.Consider that from structural safety angle and anticorrosion angle the three distinguishes not quite.Consider from the structural fatigue angle, the steel pipe pile optimum, pile for prestressed pipe is the poorest.So this engineering piles type is selected steel pipe pile.

The stake number is selected

The steel pipe pile scheme according to the stake number what, can be divided into single pile, three, clump of piles scheme.Be used widely in the at present external marine wind electric field in single pile basis, its structure is simple relatively, mainly be made up of a steel pipe pile and linkage section, the single pile base form accounts for more than 85% in the marine wind electric field that has built up, this engineering 3MW blower foundation single pile scheme stake footpath 4.8m; Three steel pipe pile bases are tripod combining form basis, this basis is mainly at sea used in oil platform, the marine beacon construction widely, steel pipe pile with 3 intermediate diameters is positioned the seabed, 3 piles are equilateral triangle and evenly lay, top tripod trussed construction is supported by steel sleeve in the stake top, constitute the combined type basis, three scheme stake footpaths of this engineering 2.5m; Clump of piles formula highrise pile cap is the common structure of seashore harbour and pier footing, is made up of foundation pile and cushion cap, and cushion cap is cast-in-situ concrete, and this engineering clump of piles scheme adopts 8 layouts, and the stake footpath is 1.5m.

In sum, can be divided into three schemes on the stake number is selected, the steel pipe pile that has produced three kinds of piles with different footpaths thus is respectively:

(3) scheme one: the single pile scheme, and the stake footpath is 4.8m;

(4) two: three schemes of scheme, the stake footpath is 2.5m;

(5) scheme three: clump of piles scheme, and the stake footpath is 1.5m;

Because the size in stake footpath has bigger influence to the local scour degree of depth around the pile foundation, therefore, need carry out the calculating of the local scour degree of depth respectively to select the most suitable engineering proposal to three kinds of schemes.

Provide the embodiment of the silt coast coastal waters wind energy turbine set wind-electricity tower local scour computational methods of the present invention's proposition at the operation of coastal waters, Xiangshui County wind energy turbine set wind-powered electricity generation unit, the technological development of maintenance below:

(1) sets up Mathematical Modeling.

The Xiangshui County is positioned at Yancheng, Jiangsu Province, Huaiyin, Lianyun Harbour San Shi intersection, and the Huanghai Sea is faced in east, whole county gross area 1378km ²It is greater coasting area about the outside 6km at center that this coastal waters, Xiangshui County wind energy turbine set is chosen in the land wind energy turbine set in Xiangshui County transformer station, and the regional depth of water is about 5m.Position according to coastal waters, Xiangshui County wind energy turbine set, set up the two-dimentional tidal current mathematical model (see figure 1) and the two-dimentional wave mathematical model (see figure 2) in engineering marine site respectively, and come the hydrodynamic condition in analysis project marine site with this, for the depth capacity of determining the wind-electricity tower local scour provides reliable drive marine parameter; Two-dimentional tidal current mathematical model and the two-dimentional wave mathematical model scope set up by Fig. 1 and the visible the present invention of Fig. 2 have covered whole engineering marine site, and model is through the field data checking, result of calculation is rationally credible, the characteristics of motion that can reflect substance trend and wave preferably can provide reliable drive marine parameter for the local scour depth calculation of wind-electricity tower.

(2) determine fundamental formular.

Because surrounding waters, Xiangshui County geology is mud matter silty clay and mud matter flour sand.The present invention has chosen and has been applicable to that bed-sit is the Jones of fine sand particle and Sheppard formula and the Han Hai fundamental formular of formula as the estimation silt coast coastal waters wind energy turbine set wind-electricity tower local scour degree of depth of holding high up.

(3) formula correction.

Formula has only been considered the influence of trend because Jones and Sheppard formula and Han Hai hold high up, and ignored wave action, and still there is stronger wave action in zone of living in, surrounding waters, Xiangshui County, so wave action must take in.Reacted in order to make acting in the formula of wave, the present invention according to " harbour hydrology standard " (JTJ213-98) in the mean flow rate formula of wave water particle, try to achieve the mean flow rate of water particle under the wave action, then the flow velocity under itself and the pure trend is superposeed, obtain more rational wave current mixture velocity, and replace flow velocity under the pure trend in the former basic formula with this wave current mixture velocity, and obtain suitable computation schema at last, see formula (10) and formula (12).

(4) analytical calculation.

Draw the trend field and the wave field in wind energy turbine set engineering marine site, coastal waters, Xiangshui County according to the Mathematical Modeling in (1), bring formula (10) and (12) into, and two results are verified with known measured data respectively, choose the formula of error calculated minimum.This draws the result of calculation and the actual error minimum of formula (12).Therefore utilization considers that Han Hai after the wave action formula of holding high up calculates coastal waters, Xiangshui County wind energy turbine set wind-electricity tower local scour degree of depth.At the scheme of stake footpath 2.5m, when the bed-sit median particle diameter when 0.05mm is changed to 0.11mm, the local scour degree of depth that using formula (12) calculates gained is 5.24m to 5.97m.

Claims (1)

1. a local scouring forecast method of coastwise wind-electricity tower footing of muddy coast is characterized in that comprising the steps:

(1) sets up Mathematical Modeling

Set up the two-dimentional tidal current mathematical model and the two-dimentional wave mathematical model in engineering marine site respectively, and come the hydrodynamic condition in analysis project marine site with two-dimentional tidal current mathematical model and two-dimentional wave mathematical model, for the depth capacity of determining the wind-electricity tower local scour provides the drive marine parameter;

(2) determine fundamental formular

Jones and Sheppard formula:

$\frac{D_s}{d_p}=c_1\left(\frac{V_m\left(1\right)-V_d\left(1\right)}{V_{\mathrm{cr}}\left(1\right)}\right)+c_2---\left(1\right)$

$c_1=(c_3-c_2){(\frac{V_m\left(1\right)}{V_{\mathrm{cr}}\left(1\right)}-1)}^{-1}---\left(2\right)$

$c_2=2.4\tanh \left[2.18{\left(\frac{D}{d_p}\right)}^{2/3}\right]---\left(3\right)$

$c_3=\tanh \left[2.18{\left(\frac{D}{d_p}\right)}^{2/3}\right]{[-0.279+0.049\exp \left(\lg \frac{d_p}{d_{50}}\right)+0.78{\left(\lg \frac{d_p}{d_{50}}\right)}^{-1}]}^{-1}---\left(4\right)$

The Han Hai formula of holding high up:

D _s＝8.48k ₁k ₂B ^0.326V _d(1) ^0.628D ^0.193d ₅₀ ^0.167 (5)

The mean flow rate formula of wave water particle:

$V_i\left(2\right)=0.2\frac{H}{D}C---\left(6\right)$

$C=\frac{\mathrm{gT}}{2\mathrm{\&pi;}}\mathrm{thkD}---\left(7\right)$

$k=\frac{2\mathrm{\&pi;}}{L}---\left(8\right)$

Wave current mixture velocity formula:

V _i(3)＝V _i(1)+V _i(2) (9)

Jones and Sheppard formula after the consideration wave action:

$\frac{D_s}{d_p}=c_1\left[\frac{V_m\left(3\right)-V_d\left(3\right)}{V_{\mathrm{cr}3}}\right]+c_2---\left(10\right)$

$c_1=(c_3-c_2){(\frac{V_m\left(3\right)}{V_{\mathrm{cr}}\left(3\right)}-1)}^{-1}---\left(11\right)$

$c_2=2.4\tanh \left[2.18{\left(\frac{D}{d_p}\right)}^{2/3}\right]---\left(3\right)$

$c_3=\tanh \left[2.18{\left(\frac{D}{d_p}\right)}^{2/3}\right]{[-0.279+0.049\exp \left(\lg \frac{d_p}{d_{50}}\right)+0.78{\left(\lg \frac{d_p}{d_{50}}\right)}^{-1}]}^{-1}---\left(4\right)$

Consider Han Hai after the wave action formula of holding high up:

D _s＝8.48k ₁k ₂B ^0.326V _d(3) ^0.628D ^0.193d ₅₀ ^0.167 (12)

More than the implication of each symbol representative be:

D _sBe pile foundation limit scour depth; d _pBe the stake footpath; D is a maximum water depth; V _i(1) is flow velocity under the pure trend; V _i(2) be the mean flow rate of wave water particle; V _i(3) be the wave current mixture velocity; V _d(j) be the bottom average largest speed of current; V _Cr(j) be the critical initial velocity of silt; V _m(j) be mean velocity in vertical; d ₅₀Be the sand grain median particle diameter; k ₁Be foundation pile layout coefficient, bar shaped gets 1.0, quincunxly gets 0.862; k ₂For foundation pile is arranged vertically coefficient, straight stake gets 1.0, and taper pile gets 1.176; B is the width that on average blocks water under the maximum water depth condition; H is a wave height; C is a velocity of wave; K is a wave number; L is a wavelength;

(3) formula correction

According to " harbour hydrology standard " (JTJ213-98) in the mean flow rate formula of wave water particle, try to achieve the mean flow rate of water particle under the wave action, then the flow velocity under itself and the pure trend is superposeed, obtain the wave current mixture velocity, and replace the flow velocity V under the pure trend in the step (2) with this wave current mixture velocity _i(1), obtains suitable computation schema;

(4) analytical calculation

Choose the described suitable computation schema of step (3), the depth capacity of forecast silt coast coastal waters wind energy turbine set wind-electricity tower local scour.

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