CN107169637A - A kind of power station layer of sand soil property liquefaction evaluation method - Google Patents

A kind of power station layer of sand soil property liquefaction evaluation method Download PDF

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CN107169637A
CN107169637A CN201710283534.3A CN201710283534A CN107169637A CN 107169637 A CN107169637 A CN 107169637A CN 201710283534 A CN201710283534 A CN 201710283534A CN 107169637 A CN107169637 A CN 107169637A
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layer
discrimination
standard
sand
soil
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王文革
张建华
李亮
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Guodian Tibet Niyang River Basin Hydropower Development Co Ltd
PowerChina Northwest Engineering Corp Ltd
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Guodian Tibet Niyang River Basin Hydropower Development Co Ltd
PowerChina Northwest Engineering Corp Ltd
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Abstract

Judge monitoring technical field, specially power station layer of sand soil property liquefaction evaluation method the present invention relates to liquefaction of soil, method includes first step and uses the first method of discrimination, standard is met after differentiation, into second step；Second step includes the second method of discrimination and the 3rd method of discrimination and the 4th method of discrimination, the second method of discrimination, the 3rd method of discrimination and the 4th method of discrimination is carried out to layer of sand respectively to differentiate, when evaluated soil layer meets any two in the second method of discrimination standard, the 3rd method of discrimination standard, the 4th method of discrimination standard, judge that soil layer liquefies.This method is used in the way of mutually confirming so that method of discrimination more accurate, reliability is higher compared with prior art more adding system.

Description

A kind of power station layer of sand soil property liquefaction evaluation method
Technical field
Judge safety monitoring technology field the present invention relates to earth and rockfill dam earthquake liquefaction, specifically propose a kind of Earth and Rockfill Dam base fluid Two-dimentional quasi-static model under the conditions of change simplifies determination methods.
Background technology
Under the influence of certain, such as under violent earthquake effect, the sand below level of ground water, property changes, performance The phenomenon for going out the special card of similar liquids is sand liquefaction, also referred to as sandblasting phenomenon.From Tangshan Earthquake, Osaka earthquake etc. is in recent decades From the point of view of the disastrous earthquake occurred, liquefaction of sand brings big disaster to the mankind.Sand liquefaction directly affect China's water conservancy, Developing rapidly for power station and city-building, is that we carry out seismic safety evaluation, provides fortification against earthquakes, the work such as prediction of earthquake calamity One important link.
Under the new situation, from environmental protection and prevent and reduce natural disasters in angle, be necessary to grind in engineering construction and planning and construction of the city Study carefully the distribution in earthquake stonebrash liquefaction area, be that engineering construction and urban construction security provide reliable scientific basis.
According to borehole data and comprehensive analysis, general riverbed engineering soil layer wherein includes sand gravel stratum containing erratic boulder With the characteristic of sand lens in the gravel layer of stone sand containing block；Conglomeratic sand；Fine sand layer；Alluviation medium-fine sand containing gravel layer；It is thin in alluviation Layer of sand；The frozen water product layer of medium-fine sand containing gravel, wherein each level depth is deepened successively, layer of sand influential on engineering mainly has riverbed Position conglomeratic sand and alluviation medium-fine sand layer, need to liquefy to it in engineering sounding and construction and degree sentence survey, to protect Card engineering be smoothed out and building shock resistance and reliability.
In for engineering soil property actual detection, there are the mode of observation and detection instrument detection, but mesh in the prior art The detection method of preceding prior art is more traditional, and evaluation method is single, and Indentification model is unsound, and result of detection reliability is not Height, therefore have the space of optimization evaluation method for current determination methods, being preferably applied for that specific actual conditions have must Want meaning.
The content of the invention
It is an object of the invention to solve the deficiencies in the prior art, optimize existing engineering soil property liquefaction of soil and degree differentiates Method, with system integrality, differentiates the technological merit that result is more accurate, reliability is high, while realization theory is tied with actual The characteristics of conjunction, facilitate application strong.
The present invention proposes a kind of power station layer of sand soil property liquefaction evaluation method, and the evaluation method comprises the following steps：The One step：Using the first method of discrimination, when layer of sand soil property meets the first discrimination standard, differentiate that layer of sand does not liquefy, no side, Continue to differentiate into second step；Second step includes the second method of discrimination and the 3rd method of discrimination and the 4th method of discrimination.
Second step：Including the second method of discrimination and the 3rd method of discrimination and the 4th method of discrimination,
Second method of discrimination is Standard piercing blow counts method, using Standard piercing blow counts Ncr as foundation, when layer of sand is real Survey injection blow counts N63.5During >=Standard piercing blow counts Ncr, then differentiate that layer of sand does not liquefy；When layer of sand surveys injection blow counts N63.5During ＜ Standard piercing blow counts Ncr, the second method of discrimination standard is met；
3rd method of discrimination is relative density diagnostic method, when the relative density of soil layer saturation cohesiveless soil is more than liquefaction During critical phase transition pH Dr, differentiate that soil layer does not liquefy；When the relative density of soil layer saturation cohesiveless soil is faced less than or equal to liquefaction During boundary relative density Dr, the 3rd discrimination standard is met；
4th method of discrimination is SEED shear stress methods of comparison, as the anti-shear stress at liquefaction τ of soil layerlMore than or equal to earthquake Cause equivalent shear stress τavWhen, differentiate that soil layer does not liquefy；As the anti-shear stress at liquefaction τ of soil layerlCause equivalent shear stress less than earthquake τavWhen, meet the 4th discrimination standard；
Carry out the second method of discrimination, the 3rd method of discrimination and the 4th method of discrimination to layer of sand respectively to differentiate, when being commented When surveying any two in the second method of discrimination standard of soil layer satisfaction, the 3rd method of discrimination standard, the 4th method of discrimination standard, sentence Determine soil layer to liquefy.
Further scheme, first method of discrimination is detection layer of sand age method, and first discrimination standard is stratum Age is Epileistocene in Quaternary Period Q3 or former.
Further scheme, first method of discrimination is grogs grain diameter measurement method, and first discrimination standard is stratum The granule content that grogs particle diameter is more than 5mm is more than or equal to 70%.
Further scheme, first method of discrimination is shear wave velocity method, and first discrimination standard is cut for soil layer Velocity of wave is cut more than upper limit shear wave velocity, the upper limit shear wave velocity calculation formula is
Vst=291 (KH·Z·γd)1/2In formula：VstFor upper limit shear wave velocity (m/s)；KHFor ground maximum horizontal Shake acceleration factor；Z is soil depth (m)；γdFor depth reduction coefficient；Z is depth reduction coefficient.
Further scheme, when the Standard piercing blow counts method Plays penetration test injection point depth and underground Water level is in the depth of experiment below ground, and actual measurement Standard piercing blow counts should be by formula N63.5=N63.5(ds+0.9dw+ 0.7)/(d ' s+0.9d ' w+0.7) is corrected, and should be with the Standard piercing blow counts N after correction63.5It is used as distinguishing rule. N ' in formula63.5For actual measurement Standard piercing blow counts；Ncr is Liquefaction Criterion in China injection critical count,Wherein ρcFor the clay content quality percentage (%) of soil；N0For liquid Change discrimination standard injection blow counts a reference value；Depth (m) of the ds Standard piercings point in below ground at that time；Dw is level of ground water In the depth (m) of below ground at that time；When d ' s are standard penetration test (SPT), depth of the Standard piercing point in below ground at that time (m)；When d ' w are standard penetration test (SPT), depth (m) of the level of ground water in below ground at that time.
This programme has the beneficial effect that：
1st, the evaluation method includes first step, second step and third step, is carried out using first step after anticipation, Soil layer situation can totally be understood, while three kinds of method of discrimination in this programme second step, are carried out using two or more methods Sentence again, to realize that two kinds differentiate results in the way of mutually confirming, when two kinds in three kinds of method of discrimination and the above are determined as not Just calculate and not liquefy during liquefaction so that differentiate that result is more accurate, while can also when only individually a kind of method of discrimination liquefies The person that gives building operation, which gives, to be pointed out, the situation of true reflection soil property, improves the reliability of soil layer differentiation.
2nd, the age method that first step is used in this programme differentiates, and Standard piercing blow counts method in second step, Relative density diagnostic method, SEED shear stress contrast law theory are reliable and sampling mode samples object etc. conveniently, representative, So that method of discrimination is more reliable, it is as a result more accurate.
3rd, when the Standard piercing blow counts method Plays penetration test injection point depth and level of ground water are on experiment ground Following depth, actual measurement Standard piercing blow counts should be by formula N63.5=N63.5 (ds+0.9dw+0.7)/(d '
S+0.9d ' w+0.7) it is corrected, and should be with the Standard piercing blow counts N after correction63.5It is used as distinguishing rule.Adopt With correcting mode so that method of discrimination incorporates actual conditions so that method of discrimination is more cut more according to actual soil property and landform Nearly application is actual, differentiates that result is more accurate.
Brief description of the drawings
Fig. 1 is a kind of power station layer of sand soil property liquefaction evaluation method process step block diagram of the invention.
Embodiment
In order to make the purpose , technical scheme and advantage of the present invention be clearer, below in conjunction with accompanying drawing and specific implementation Mode, the present invention will be described in further detail.It should be appreciated that embodiment described herein is only to explain this Invention, is not intended to limit the present invention.
Soil layer background check：
Clay distribution structure in engineering construction is expanded on further by taking NORTHWEST CHINA some hydropower station as an example and specifically explains for the present embodiment The soil property background of the specific implementation process of the inventive method is stated, power station is specially Dam Site area except right dam abutment has a small amount of base Outside rock exposure, remaining position is that deep stratum is covered by the 4th.Dam Site overburden cover 20.55m~~359.3m, puts down Equal thickness is 300.5m.According to coating grain composition, particle size and material composition, ground according to borehole data and comprehensive analysis Study carefully, Dam Site coating is divided into 14 layers, each thickness degree statistical result is shown in Table 1.
Each rock group thickness statistical form of the deep covering layer of table 1
Rock (soil) layer is numbered and title Value range (m) Average value (m)
1st layer (Landslide deposit block gravelly soil) 6.00-48.80 18.29
2nd layer (sand gravel stratum containing erratic boulder) 2.70-7.88 5.29
3rd layer (gravel layer of stone sand containing block) 4.47-11.39 8.91
4th layer (conglomeratic sand) 15-35 25
5th layer (fine sand layer) 1.14-13.90 7.57
6th layer (alluviation medium-fine sand containing gravel layer) 5.40-24.11 19.03
7th layer (alluviation stone sand containing block gravel layer) 6.35-16.13 11.06
8th layer (alluviation medium-fine sand layer) 9.25-16.92 13.63
9th layer (alluviation stone sand containing block gravel layer) 6.23-9.63 8.04
10th layer (frozen water product stone sand containing block gravel layer) 15.47-26.11 21.10
11th layer (frozen water product chad containing block layer of sand) 23.00-25.50 24.79
12nd layer (frozen water product medium-fine sand containing gravel layer) 32.39-38.93 35.80
13rd layer (frozen water product stone sand containing block gravel layer) 24.88-27.76 26.38
14th layer (frozen water product chad containing block layer of sand) 64.98 64.98
Earth's surface and basement rock peak accelerator during 50 Annual exceeding probability 10% of engineering ground power station be respectively 0.206g, 0.140g, characteristic periods of response spectra is respectively 0.65s, 0.70s, and basic earthquake intensity is VII degree, and engineering design is set up defences by VIII degree. This engineering Riverbed is thicker, and different geologic(al) period Q4, Q3 (away from modern 12000~1,000,000 years), Q2 thickness is distributed with Layer of sand, i.e., the characteristic of sand lens in the 2nd layer sand gravel stratum containing erratic boulder and the 3rd layer of gravel layer of stone sand containing block；4th layer contains Gravel layer；5th layer of fine sand layer；6th layer of alluviation medium-fine sand containing gravel layer；8th layer of alluviation medium-fine sand layer；12nd layer of frozen water product contains Gravel medium-fine sand layer.Layer of sand influential on engineering mainly has the 6th layer of riverbed position (alluviation medium-fine sand containing gravel layer), the 8th layer of (punching Product medium-fine sand layer).
Specific embodiment scheme：
As shown in figure 1, the present invention proposes a kind of power station layer of sand soil property liquefaction evaluation method, the evaluation method include with Lower step：
First step (S1)：Layer of sand is differentiated using the first method of discrimination, mark is differentiated when layer of sand soil property meets first On time, differentiate that layer of sand does not liquefy, no side continues to differentiate into second step；
Second step (S2)：Including the second method of discrimination and the 3rd method of discrimination and the 4th method of discrimination,
Second method of discrimination is Standard piercing blow counts method, using Standard piercing blow counts Ncr as foundation, when layer of sand is real Survey injection blow counts N63.5During >=Standard piercing blow counts Ncr, then differentiate that layer of sand does not liquefy；When layer of sand surveys injection blow counts N63.5During ＜ Standard piercing blow counts Ncr, the second method of discrimination standard is met；
3rd method of discrimination is relative density diagnostic method, when the relative density of soil layer saturation cohesiveless soil is more than liquefaction During critical phase transition pH Dr, differentiate that soil layer does not liquefy；When the relative density of soil layer saturation cohesiveless soil is faced less than or equal to liquefaction During boundary relative density Dr, the 3rd discrimination standard is met；
4th method of discrimination is SEED shear stress methods of comparison, as the anti-shear stress at liquefaction τ of soil layerlMore than or equal to earthquake Cause equivalent shear stress τavWhen, differentiate that soil layer does not liquefy；As the anti-shear stress at liquefaction τ of soil layerlCause equivalent shear stress less than earthquake τavWhen, meet the 4th discrimination standard；
Carry out the second method of discrimination, the 3rd method of discrimination and the 4th method of discrimination to layer of sand respectively to differentiate, when being commented When surveying any two in the second method of discrimination standard of soil layer satisfaction, the 3rd method of discrimination standard, the 4th method of discrimination standard, sentence Determine soil layer to liquefy.For example meet the second method of discrimination standard and can determine whether that liquid occurs for soil layer with the 3rd method of discrimination standard Change, or it is that can determine whether that soil layer liquefies with the 3rd method of discrimination standard to meet the first method of discrimination standard, so using two Kind of method mutually to confirm, improve the reliability of differentiation.
A kind of embodiment of first method of discrimination is：First method of discrimination is detection layer of sand age method, described first Discrimination standard is that stratum age is Epileistocene in Quaternary Period Q3 or former.Using electron spin resonance (Electron Spin Resonance, abbreviation ESR) survey the soil layer age be Epileistocene in Quaternary Period Q3 therefore, detection layer of sand age method at the beginning of sentence soil layer not Liquefaction.Otherwise, then there is liquefaction possibility, it is necessary to further be analyzed into second step.
Another embodiment of first method of discrimination is：First method of discrimination is grogs grain diameter measurement method, described the One discrimination standard is that stratum grogs particle diameter is more than 5mm granule content more than or equal to 70%.
When stratum grogs particle diameter is more than 5mm granule contents ρ 5 >=30%, and clay (particle diameter is less than 0.005mm) content is full During sufficient table 2, it can be judged to not liquefy；Otherwise, then with liquefaction possibility.
The clay content of table 2 differentiates sand liquefaction standard
Seismic fortification intensity Seven degree Octave Nine degree
Clay content (%) ≥16 ≥18 ≥20
Liquefaction Do not liquefy Do not liquefy Do not liquefy
According to grogs grain diameter measurement method in the present embodiment, contrast each layer of sand particle diameter and judge to be shown in Table 3.As can be seen from Table 3, respectively Rock group soil layer particle diameter is less than 5mm granule contents more than 90%, and clay content only has 2.48%~4.7%, respectively less than Shake the clay content (18%) that fortification intensity is VIII degree.Therefore, each layer of sand is sentenced at the beginning of particle diameter method and there is liquefied possibility.
The layer of sand particle diameter method Liquefaction result of table 3
Another embodiment of first method of discrimination is：First method of discrimination is shear wave velocity method, and described first sentences Other standard is more than upper limit shear wave velocity for the shear wave velocity of soil layer, when the upper limit that the shear wave velocity of soil layer is more than formula (1) calculating is cut When cutting velocity of wave, it can be judged to not liquefy.
Vst=291 (KH·Z·γd)1/2 (1)
V in formulastUpper limit shear wave velocity (m/s)；KH, can be by earthquake protection for ground maximum horizontal seismic acceleration coefficient Seven degree of earthquake intensity, octave and nine degree, are respectively adopted 0.1,0.2 and 0.4；Z is soil depth (m)；Z is depth reduction coefficient；Depth Reduction coefficient can be calculated by following equation：
Z=0~10m ,=1.0-0.01Z
Z=10m~20m ,=1.1-0.02Z
Z=20m~30m ,=0.9-0.01Z
Dam Site carries out shear-wave velocity Vs tests in layer of sand.8 hole side segment length 73.5m are altogether.
In specific implementation, according to test achievement, using formula (1) calculating upper limit shear wave velocity, shear wave velocity is tested in control, Carry out test section liquefaction of sand differentiation.Test is only calculated during calculating at 20 meters with epimere, the 8th layer is not tested, the results are shown in Table 4. So sentencing at the beginning of shear wave velocity method, the 6th layer may occur liquefaction (local buried depth is compared with shallow-layer).
The shearing wave soil liquefaction discrimination outcome table of table 4
Just sentence result to show, tested soil layer may liquefy.Therefore, need to by the idiographic flow step of this programme to the 6th layer and The further differentiation of 8th layer of progress next step.
Second step (S2)：Including the second method of discrimination and the 3rd method of discrimination and the 4th method of discrimination,
Second method of discrimination is Standard piercing blow counts method, using Standard piercing blow counts Ncr as foundation, when actual measurement is passed through Enter blow counts N63.5During >=Standard piercing blow counts Ncr, then differentiate that soil layer does not liquefy；As actual measurement injection blow counts N63.5＜ standards During injection blow counts Ncr, the second method of discrimination standard is met；
When Standard piercing blow counts method standard penetration test (SPT) injection point depth and level of ground water are testing the depth of below ground Degree, when normally being used different from engineering, actual measurement injection blow counts should be corrected as the following formula, and should be with the Standard piercing after correction Blow counts N63.5As sentencing foundation again.
N63.5=63.5(ds+0.9dw+0.7)/(d ' s+0.9d ' w+0.7) wherein N '63.5For actual measurement injection blow counts；Ncr For Liquefaction Criterion in China injection critical count,
Wherein ρ c are native clay content quality percentage (%), as ρ c<When 3%, 3% is taken；N0For Liquefaction Criterion in China Injection blow counts a reference value, is shown in Table 6；
When ds is that engineering is normally used, depth (m) of the Standard piercing point in below ground at that time；When Standard piercing point is on ground During depth within 5m below face, it should be calculated using 5m；When dw is that engineering is normally used, level of ground water is in below ground at that time Depth (m)；When d ' s are standard penetration test (SPT), depth (m) of the Standard piercing point in below ground at that time；D ' w try for Standard piercing When testing, depth (m) of the level of ground water in below ground at that time；If ground is submerged in below the water surface at that time, d ' w take 0.
The Liquefaction Criterion in China injection blow counts a reference value of table 6
6th layer of superstratum is relatively thin, it is adaptable to injection blow counts method, and the 8th layer of buried depth of bottom is unsuitable for this side more than 20m Method.This Liquefaction Criterion in China injection blow counts a reference value is VIII degree of consideration by seismic fortification intensity.Built according to above-mentioned specification Formula is discussed, result of calculation is sorted out and is shown in Table 7.
The Standard piercing blow counts method Liquefaction statistical form (the 6th layer) of table 7
Table 7 shows, the 6th layer have 11 groups in VIII degree of seismic fortification intensity N63.5<Ncr, it is possible to create layer of sand liquefies, Account for the 28.9% of experimental group number.Therefore, sentenced again by Standard piercing blow counts method, the 6th layer may occur layer of sand at riverbed position Liquefaction.
3rd method of discrimination is relative density diagnostic method, when the relative density of soil layer saturation cohesiveless soil is more than liquefaction During critical phase transition pH Dr, differentiate that soil layer does not liquefy；When the relative density of soil layer saturation cohesiveless soil is faced less than or equal to liquefaction During boundary relative density Dr, the 3rd discrimination standard is met, into the 4th method of discrimination；" when saturation cohesiveless soil (including sand and particle diameter Gravel more than 2mm) relative density when being not more than the liquefaction critical phase transition pH in table 8, can determine whether as may liquefying soil.The 6 layers of relative density Liquefaction the results are shown in Table 9.
The liquefaction critical phase transition pH of the saturation cohesiveless soil of table 8
Seismic fortification intensity Six degree Seven degree Octave Nine degree
Liquefy critical phase transition pH (Dr) cr (%) 65 70 75 85
The relative density method Liquefaction result of table 9 (the 6th layer (Q3al- IV 1))
Table 9 shows that the 6th layer has carried out 14 groups of relative density tests altogether, seismic fortification intensity be VIII degree when, have 3 groups can Layer of sand liquefaction can be produced, the 21.4% of experimental group number is accounted for, so, sentenced again by relative density test, the 6th layer has at riverbed position The liquefied possibility of generation layer of sand.
4th method of discrimination is SEED shear stress methods of comparison, as the anti-shear stress at liquefaction τ of soil layerlMore than or equal to earthquake Cause equivalent shear stress τavWhen, differentiate that soil layer does not liquefy；As the anti-shear stress at liquefaction τ of soil layerlCause equivalent shear stress less than earthquake τavWhen, the 4th discrimination standard is met, into third step；
It is determined that the live anti-shear stress at liquefaction of soil layer and earthquake cause equivalent shear stress to carry out Liquefaction according to the following formula：
τl＞ τavDo not liquefy
τl＜ τavLiquefaction
6th layer of top is mainly the 2nd layer, and thickness range 2.70-7.88m takes average thickness 5.29m, therefore, the 6th layer The buried depth scope of (Q3al- IV 1) is 5.29-29.4m, and the 8th layer of top is mainly the 2nd layer, the 6th layer and the 7th layer, wherein the 6th layer Thickness range 5.40-24.11m, take average thickness 19.03m, the 7th layer of thickness range 6.35-16.13m, take average thickness 11.06m, therefore, the 8th layer of buried depth scope is 35.38-52.3m.Taken because Seed simplifies the stress reduction factor in formula It is worth scope and is no more than 40m, therefore is only applicable to the liquefaction evaluation of layer of sand of the buried depth no more than 40m.During liquefaction evaluation, to the 6th layer (Q3al- IV 1), judges that scope takes 5-30m；For the 8th layer, the too conservative buried depths of 35~40m are taken to carry out more than 40m, during judgement Judge.
Design parameter value during judgement：
(a) according to geology exploration report and this result of the test, the 2nd layer of dry density takes 2.14g/cm3, than refetching 2.69th, the 6th layer of dry density takes 1.57g/cm3, than refetching 2.69, the 7th layer of dry density take 1.80g/cm3,Than refetching 2.68, 8th layer of dry density takes 1.60g/cm3, than refetching 2.69, the saturation that calculating obtains the 2nd layer, the 6th layer, the 7th layer and the 8th layer is held It is respectively 23.4kN/m again3、19.9kN/m3、21.2kN/m3And 20.1kN/m3；
(b)σd/2σ'0By three axle fatigue resistances test determine, taken during specific value 10 weeks and 30 weeks shake frequencies under it is liquefied average Value, is shown in Table 10；
(c) correction factor Cr, it is comprehensive to be taken as 0.6；
(d) stress reduction factor γd, the artificial center line value for reading 0~30m in P468 figures in earthwork principle；30m is arrived 40m, 30m take 0.5, and depth often increases 2m, γd0.02 is reduced, the γ when depth is 40mdFor 0.4；
(e)amax, earthquake intensity is that 0.140g, earthquake intensity are 0.206g when being VIII degree when being VII degree.Specific result of determination It is shown in Table 10.
The value that fatigue resistance is tested under the different earthquake earthquake intensity of table 10
By the above, according to indoor three axles dynamic test, layer of sand liquefaction is sentenced again, 11 are the results are shown in Table.
The SEED shear stress method of comparison layer of sand Liquefaction statistical forms of table 11
Table 11 shows that the 6th layer there occurs that layer of sand liquefies under VIII degree of seismic fortification intensity, within buried depth 25m.So, Diagnostic method is contrasted by seed shear stress again to sentence, the 6th layer may occur layer of sand liquefaction, and the 8th layer under VIII degree of seismic fortification intensity Do not occur layer of sand liquefaction.When evaluated soil layer meets the second method of discrimination standard, the 3rd method of discrimination standard, the 4th differentiation side During any two in method standard, judge that soil layer liquefies.For tested three kinds of differentiations of soil layer data display in the present embodiment Method shows that tested soil layer liquefies, then is ultimately determined to tested soil layer and liquefies.
The engineering coating that the present embodiment is selected is deep, sand gravel layer and the development of layer of sand alternating layers, and wherein layer of sand, which is divided into, is furnished with 6 Layer, layer of sand influential on engineering mainly has the 2nd layer, the thin layer characteristic of sand lens in the 3rd layer of sand gravel stratum and riverbed position 6th layer, the 8th layer of clean sand.Integrate and sentence again through multifactor, multinomial characteristics index value, the 2nd layer, press from both sides Extra-fine sand in the 3rd layer of rock group Vibrating liquefaction may occur for layer lenticular body.But its buried depth is shallow, thickness of thin, and it is discontinuously arranged in lenticular, it is to engineering harm Property it is relatively small, when engineering excavation is met remove.6th layer VIII degree of earthquake intensity occur the liquefied possibility of layer of sand compared with Greatly；Project treatment need to be done.And the 8th layer in VIII degree of earthquake intensity, will not occur layer of sand liquefaction.
Different engineering treatments are taken on different engineering positions, design, are adopted in river bed dam section difficult to deal with Add the comprehensive means such as vibro-replacement stone column with pressure slope behind dam, handled through integration engineering, effectively solving layer of sand may Liquefaction.
The present invention program is one of engineering geological problems for running into being constructed for actual design, proposition it is a kind of excellent Change liquefaction of soil method of discrimination, in view of the remarkable result in actual application, with reliability height, differentiates that result is accurate Feature, the promotion effect casted a brick to attract jade is played simultaneously for industry or Practical Project construction.

Claims (5)

  1. The evaluation method 1. a kind of power station layer of sand soil property liquefies, it is characterised in that：The evaluation method comprises the following steps：
    First step：Using the first method of discrimination, when layer of sand meets the first discrimination standard, differentiate that layer of sand does not liquefy, it is no Side, continues to differentiate into second step；
    Second step：Including the second method of discrimination and the 3rd method of discrimination and the 4th method of discrimination,
    Second method of discrimination is Standard piercing blow counts method, using Standard piercing blow counts Ncr as foundation, when layer of sand actual measurement is passed through Enter blow counts N63.5During >=Standard piercing blow counts Ncr, then differentiate that layer of sand does not liquefy；As layer of sand actual measurement injection blow counts N63.5＜ During Standard piercing blow counts Ncr, the second method of discrimination standard is met；
    3rd method of discrimination is relative density diagnostic method, when the relative density of soil layer saturation cohesiveless soil is critical more than liquefying During relative density Dr, differentiate that soil layer does not liquefy；When the relative density of soil layer saturation cohesiveless soil is less than or equal to liquefaction critical phase During to density Dr, the 3rd discrimination standard is met；
    4th method of discrimination is SEED shear stress methods of comparison, as the anti-shear stress at liquefaction τ of soil layerlCause more than or equal to earthquake Equivalent shear stress τavWhen, differentiate that soil layer does not liquefy；As the anti-shear stress at liquefaction τ of soil layerlCause equivalent shear stress τ less than earthquakeavWhen, Meet the 4th discrimination standard；
    Carry out the second method of discrimination, the 3rd method of discrimination and the 4th method of discrimination to layer of sand respectively to differentiate, when evaluated soil When layer meets any two in the second method of discrimination standard, the 3rd method of discrimination standard, the 4th method of discrimination standard, soil is judged Layer liquefies.
  2. The evaluation method 2. layer of sand soil property in power station as claimed in claim 1 liquefies, it is characterised in that：First method of discrimination For detection layer of sand age method, first discrimination standard is that stratum age is Epileistocene in Quaternary Period Q3 or former.
  3. The evaluation method 3. layer of sand soil property in power station as claimed in claim 1 liquefies, it is characterised in that：First method of discrimination For grogs grain diameter measurement method, first discrimination standard is that granule content of the stratum grogs particle diameter more than 5mm is more than or equal to 70%.
  4. The evaluation method 4. layer of sand soil property in power station as claimed in claim 1 liquefies, it is characterised in that：First method of discrimination For shear wave velocity method, first discrimination standard is more than upper limit shear wave velocity, the upper limit shearing wave for the shear wave velocity of soil layer Fast calculation formula is Vst=291 (KH·Z·γd)1/2
    In formula：VstFor upper limit shear wave velocity (m/s)；KHFor ground maximum horizontal seismic acceleration coefficient；Z is soil depth (m)；γdFor depth reduction coefficient；Z is depth reduction coefficient.
  5. 5. the power station layer of sand soil property liquefaction evaluation method as described in claim 1-4 any one, it is characterised in that：When described Standard piercing blow counts method Plays penetration test injection point depth and level of ground water are in the depth of experiment below ground, half-mark Quasi- injection blow counts should be by formula N63.5=N '63.5(ds+0.9dw+0.7)/(d " s+0.9d ' w+0.7) is corrected, and should be with school Standard piercing blow counts N after just63.5It is used as distinguishing rule；
    N ' in formula63.5For actual measurement Standard piercing blow counts；Ncr is Liquefaction Criterion in China injection critical count, Ncr=N0 [0.9+0.1(ds-dw)]Wherein, ρcFor the clay content quality percentage (%) of soil；N0For Liquefaction Criterion in China injection Blow counts a reference value；Depth (m) of the ds Standard piercings point in below ground at that time；Dw is level of ground water in below ground at that time Depth (m)；When d ' s are standard penetration test (SPT), depth (m) of the Standard piercing point in below ground at that time；D ' w try for Standard piercing When testing, depth (m) of the level of ground water in below ground at that time.
CN201710283534.3A 2017-04-26 2017-04-26 A kind of power station layer of sand soil property liquefaction evaluation method Pending CN107169637A (en)

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CN111368382A (en) * 2018-12-06 2020-07-03 中国石油天然气股份有限公司 Method and system for determining earthquake liquefaction index
CN114297742A (en) * 2021-11-22 2022-04-08 浙江杰地建筑设计有限公司 Anti-liquefaction processing method based on average seismic subsidence and differential seismic subsidence

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CN111368382A (en) * 2018-12-06 2020-07-03 中国石油天然气股份有限公司 Method and system for determining earthquake liquefaction index
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