CN103726475A - Earth-rock dam break centrifugal model test analysis method - Google Patents

Abstract

An earth-rock dam break centrifugal model test analysis method is characterized by comprising the following steps that (1) an earth-rock dam break test special model box is arranged; (2) the working principle and the stress similarity criterion of a centrifugal machine are used, an earth-rock dam prototype and a 1/N-contraction-scale centrifugal test model are obtained, under the Ng centrifugal acceleration condition, the linear size ratio of the model and the prototype is 1/N, and the earthing stress of the model and the prototype is the same; (3) according to the seepage similarity criterion, the obtained permeability coefficient of centrifugal model earth is N times of the permeability coefficient of prototype earth; (4) according to the shearing strength similarity criterion, the particle diameter of model cohesiveless earth-rock materials is reduced by N times; and (5) according to the water flow similarity criterion, the similarity criterion of commonly-used physical quantity in an earth-rock dam break centrifugal model test is obtained. The method is not limited or restricted by fields, a large amount of earth and a large number of water resources are of no need during testing, and the method has the advantages of being low in cost and short in time.

Description

Soil bank of stone dam dam break centrifugal model test analytical method

Technical field

The invention belongs to test theory technical field, relate in particular to a kind of native bank of stone dam dam break centrifugal model test analytical method, be specially adapted to the experimental study of native bank of stone dam mechanism of collapsed dam, the crevasse rule of development and dam bursting flood discharge process.

Background technology

At present, more than 9.8 ten thousand of the built reservoir dam of China, 100,000 kilometers of important dyke numbers, the overwhelming majority is Tu Shidiba, these reservoir dams and dyke, when bringing enormous benefits to us, also exist the risk of bursting.1954 so far, and existing 3524 reservoir dams of China and many places dyke burst, and have caused great life and property loss and ecological environment disaster.For this reason, recent domestic has been carried out a large amount of experimental studies for mechanism of collapsed dam, the crevasse rule of development and the dam bursting flood discharge process of Tu Shidiba, to cause the analysis of calamity Consequence calculation for the evolution of dam bursting flood downstream, provide reliable foundation, further promote the security level control of Tu Shidiba, the loss that alleviates or avoid causing because of the dam dam break of the native bank of stone.

Conventional model test method can be divided into two classes both at home and abroad at present:

(1) indoor little guide dam break model testing.

Such test is mainly carried out in indoor water tank, the general ﹤ 1.0m of maximum height of dam.Obviously such test model physical dimension is little, and model and prototype physical dimension and stress level differ greatly, and consider that stress level has material impact to earth and stone material mechanical characteristic, and therefore, the reasonability of such result of the test is under suspicion always.

(2) outdoor large guide dam break model testing.

Dykes and dams are built in the place that such test is general selects to be applicable to carry out dam-break experiments in the wild, construct reservoir (reservoir), or directly utilize discarded reservoir dam to carry out dam-break experiments.In recent years, America and Europe, Japan and China had carried out repeatedly outdoor large guide dam break model testing both at home and abroad, and maximum height of dam has reached 9.7m, to disclosing native bank of stone dam breaking mechanism and crevasse evolution, has brought into play important function.But such test is generally difficult to search out suitable test site, find exactly suitable test site, in process of the test, also can take a large amount of soils and water resource, high, the consuming time length of expense, particularly, along with the increase of height of dam, it is very difficult that the risk control of test will become.

For this reason, we utilize geotechnical centrifuge the produced high acceleration that runs up can promote this principle of stress level in scale model, succeed in developing a set of native bank of stone dam dam break centrifugal model test system, and successfully applied to native bank of stone dam mechanism of collapsed dam and the research of dam break process testing.

Summary of the invention

The object of the present invention is to provide a kind of native bank of stone dam dam break centrifugal model test analytical method, to overcome above-mentioned defect.

Technical scheme of the present invention is:

A native bank of stone dam dam break centrifugal model test analytical method, comprises the following steps:

Step 1) arranges earth and rockfill dam dam-break experiments die for special purpose molding box, levee slope, downstream levee slope and downstream river course section have been set in model casing, the interior layout of case pipeline is accepted water flow control system and is carried out the water yield, pipeline water side is provided with filter screen in case large floating thing enters in model casing, electromagnetic type flow meter is installed on pipeline, with real time record, carrys out discharge Q simultaneously _in, downstream water outlet is dam break current, in order to measure dam break discharge process, at model casing right-hand member, one rectangle crest of weir is set, and crest of weir top thinnest part is 2mm, and angle 30 degree, measure head h more than crest of weir by water-level gauge before crest of weir ₂, utilize weir flow flow formula to calculate dam break discharge process, calculate required discharge coefficient m, by the test of centrifuge flow, demarcate and obtain in advance;

Step 2) utilize operating principle and the stress similitude criterion of centrifuge, at the ratio N(that determines prototype and model physical dimension, it is geometric similarity ratio, claim again guide how much) after, obtain the centrifugal test model of native bank of stone dam prototype and 1/N reduced scale under Ng centrifugal acceleration condition, making model and the linear dimension ratio of prototype is 1/N, and model is consistent with prototype earthing stress;

Step 3) is according to seepage flow similarity criterion, the transmission coefficient that obtains centrifugal model soil be prototype soil transmission coefficient N doubly;

Step 4), according to shear stress similarity criterion, is dwindled N doubly by the grain diameter of model cohesionless soil building stones compared with prototype

Step 5) is utilized flow similarity criterion, and the similarity criterion that obtains conventional physical quantity in the dam break centrifugal model test of native bank of stone dam can be provided by table 1, and after how much guide N values are determined, other physical quantity likelihood ratio is determined immediately.Conventionally N span is between 30～150.

Conventional physical quantity similarity criterion in the dam dam break centrifugal model test of the native bank of stone of table 1

Described step 3) comprises the following steps: according to Darcy law, the average water velocity in the soil body can be expressed as:

v＝ki (1)

Wherein k represents transmission coefficient, and i represents hydraulic gradient, and transmission coefficient meets:

$k=K\frac{\mathrm{\γ}}{\mathrm{\μ}}=K\frac{\mathrm{\ρg}}{\mathrm{\μ}}---\left(2\right)$

In formula, K represents intrinsic permeability; The severe of γ express liquid; The coefficient of dynamic viscosity of μ express liquid.

Hydraulic gradient meets:

$i=-\frac{\mathrm{\Δ}\stackrel{\‾}{h}}{\mathrm{\ΔL}}---\left(3\right)$

Wherein gross head is poor:

$\mathrm{\Δ}\stackrel{\‾}{h}=\left[\frac{\mathrm{\ΔP}}{\mathrm{\ρg}}\right]+\left[\frac{\mathrm{\Δ}\left(v^2\right)}{2g}\right]+\mathrm{\Δz}---\left(4\right)$

In formula, first, right side is that pressure head is poor; Second is that velocity head is poor; The 3rd for elevating head poor.

Generally, velocity head can be ignored, and simultaneous formula (1)-(4) can obtain:

$v=\frac{K}{\mathrm{\μ}}\·\frac{\mathrm{\Δ}(P+\mathrm{z\ρg})}{\mathrm{\ΔL}}---\left(5\right)$

In centrifugal model test, (Δ L) _p=N (Δ L) _m, Δ (P+z ρ g) _p=Δ (P+z ρ g) _pthrough type (5) can be found out, under native intrinsic permeability and the constant condition of the hydrodynamic coefficient of viscosity, the energy gradient of centrifugal model than the large N of the energy gradient of prototype doubly, therefore the seepage velocity in model than the large N of prototype doubly, the transmission coefficient of centrifugal model soil be prototype soil transmission coefficient N doubly.

The invention has the beneficial effects as follows:

The native bank of stone of the present invention dam dam break centrifugal model test analytical method is reliably reasonable, meets engineering actual demand.

The native bank of stone of the present invention dam dam break centrifugal model test analytical method is not subject to restriction and the restriction in place, in process of the test, without taking a large amount of soils and water resource, has advantages of that expense is low, consuming time short, and meanwhile, the risk control of test will become and easily carry out.

Accompanying drawing explanation

Fig. 1 is the plane structure schematic diagram of earth and rockfill dam dam-break experiments die for special purpose molding box of the present invention.

Fig. 2 is the facade structures schematic diagram of earth and rockfill dam dam-break experiments die for special purpose molding box of the present invention.

Fig. 3 is the stress schematic diagram of prototype under 1g gravitational field and Ng centrifugal force field.

Fig. 4 is the stress schematic diagram of model under 1g gravitational field and Ng centrifugal force field.

Fig. 5 is channel flow force analysis schematic diagram of the present invention.

Fig. 6 is that cohesionless soil washes away one of stressed schematic diagram of particle in process.

Fig. 7 be cohesionless soil wash away the stressed schematic diagram of particle in process two.

Fig. 8 is one of homogeneous earth dam model schematic diagram.

Fig. 9 be homogeneous earth dam model schematic diagram two.

Figure 10 is one of crevasse net shape.

Figure 11 is one of crevasse net shape.

Figure 12 is crevasse discharge process figure.

Figure 13 is three kinds of different height of dam crevasse discharge process figure.

The specific embodiment

Below in conjunction with accompanying drawing, the invention will be further described:

(1) system for controlling high-flow water flow of centrifugal machine

System for controlling high-flow water flow of centrifugal machine is developed in success, and this system can provide 0.01～0.05m under the high centrifugal acceleration condition of 100g ³(prototype is 100～500m to/s ³/ s) the test current of flow, the duration can reach 20min (prototype is 33.3h), can carry out the dam break model testing of the various dam types of earth and rockfill dam.(obtained national inventing patent, the patent No.: 20110434073.8).

(2) developed earth and rockfill dam dam-break experiments die for special purpose molding box, model casing work schematic diagram is shown in shown in Fig. 1, Fig. 2.This model casing inside dimension is 1.2m * 0.4m * 0.8m, compares with common centrifugal mold molding box, has strengthened lengthwise dimension, to facilitate layout downstream river course; Casing is that the aluminum alloy materials of thickness 65mm is made, one side is pmma material, so that the collection of image in process of the test, top, organic glass face and downstream face split three high-definition cameras by camera fixed mount, and arrange lamp source, with the clear dam break overall process that records.

The operating principle of model casing is: the pipeline of employing diameter 100mm is accepted water flow control system and carried out the water yield, and pipeline water side is provided with filter screen in case large floating thing enters in model casing, electromagnetic type flow meter is installed on pipeline simultaneously, with real time record, carrys out discharge Q _in.Downstream water outlet is dam break current, because discharge changes rapidly, and accompanies earth and stone material, has been not suitable for its letdown flow of duct type flowmeter survey Q _out.In order to measure dam break discharge process, at model casing right-hand member, one rectangle crest of weir is set, according to the weir designing requirement of Sheet Rectangular flow, crest of weir top thinnest part is only 2mm, angle 30 degree.By water-level gauge before crest of weir, measure head h more than crest of weir ₂, utilize weir flow flow formula can calculate dam break discharge process.And calculate required discharge coefficient m, by the test of centrifuge flow, demarcate and obtain in advance.

(3) native bank of stone dam centrifugal model dam-break experiments similarity criterion has been proposed

Soil bank of stone dam breaking process is a complicated water and soil coupling process, relates to hydraulics, soil mechanics and the mechanics of materials similar.

1, the operating principle of centrifuge and stress similitude criterion

Newton's gravity and inertia force are equivalent, so the physical effect of the centrifugal force that the gravity that prototype is born bears on centrifuge with model is consistent.Centrifugal model test utilizes centrifugal force to carry out simulated gravity, thereby makes the deadweight of earth and rockfill dam bring up to archetype state, makes the stress state of model and prototype consistent.

The centrifugal test model that Fig. 3, Fig. 4 are respectively native bank of stone dam prototype and 1/N reduced scale is the stress schematic diagram under 1g gravitational field and Ng centrifugal force field respectively, under Ng centrifugal acceleration condition, model is with the linear dimension of prototype than being 1/N, and model is consistent with prototype earthing stress.

2, seepage flow similarity criterion

According to Darcy law, the average water velocity in the soil body can be expressed as:

v＝ki (1)

Wherein k represents transmission coefficient, and i represents hydraulic gradient, and transmission coefficient meets:

$k=K\frac{\mathrm{\γ}}{\mathrm{\μ}}=K\frac{\mathrm{\ρg}}{\mathrm{\μ}}---\left(2\right)$

In formula, K represents intrinsic permeability; The severe of γ express liquid; The coefficient of dynamic viscosity of μ express liquid.

Hydraulic gradient meets:

$i=\frac{\mathrm{\Δ}\stackrel{\‾}{h}}{\mathrm{\ΔL}}---\left(3\right)$

Wherein gross head is poor:

$\mathrm{\Δ}\stackrel{\‾}{h}=\left[\frac{\mathrm{\ΔP}}{\mathrm{\ρg}}\right]+\left[\frac{\mathrm{\Δ}\left(v^2\right)}{2g}\right]+\mathrm{\Δz}---\left(4\right)$

In formula, first, right side is that pressure head is poor; Second is that velocity head is poor; The 3rd for elevating head poor.

Generally, velocity head can be ignored, and simultaneous formula (1)-(4) can obtain:

$v=\frac{K}{\mathrm{\μ}}\·\frac{\mathrm{\Δ}(P+\mathrm{z\ρg})}{\mathrm{\ΔL}}---\left(5\right)$

In centrifugal model test, (Δ L) _p=N (Δ L) _m, Δ (P+z ρ g) _p=Δ (P+z ρ g) _pthrough type (5) can be found out, under native intrinsic permeability and the constant condition of the hydrodynamic coefficient of viscosity, the energy gradient of centrifugal model than the large N of the energy gradient of prototype doubly, therefore the seepage velocity in model than the large N of prototype doubly, the transmission coefficient of centrifugal model soil be prototype soil transmission coefficient N doubly.

3, shear stress similarity criterion

Analysis by native bank of stone dam mechanism of collapsed dam can find out, the shear stress of water and soil interface is the principal element that affects crevasse development.

Investigate channel flow shown in Fig. 5, have:

Gsinθ+F ₁-F ₂-F _τ＝ma (6)

In formula, G is fluid weight, under Ng centrifugal acceleration, and G=ρ _wngV; V is fluid volume, supposes that A is cross-sectional area, V=AL; F ₁and F ₂the active force that represents respectively upstream and downstream face; F _τfor the suffered frictional resistance of diagram channel flow; A is acceleration; θ is slope angle.

For uniform-flow, there is a=0, F ₁=F ₂, therefore:

F _τ＝Gsinθ＝GJ (7)

In formula, J is hydraulic gradient; Suppose that χ is wetted perimeter, R is hydraulic radius, and current to the average shearing stress of gool are:

$\mathrm{\τ}=\frac{\mathrm{GJ}}{\mathrm{xl}}={\mathrm{\ρ}}_w\mathrm{NgRJ}---\left(8\right)$

Due to R _m=R _p/ N, J _m=J _p, in model and prototype, current equate the shear stress of crevasse sidewall, that is:

τ _m＝τ _p (9)

Cohesionless soil mainly contains slippage and rolls two kinds and is subject to force mode in the process of washing away, and White proposes the slippage situation of cohesionless soil particle and can analyze by pattern shown in Fig. 6, and critical shear stress meets:

In formula,

for angle of internal friction; A _ebe two intergranular effective contacts area.For circular granular, have:

In formula, α is the effective ratio of contact area and the maximum cross-section area between soil particle; d ₅₀for average grain diameter.

Cohesionless soil rolling situation can be analyzed by pattern shown in Fig. 7, and critical shear stress meets:

${\mathrm{\τ}}_c=\frac{\mathrm{Wb}}{A_{e}a}---\left(12\right)$

For circular granular, have:

${\mathrm{\τ}}_c=\frac{2({\mathrm{\ρ}}_s-{\mathrm{\ρ}}_w)\mathrm{Ng}\sin \mathrm{\β}}{3\mathrm{\α}(1+\cos \mathrm{\β})}{d}_{50}---\left(13\right)$

In above formula, the implication of parameter a, b, β as shown in Figure 7.

Contrast (12) and (13) can find out, under the certain condition of centrifugal acceleration, the proportional routine relation of the critical shear stress of cohesionless soil and average grain diameter, introduces parameter ξ, and the critical shear stress of cohesionless soil can be expressed as:

τ _c＝ξρ _wNg(G _s-1)d ₅₀ (14)

As τ > τ _ctime, soil particle starts, and current start the erosion of the soil body, introduce discriminant parameter F _s, have:

$F_s=\frac{\mathrm{\&tau;}}{{\mathrm{\&tau;}}_c}=\frac{{\mathrm{\&rho;}}_w\mathrm{NgRJ}}{{\mathrm{\&xi;\&rho;}}_w\mathrm{Ng}(G_s-1){\mathrm{<figure-callout\; id="50"\; label="d"\; filenames="HDA0000457193120000061.png"\; state="\{\{state\}\}">d</figure-callout>}}_{50}}=\frac{\mathrm{RJ}}{\mathrm{\&xi;}(G_s-1)d_{50}}---\left(15\right)$

By upper surface analysis, can find out, for cohesionless soil, work as F _s>=1 o'clock, soil particle started by erosion, in centrifugal model test, guarantee that model is similar with prototype, need have (F _s) _m=(F _s) _p, due to R _m=R _p/ N, so, in order to guarantee the accuracy of centrifugal model test simulation cohesionless soil bank of stone dam breaking process, the grain diameter of model cohesionless soil building stones need be dwindled to N doubly compared with prototype, that is:

${\left(d_{50}\right)}_m=\frac{{\left(d_{50}\right)}_p}{N}---\left(16\right)$

In clay dykes and dams Dam Break Problems, it is not often that simple grain starts that clay washes away, but a kind of the form that group starts, increase along with water velocity, grain group size also can constantly change, and finally show as the form that block washes away, so grain diameter is not principal element.

(4) flow similarity criterion

Earth and rockfill dam bursts, and to cause calamity consequence and dam bursting flood discharge process and dam bursting flood peak value closely related.Dam Break Problems is studied in application centrifugal model test, need to set up the similarity criterion of water flow and prototype current.Suppose that in earth and rockfill dam dam break process, unrestrained top current are stationary flow, according to Chezy formula, flow rate of water flow can be expressed as:

$v={\left(\frac{8g}{f}\right)}^{\frac{1}{2}}{R}^{\frac{1}{2}}{J}^{\frac{1}{2}}---\left(17\right)$

In formula, f is roughness coefficient, irrelevant with centrifugal acceleration, so the water velocity of model and prototype equates.

The area of supposing the crevasse cross-section of river is A, and crevasse flow Q=vA, because A _m=A _p/ N ²so, have:

$Q_m=\frac{Q_p}{N^2}---\left(18\right)$

By above analysis, in the dam break centrifugal model test of native bank of stone dam, the similarity criterion of conventional physical quantity can be provided by table 1.

Conventional physical quantity similarity criterion in the dam dam break centrifugal model test of the native bank of stone of table 1

In order to verify the dam break centrifugal model test system of invention and the reliable reasonability of test analysis method, utilize actual unrestrained top, reservoir soil bank of stone dam, Chuzhou City Dawa County, Anhui Province dam-break experiments result to verify it.This reservoir dam is homogeneous earth dam, aggregate storage capacity 100,000 m3, dam overall length 120.0m, top width 3.0m, maximum height of dam 9.7m.2008-2009, Zhang Jianyun etc. utilized this dam to carry out many groups of tests for mechanism of collapsed dam and the dam break process of homogeneous dam, obtain good result.Dam break centrifugal model test adopts the clay of the on-the-spot unrestrained top dam-break experiments F1 group of Dawa County's reservoir earth and rockfill dam time, and the test parameters of F1 group time clay and result of the test are in Table 2 and table 3.

Table 2F1 group time on-the-spot dam-break experiments major parameter.

Table 3F1 group time on-the-spot dam-break experiments result.

The model height of dam 19.4cm that test adopts, width at dam crest 6.0cm, upstream and downstream dam slope slope ratio is 1:2, the reserved wide 4.0cm of breach in dam crest middle part, dark 2.0cm, dam is homogeneous earth dam, dam body materials dry density 1.57g/cm ³, cohesion 9.3kPa, 28.25 ° of angle of internal friction, dam body degree of compaction 97%, is shown in Fig. 8, Fig. 9.By adjusting centrifuge acceleration, be 50g, the unrestrained process of bursting of pushing up of simulation Dawa County, Chuzhou reservoir homogeneous earth dam.

In dam break centrifugal model test process, find, first unrestrained dam current carry out erosion to downstream dam slope, at downstream dam slope, form low wide and up narrow " cucurbit " shape jet-bedding, then jet-bedding lasting incision under flow action deepens, near spiral flow jet-bedding sidewall also continues oppose side wall and carries out scour, and it is constantly broadened.Along with increasing and the flow velocity of crevasse flow are accelerated, jet-bedding advances to dam body upstream gradually, there is intermittent unstability and cave in jet-bedding (crevasse) side slope, there is laterally large expansion in crevasse, form final crevasse as shown in Figure 9, Figure 10, crevasse top width 30cm, crevasse bottom width 22cm, crevasse degree of depth 10cm, be inverted trapezoidal (according to similarity criterion, crevasse is of a size of top width 15.0m, bottom width 11.0m, degree of depth 5.0m), basically identical with on-the-spot dam-break experiments crevasse shape.Crevasse peak flow is 46.0m ³/ s, the 14min that peak flow appears at after dam break occurs is shown in Figure 12, basically identical with site test results, thereby has verified the reliable reasonability of institute's invention dam break centrifugal model test system and test method.

Further, by regulating centrifuge acceleration magnitude, simulated respectively the bad process of bursting of unrestrained bursting of height of dam 9.6m, 16.0m and 32.0m homogeneous soil masonry dam.The model height of dam that test adopts is 32.0cm, top width 10.0cm, and upstream and downstream dam slope slope ratio is 1:2.By adjusting centrifuge acceleration, be 30g, 50g and 100g, simulate respectively the unrestrained top dam break process of height of dam 9.6m, 16.0m and 32.0m height of dam homogeneous soil masonry dam, obtain three kinds of different height of dam crevasse discharge curves as shown in figure 13.

Result of the test shows, different height of dam homogeneous soil stone dam-break mechanism and entity dam result of the test are basically identical, be that the dam slope crevasse evolution of dam body downstream is mainly comprised of " continuous vertical that current scour causes is to incision and laterally lasting expansion " and " the laterally large expansion at intermittence that crevasse slope instability caves in and causes ", but the increase along with height of dam, crevasse development speed is obviously accelerated, crevasse peak flow is larger and go out now more early, bursting, it is also shorter to last, contrast height of dam 32.0m homogeneous soil masonry dam and the height of dam 9.6m homogeneous soil masonry dam process of bursting can be found, increase due to crevasse flow, during the dam break of height of dam 32.0m homogeneous soil masonry dam, peak flow is half of height of dam 9.6m homogeneous soil masonry dam the time of advent, peak flow is 14.6 times of 9.6m dam, therefore it causes calamity consequence by even more serious.

Embodiment recited above is described the preferred embodiment of the present invention; not the spirit and scope of the present invention are limited; do not departing under design concept prerequisite of the present invention; various modification and improvement that in this area, common engineers and technicians make technical scheme of the present invention; all should fall into protection scope of the present invention, the technology contents that the present invention asks for protection is all documented in claims.

Claims (2)

1. a native bank of stone dam dam break centrifugal model test analytical method, is characterized in that comprising the following steps:

Step 1) arranges earth and rockfill dam dam-break experiments die for special purpose molding box, levee slope, downstream levee slope and downstream river course section have been set in model casing, the interior layout of case pipeline is accepted water flow control system and is carried out the water yield, pipeline water side is provided with filter screen in case large floating thing enters in model casing, electromagnetic type flow meter is installed on pipeline, with real time record, carrys out discharge Q simultaneously _in, downstream water outlet is dam break current, in order to measure dam break discharge process, at model casing right-hand member, one rectangle crest of weir is set, and crest of weir top thinnest part is 2mm, and angle 30 degree, measure head h more than crest of weir by water-level gauge before crest of weir ₂, utilize weir flow flow formula to calculate dam break discharge process, calculate required discharge coefficient m, by the test of centrifuge flow, demarcate and obtain in advance;

Step 2) utilize operating principle and the stress similitude criterion of centrifuge, at the ratio N(that determines prototype and model physical dimension, it is geometric similarity ratio, claim again guide how much) after, obtain the centrifugal test model of native bank of stone dam prototype and 1/N reduced scale under Ng centrifugal acceleration condition, making model and the linear dimension ratio of prototype is 1/N, and model is consistent with prototype earthing stress;

Step 3) is according to seepage flow similarity criterion, the transmission coefficient that obtains centrifugal model soil be prototype soil transmission coefficient N doubly;

Step 4), according to shear stress similarity criterion, is dwindled N doubly by the grain diameter of model cohesionless soil building stones compared with prototype

Step 5) is utilized flow similarity criterion, and the similarity criterion that obtains conventional physical quantity in the dam break centrifugal model test of native bank of stone dam can be provided by table 1, and after how much guide N values are determined, other physical quantity likelihood ratio is determined immediately.Conventionally N span is between 30～150.

Conventional physical quantity similarity criterion in the dam dam break centrifugal model test of the native bank of stone of table 1

Physical quantity title The likelihood ratio Ng Gravity Models

(prototype amount/model value) Length δ _l N Flow velocity δ _v 1 Flow δ _a N ² Time δ _t N Quality δ _m N ³ Density δ _ρ 1 Power δ _F N ² Stress, pressure δ _P 1 Acceleration δ _a 1/N Transmission coefficient δ _k N Cohesionless soil building stones particle diameter δ _d N

2. the native bank of stone according to claim 1 dam dam break centrifugal model test analytical method, is characterized in that described step 3) comprises the following steps: according to Darcy law, the average water velocity in the soil body can be expressed as:

v＝ki (1)

Wherein k represents transmission coefficient, and i represents hydraulic gradient, and transmission coefficient meets:

$k=K\frac{\mathrm{\&gamma;}}{\mathrm{\&mu;}}=K\frac{\mathrm{\&rho;g}}{\mathrm{\&mu;}}---\left(2\right)$

In formula, K represents intrinsic permeability; The severe of γ express liquid; The coefficient of dynamic viscosity of μ express liquid.

Hydraulic gradient meets:

$i=\frac{\mathrm{\&Delta;}\stackrel{\&OverBar;}{h}}{\mathrm{\&Delta;L}}---\left(3\right)$

Wherein gross head is poor:

$\mathrm{\&Delta;}\stackrel{\&OverBar;}{h}=\left[\frac{\mathrm{\&Delta;P}}{\mathrm{\&rho;g}}\right]+\left[\frac{\mathrm{\&Delta;}\left(v^2\right)}{2g}\right]+\mathrm{\&Delta;z}---\left(4\right)$

In formula, first, right side is that pressure head is poor; Second is that velocity head is poor; The 3rd for elevating head poor.

Generally, velocity head can be ignored, and simultaneous formula (1)-(4) can obtain:

$v=\frac{K}{\mathrm{\&mu;}}\&CenterDot;\frac{\mathrm{\&Delta;}(P+\mathrm{z\&rho;g})}{\mathrm{\&Delta;L}}---\left(5\right)$

In centrifugal model test, (Δ L) _p=N (Δ L) _m, Δ (P+z ρ g) _p=Δ (P+z ρ g) _pthrough type (5) can be found out, under native intrinsic permeability and the constant condition of the hydrodynamic coefficient of viscosity, the energy gradient of centrifugal model than the large N of the energy gradient of prototype doubly, therefore the seepage velocity in model than the large N of prototype doubly, the transmission coefficient of centrifugal model soil be prototype soil transmission coefficient N doubly.

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