CN101074912A - Apparatus and method for testing cement concrete penetration performance under loading action - Google Patents

Abstract

A device used for testing permeation performance of hydraulic engineering concrete under load action is prepared forming pressurizing unit by steel chassis, steel plate, steel vertical column, spring, nut and bolt; forming test-piece chamber by sleeve, up-pressing steel plate, down-pressing steel plate, ball base and concrete test-piece. Its testing method is also disclosed.

Description

Permeance property proving installation and the method for testing of concrete for hydraulic structure under load action

One, technical field

The present invention relates to a kind of proving installation of measuring the concrete for hydraulic structure permeance property, specifically relate to a kind of under continual and steady load action the proving installation and the method for testing thereof of concrete for hydraulic structure permeance property.

Two, background technology

Some endurance issues of concrete for hydraulic structure comprise: infiltration corrosion, alkali, carbonization and the steel bar corrosion of chlorion erosion, water, freeze thawing circulation destruction etc. are all closely related with perviousness.Good impermeability is to guarantee many important engineering safeties, durable necessary condition.People launch but mostly center on single influence factor to the concrete for hydraulic structure perviousness and because the endurance issues that the infiltration of gas-liquid medium causes is studied for many years.Yet the concrete for hydraulic structure in the engineering reality is not to work under single factors, generally the factor acting in conjunction of all bearing two or more.During multiple factor acting in conjunction, be not the simple superposition of each single factors effect to the damaging action of concrete for hydraulic structure, the reciprocation that each factor produces makes that the destructive process of concrete for hydraulic structure is complicated in the actual military service process.In actual engineering, nearly all concrete for hydraulic structure all can bear dissimilar load actions, and load often causes that microfracture produces and expansion in the concrete for hydraulic structure, thereby influences the perviousness of concrete for hydraulic structure.The infiltration height method that the impervious test of China's concrete for hydraulic structure is at present adopted, being about to go up bore is that the butt filled circles cone concrete sample that 175mm, following bore are 185mm, high 150mm is put into permeameter, at test specimen lower surface plus-pressure water, until upper surface the infiltration phenomenon appears by permeameter.This method can only be estimated concrete for hydraulic structure in the perviousness that is subjected under the effect of water pressure single factors, and the effect that actual in commission concrete for hydraulic structure structure is often being born load simultaneously, and normal experiment apparatus structure simple (conical butt metal cylinder), and can not load to test specimen, therefore, be subjected to the restriction of experimental provision, the research of concrete for hydraulic structure water permeability under load action is almost blank.In addition, when measuring the concrete for hydraulic structure infiltration coefficient with conventional method and experimental provision, because the concrete for hydraulic structure perviousness is very little, make the water of capacity see through concrete for hydraulic structure to guarantee measuring accuracy, experiment often needs last very long.For the permeability test under the no load action, to the time is hard-core, but for the permeability test that load action is arranged, if adopt hydraulic press machine commonly used as charger, the long time not only can not guarantee the continual and steady of load, also can cause hydraulic pressure testing machine fault, shorten its serviceable life, bigger to its infringement.Therefore, it is worthless adopting the hydraulic pressure testing machine to load to test specimen.

Three, summary of the invention

The objective of the invention is to load and to adopt the hydraulic pressure testing machine to load to guarantee problems such as load is continual and steady to test specimen at the conventional test device, and provide the permeance property proving installation of a kind of concrete for hydraulic structure under load action, this device can not only load to test specimen, and load that test specimen adds is no longer provided for a long time by hydraulic press machine commonly used, new charger can guarantee the long-term continual and steady of load, avoids the interference of the shakiness of load to experimental result.

Another object of the present invention is to utilize the method for testing of this proving installation to concrete for hydraulic structure permeance property under load action.

The objective of the invention is to realize: this device design is as follows: as depicted in figs. 1 and 2 by following technical scheme:

A kind of concrete for hydraulic structure is the permeance property proving installation under load action, it is characterized in that it is made up of pressue device and concrete sample chamber two parts, wherein pressue device is by steel bottom plate (1), steel column (2), steel plate (3), steel plate (4), spring (5), nuts (6) constitutes, steel bottom plate (1), respectively be drilled with four circular holes of symmetry around steel plate (3) and the steel plate (4), four circular steel columns (2) are passed steel bottom plate (1) respectively, steel plate (3), in four circular holes on the steel plate (4), between steel bottom plate (1) and steel plate (4), place concrete sample chamber (17), put a spring (5) respectively on four steel principal posts (2) between steel plate (3) and the steel plate (4), use nuts (6) fixing then respectively; Circular sleeve (7) in the concrete sample chamber (17) is fixed on the steel bottom plate (1), cylindrical shape concrete sample (12) is placed in the sleeve (7), the bottom pad lastblock of concrete sample (12) presses down billet (9), compressed steel backing plate (8) on its top cover lastblock is placed a ball seat (10) between last compressed steel backing plate (8) and steel plate (4).

Above-mentioned proving installation is characterized in that the base portion of described circular steel column (2) is a stand, and top is threaded.

Above-mentioned proving installation is characterized in that described circular sleeve (7) is to make with organic glass, and is adhesively fixed with epoxy resin and fixes on the steel bottom plate (1), and a side of sleeve (7) has a spout hole (11).

Above-mentioned proving installation is characterized in that all leaving the water-filling space between described concrete sample (12) and sleeve (7) both sides, and covers with rubber band (14) on the space of both sides.

Above-mentioned proving installation is connected on the Anti-leakage instrument after it is characterized in that having an aperture (15) and water inlet pipe (16) linking to each other in the described upward compressed steel backing plate (8) again.

The principle of work of this device and method of testing are: by the hydraulic pressure testing machine spring is pressurizeed during work, the force value size is then controlled by reading pressing machine dial plate numerical value, immediately bolt is tightened and removed pressing machine when arriving the authorised pressure value, the suffered outside of test specimen this moment presses load just to be provided by spring (5).Because spring force is subjected to the influence of factors such as concrete deformation very little, pressure maintaining performance is good and stress loss is little, be not subjected to the influence of disturbing factor such as outside outage, so can carry out for a long time the research that concrete under the load action state continually and steadily permeates performance such as corrosion.The pressure that spring (5) produces passes through steel plate (4), ball seat (10), goes up compressed steel backing plate (8) transfer function to test specimen (12).Water inlet pipe (16) on the last compressed steel backing plate (8) is connected to Anti-leakage instrument, press water is by providing through Anti-leakage instrument and the aperture (15) of water inlet pipe of flowing through (16) and last compressed steel backing plate inside acts on the inside surface of cylindrical shape test specimen (12), and hydraulic pressure is regulated control by the tensimeter on the Anti-leakage instrument.The test specimen outside surface is immersed in the organic glass sleeve (7) of fills with water, and the sleeve top covers to avoid the water evaporation with rubber band (14).Spout hole on the sleeve (11) control water level connects spout hole (11) to the graduated cylinder that is put in lower with a plastic tube, and the amount of seepage that sees through ring-like test specimen wall like this can be collected by graduated cylinder.The experimental test step is as follows: step 1: pressing machine is tightened and removed to the hydraulic pressure testing machine to spring (5) pressurization, with bolt (6) by steel plate (3) immediately when arriving the authorised pressure value, and this moment, the outside load of pressing was just provided by spring (5); Step 2: the pressure that spring (5) produces passes through steel plate (4), ball seat (10), goes up compressed steel backing plate (8) transfer function to cylindrical shape concrete sample (12); Step 3: Anti-leakage instrument produces press water, press water is injected the inside surface of concrete sample (12) by water inlet pipe (16) and aperture (15); Step 4: give space water filling between concrete sample (12) outside surface and the organic glass sleeve (7), the water surface is flushed with spout hole (11), use rubber band (14) to cover sleeve (7) then to avoid the water evaporation; Step 5: the spout hole (11) of collection on sleeve (7) flow to the infiltration water in the external graduated cylinder; Step 6: utilize the infiltration water in the graduated cylinder, convert with following derivation formula and try to achieve concrete infiltration coefficient.

Circular ring type concrete sample infiltration coefficient computing formula:

$k=-\frac{\mathrm{\&mu;q}\&CenterDot;\ln \frac{r_1}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="A20071002313900131.png"\; state="\{\{state\}\}">r</figure-callout>}}_2}}{2\mathrm{\&pi;}\&CenterDot;h\&CenterDot;\mathrm{\&Delta;h}}$

In the formula: k-infiltration coefficient (cm/s); Discharge (the cm that collects in the q-unit interval ³/ s); r ₂The external radius of-annular test-piece (cm); r ₁The inside radius of-annular test-piece (cm); The height of h-annular test-piece (cm); Δ h-water flows into the head difference between face and effluent face, the viscosity of μ-water.

The invention solves the conventional test device can not load to test specimen, and adopt the hydraulic pressure testing machine to load to guarantee problems such as load is continual and steady, and the present invention is to be the pressure permeation experimental provision of load with the compression spring, research continues the influence of press loading effect to the water permeability of concrete for hydraulic structure, thereby disclose the mechanism and the combination mechanism of the aging and pathology of concrete for hydraulic structure under the multifactor combination condition, if its achievement in research is applied to actual engineering, for the reinforcing of disease danger concrete for hydraulic structure structure and the design and construction and the operation on high concrete dam provide the source technical support.

Four, description of drawings

Below in conjunction with drawings and Examples apparatus of the present invention are described further:

Fig. 1 is the structural representation that is subjected to load action concrete sample water permeability test charger

Fig. 2 is the structural representation of concrete sample chamber

Reference numeral: 1. steel bottom plate, 2. steel column, 3. steel plate 1., 4. steel plate 2., 5. spring, 6. nuts, 7. sleeve is 8. gone up the compressed steel backing plate, 9. presses down billet, 10. ball seat, 11. spout holes, 12. concrete samples, 13. water, 14. rubber bands, 15. apertures, 16. water inlet pipes, 17 specimen chambers.

Five, embodiment

The permeance property proving installation of embodiment 1 concrete for hydraulic structure under load action

This proving installation is made up of pressue device and specimen chamber (17) two parts, the steel bottom plate in the pressue device (1) wherein, steel plate (3) and steel plate (4), be respectively long 340mm, wide 170mm, high 28mm, the diameter that respectively is drilled with 4 symmetries around it is the circular hole of 18mm, with four long 650mm, diameter is the stand of 25mm for there is diameter the 16mm lower end, upper end screwed steel column (2) penetrates in four circular holes on the steel bottom plate (1), and steel bottom plate (1) is gone up and placed specimen chamber (17), it is to be 130mm by diameter, high 120mm, the organic glass sleeve (7) of thick 8mm is placed on the steel bottom plate (1), and inner and outer diameter is respectively 30mm and 110mm, the concrete sample of high 110mm (12) is put into sleeve (7), test specimen (12) a diameter 110mm be arranged at the bottom, high 10mm presses down billet (9), it is 120mm that a diameter is placed on the top of test specimen (12), the last compressed steel backing plate (8) of high 18mm, the ball seat (10) that to place a diameter again on billet (8) be 35mm; Again steel plate (4) is inserted on the steel column (2) by four circular holes, make steel plate (4) and ball seat (10) close proximity, and to put diameter on four steel columns (2) respectively be 3mm, the spring of high 450mm (5), from four circular holes, be enclosed within steel plate (3) on four steel columns (2) then, use nuts (6) to tighten fixation steel plate (3) at last, be drilled with a small sircle hole (15) in the last compressed steel backing plate (8), and put on the Anti-leakage instrument with connecing again after water inlet pipe (16) is connected, water-filling (13) between concrete sample (12) and sleeve (7), and the water surface is flushed with spout hole (11), sleeve behind the water-filling (7) top covers with rubber band (14), spout hole (11) connects graduated cylinder by proofed sleeve, accumulates the percolating water that flows out from spout hole (11), obtains the leak factor value according to water amount of seepage with infiltration coefficient computing formula (3).

The method of testing of 2 pairs of concrete for hydraulic structure loads of embodiment infiltration coefficient.

1, starting material and test specimen

With PO32.5 class g cement (physical property sees Table 1), II level flyash, modulus of fineness is 2.5 river sand, artificial rubble of the ls of maximum particle diameter 10mm and tap water are pressed the concrete batching of match ratio shown in the table 2, be molded into the cylindrical shape test specimen that inside and outside diameter is respectively 30mm and 110mm, 6 on every group of sample.Test specimen is clipped test specimen two with diamond saw blade behind concrete standard fog room maintenance 28d, obtains highly being the test specimen of 110mm.Get 3 in every group of test specimen and measure compressive strength, the reference of loading size when carrying out impervious experiment as all the other test specimens.Each compressive strength of organizing test specimen sees Table 2.

The basic physical property of table 1 cement

Specific surface area/m 2/kg	Setting time/min		Compressive strength/MPa		Rupture strength/MPa
							Initial set	Final set	3d	28d	3d	28d
	305	185	240	4.6	8.7	19.2							41.2

Table 2 concrete sample match ratio and compressive strength

The test specimen group	Concrete mix/kg/m 3						Compressive strength f c /MPa
								Cement	Flyash	Sand	Rubble	Water	FDN
	Cs1 Cs2 Cs3	192 234 290	48 59 72	652 636 611	1324 1287 1241	175 175 175								1.20 1.47 1.81	19.8 25.4 30.1

2, test procedure

Every group of test specimen got 2 and tested respectively.

Step 1: it is that 120mm, high 18mm go up compressed steel backing plate (8) and diameter is that 110mm, high 10mm press down on the billet (9) that the cylindrical shape concrete sample (12) that during test inside and outside diameter is respectively 30mm and 110mm, high 110mm earlier sticks on diameter with epoxy resin mortar, treat that putting into the vacuum dehydration instrument behind the epoxy cure vacuumizes 3h, suck tap water subsequently and keep vacuum 1h, close the vacuum dehydration instrument by the test specimen 18h that absorbs water, so that reach seepage stability at the trial as early as possible.

Step 2: pretreated test specimen seepage flow under the hydraulic pressure of 0.8MPa is basicly stable to water flow.

Step 3: the big or small f that determines first load application.First load application f is the compressive strength f of test specimen _c0.1 times, i.e. stress ratio η (η=f/f _c) be 0.1.

Step 4: the hydraulic pressure testing machine is spring (5) pressurization of 3mm, high 450mm to diameter by the steel plate (3) of long 340mm, wide 170mm, high 28mm, immediately pressing machine is tightened and removed to bolt (6) when arriving authorised pressure value f, this moment, the outside load of pressing was just provided by spring (5).The pressure that spring (5) produces passes through the ball seat (10) of long 340mm, the steel plate (4) of wide 170mm, high 20mm, high 35mm, last compressed steel backing plate (8) transfer function to test specimen (12).

Step 5: Anti-leakage instrument produces the press water of 0.8MPa, is the inside surface of the water inlet pipe (16) of 5mm and aperture (15) the injection test specimen (12) that diameter is 5mm by internal diameter with press water.

Step 6: giving test specimen (12) outside surface and external diameter is water filling between the organic glass sleeve (7) of 138mm, thick 4mm, and covers sleeve (7) with rubber band (14) and evaporate to avoid water.

Step 7: after the seepage flow duration was 7～10h, the internal diameter of collecting on sleeve (7) was that 4mm spout hole (11) flow to the infiltration water in the external graduated cylinder, and was the electronic scales metering of 0.1g with precision.Weight, the size of pressure f, the seepage flow duration of record infiltration water.

Step 8: increase load f, repeating step 4～step 7.Load increment is controlled by η, and each η increases 0.1, and till η reaches 0.8 (η=0.1,0.2 ..., 0.8), therefore, each test specimen can obtain 8 groups of test findings.

Step 9: to other test specimen repeating step 1～step 8, until the experiment work of finishing 6 whole test specimens.

3, test findings

(1) infiltration coefficient calculating formula

Concrete infiltration coefficient calculates according to Darcy's law, promptly

$q=k\frac{\mathrm{\&mu;S\&Delta;h}}{L}---\left(1\right)$

In the formula: the flow (cm in the q-unit interval ³/ s); K-infiltration coefficient (cm/s); S-discharge area (cm ²); The inflow face of Δ h-water and the head difference between effluent face (cm); L-seepage distance (cm); The viscosity of μ-water.

Darcy formula requires the parallel horizontal infiltration that do not take place of hole, and material continuous variation complicated to the inside concrete pore structure is difficult to accomplish, but Chinese scholars is thought what Darcy's law still was suitable for for cement concrete at present.Radial penetration is only taken place annular test specimen hypothesis, when flow q one timing, is r at radius, and thickness is the differential water pressures Δ h on the thin-walled both sides of Δ r _rFor

$\mathrm{\&Delta;}{h}_r=\frac{\mathrm{q\&Delta;r}}{\mathrm{k\&mu;}\&CenterDot;2\mathrm{\&pi;r}\&CenterDot;h}---\left(2\right)$

Integration is made on formula (2) both sides

$q\&CenterDot;{\&Integral;}_{r_1}^{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="A20071002313900131.png"\; state="\{\{state\}\}">r</figure-callout>}}_2}\frac{\mathrm{dr}}{r}=\mathrm{k\&mu;}\&CenterDot;2\mathrm{\&pi;}\&CenterDot;h\&CenterDot;{\&Integral;}_{h_1}^{{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="A20071002313900131.png"\; state="\{\{state\}\}">h</figure-callout>}}_2}\mathrm{dh}$

Can get circular ring type test specimen infiltration coefficient computing formula

$k=-\frac{\mathrm{\&mu;q}\&CenterDot;\ln \frac{r_1}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="A20071002313900131.png"\; state="\{\{state\}\}">r</figure-callout>}}_2}}{2\mathrm{\&pi;}\&CenterDot;h\&CenterDot;\mathrm{\&Delta;h}}---\left(3\right)$

In the formula: k-infiltration coefficient (cm/s); Discharge (the cm that collects in the q-unit interval ³/ s); r ₂The external radius of-annular test-piece (cm); r ₁The inside radius of-annular test-piece (cm); The height of h-annular test-piece (cm); Δ h-water flows into the head difference between face and effluent face, is mortar permeameter pressure gauge reading in this experiment; The viscosity of μ-water.

(2) load is to the influence of concrete permeability

Osmotic coefficient k/10 of concrete sample under the different stress ratios of table 3 ^-10Cm.s ^-1

η	Cs11	Cs12	Cs21	Cs22	Cs31	Cs32
							0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8	10.02 9.44 7.40 6.37 5.82 5.21 4.85 17.88	8.02 6.75 5.01 4.02 3.56 3.10 8.28 19.95	40.06 36.23 29.22 26.49 22.14 23.07 38.64 71.61	54.19 49.03 36.11 29.56 28.15 24.32 51.60 77.33	21.24 19.26 14.88 11.82 10.43 10.71 21.631 31.60	15.70 14.25 11.97 9.83 8.86 8.45 16.63 30.333

Table 3 is respectively the variation of the osmotic coefficient k of different mixture ratio, varying strength concrete sample with stress ratio η.Find out by table 3:

1. the perviousness of concrete sample and compressive strength are closely related, and intensity is high more, and infiltration coefficient is more little.The concrete sample that intensity is high, not only because the moulding water cement ratio is lower, cement paste structure is fine and close, and also consumption is less because unit volume is gathered materials, and therefore gathers materials-and the cement slurry interface is less.Yet, gather materials-cement slurry zone of transition at the interface is the weak part in the concrete, becomes the passage of water infiltration easily, also causes the generation and the expansion in crack when being subjected to stress easily.

2. the infiltration coefficient of each test specimen is basic identical with the Changing Pattern of stress ratio.When stress ratio less than 0.3 the time, the infiltration coefficient of each test specimen increases with stress ratio and reduces gradually, except that indivedual test specimens, it is minimum to be about stress ratio that 0.6 left and right sides infiltration coefficient reaches greatly.After stress ratio surpassed 0.6, infiltration coefficient increased suddenly.

Trace it to its cause, the variation of the concrete permeability that stress causes is obviously relevant with the variation of structural change, especially cement slurry-gather materials interface and crack state.Test specimen suffered be axle pressure, the load direction is vertical with the seepage direction of water.Pressure has two opposite effects to crack state and perviousness in the concrete: within the specific limits, that pressure will cause will be parallel with the load direction in the concrete, in other words with the expansion of the less pre-existing fractures of the load deviation of directivity and the formation in newborn crack, cause the increase of concrete permeability; And on the other hand, pressure direction then to a certain extent by " pressing ", makes the reduction of concrete permeability perpendicular to pre-existing fractures.Therefore, pressure is the comprehensive effect of these two kinds of effects to the influence of concrete permeability.It should be noted that, used concrete sample is cylindric test specimen in this experiment, when being subjected to press loading effect, it is parallel with the seepage direction of water that the test specimen axial deformation causes by " pressing " crack (strictness is said and is " broken face "), the crack (broken face) that radial deformation produces is then most vertical with the seepage direction of water, and this two classes crack is to have than big-difference to the influence degree of concrete infiltration coefficient.

3. owing to above two kinds of effects, concrete is lower than 30% ultimate stress f at the compression chord f of institute _cThe time, gathering materials wherein-cement slurry interface seam is stable, can not expand.When f reaches 30～50%f _cThe time, the interface seam will slowly expansion in zone of transition.When f surpasses f _c50% o'clock, crack propagation just can extend in the cement matrix.Surpass f and work as f _c75% o'clock, the crack in the cement matrix also can not stop the expansion, finally cause concrete destruction.Concrete sample is 0.1～0.2 o'clock in stress ratio in this experiment, and infiltration coefficient slightly reduces but changes less.And in the time of stress ratio 0.3, infiltration coefficient can diminish suddenly, and this is that compressive stress makes due to some original microfracture close downs of inside concrete, and this moment, stress can't make aggregate and generation crack, cement slurry interface.When stress ratio is increased to 0.3～0.6, infiltration coefficient continues to reduce, theoretically, this moment, load was enough to cause the expansion in crack, thus the expansion that continues to reduce to illustrate crack this moment of infiltration coefficient with form to the increase effect of concrete permeability still less than with in the parallel crack of water seepage direction " pressing " to infiltrative reduction effect.Stress ratio further is increased at 0.6 o'clock, and infiltration coefficient transfers increase to, and this is because aggregate and crack, cement slurry interface constantly produce new crack and begin expansion.Infiltration coefficient is remarkable increase when stress reaches 0.7 and 0.8.Produce propagation law according to crack in the concrete, at this moment the part of the mortar in the test specimen also begins to produce the crack, and the broken hair exhibition does not interconnect with pore isotonic water passage, and crack propagation has substantially exceeded the influence of crack " pressing " to infiltrative influence.

(3) infiltration coefficient and the stress relation of concrete strength when

According to this experimental result, when stress ratio less than 0.6 the time, infiltration coefficient reduces along with the increase of stress ratio, infiltration coefficient is along with the variation tendency of stress ratio is seen, both are similar to the negative exponential function relation that is.Therefore, respectively organize test specimen (2 every group) experimental data in the his-and-hers watches 3 and carry out match by following formula:

k＝k ₀e ^-aη (4)

In the formula: concrete infiltration coefficient (10 during the different stress ratio η of k-(η≤0.6) ^-10Cm/s); k ₀With a-regression coefficient, wherein k ₀Physical significance concrete infiltration coefficient (10 under the unstress state just ^-10Cm/s).

Result (k by formula (4) match ₀, a) see Table 4.

Experimental data is by formula (4) fitting result in table 4 table 3

Test specimen	k 0	a	R 2
				Cs1 Cs2 Cs3	54.86 21.02 10.68	1.475 1.377 1.482	0.789 0.758 0.736

As seen from Table 4:

1. infiltration coefficient and stress ratio are closely related.Utilize formula (4) only to need test to draw the average infiltration coefficient that does not have test specimen under the external stress effect like this, just can estimate the infiltration coefficient of this group test specimen under certain stress ratio (less than 0.6).

2. the perviousness of concrete sample and compressive strength are closely related, and intensity is high more, and infiltration coefficient is more little.From the fitting result of table 4 also can, in the different fitting parameter of respectively organizing test specimen of compressive strength, the value of a is more or less the same, promptly pressure is basic identical to the concrete infiltrative influence of varying strength.Different compressive strength test specimen k ₀It is bigger that value differs, and illustrates that concrete infiltration coefficient and compressive strength are closely related under the unstress state.

According to result in the table 4, with following formula to kf _c ⁴～η relation is carried out match:

${\mathrm{kf}}_c^4=k_1{e}^{-a_1\mathrm{\&eta;}}---\left(5\right)$

Wherein the unit of k is 10 ^-10Cm/s, f _cUnit be MPa.Fitting result is: k ₁=8.694 * 10 ⁶, a ₁=1.4425, coefficient of multiple correlation R=0.865.

From fitting result as can be seen, each organizes test specimen does not have significant difference by formula (5) and formula (4) fitting result.Comparison expression (5) and formula (4) in fact can be regarded as $k_0=k{f}_c^{-4},$ Be that concrete infiltration coefficient gets reciprocal being directly proportional with compressive strength 4 powers under the unstress state.Can be under simulated condition according to formula (5), the infiltration coefficient of the varying strength concrete of preparation under the condition of difference pressure load estimated the infiltration coefficient of a certain intensity concrete under corresponding pressure load.

To sum up analyze, press the existence of load can influence concrete perviousness.When compressive stress was lower than 60% ultimate stress, pressure made the concrete pre-existing fractures vertical with the load direction then to a certain extent by " pressing ", made concrete infiltration coefficient be similar to the increase of stress ratio and was negative exponential function and reduces.After compressive stress reached 70% ultimate stress, the crack propagation that load causes had surpassed the influence of crack " pressing " to infiltrative influence, and concrete perviousness enlarges markedly with the increase of stress ratio.There is close correlativity in the inverse of concrete infiltration coefficient and its compressive strength 4 powers.

Claims (6)

1. a concrete for hydraulic structure oozes saturating performance testing device under the effect at load, it is characterized in that it is made up of pressue device and concrete sample chamber two parts, wherein pressue device is by steel bottom plate (1), steel column (2), steel plate (3), steel plate (4), spring (5), nuts (6) constitutes, steel bottom plate (1), respectively be drilled with four circular holes of symmetry around steel plate (3) and the steel plate (4), four circular steel columns (2) are passed steel bottom plate (1) respectively, steel plate (3), in four circular holes on the steel plate (4), between steel bottom plate (1) and steel plate (4), place concrete sample chamber (17), put a spring (5) respectively on four steel principal posts (2) between steel plate (3) and the steel plate (4), use nuts (6) fixing then respectively; Circular sleeve (7) in the concrete sample chamber (17) is fixed on the steel bottom plate (1), cylindrical shape concrete sample (12) is placed in the sleeve (7), the bottom pad lastblock of concrete sample (12) presses down billet (9), compressed steel backing plate (8) on its top cover lastblock is placed a ball seat (10) between last compressed steel backing plate (8) and steel plate (4).

2. proving installation according to claim 1 is characterized in that the base portion of described circular steel column (2) is a stand, and top is threaded.

3. proving installation according to claim 1 is characterized in that described circular sleeve (7) is to make with organic glass, and is adhesively fixed with epoxy resin and fixes on the steel bottom plate (1), and a side of sleeve (7) has a spout hole (11).

4. proving installation according to claim 1 is characterized in that all leaving the water-filling space between described concrete sample (12) and sleeve (7) both sides, and covers with rubber band (14) on the space of both sides.

5. proving installation according to claim 1 is connected on the Anti-leakage instrument after it is characterized in that having an aperture (15) and water inlet pipe (16) linking to each other in the described upward compressed steel backing plate (8) again.

6. one kind with the proving installation of claim 1 method of testing to concrete for hydraulic structure permeance property under load action, it is characterized in that testing procedure is as follows:

(1) pressing machine is tightened and removed to the hydraulic pressure testing machine to spring (5) pressurization, with nuts (6) by steel plate (3) immediately when arriving the authorised pressure value, and this moment, the outside load of pressing was just provided by spring (5);

(2) pressure of spring (5) generation passes through steel plate (4), ball seat (10), goes up compressed steel backing plate (8) transfer function to cylindrical shape concrete sample (12);

(3) Anti-leakage instrument produces press water, press water is injected the inside surface of concrete sample (12) by water inlet pipe (16) and aperture (15);

(4) give space water filling between concrete sample (12) outside surface and the organic glass sleeve (7), the water surface is flushed with spout hole (11), use rubber band (14) to cover sleeve (7) then to avoid the water evaporation;

(5) spout hole (11) of collection on sleeve (7) flows into the infiltration water in the external graduated cylinder;

(6) utilize infiltration water in the graduated cylinder, convert with following derivation formula and try to achieve concrete infiltration coefficient; Circular ring type concrete sample infiltration coefficient computing formula:

$k=\frac{\mathrm{\&mu;q}\&CenterDot;\ln \frac{r_1}{r_2}}{2\mathrm{\&pi;}\&CenterDot;h\&CenterDot;\mathrm{\&Delta;h}}$

In the formula: k-infiltration coefficient (cm/s); Discharge (the cm that collects in the q-unit interval ³/ s); r ₂The external radius of-annular test-piece (cm); r ₁The inside radius of-annular test-piece (cm); The height of h-annular test-piece (cm); Δ h-water flows into the head difference between face and effluent face, the viscosity of μ-water.

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