CN102505622A - Method for pavement condition nondestructive detection based on FWD - Google Patents

Abstract

The invention discloses a method for pavement condition nondestructive detection based on FWD, which comprises the following steps: 1) performing damage investigation of a pavement surface layer, determining surface layer damage when structural damage is observed on the pavement; 2) performing deflection detection by FWD, recording a deflection value of each testing point and performing correction; 3) determining whether the surface layer is damaged according to a surface modulus difference value between two adjacent testing points; 4) determining whether a base layer is damaged according to a curvature index and the surface modulus difference value between two adjacent testing points; 5) obtaining a subgrade modulus according to a deflection basin index. The technology can perform nondestructive detection of the condition of each structural layer of a semi-rigid base layer damaged pavement by FWD equipment, determine whether the pavement is intact without destroying the pavement structural layers, estimate the damage conditions of the semi-rigid base layer in advance, perform inverse calculation of the subgrade modulus, and determine whether the subgrade condition is good.

Description

Method based on FWD nondestructive testing pavement behavior

Technical field

The invention belongs to the Road Detection field, relate to a kind of pavement behavior detection method, especially a kind of method based on FWD nondestructive testing pavement behavior.

Background technology

Traditional pavement recapping generally is divided into surface layer according to the pavement destruction degree and overhauls with surface layer basic unit and overhaul jointly.Estimate and confirm that the degree of overhauling need have more accurately basic unit's situation even soil matrix situation.Traditional way is that the core of getting that diminishes formula detects, and perhaps after the surface layer milling, judges basic unit's extent of damage.Get the core method and detect comparatively complicatedly, and road pavement causes more badly damagedly, is difficult to the detection density that reaches enough; Judge basic unit's situation after the milling again, judged result is more accurate, but causes construction plan to lag behind, to the formulation of maintenance plan and arrange unfavorable.

One of major technique of utilizing FWD (Falling Weight Deflectometer, FWD) detection evaluation road surface is to utilize the deflection basin that records to carry out the modular inverse calculation of each deck, and using wider method has database method and iterative method.General achievement in research is all based on continuous layered system, for each layer modulus on intact road surface the quite good detecting result arranged.

External close has or not damage structure layer modular inverse calculation technological.Reverse calculation algorithms mainly contains database search method and iterative method.

1) basic principle of database search method: elder generation is according to the possible range of each layer thickness of road surface, material poisson's ratio and modulus of elasticity; Using the multilayer linear elastic theory calculates; Try to achieve the theoretical deflection basin under the various modulus combinations; And, utilize pattern search and lagrange-interpolation to confirm one group of modulus then with the form preservation of Theoretical Calculation result with database, make the calculating deflection basin the most approaching with the actual measurement deflection basin.The advantage of this method is to find the solution stable, rapid, has avoided " morbid state " problem in the back analysis.Its shortcoming is need set up corresponding database to the different road structure, does not have versatility, and it represents software is MODULUS.

2) iterative method is the method for studying at most at present.Its basic process is: define road surface layers of material characteristic; Use the deflection value of road surface mechanics Model Calculation corresponding to FWD device senses device position; And compare with actual deflection value, adjust each layer parameter of road surface in view of the above, reach minimum up to the error of calculating between deflection basin and the actual measurement deflection basin.The advantage of this method is that the inverse precision is high, is convenient to introduce various mechanics analysis model, is with good expansibility.Its shortcoming is to avoid the problem of initial value and local minimum.Representational software is MODCOMP3 and WESDEF etc.

But what said method utilized that the FWD deflection test detects that road structure solved is the inverse to the Research on Structural Modulus on intact road surface (road structure does not exist and causes the discontinuous damage of structure), estimates the structural strength on intact road surface.The deficiency that is faced is to differentiate the road surface and damages the order of severity that whether exists and damage.

Summary of the invention

The objective of the invention is to propose a kind of method, but facings, basic unit and soil layer are realized nondestructive testing based on FWD nondestructive testing pavement behavior.

For reaching above purpose, the solution that the present invention adopted is:

A kind of method based on FWD nondestructive testing pavement behavior, it may further comprise the steps:

1) the road pavement surface layer damages investigation, exists structural damage then to assert the surface layer damage if observation obtains the road surface;

2) carry out flexure with FWD and detect, write down the deflection value and the correction of each measuring point;

3), judge whether surface layer exists damage according to the surperficial modulus difference of adjacent two measuring points;

4), judge whether basic unit exists damage according to the surperficial modulus difference of curvature index and adjacent two measuring points;

5), try to achieve the value of soil modulus according to the deflection basin index.

Further, said step 2) correction of deflection value in, according to following formula correction,

Wherein, P is the actual loading that FWD detects; D is the pavement deflection value under the proof load effect; d _PBe the pavement deflection value under the actual loading effect.

The surperficial modulus of adjacent two measuring points is respectively E in the said step 3) _{S (i-1)}And E _{S (i)}, i=2,3 ..., 6, wherein, E _{S (i)}Be the surperficial modulus at measuring point i place, E _{S (i-1)}Surperficial modulus for measuring point i-1 place; And if E _{S (i-1)}-E _{S (i)}＜0, judge that then there is damage in surface layer.

The surperficial modulus of adjacent two measuring points is respectively E in the said step 4) _{S (i-1)}And E _{S (i)}, i=2,3 ..., 6, wherein, E _{S (i)}Be the surperficial modulus at measuring point i place, E _{S (i-1)}Surperficial modulus for measuring point i-1 place; The curvature index is CI ₃=d ₃-d ₄, d ₃, d ₄Be respectively the table deflection value that FWD detects on the road at measuring point 3,4 places; And,

If CI ₃＜16 μ m judge that then basic unit is intact;

If CI ₃＞50 μ m or E _{S (i-1)}-E _{S (i)}＜0, then judge basic unit's fritter cracking or loose;

If CI ₃=16～50 μ m then judge basic unit's bulk cracking.

Said $E_{S\left(i\right)}=\left\{\begin{array}{cc}\frac{2\mathrm{Pa}(1-u^2)}{d_1}& (r_1=0)\\ \frac{{\mathrm{Pa}}^2(1-u^2)}{d_i\×r_i}F(\frac{1}{2},\frac{1}{2};1;\frac{a^2}{{r_i}^2})& (r_i\≥a,i=\mathrm{2,3},...,9)\end{array}\right.,$ Wherein:

$F(\frac{1}{2};\frac{1}{2};1;\frac{a^2}{r_i^2})=1+0.125{\left(\frac{a}{r}\right)}^2+0.047{\left(\frac{a}{r}\right)}^4+0.024{\left(\frac{a}{r}\right)}^6+0.015{\left(\frac{a}{r}\right)}^8-\·\·\·;$ d ₁Be the road table deflection value of load center, d _iBe the road sign deflection value at measuring point i place, r _iBe the distance of measuring point i apart from the load center, p is an evenly distributed load, and a is the loaded plate radius, and u is the poisson's ratio of soil.

The deflection basin index is CI7 and F8 in the said step 5),

Wherein, k ₁, k ₂Be respectively regression coefficient, its value is relevant with soil modulus, according to k ₁, k ₂Confirm the value of soil modulus with the relation of soil modulus.

Said k ₁, k ₂As shown in the table with the relation of soil modulus

Said deflection basin index CI ₇=d ₇-d ₈, D wherein _iBe the road table deflection value at measuring point i place, i=1,2 ..., 9.

Owing to adopted such scheme; The present invention has following characteristics: the present invention can carry out nondestructive testing through FWD facings, basic unit and soil matrix; And in actual application, develop handling procedure and not only can reduce workload and intractability, and improved the efficient of road surface structare layer status evaluation greatly.

Description of drawings

Fig. 1 is the flow chart of the inventive method.

Fig. 2 is the deflection basin index CI among the present invention ₇And F ₈Graph of a relation.

Fig. 3 is the deal with data flow process figure of the inventive method.

Fig. 4 calculates surface modes amount difference figure as a result in the embodiment of the invention.

Fig. 5 is embodiment of the invention mean curvature index CI ₃Figure as a result.

The specific embodiment

Below in conjunction with the accompanying drawing illustrated embodiment the present invention is further described.

Research of the present invention is based on that Pavement on Semi-rigid Type Base carries out, and result of study also is only applicable to the Pavement on Semi-rigid Type Base structure.

(1) road surface breakage evaluation

When serious discontinuous situation appears in asphalt surface course, the flexure of FWD will occur irregularly shaped.When existing through crack or intermediate layer loose in the road structure, the surface modes discharge curve will appear irregularly shaped, and surperficial modulus reduces along with the increase apart from load centre distance increases afterwards earlier.So E _{S (i-1)}-E _{S (i)}＜0, i=2,3 ..., 6, wherein, E _{S (i)}Be the surperficial modulus at measuring point i place, Mpa; E _{S (i-1)}Be the surperficial modulus at measuring point i-1 place, Mpa can be used as and judges whether road surface structare layer runs through cracking and the loose standard in intermediate layer.

Therefore, at first road pavement just surface layer carry out naked-eye observation investigation, have cracking if find the road surface, assert that so surface layer structure damages; Detect through FWD again,, will judge that this measuring point is a breaking point if minus situation appears in above-mentioned surperficial modulus difference.

(2) basic unit's situation is judged:

Through surface modes figureofmerit E _{S (i)}With curvature index CI ₃Estimate.E _{S (i)}Be the surperficial modulus at measuring point i place, Mpa; CI ₃=d ₃-d ₄, d ₃, d ₄Be respectively the road table deflection value at FWD measuring point 3,4 places.

Surface modes figureofmerit E _{S (i)}Design formulas following

$E_{S\left(i\right)}=\left\{\begin{array}{cc}\frac{2\mathrm{pa}(1-u^2)}{d_1}& (r_1=0)\\ \frac{{\mathrm{pa}}^2(1-u^2)}{d_i\×r_i}F(\frac{1}{2},\frac{1}{2};1;\frac{a^2}{{r_i}^2})& (r_i\≥a,i=\mathrm{2,3},...,9)\end{array}\right.---\left(1\right)$

In the formula:

$F(\frac{1}{2};\frac{1}{2};1;\frac{a^2}{r_i^2})=1+0.125{\left(\frac{a}{r}\right)}^2+0.047{\left(\frac{a}{r}\right)}^4+0.024{\left(\frac{a}{r}\right)}^6+0.015{\left(\frac{a}{r}\right)}^8-\·\·\·;$

E _{S (i)}Be the surperficial modulus at measuring point i place, Mpa; d ₁Be the road table deflection value of load center, cm; d _iBe the road sign deflection value at measuring point i place, cm; r _iBe the distance of measuring point i apart from the load center, cm; P is an evenly distributed load, 0.7Mpa; A is the loaded plate radius, 15cm; U is the poisson's ratio of soil, and general with 0.2 or 0.3 on the engineering, concrete available experiment is confirmed.

The criterion of basic unit's situation:

Serviceable condition is meant that road structure is complete, and is in good condition; The bulk cracking is meant that semi-rigid type base is chipping, but cracked size is bigger, for semi-rigid type base, also belongs to normal condition; And fritter cracking surface, semi-rigid type base occurs than fine grained chippings, and base layer structure damages more serious.

Table 1. basic unit state criterion

(3) the soil modulus inverse is theoretical

Because deflection basin index CI ₇With F ₈Be power function relationship (Fig. 1):

${\mathrm{CI}}_7=k_1\left(F_8^{k_2}\right)---\left(2\right)$

In the formula: k ₁, k ₂Be respectively regression coefficient, its value is relevant with soil modulus.

Get k under the situation of different value in soil modulus ₁, k ₂Like following table:

Table 2. regression coefficient k ₁, k ₂

Wherein, CI ₇=d ₇-d ₈,

(d _i, i=1,2 ..., 9 is the road table deflection value at FWD measuring point i place, μ m.)

Because there is above-mentioned CI ₇And F ₈Relation, as long as after actual measurement goes out the FWD data of this point, calculate the CI of this point according to data measured ₇And F ₈Value confirms table 2 which it meets, and soil modulus is exactly that the pairing soil modulus that meets.And show that through research pavement cracking and interlayer slip are very little to the influence of above-mentioned relation.

Said method has solved: judge through the processing that FWD is detected data whether the road surface exists breakage 1.; 2. the deck modular inverse calculation technology that under the intact situation in road surface, can utilize in the background technology to be mentioned is estimated.There is breakage if judged result is the road surface, then utilizes the curvature index, the surface modes figureofmerit that propose among the present invention that the damage situation of basic unit is estimated; 3. the soil modulus reverse calculation algorithms that not influenced by road surface breakage has also been proposed.The state evaluation of surface layer, basic unit and soil matrix through above 3 Pavement on Semi-rigid Type Base that solve respectively is applicable to semi-rigid asphalt pavement, can foundation be provided for the maintenance of surface and the regulation plan in later stage.

Below in conjunction with embodiment method of the present invention is explained in detail.

As shown in Figure 1, at first the historical investigation of road surface breakage, maintenance is carried out in the highway section, the pavement disease investigation is the road surface condition survey of highway maintenance stage routine property, this present invention's pavement investigation is main with the damage of road structure property, like cracking, loose, depression etc.Investigation result is added up in application form, as one of foundation of the intact deciding degree in follow-up road surface.

Secondly, carrying out the FWD flexure detects.This flexure of accurate recording detects pile No., and the initial data that FWD measures each measuring point of gained comprises hammering number, D (1), D (2), D (3), D (4), D (5), D (6), D (7), D (8), D (9), kPa, kN, environment, road table, artificial, burst length information.

Utilize the load correction that the deflection basin under the effect of carrying of nonstandard fiducial axis is converted into the standard deflection basin under the standard axle load, formula is following:

$d=d_P\×{\left(\frac{50}{P}\right)}^{0.98}---\left(3\right)$

In the formula: P is the actual loading that FWD detects, kN; D is the pavement deflection value under proof load (50kN) effect, μ m; d _PBe the pavement deflection value under the actual loading effect, μ m.

Actual measurement highway section period is 262100～239156 can combine the E that calculates among factual survey result and Fig. 4 _{S (i-1)}-E _{S (i)}Whether judge less than 0 whether the road surface is damaged.Specifically, according to road surface breakage investigation discovery pavement cracking is arranged, promptly no matter pass through the E that the surface modes figureofmerit calculates if detect pile No. place, track _{S (i-1)}-E _{S (i)}Whether the result will here be labeled as top course breakage greater than 0; If in the road surface breakage investigation, demarcate this pile No. place through crack is not arranged, but the E that when gauging surface modulus index, obtains _{S (i-1)}-E _{S (i)}The result thinks still that then there is structural failure in surface layer here, but possibly not be through to the surface less than 0.Have only in the damaged investigation of road conditions and do not have disrepair phenomenon, and E _{S (i-1)}-E _{S (i)}The result is not less than 0 situation and assert that just top course is intact road surface here.

Continue to calculate the CI of each point for damaged road surface ₃Index utilizes the criterion in the table 1 to judge this basic unit's state, result such as Fig. 5 then.Can find out that by figure locating basic unit's situation at 261337,261304,261,134 3 is fritter cracking or loose.

The inverse of soil modulus takes to calculate the CI of each point ₇And F ₈Value is then to CI under 70Mpa, 125Mpa, 150Mpa, 175Mpa, 225Mpa, 250Mpa, 275Mpa and the 300Mpa ₇And F ₈Relation curve carries out inserting in 2 times.

The above-mentioned description to embodiment is can understand and use the present invention for ease of the those of ordinary skill of this technical field.The personnel of skilled obviously can easily make various modifications to these embodiment, and needn't pass through performing creative labour being applied in the General Principle of this explanation among other embodiment.Therefore, the invention is not restricted to the embodiment here, those skilled in the art are according to announcement of the present invention, and not breaking away from the improvement that category of the present invention makes and revise all should be within protection scope of the present invention.

Claims (8)

1. method based on FWD nondestructive testing pavement behavior, it is characterized in that: it may further comprise the steps:

1) the road pavement surface layer damages investigation, exists structural damage then to assert the surface layer damage if observation obtains the road surface;

2) carry out flexure with FWD and detect, write down the deflection value and the correction of each measuring point;

3), judge whether surface layer exists damage according to the surperficial modulus difference of adjacent two measuring points;

4), judge whether basic unit exists damage according to the surperficial modulus difference of curvature index and adjacent two measuring points;

5), try to achieve the value of soil modulus according to the deflection basin index.

2. the method based on FWD nondestructive testing pavement behavior as claimed in claim 1 is characterized in that:

Said step 2) correction of deflection value in, according to following formula correction,

Wherein, P is the actual loading that FWD detects; D is the pavement deflection value under the proof load effect; d _PBe the pavement deflection value under the actual loading effect.

3. the method based on FWD nondestructive testing pavement behavior as claimed in claim 1 is characterized in that:

The surperficial modulus of adjacent two measuring points is respectively E in the said step 3) _{S (i-1)}And E _{S (i)}, i=2,3 ..., 6, wherein, E _{S (i)}Be the surperficial modulus at measuring point i place, E _{S (i-1)}Surperficial modulus for measuring point i-1 place; And if ES _(i-1)-ES _(i)＜0, judge that then there is damage in surface layer.

4. the method based on FWD nondestructive testing pavement behavior as claimed in claim 1 is characterized in that:

The surperficial modulus of adjacent two measuring points is respectively E in the said step 4) _{S (i-1)}And E _{S (i)}, i=2,3 ..., 6, wherein, E _{S (i)}Be the surperficial modulus at measuring point i place, E _{S (i-1)}Surperficial modulus for measuring point i-1 place; The curvature index is CI ₃=d ₃-d ₄, d ₃, d ₄Be respectively the table deflection value that FWD detects on the road at measuring point 3,4 places; And,

If CI ₃＜16 μ m judge that then basic unit is intact;

If CI ₃＞50 μ m or E _{S (i-1)}-E _{S (i)}＜0, then judge basic unit's fritter cracking or loose;

If CI ₃=16～50 μ m then judge basic unit's bulk cracking.

5. like claim 3 or 4 described methods, it is characterized in that based on FWD nondestructive testing pavement behavior:

Said $E_{S\left(i\right)}=\left\{\begin{array}{cc}\frac{2\mathrm{Pa}(1-u^2)}{d_1}& (r_1=0)\\ \frac{{\mathrm{Pa}}^2(1-u^2)}{d_i\×r_i}F(\frac{1}{2},\frac{1}{2};1;\frac{a^2}{{r_i}^2})& (r_i\≥a,i=\mathrm{2,3},...,9)\end{array}\right.,$ Wherein:

$F(\frac{1}{2};\frac{1}{2};1;\frac{a^2}{r_i^2})=1+0.125{\left(\frac{a}{r}\right)}^2+0.047{\left(\frac{a}{r}\right)}^4+0.024{\left(\frac{a}{r}\right)}^6+0.015{\left(\frac{a}{r}\right)}^8-\·\·\·;$ d ₁Be the road table deflection value of load center, d _iBe the road sign deflection value at measuring point i place, r _iBe the distance of measuring point i apart from the load center, p is an evenly distributed load, and a is the loaded plate radius, and u is the poisson's ratio of soil.

6. the method based on FWD nondestructive testing pavement behavior as claimed in claim 1 is characterized in that: the deflection basin index is CI in the said step 5) ₇With F ₈,

Wherein, k ₁, k ₂Be respectively regression coefficient, its value is relevant with soil modulus, according to k ₁, k ₂Confirm the value of soil modulus with the relation of soil modulus.

7. the method based on FWD nondestructive testing pavement behavior as claimed in claim 6 is characterized in that:

Said k ₁, k ₂As shown in the table with the relation of soil modulus

8. the method based on FWD nondestructive testing pavement behavior as claimed in claim 6 is characterized in that: said deflection basin index CI ₇=d ₇-d ₈,

D wherein _iBe the road table deflection value at measuring point i place, i=1,2 ..., 9.

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