CN102734556B - Trenchless construction method for power pipes - Google Patents

Abstract

The invention discloses a trenchless construction method for power pipes, and belongs to the field of construction. The trenchless construction method for the power pipes comprises a horizontal directional drilling construction method. The trenchless construction method for the power pipes at least comprises the following steps of: drilling a guide hole according to a design curve; forming a composite structure of a power pipe bundle by using a plurality of power pipes; pulling the power pipe bundle back into a guide hole along the guide hole to finish pipeline crossing work, wherein in a pullback process, a multi-pipe pullback effect is considered, the power pipe bundle is regarded as a whole, and water injection pullback is not considered; on the premises of considering the multi-pipe pullback effect, regarding the power pipe bundle as the whole and considering the water injection pullback in the pullback process, the total tension of the pipe bundle of the power pipes at each point along a drilling track in a pullback process, the average axial tension stress corresponding to each pipeline and the tension safety condition of a pullback pipeline are determined; after the power pipe bundle is pulled back in a position and when compaction grouting is performed, the grouting pressure is considered as an external pressure of the pipeline; and by the method, the safety in power pipe construction is ensured. The trenchless construction method for the power pipes can be widely used in the field such as the design, the construction and the management of power pipelines.

Description

A kind of non-excavating construction method of electric power comb

Technical field

The invention belongs to construction field, relate in particular to a kind of laying method for electric power comb.

Background technique

Along with the fast development of urban economy and the quickening of urbanization process, power engineering construction project is increasing.Need to not set up tower and conductor on road surface, not take up an area space of planes, be easy to keep the power cable engineering of appearance of the city neat appearance also more and more.

The construction of normal cable engineering is all that fluting is laid power pipe, causes and makes the disgustful road of citizen " slide fastener phenomenon ".Simultaneously building in power channel process, unavoidably run into and cannot excavate node that technique passes through as all kinds of municipal pipelines point of intersection, highway, railway, bridge, river course and above ground structure etc. by tradition.Therefore, conventional heavy excavation construction technology is more and more not suitable with the needs of urban development.

An emerging technology in recent years---trenchless technology has obtained application more and more widely in power pipe engineering.Although trenchless technology is started late, along with popularizing of application, no matter in theory trenchless technology, still, aspect construction process, has had the development of advancing by leaps and bounds.Although trenchless technology comes out first with high-tech advantage, also there are many directly and indirectly risks in trenchless technology in construction.Because construction under earth's surface has scene property, complexity, discontinuity and comprehensive feature, in construction, easily cause the damage of surface buildings depression, roadbed subsidence cracking, underground structure and underground existing pipeline etc. problem.

Because Horizontal Directional Drilling has many advantages with respect to the method for tradition excavation, make it more and more extensive in the application of laying urban electric power pipeline.

Power pipe construction exists multitube to combine back to drag and the construction characteristic such as compaction grouting, resistance increment while not only making back to drag, and the grouting pressure acting on pipeline outer wall can reduce pipeline critical external compressive resistance ability simultaneously, drag construction to have significant difference with returning of single pipe.

For ensureing the safety of pipeline self and the quality of engineering, the pull-back force before going back to hauling pipe road in reply construction calculates, and electric power comb is carried out to force analysis, thereby ensures the safety in pipeline returning and mortar depositing construction.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of non-excavating construction method of electric power comb, its consideration multitube returns and drags effect, regard the tube bank of comb as entirety, utilize the equivalent redius of tube bank and the equivalent friction factor of tube bank and hole wall, conventional ASTM pull-back force computational methods are improved, made its more suitable power pipeline back drag force calculating; Simultaneously using grouting pressure as the suffered pressure outside of pipeline, the stress of pipeline while analyzing slip casting, thus ensure the safety in pipeline returning and mortar depositing construction.

Technological scheme of the present invention is: a kind of non-excavating construction method that electric power comb is provided, comprise horizontal directional drilling construction method, horizontal directional drilling construction method described in it first bores a pilot hole according to design curve, and described pilot hole is by the point that buries, the first inclination section that connect successively; Horizontal segment, the second inclination section and unearthed point form; By the composite structure of an electric power comb tube bank of many electric power comb compositions; The tube bank of electric power comb is returned and is dragged in pilot hole along pilot hole, complete traversing pipe line work; It is characterized in that described non-excavating construction method at least comprises the following steps:

Drag in process returning, consider that multitube returns and drags effect, regard the tube bank of electric power comb as entirety, and do not consider that water filling is returned and drag;

Putting before this, determine electric power comb return drag process in along the suffered total pulling force of tube bank of drilling track each point, the average every corresponding axial tension stress of pipeline with return hauling pipe road tension safety condition;

Electric power comb is restrained back and is dragged while carrying out compaction grouting after in place, and grouting pressure is taken into account as the suffered external pressure of pipeline;

By said method, ensure electric power comb return drag with mortar depositing construction in safety;

Wherein, described electric power comb return drag process in along the suffered total pulling force parameter of tube bank of pilot hole track each point, determine according to following representation:

$T_1=e^{{\mathrm{\υ}}_a\mathrm{\α}}\left[{\mathrm{\υ}}_a{\mathrm{\ω}}_a(L_1+L_2+L_3+L_4)\right]$

$T_2=e^{{\mathrm{\α}}_b\mathrm{\α}}(T_1+T_h+{\mathrm{\υ}}_b|{\mathrm{\ω}}_b|L_2+{\mathrm{\ω}}_{b}H-{\mathrm{\υ}}_a{\mathrm{\ω}}_a{L}_2{e}^{{\mathrm{\υ}}_a\mathrm{\α}})$

$T_3=T_2-e^{{\mathrm{\υ}}_b\mathrm{\α}}\left({\mathrm{\υ}}_a{\mathrm{\ω}}_a{L}_3{e}^{{\mathrm{\υ}}_a\mathrm{\α}}\right)+T_h+{\mathrm{\υ}}_b\left|{\mathrm{\ω}}_b\right|L_3$

$T_4=e^{{\mathrm{\υ}}_a\mathrm{\β}}[T_3+T_h+{\mathrm{\υ}}_b|{\mathrm{\ω}}_b|L_4-{\mathrm{\ω}}_{b}H-e^{{\mathrm{\υ}}_a\mathrm{\α}}\left({\mathrm{\υ}}_a{\mathrm{\ω}}_a{L}_4{e}^{{\mathrm{\υ}}_a\mathrm{\α}}\right)]$

$T_h=P_h\frac{\mathrm{\π}}{8}(D_h^2-D_m^2)$

$D_m=\sqrt{n}D$

${\mathrm{\ω}}_a=\frac{1.06\mathrm{n\π}{D}^2{\mathrm{\γ}}_a(\mathrm{DR}-1)}{{\mathrm{DR}}^2}$

${\mathrm{\ω}}_b=\frac{\mathrm{\π}{D}^2{\mathrm{\γ}}_b}{4}-\frac{1.06\mathrm{\π}{D}^2{\mathrm{\γ}}_a(\mathrm{DR}-1)}{{\mathrm{DR}}^2}$

Wherein, T ₁locate to restrain total pull-back force (KN) for burying; T ₂be that the first inclination section destination county is restrained total pull-back force (KN); T ₃be that total pull-back force (KN) is restrained at the second inclination section starting point place; T ₄for restraining total pull-back force (KN) in unearthed point place; L ₁for the additional length (m) of tube bank; L ₂bury and a little arrive the horizontal length (m) of deflecting terminal for tube bank; L ₃for tube bank horizontal section length (m); L ₄for tube bank horizontal segment terminal is to the horizontal length (m) of unearthed point; H is the height (m) of tube bank apart from ground; υ _afor tube bank and the friction factor on ground, get 0.5; υ _bfor the friction factor of tube bank in hole, get 0.3, multitube returns while dragging between 0.3～0.5, and maximum is got υ _a; ω _afor the total weight (KN/m) of unit length blank pipe bundle; ω _bfor unit length is restrained net buoyancy (KN/m) upwards; The penetrating angle (rad) of tube bank when α is back to drag; The unearthed angle (rad) of tube bank when β is back to drag; γ _afor the weight of per unit volume pipeline material; γ _bfor the weight (KN/m of mud in per unit volume annular space and landwaste mixture ³); P _hfor the kinetic pressure of annular space mud to pipeline, get 0.035～0.070MPa; D is the external diameter (m) of single pipe; D _hfor bore diameter (m); D _mfor diameter (m) after tube bank area equivalent; DR is the ratio of single pipe external diameter and wall thickness; N is the number that comprises pipeline in tube bank.

Concrete, the corresponding axial tension stress parameter of average every pipeline described in it, adopts following representation to determine:

${\mathrm{\σ}}_x=\frac{T_x}{\mathrm{n\π}{D}^2}\frac{{\mathrm{DR}}^2}{\mathrm{DR}-1}$

Wherein, σ _xfor axial tension stress (MPa) in the average every pipeline of pilot hole respective point; T _xfor pilot hole respective point is restrained total pull-back force (KN); D is the external diameter (m) of single pipe; DR is the ratio of single pipe external diameter and wall thickness; N is the number that comprises pipeline in tube bank.

Concrete, the hauling pipe road tension security parameter condition of returning described in it, must meet following condition:

σ _p<σ _allow

Wherein, σ _p=σ _x+ σ _a;

${\mathrm{\&sigma;}}_a=\frac{E_{24}D}{2R_{\mathrm{avg}}}$

$R_{\mathrm{avg}}=\frac{2H}{{\mathrm{\&theta;}}^2}$

σ _pfor the bending section interior conduit maximum tension stress (MPa) at respective point place; σ _afor respective point place bending section interior conduit maximum stress in bend (MPa); E ₂₄for the Young's modulus (MPa) in pipeline 24 hours; R _avgfor the mean radius of curvature (m) of pipeline in hole; θ is penetrating angle or unearthed angle (rad) of pipeline, σ _allowfor the allowable tensile stress (MPa) of pipeline material; H is the height (m) of tube bank apart from ground; D is the external diameter (m) of single pipe.

Further, carry out tension when checking computations in the tube bank to described, the allowable tensile stress parameter of every pipeline in tube bank, must be less than its axial tension stress and flexural stress with, that is: σ _allow< σ _x+ σ _a;

Wherein, σ _allowfor the allowable tensile stress of every pipeline, σ _xfor axial tension stress (MPa) in the average every pipeline of pilot hole respective point, σ _afor respective point place bending section interior conduit maximum stress in bend (MPa).

Further, in the time carrying out described compaction grouting, the suffered pressure outside parameter of pipeline adopts following representation to determine:

P _net＝p+γ _csH+P _ch-P _i

Wherein, P _netthe suffered pressure outside of pipeline during for compaction grouting; P is grouting pressure (MPa); γ _csfor the weight (KN/m of per unit volume cement slurry ³); H is the thickness (m) of upper overburden layer; P _chfor the kinetic pressure (MPa) of cement slurry to pipeline, be approximately equal to P _h; P _hfor annular space mud acts on the kinetic pressure (MPa) on pipeline; P _ifor acting on the internal pressure (MPa) on pipeline.

Compared with the prior art, advantage of the present invention is:

1. trenchless technology is combined with laying of power cable, for ensureing the safety of pipeline self and the quality of engineering, pull-back force before going back to hauling pipe road in reply construction calculates, and electric power comb is carried out to force analysis, thereby ensures the safety in pipeline returning and mortar depositing construction.

2. pair current power transmission and transformation comb trenchless engineering method of construction has carried out effectively supplementing, also specification Supervisory basis and the supervision behavior of supervisor in the construction of non-excavation laying power pipe.

Brief description of the drawings

Fig. 1 is Pipeline Crossing by Horizontal Directional Drilling track schematic diagram;

Fig. 2 is hoop amount of deflection percentage and penalty coefficient curve.

Embodiment

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

In Fig. 1, pilot hole by connect successively bury a little 1, intersection point 3, the second inclination section L4 and the unearthed point 4 of intersection point 2, horizontal segment L3, horizontal segment and second inclination section of the first inclination section L2, the first inclination section and horizontal segment form.

The difference of electric power comb and general Pipeline Crossing by Horizontal Directional Drilling maximum shows both ways: the one, and multitube combines back and drags, not only cause the increase of pipeline net buoyancy, and cause thus pipeline directly to contact with hole wall, cause friction factor to increase, multitube effect also, by changing the suffered fluid resistance of pipeline, all will increase the suffered pull-back force of pipeline ^[7]; The 2nd, after pipeline returning, to carry out compaction grouting at annular space, can apply an additional pressure outside to pipeline, thereby need to analyze grouting pressure, make it to be less than the anti-outer rupture pressure that squeezes of pipeline.

Therefore the non-excavating construction method that the technical program provides at least comprises the following steps:

First bore a pilot hole according to design curve, described pilot hole is by the point that buries, the first inclination section that connect successively; Horizontal segment, the second inclination section and unearthed point form;

By the composite structure of an electric power comb tube bank of many electric power comb compositions;

The tube bank of electric power comb is returned and is dragged in pilot hole along pilot hole, complete traversing pipe line work;

Wherein, drag in process returning, consider that multitube returns and drags effect, regard the tube bank of electric power comb as entirety, and do not consider that water filling is returned and drag;

Putting before this, determine electric power comb return drag process in along the suffered total pulling force of tube bank of drilling track each point, the average every corresponding axial tension stress of pipeline with return hauling pipe road tension safety condition;

Electric power comb is restrained back and is dragged while carrying out compaction grouting after in place, and grouting pressure is taken into account as the suffered external pressure of pipeline;

By said method, ensure electric power comb return drag with mortar depositing construction in safety.

Further, after described guiding hole drill is complete, pilot hole is carried out to reaming; Electric power comb tube bank is returned and is dragged in pilot hole along the pilot hole having expanded, complete traversing pipe line work.

Concrete, the technical program is considered that multitube returns and is dragged effect, regards the tube bank of comb as entirety, and does not consider that water filling is returned and drag; ASTM method is calculated to the formula of pull-back force and revises, obtain electric power comb return drag in process as follows along the suffered total pulling force of the each point of drilling track shown in Fig. 1 tube bank:

$T_1=e^{{\mathrm{\&upsi;}}_a\mathrm{\&alpha;}}\left[{\mathrm{\&upsi;}}_a{\mathrm{\&omega;}}_a(L_1+L_2+L_3+L_4)\right]---\left(1\right)$

$T_2=e^{{\mathrm{\&alpha;}}_b\mathrm{\&alpha;}}(T_1+T_h+{\mathrm{\&upsi;}}_b|{\mathrm{\&omega;}}_b|L_2+{\mathrm{\&omega;}}_{b}H-{\mathrm{\&upsi;}}_a{\mathrm{\&omega;}}_a{L}_2{e}^{{\mathrm{\&upsi;}}_a\mathrm{\&alpha;}})---\left(2\right)$

$T_3=T_2-e^{{\mathrm{\&upsi;}}_b\mathrm{\&alpha;}}\left({\mathrm{\&upsi;}}_a{\mathrm{\&omega;}}_a{L}_3{e}^{{\mathrm{\&upsi;}}_a\mathrm{\&alpha;}}\right)+T_h+{\mathrm{\&upsi;}}_b\left|{\mathrm{\&omega;}}_b\right|L_3---\left(3\right)$

$T_4=e^{{\mathrm{\&upsi;}}_a\mathrm{\&beta;}}[T_3+T_h+{\mathrm{\&upsi;}}_b|{\mathrm{\&omega;}}_b|L_4-{\mathrm{\&omega;}}_{b}H-e^{{\mathrm{\&upsi;}}_a\mathrm{\&alpha;}}\left({\mathrm{\&upsi;}}_a{\mathrm{\&omega;}}_a{L}_4{e}^{{\mathrm{\&upsi;}}_a\mathrm{\&alpha;}}\right)]---\left(4\right)$

$T_h=P_h\frac{\mathrm{\&pi;}}{8}(D_h^2-D_m^2)---\left(5\right)$

$D_m=\sqrt{n}D---\left(6\right)$

${\mathrm{\&omega;}}_a=\frac{1.06\mathrm{n\&pi;}{D}^2{\mathrm{\&gamma;}}_a(\mathrm{DR}-1)}{{\mathrm{DR}}^2}---\left(7\right)$

${\mathrm{\&omega;}}_b=\frac{\mathrm{\&pi;}{D}^2{\mathrm{\&gamma;}}_b}{4}-\frac{1.06\mathrm{\&pi;}{D}^2{\mathrm{\&gamma;}}_a(\mathrm{DR}-1)}{{\mathrm{DR}}^2}---\left(8\right)$

Wherein, T ₁---total pull-back force (KN) is restrained at Fig. 1 mid point 1 place;

T ₂---total pull-back force (KN) is restrained at Fig. 1 mid point 2 places;

T ₃---total pull-back force (KN) is restrained at Fig. 1 mid point 3 places;

T ₄---total pull-back force (KN) is restrained at Fig. 1 mid point 4 places;

L ₁---the additional length (m) of tube bank;

L ₂---tube bank is buried and is a little arrived the horizontal length (m) of deflecting terminal;

L ₃---tube bank horizontal section length (m);

L ₄---tube bank horizontal segment terminal is to the horizontal length (m) of unearthed point;

H---tube bank is apart from the height (m) on ground;

υ _a---the friction factor on tube bank and ground, conventionally get 0.5;

υ _b---the friction factor of tube bank in hole, conventionally get 0.3, multitube returns while dragging between 0.3～0.5, and maximum is got υ _a;

ω _a---the weight (KN/m) that unit length blank pipe bundle is total;

ω _b---unit length is restrained net buoyancy (KN/m) upwards;

α---return the penetrating angle (rad) of tube bank while dragging;

β---go back to the unearthed angle (rad) of tube bank while dragging;

γ _a---the weight of per unit volume pipeline material;

γ _b---the weight (KN/m of mud and landwaste mixture in per unit volume annular space ³);

P _h---the kinetic pressure of annular space mud to pipeline, conventionally get 0.035～0.070MPa ^[1];

The external diameter (m) of D---single pipe;

D _h---bore diameter (m);

D _m---diameter (m) after tube bank area equivalent;

DR---the ratio of single pipe external diameter and wall thickness;

N---in tube bank, comprise the number of pipeline.

Pull-back force by tube bank each point can obtain the on average every corresponding axial tension stress formula of pipeline:

${\mathrm{\&sigma;}}_x=\frac{T_x}{\mathrm{n\&pi;}{D}^2}\frac{{\mathrm{DR}}^2}{\mathrm{DR}-1}---\left(9\right)$

σ _x---axial tension stress (MPa) in the average every pipeline of respective point;

T _x---respective point is restrained total pull-back force (KN).

Pipeline produces flexural stress because self is bending at bending section ^[10], after flexural stress and axial tension stress stack, the suffered maximum stress of pipeline can be represented by the formula:

σ _p＝σ _x+σ _a(10)

${\mathrm{\&sigma;}}_a=\frac{E_{24}D}{2R_{\mathrm{avg}}}---\left(11\right)$

$R_{\mathrm{avg}}=\frac{2H}{{\mathrm{\&theta;}}^2}---\left(12\right)$

Wherein, σ _p---the bending section interior conduit maximum tension stress (MPa) at respective point place;

σ _a---respective point place bending section interior conduit maximum stress in bend (MPa);

E ₂₄---the Young's modulus (MPa) in pipeline 24 hours;

R _avg---the mean radius of curvature (m) of pipeline in hole;

The penetrating angle of θ---pipeline or unearthed angle (rad);

In sum, can return hauling pipe road tension safety condition is: σ _p< σ _allow(allowable tensile stress of pipeline material).

No matter installing in the process of still operation in underground pipeline, all can be subject to effect in outer year of various combination.Pipeline can produce circumferential pressure under external load function in tube wall, and initial ring is to deflection thus.The load that makes pipeline produce hoop deflection has pressure outside, bending load and the buoyancy etc. such as upper overburden layer pressure and mud pressure.

When pipeline returning, suffered pressure outside depends primarily on the stability of hole wall, returns pipeline while dragging and is surrounded by annular space mud and detrital mixture, and the similar bury of character of this mixture, does not consider its supporting effect to pipeline conventionally when calculating.

Under the condition of therefore caving at hole wall the suffered pressure outside of pipeline have on the pressure that produces of earthing pressure, groundwater pressure and live load, drag the pressure outside being subject to be mainly mud pressure and hydrodynamic pressure and return at the complete boring interior conduit of hole wall, formula is as follows:

The suffered external pressure formula of pipeline when hole wall collapse:

P _net＝γ _sH _s+P _w+P _l-P _i(13)

The suffered external pressure formula of pipeline when hole wall is stablized:

P _net＝γ _bH+P _h-P _i(14)

P _net---the pressure outside (MPa) that pipeline is suffered;

γ _s---the weight (KN/m of upper overburden layer per unit volume ³);

H _s---the thickness (m) of upper overburden layer;

P _w---the pressure outside (MPa) of groundwater effect on pipeline;

P _l---live load acts on the pressure outside (MPa) on pipeline;

P _i---act on the internal pressure (MPa) on pipeline;

P _h---annular space mud acts on the kinetic pressure (MPa) on pipeline.

Under normal circumstances the pipe ring more than phreatic surface reach 20% to deflection will unstability, the pipe ring below phreatic surface reaches 15% to deflection will there is unstability.Pipe ring to surrender and destruction be to determine the key factor of pipe safety, thereby must carry out critical external compressive resistance failure analysis to pipeline.

Under external pressure effect, the hoop amount of deflection percentage formula of pipeline is:

$\%\mathrm{\&Delta;D}=\frac{0.0125P_{\mathrm{net}}}{\frac{E_l}{12{(\mathrm{DR}-1)}^3}}\&times;100---\left(15\right)$

The hoop amount of deflection percentage formula of pipeline under floating function:

$\%\mathrm{\&Delta;}{D}_b=\frac{0.088{\mathrm{\&gamma;}}_{b}D}{E_L}\frac{{(\mathrm{DR}-1)}^4}{\mathrm{DR}}---\left(16\right)$

E _l---the long-run elasticity modulus (MPa) of pipeline.

Conventionally get under external pressure effect and floating function under amount of deflection percentage maximum value calculation.

Afterwards carry out compaction grouting at annular space for electric power comb owing to returning to drag, also need to consider the impact of grouting pressure.Therefore the failure analysis of electric power comb critical external compressive resistance comprises two-part: the one, return the critical external compressive resistance failure analysis of dragging in process, and the 2nd, the critical external compressive resistance failure analysis in slip casting process.

Due to the stable case difference of hole wall, the external pressure combination difference that pipeline is suffered, selects formula (13) or (14) to calculate the suffered external pressure of pipeline according to actual conditions in actual checking computations.

According to Levy formula, the critical surrender pressure outside that obtains pipeline is:

$P_u=\frac{2E_L}{1-{\mathrm{\&mu;}}^2}{\left(\frac{1}{\mathrm{DR}-1}\right)}^3\frac{f_o}{N}---\left(17\right)$

The Poisson's ratio of μ---pipeline material;

F _o---ovality penalty coefficient;

N---safety coefficient, gets 2 conventionally.

Ovality penalty coefficient f ₀can be by the maximum loop of calculating pipeline to amount of deflection percentage % Δ D, hoop amount of deflection percentage and penalty coefficient curve are as shown in Figure 2 tried to achieve.

The critical external compressive resistance yield factor of safety of pipeline:

In the time that safety coefficient is greater than 1, pipeline can not be surrendered under external pressure; Otherwise surrender.

Return and drag in process in reality, pipeline is often subject to axial tension and pressure outside effect simultaneously.Due to the effect of axial tension, can make pipeline produce contraction strain radially, this effect can reduce the critical external compressive resistance performance of pipeline.Therefore calculate critical rupture pressure and need to be multiplied by axial stress reduction coefficient to the critical pressure of Levy formula calculating.

The critical destruction pressure outside of pipeline formula:

$P_{\mathrm{cr}}=\frac{2E_{24}}{1-{\mathrm{\&mu;}}^2}{\left(\frac{1}{\mathrm{DR}-1}\right)}^3\frac{f_o{f}_R}{N}---\left(18\right)$

$f_R=\sqrt{[5.57-{(\frac{{\mathrm{\&sigma;}}_x}{2{\mathrm{\&sigma;}}_{\mathrm{sp}}}+1.09)}^2]}-1.09---\left(19\right)$

${\mathrm{\&sigma;}}_{\mathrm{sp}}={\mathrm{\&sigma;}}_{\mathrm{allow}}-\frac{\mathrm{ED}}{{2R}_{\mathrm{avg}}}---\left(20\right)$

F _r---axial stress reduction coefficient;

σ _allow---the allowable tensile stress (MPa) of pipeline material;

σ _sp---pipe safety returns the tensile stress (MPa) of dragging.

Pipeline critical external compressive resistance destroys safety coefficient:

In the time that safety coefficient is greater than 1, pipeline can not destroy under external pressure; Otherwise destroy.

The suffered pressure outside of pipeline when compaction grouting:

P _net＝p+γ _csH+P _ch-P _i(21)

P---grouting pressure (MPa);

γ _cs---the weight (KN/m of per unit volume cement slurry ³);

P _ch---the kinetic pressure (MPa) of cement slurry to pipeline, is approximately equal to P _h.

Critical external compressive resistance failure analysis formula when compaction grouting and step and return while dragging basic identically, just external pressure changes.By above-mentioned external pressure formula substitution formula (17), the critical external compressive resistance yield factor of safety and the critical external compressive resistance that calculate respectively pipeline destroy safety coefficient, and whether checking computations grouting pressure meets safety requirement.

In sum, (1) electric power comb drags because multitube combines back, make on the one hand the suffered slurry resistance of pipeline increase, on the other hand along with number of tubes increases, restraining suffered gravity or net buoyancy increases, tube bank directly contacts with hole wall, thereby increases its suffered surface friction drag, and this all makes pull-back force increase.

(2) tube bank is carried out to tension when checking computations, should make that the allowable tensile stress of every pipeline wherein must be less than its axial tension stress and flexural stress with, i.e. σ _allow< σ _x+ σ _a.

(3) pipeline produces contraction strain radially under external pressure effect and axial tension effect, and this effect can reduce the critical external compressive resistance performance of pipeline, will be multiplied by axial stress reduction coefficient so calculate the critical destruction pressure outside of pipeline.

(4) electric power comb returns to drag after in place and will carry out compaction grouting, grouting pressure be taken into account as the suffered external pressure of pipeline, therefore will respectively the critical external compressive resistance in pipeline returning process and in slip casting process be destroyed and be analyzed.

Drag effect owing to considering in technological scheme of the present invention that multitube returns, regard the tube bank of electric power comb as entirety, utilize the equivalent redius of tube bank and the equivalent friction factor of tube bank and hole wall, conventional ASTM pull-back force computational methods are improved, make its more suitable power pipeline back drag force calculating; Simultaneously using grouting pressure as the suffered pressure outside of pipeline, the stress of pipeline while analyzing slip casting, thus ensure the safety in pipeline returning and mortar depositing construction.

The present invention can be widely used in design, construction and the surveillance field of power pipe.

Claims (5)

1. a non-excavating construction method for electric power comb, comprises horizontal directional drilling construction method, and the horizontal directional drilling construction method described in it first bores a pilot hole according to design curve, and described pilot hole is by the point that buries, the first inclination section that connect successively; Horizontal segment, the second inclination section and unearthed point form; By the composite structure of an electric power comb tube bank of many electric power comb compositions; The tube bank of electric power comb is returned and is dragged in pilot hole along pilot hole, complete traversing pipe line work; It is characterized in that described non-excavating construction method at least comprises the following steps:

Drag in process returning, consider that multitube returns and drags effect, regard the tube bank of electric power comb as entirety, and do not consider that water filling is returned and drag;

Putting before this, determine electric power comb return drag process in along the suffered total pulling force of tube bank of drilling track each point, the average every corresponding axial tension stress of pipeline with return hauling pipe road tension safety condition;

Electric power comb is restrained back and is dragged while carrying out compaction grouting after in place, and grouting pressure is taken into account as the suffered external pressure of pipeline;

By said method, ensure electric power comb return drag with mortar depositing construction in safety;

Wherein, described electric power comb return drag process in along the suffered total pulling force parameter of tube bank of pilot hole track each point, determine according to following representation:

$T_1=e^{{\mathrm{\&upsi;}}_a\mathrm{\&alpha;}}\left[{\mathrm{\&upsi;}}_a{\mathrm{\&omega;}}_a(L_1+L_2+L_3+L_4)\right]$

$T_2=e^{{\mathrm{\&alpha;}}_b\mathrm{\&alpha;}}(T_1+T_h+{\mathrm{\&upsi;}}_b|{\mathrm{\&omega;}}_b|L_2+{\mathrm{\&omega;}}_{b}H-{\mathrm{\&upsi;}}_a{\mathrm{\&omega;}}_a{L}_2{e}^{{\mathrm{\&upsi;}}_a\mathrm{\&alpha;}})$

$T_3=T_2-e^{{\mathrm{\&upsi;}}_b\mathrm{\&alpha;}}\left({\mathrm{\&upsi;}}_a{\mathrm{\&omega;}}_a{L}_3{e}^{{\mathrm{\&upsi;}}_a\mathrm{\&alpha;}}\right)+T_h+{\mathrm{\&upsi;}}_b\left|{\mathrm{\&omega;}}_b\right|L_3$

$T_4=e^{{\mathrm{\&upsi;}}_a\mathrm{\&beta;}}[T_3+T_h+{\mathrm{\&upsi;}}_b|{\mathrm{\&omega;}}_b|L_4-{\mathrm{\&omega;}}_{b}H-e^{{\mathrm{\&upsi;}}_a\mathrm{\&alpha;}}\left({\mathrm{\&upsi;}}_a{\mathrm{\&omega;}}_a{L}_4{e}^{{\mathrm{\&upsi;}}_a\mathrm{\&alpha;}}\right)]$

$T_h=P_h\frac{\mathrm{\&pi;}}{8}(D_h^2-D_m^2)$

$D_m=\sqrt{n}D$

${\mathrm{\&omega;}}_a=\frac{1.06\mathrm{n\&pi;}{D}^2{\mathrm{\&gamma;}}_a(\mathrm{DR}-1)}{{\mathrm{DR}}^2}$

${\mathrm{\&omega;}}_b=\frac{\mathrm{\&pi;}{D}^2{\mathrm{\&gamma;}}_b}{4}-\frac{1.06\mathrm{\&pi;}{D}^2{\mathrm{\&gamma;}}_a(\mathrm{DR}-1)}{{\mathrm{DR}}^2}$

Wherein, T ₁locate to restrain total pull-back force (KN) for burying; T ₂be that the first inclination section destination county is restrained total pull-back force (KN); T ₃be that total pull-back force (KN) is restrained at the second inclination section starting point place; T ₄for restraining total pull-back force (KN) in unearthed point place; L ₁for the additional length (m) of tube bank; L ₂bury and a little arrive the horizontal length (m) of deflecting terminal for tube bank; L ₃for tube bank horizontal section length (m); L ₄for tube bank horizontal segment terminal is to the horizontal length (m) of unearthed point; H is the height (m) of tube bank apart from ground; υ _afor tube bank and the friction factor on ground, get 0.5; υ _bfor the friction factor of tube bank in hole, get 0.3, multitube returns while dragging between 0.3～0.5, and maximum is got υ _a; ω _afor the total weight (KN/m) of unit length blank pipe bundle; ω _bfor unit length is restrained net buoyancy (KN/m) upwards; The penetrating angle (rad) of tube bank when α is back to drag; The unearthed angle (rad) of tube bank when β is back to drag; γ _afor the weight of per unit volume pipeline material; γ _bfor the weight (KN/m of mud in per unit volume annular space and landwaste mixture ³); P _hfor the kinetic pressure of annular space mud to pipeline, get 0.035～0.070MPa; D is the external diameter (m) of single pipe; D _hfor bore diameter (m); D _mfor diameter (m) after tube bank area equivalent; DR is the ratio of single pipe external diameter and wall thickness; N is the number that comprises pipeline in tube bank.

2. according to the non-excavating construction method of electric power comb claimed in claim 1, it is characterized in that the described corresponding axial tension stress parameter of average every pipeline, adopt following representation to determine:

${\mathrm{\&sigma;}}_x=\frac{T_x}{\mathrm{n\&pi;}{D}^2}\frac{{\mathrm{DR}}^2}{\mathrm{DR}-1}$

Wherein, σ _xfor axial tension stress (MPa) in the average every pipeline of pilot hole respective point; T _xfor pilot hole respective point is restrained total pull-back force (KN); D is the external diameter (m) of single pipe; DR is the ratio of single pipe external diameter and wall thickness; N is the number that comprises pipeline in tube bank.

3. according to the non-excavating construction method of electric power comb claimed in claim 1, it is characterized in that the described hauling pipe road tension security parameter condition of returning, must meet following condition:

σ _p<σ _allow

Wherein, σ _p=σ _x+ σ _a;

${\mathrm{\&sigma;}}_a=\frac{E_{24}D}{2R_{\mathrm{avg}}}$

$R_{\mathrm{avg}}=\frac{2H}{{\mathrm{\&theta;}}^2}$

σ _pfor the bending section interior conduit maximum tension stress (MPa) at respective point place; σ _afor respective point place bending section interior conduit maximum stress in bend (MPa); E ₂₄for the Young's modulus (MPa) in pipeline 24 hours; R _avgfor the mean radius of curvature (m) of pipeline in hole; θ is penetrating angle or unearthed angle (rad) of pipeline, σ _allowfor the allowable tensile stress (MPa) of pipeline material; H is the height (m) of tube bank apart from ground; D is the external diameter (m) of single pipe.

4. according to the non-excavating construction method of electric power comb claimed in claim 3, it is characterized in that in the time that tension checking computations are carried out in the tube bank to described, the allowable tensile stress parameter of every pipeline in tube bank, must be less than its axial tension stress and flexural stress with, that is: σ _allow< σ _x+ σ _a;

Wherein, σ _allowfor the allowable tensile stress of every pipeline, σ _xfor axial tension stress (MPa) in the average every pipeline of pilot hole respective point, σ _afor respective point place bending section interior conduit maximum stress in bend (MPa).

5. according to the non-excavating construction method of electric power comb claimed in claim 1, it is characterized in that in the time carrying out described compaction grouting, the suffered pressure outside parameter of pipeline adopts following representation to determine:

P _net＝p+γ _csH+P _ch-P _i

Wherein, P _netthe suffered pressure outside of pipeline during for compaction grouting; P is grouting pressure (MPa); γ _csfor the weight (KN/m of per unit volume cement slurry ³); H is the thickness (m) of upper overburden layer; P _chfor the kinetic pressure (MPa) of cement slurry to pipeline, be approximately equal to P _h; P _hfor annular space mud acts on the kinetic pressure (MPa) on pipeline; P _ifor acting on the internal pressure (MPa) on pipeline.