CN104794369B - Friction pile stake spacing and peg board soil pressure based on soil arching effect determine method - Google Patents

Abstract

The present invention relates to a kind of friction pile stake spacing based on soil arching effect and the determination method of peg board soil pressure, belong to the retaining engineering technical field such as landslide, side slope, foundation ditch.This method comprises the following steps：Step one：Landslide control engineering scene is explored, geological mapping data is grasped, geological mapping report is formed；Step 2：The calculating of Thrust of Landslide is carried out according to geology exploration report；Step 3：It is determined that the wide b of stake；Step 4：Given accuracy controlled quentity controlled variable eps；Step 5：Determine the minimum value Φ of function phi_minIf, Φ_min≤ eps, then go to step 6, otherwise terminates and calculates, and shows that this landslide engineering is improper using anti-slide pile design；Step 6：It is determined that stake spacing and soil arch equation；Step 7：Calculate peg board soil pressure.This method compared with prior art, can improve the reasonability of anti-slide pile design, increase the utilization of friction pile ability in engineering.

Description

Friction pile stake spacing and peg board soil pressure based on soil arching effect determine method

Technical field

The invention belongs to come down, the retaining engineering technical field such as side slope, foundation ditch, be related to a kind of antiskid based on soil arching effect The determination method of stake stake spacing and peg board soil pressure.

Background technology

Friction pile is for bearing the cylindrical component based on the horizontal applied forces such as Thrust of Landslide, resistance of soil, pile body section Frequently with big cross section Reinforced Concrete Materials, widely used in fields such as landslide, side slope, foundation ditch supporting and retaining systems.It is determined that the spacing of stake, is One important content of anti-slide pile design.While stake produces resistance to the downslide soil body, extruding occurs in the soil body between stake, together When, if stake spacing is too small and investment waste in engineering is caused, therefore the determination of rationally stake spacing, it has also become engineering design Key issue.Stake spacing is excessive, and inter-pile soil body will be skidded off between stake, not have expected project benefit；Stake spacing takes too Small, construction costs is just high.

It is usually the landslide being not less than with the frictional resistance produced by inter-pile soil body and two sides between stake in real work Thrust is that control condition is estimated.This method does not account for Soil arch between piles effect, it is clear that overly conservative, estimation result is general Very little, often below empirical value.When friction pile stake front boom section faces space-time, baffle plate need to be often set between stake, baffle plate can be using flat Plate or arch (folding) plate.In Practical Project, the computational methods of soil lateral pressure are varied on baffle plate between stake, do not there is one yet so far Unified understanding.

Stake spacing and peg board soil pressure by Thrust of Landslide size, pile-type and cross dimensions, the length of stake and anchorage depth, The factors influence such as anchoring section formation strength, the compactness of the soil body and intensity, execution conditions, there is no very ripe calculating at present Method, due to the complexity of rock and soil properties, the design of friction pile stills need the experience by engineers and technicians at many aspects, Therefore scientifically and rationally determine that stake spacing and peg board soil pressure are of great importance for the safety and economy of stabilizing piles.

The content of the invention

In view of this, it is an object of the invention to provide a kind of friction pile stake spacing and peg board soil pressure based on soil arching effect The determination method of power, this method can improve the reasonability of anti-slide pile design, increase the utilization of friction pile ability in engineering.

To reach above-mentioned purpose, the present invention provides following technical scheme：

A kind of determination method of friction pile stake spacing and peg board soil pressure based on soil arching effect, comprises the following steps：

Step one：Landslide control engineering scene is explored, geological mapping data is grasped, geological mapping report is formed；

Step 2：The calculating of Thrust of Landslide is carried out according to geology exploration report；

Step 3：It is determined that the wide b of stake；

Step 4：Given accuracy controlled quentity controlled variable eps；

Step 5：Determine the minimum value Φ of function phi_minIf, Φ_min≤ eps, then go to step 6, otherwise terminates and calculates, Show that this landslide engineering is improper using anti-slide pile design；

Step 6：It is determined that stake spacing and soil arch equation；

Step 7：Calculate peg board soil pressure.

Further, in step one, the report of engineering geological exploration of landslide control engineering Treatment design, including cunning need to be grasped Slope geological map；Landslide boundary, form and coverage；Landslide engineering log sheet；Slider bed contour map and base Scar contour map；The engineering geology and hydrogeology of slide area；Determine that landslide slip and the physical mechanics of slider bed rock (soil) refer to Mark (c, φ value containing different sections and in validity period, in fact it could happen that least favorable situation etc.), slider bed rock (soil) level holds Carry coefficient of subgrade reaction of power characteristic value and Rock And Soil etc..

Further, in step 2, foundation is reported as with geological mapping, least favorable design conditions are selected, is using transmission Number method carries out the calculating of Thrust of Landslide, reference can be made to related specifications, or the Thrust of Landslide value provided according to exploration report are chosen.

Further, in step 3, the wide b of stake is not less than friction pile arm length 1/6.

Further, in step 4, eps, close to 0 numerical value, can use 1 × 10 for one^-5。

Further, in step 5, nonlinear function optimization method solved function Φ (a, f, α) minimum values Φ is passed through_min。

Further, scan for solving using the fminsearch in matlab softwares, initial value needed for search finding Desirable a₀=5b, f₀=2b, α₀=φ；

Function phi (a, f, α) value is solved using following formula：

Wherein：

Wherein, a is that friction pile clear spacing, f are that native sagitta, α are a rear triangle soil body densification area and stake back side angle, b Wide for stake, c is the cohesive strength of the soil body, and φ is internal friction angle, and λ is coefficient of horizontal pressure, and q is Thrust of Landslide load intensity, and K is for safety Number.

Further, in step 6, according to the independent variable a, f, α for function phi (a, f, α) is reached minimum value in step 5 It is determined that stake spacing and soil arch equation：

Stake spacing l：L=a+b

Soil arch equation：

Wherein：

λ is coefficient of horizontal pressure, and a is friction pile clear spacing, and b is that stake is wide, and f is native sagitta, and soil arch equation is the one of elliptic curve Part, B is the axial length of Y-direction half, and elliptical center point coordinates is (0, B).

The beneficial effects of the present invention are：The stake spacing of the friction pile based on soil arching effect and peg board soil pressure that the present invention is provided Power determines method for existing method, can improve the reasonability of anti-slide pile design, increases friction pile ability in engineering Utilization.

Brief description of the drawings

In order that the purpose of the present invention, technical scheme and beneficial effect are clearer, the present invention provides drawings described below and carried out Explanation：

Fig. 1 is that friction pile is arranged and natural arch schematic diagram；

Fig. 2 is natural equilibrium soil arch stress sketch；

Fig. 3 is arch springing block plan；

Fig. 4 is arch springing transition region force analysis schematic diagram；

Fig. 5 is soil body triangle densification area force analysis schematic diagram after stake；

Fig. 6 is crown section distribution of force figure；

Fig. 7 is that planization silo method calculates supporting and retaining system sketch between stake；

Fig. 8 is the schematic flow sheet of the method for the invention.

Embodiment

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described in detail.

Fig. 8 is the schematic flow sheet of the method for the invention, as illustrated, this method comprises the following steps：Step one：Survey Landslide control engineering scene is visited, geological mapping data is grasped, geological mapping report is formed；Step 2：According to geology exploration report Carry out the calculating of Thrust of Landslide；Step 3：It is determined that the wide b of stake；Step 4：Given accuracy controlled quentity controlled variable eps；Step 5：Determine function Φ minimum value Φ_minIf, Φ_min≤ eps, then go to step 6, otherwise terminates and calculates, shows that this landslide engineering uses friction pile Design is improper；Step 6：It is determined that stake spacing and soil arch equation；Step 7：Calculate peg board soil pressure.

It is described as follows：

Fig. 2 is that friction pile is arranged and natural arch schematic diagram, wherein, friction pile, the wide b of stake, stake clear distance a are pushed away on landslide Pressure arch curve under power load intensity q and lateral load intensity λ q effects, is natural equilibrium arch shape, the rise of arch is f, λ For coefficient of horizontal pressure, it can be calculated by coefficient of static earth pressureν is Poisson's ratio, because the Poisson's ratio of soil is not easy to survey , approximate calculation can be carried out with λ=1-sin φ.

Fig. 2 is natural equilibrium soil arch stress sketch, due to arch and the symmetry of stress, arch is splitted from centre, from a left side Take OM sections to be studied on semiarch, have the horizontal thrust T that right semiarch part is transmitted in the effect of O points, effect has uniform lotus after arch Q is carried, there are evenly load λ q in the effect of arch side, the feature of tensile property, the form of pressure arch is much larger than according to ground compressive property Optimal natural equilibrium form is regarded as, in the absence of shearing and moment of flexure, therefore axial compressive force W is only existed at M points section, by Stable soil encircles each point stress balance, and these power are to the equilibrium equation of M point power taking squares：

Consider the whole equilibrium equation of left semiarch in X direction：

T=λ qf+R_x (2)

Consider whole equilibrium equation of the left semiarch along Y-direction：

R_y=qa/2 (3)

For left semiarch, O points are taken away from：

Formula (3) is substituted into above formula：

R_oxR_oyIt is counter-force R at arch springing in X, the component of Y-direction.

By formula (2), (4), (5) substitute into (1) formula and derive from so arch equation：

Wherein

From formula (6), the part for being shaped as elliptic curve of natural arch, this oval X is to half axial length The axial length B of Y-direction half, the coordinate of elliptical center point is (0, B), and elliptical center point is in the lower section of AB lines.

Under conditions of it can be sufficiently formed soil arch, arch springing includes three parts, and one is to encircle arch springing supporting member as soil Pile body, two be soil body compressive region after stake, and three be the transition region of arch springing and arch body, as shown in Figure 3.

According to Fig. 4 arch springing transition region force diagrams, X, Y-direction component point of the transition region with triangular compressive region intersection section It is not：

T is soil arch thickness,

For stake rear triangle densification area, it is assumed that transition region is pressurized with triangle hands over resultant direction at regional boundary to be hung down with section Directly, Fig. 5 is seen：

Formula (8), (9) are substituted into above formula and obtained：

Now, the counter-force that stake is provided is：

The compression of triangle pressure area boundary is identical it can be seen from upper two formula and symmetry, namely in this area respectively Point is in hydrostatic pressure state, is stabilizer pole state, it is possible thereby to illustrate that above-mentioned hypothesis is rational.

According to arch springing failure condition, strength of Mohr Coulomb criterion is met at unfavorable section, it is considered to which safety coefficient K is obtained：

KR_y=R_xtanφ+cb/sin2α (14)

Such as Fig. 6, when the unfavorable section of vault is in state of limit equilibrium, its compression is trapezoidal, wherein

σ_max=q tan²(45°+φ/2)+c tan(45°+φ/2)

σ_min=c tan (45 ° of+φ/2)

Then the limit gross pressure at section is：

Consider safety coefficient K, vault destruction bar is：

KT=T_max (16)

The determination of stake spacing and soil arch parameter：

By (3), (5), (8), (9) substitute into formula (10) and obtained：

By (3), (5) substitute into formula (14) and obtained：

By (2), (5), (15) substitute into formula (16) and obtained：

Thus, the native arch problem of friction pile can be attributed to solution three unknown quantitys a, α and f, meet the non-linear side of three above Journey.The problem is equal to the null value problem for seeking following formula function phi：

The solution of above formula can be obtained by solved function Φ minimum and minimum for 0, and when Φ minimum is not zero When, illustrate under the wide effect with Thrust of Landslide of the given stake of institute, it is inappropriate to carry out landslide control using friction pile.

It can be solved using the matlab fminsearch functions provided, this function only needs to set up Φ Function Modules Block and give an initial value can search out the minimum of function, as long as provide suitable initial value (typically can use a=3b, f =a/3, α=φ), search is than relatively rapid.

Supporting and retaining system position between stake in step 7, is arranged on a leading edge and faces sky side, it is contemplated that supporting and retaining system can be intended between soil arching effect, stake A side wall of a silo that supporting and retaining system is constituted between stake, soil arch and stake is turned to calculate the thrust that it is born.To Fig. 6 situations Analyzed, sidewall horizontal Earth Pressure is：

Wherein q_x--- horizontal thrust of the inter-pile soil to baffle plate；

A --- ABCED area；

P --- closed section ABCED girth；

γ --- gliding mass soil severe；

φ --- the internal friction angle of gliding mass soil；

Z --- point is calculated to stake top face depth；

D --- the length of side in stake parallel, horizontal Thrust of Landslide direction；

δ --- Weir Plate Thickness；

K=tan φ tan²(π/4-φ/2)。

Fig. 7 is that planization silo method calculates supporting and retaining system sketch between stake.

Embodiment：

As Thrust of Landslide Q=640kN/m, cantilever segment length H=8.0m, then thrust is along the long distributed force q=80kN/m of stake, And take a cross-sectional length d=3m, width b=2m, cohesive strength c=40kP_aC=40.0kPa, internal friction angleSafety system Number K=1.2.1 is shown in Table by result of calculation of the present invention.

Baffle plate soil pressure distribution result between 1, table

Finally, it is noted that preferred embodiment above is merely illustrative of the technical solution of the present invention and unrestricted, although The present invention is described in detail by above preferred embodiment, it is to be understood by those skilled in the art that can be with Various changes are made to it in the form and details, without departing from claims of the present invention limited range.

Claims (5)

1. a kind of determination method of friction pile stake spacing and peg board soil pressure based on soil arching effect, it is characterised in that：Including with Lower step：

Step one：Landslide control engineering scene is explored, geological mapping data is grasped, geological mapping report is formed；

Step 2：The calculating of Thrust of Landslide is carried out according to geology exploration report；

Step 3：It is determined that the wide b of stake；

Step 4：Given accuracy controlled quentity controlled variable eps；

Step 5：Determine the minimum value Φ of function phi_minIf, Φ_min≤ eps, then go to step 6, otherwise terminates and calculates, shows This landslide engineering is improper using anti-slide pile design；

Step 6：It is determined that stake spacing and soil arch equation；

Step 7：Calculate peg board soil pressure；

In step 5, pass through nonlinear function optimization method solved function Φ (a, f, α) minimum values Φ_min；

Scan for solving using the fminsearch in matlab softwares, initial value needed for search finding takes a₀=5b, f₀= 2b, α₀=φ；

Function phi (a, f, α) value is solved using following formula：

$\mathrm{\Φ}(a,f,\mathrm{\α})={\mathrm{\Φ}}_1^2+{\mathrm{\Φ}}_2^2+{\mathrm{\Φ}}_3^2$

Wherein：

${\mathrm{\Φ}}_2=(\frac{{\mathrm{qa}}^2}{4f}-\mathrm{\λ}qf)tan\mathrm{\φ}+2cb/sin2\mathrm{\α}-Kqa$

Wherein, a is that friction pile clear spacing, f are that native sagitta, α are a rear triangle soil body densification area and stake back side angle, and b is stake Width, c is the cohesive strength of the soil body, and φ is internal friction angle, and λ is coefficient of horizontal pressure, and q is Thrust of Landslide load intensity, and K is safety coefficient；

In step 6, according to the independent variable a for making function phi (a, f, α) reach minimum value in step 5, f, α determine stake spacing and Soil arch equation：

Stake spacing l：L=a+b

Soil arch equation：

Wherein：

Wherein：Soil arch equation is a part for elliptic curve, and B is the axial length of Y-direction half, and elliptical center point coordinates is (0, B)；

Peg board soil pressure：

Wherein A --- the area that baffle plate and soil arch are surrounded between two friction piles, stake；

$A=a(d-\mathrm{\δ})+2B{\∫}_{{\mathrm{\θ}}_0}^{\mathrm{\π}/2}\sqrt{{\mathrm{\λsin}}^2\mathrm{\θ}+{\cos }^2\mathrm{\θ}}d\mathrm{\θ}$

${\mathrm{\θ}}_0=\arccos \left(\frac{a}{2B\sqrt{\mathrm{\λ}}}\right)$

P --- baffle plate and soil arch surround the girth of regional cross section between two friction piles, stake；

$\begin{array}{c}P=2\left(d-\mathrm{\δ}\right)+2a{\∫}_{{\mathrm{\θ}}_0}^{\mathrm{\π}/2}\sin \mathrm{\θ}\left(B-f-B\sin \mathrm{\θ}\right)d\mathrm{\θ}\\ =2\left(d-\mathrm{\δ}\right)+2a\[\sin 2{\mathrm{\θ}}_0/4+\left(B-f\right){\mathrm{cos\θ}}_0+{\mathrm{B\θ}}_0/2-\mathrm{\π}B/4-B+f\]\end{array}$

γ --- gliding mass soil severe；φ --- the internal friction angle of gliding mass soil；Z --- point is calculated to stake top face depth；D --- stake is put down The length of side of the smooth slope thrust direction of water-filling；δ --- Weir Plate Thickness；K=tan φ tan²(π/4-φ/2)。

2. a kind of friction pile stake spacing and peg board soil pressure based on soil arching effect according to claim 1 determine method, It is characterized in that：In step one, the report of engineering geological exploration of landslide control engineering Treatment design, including landslide work need to be grasped Journey geological map；Landslide boundary, form and coverage；Landslide engineering log sheet；Slider bed contour map and bedrock surface Contour map；The engineering geology and hydrogeology of slide area；Determine landslide slip and slider bed rock/mechanics index of physics of soil, cunning The coefficient of subgrade reaction of bed rock/soil horizontal bearing capacity characteristic value and Rock And Soil.

3. the determination side of a kind of friction pile stake spacing and peg board soil pressure based on soil arching effect according to claim 1 Method, it is characterised in that：In step 2, foundation is reported as with geological mapping, least favorable design conditions are selected, using carry-over factor Method carries out the calculating of Thrust of Landslide.

4. the determination side of a kind of friction pile stake spacing and peg board soil pressure based on soil arching effect according to claim 1 Method, it is characterised in that：In step 3, the wide b of stake is not less than friction pile arm length 1/6.

5. the determination side of a kind of friction pile stake spacing and peg board soil pressure based on soil arching effect according to claim 1 Method, it is characterised in that：In step 4, eps, close to 0 numerical value, can use 1 × 10 for one^-5。