CN104794369A - Antiskid pile space based on soil arch effect and pile-slab soil pressure determination method - Google Patents

Abstract

The invention relates to an antiskid pile space based on a soil arch effect and a pile-slab soil pressure determination method, and belongs to the technical field of retaining engineering such as a landslide, a side slope and a foundation pit. The method comprises the following steps: step I: exploring landslide governing engineering site, controlling the geographic survey data, and forming a geological survey report; step II: calculating the landslide thrust force according to the geological survey report; step III: determining a pile width b; step IV: giving precision control quantity eps; step V: determining a minimum value pi min of a function pi, entering step VI if pi min is less than or equal to eps, otherwise, ending the calculation, thus showing that the antiskid pile design is improper for the landslide engineering; step VI: determining the pile space and a soil arch equation; step VII: calculating the pile-slab soil pressure. Compared with the prior art, the reasonability of the antiskid pile design can be improved, and the utilization of the capability of the antiskid pile in the engineering can be improved.

Description

Based on friction pile pile spacing and the stake plate soil pressure defining method of soil arching effect

Technical field

The invention belongs to the retaining engineering technical fields such as landslide, side slope, foundation ditch, relate to the defining method of a kind of friction pile pile spacing based on soil arching effect and stake plate soil pressure.

Background technology

It is main cylindrical component that friction pile is used to bear the horizontal applied force such as Thrust of Landslide, resistance of soil, and pile body cross section often adopts big cross section Reinforced Concrete Materials, props up the fields such as gear widely use at landslide, side slope, foundation ditch.Determining the spacing of stake, is an important content of anti-slide pile design.While stake produces resistance to the downslide soil body, the soil body between stake there will be extruding, and meanwhile, if the too small investment waste caused again in engineering of pile spacing, the therefore determination of rational spacing between adjacent, has become the key issue of engineering design.Pile spacing is excessive, and inter-pile soil body will skid off between stake, does not have the project benefit of expection; It is too little that pile spacing is got, and construction costs is just high.

In real work, be generally that the friction resistance produced with inter-pile soil body and two sides is not less than Thrust of Landslide between stake for controlled condition and estimates.This method does not consider Soil arch between piles effect, obviously too conservative, and estimation result is general very little, often lower than empirical value.When friction pile stake front boom section faces sky, often need arrange baffle plate between stake, baffle plate can adopt flat board or arch (folding) plate.In Practical Project, between stake, on baffle plate, the computing method of soil lateral pressure are varied, do not have the understanding that one unified so far yet.

Pile spacing and stake plate soil pressure are subject to Thrust of Landslide size, pile-type and cross dimensions, the length of stake and anchorage depth, anchoring section formation strength, the packing of the soil body and the many factors such as intensity, execution conditions, there is no very ripe computing method at present, due to the complicacy of rock and soil properties, the design of friction pile still needs the experience relying on engineering technical personnel in a lot, therefore determines that pile spacing and stake plate soil pressure are of great importance for the safety of stabilizing piles and economy scientifically and rationally.

Summary of the invention

In view of this, the object of the present invention is to provide the defining method of a kind of friction pile pile spacing based on soil arching effect and stake plate soil pressure, the method can improve the rationality of anti-slide pile design, adds the utilization of friction pile ability in large-engineering.

For achieving the above object, the invention provides following technical scheme:

Based on the friction pile pile spacing of soil arching effect and a defining method for stake plate soil pressure, comprise the following steps:

Step one: exploration landslide control engineering is on-the-spot, grasps geological mapping data, forms geological mapping report;

Step 2: the calculating carrying out Thrust of Landslide according to geology exploration report;

Step 3: determine the wide b of stake;

Step 4: given accuracy controlled quentity controlled variable eps;

Step 5: the minimum value Φ determining function phi _minif, Φ _min≤ eps, then forward step 6 to, otherwise stop calculating, and shows that this landslide engineering adopts anti-slide pile design improper;

Step 6: determine pile spacing and soil arch equation;

Step 7: calculate stake plate soil pressure.

Further, in step one, the report of engineering geological exploration of landslide control engineering Treatment design need be grasped, comprise landslide engineering geological map; Landslide boundary, form and coverage; Landslide engineering log sheet; Sliding bed contour map and bedrock surface contour map; The engineering geology and hydrogeology of slide area; Determine the foundation coefficient etc. of the mechanics index of physics (containing c, φ value of different section and within the operating period, the least favorable situation etc. that may occur) of landslide slip and sliding bed rock (soil), sliding bed rock (soil) horizontal bearing capacity eigenwert and Rock And Soil.

Further, in step 2, be reported as foundation with geological mapping, select least favorable design conditions, adopt coefficient transfer method to carry out the calculating of Thrust of Landslide, see related specifications, or can choose according to the Thrust of Landslide value that exploration report provides.

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

Further, in step 4, eps be one close to 0 numerical value, desirable 1 × 10 ^-5.

Further, in step 5, by nonlinear function optimization method solved function Φ (a, f, α) minimum value Φ _min.

Further, the fminsearch in matlab software is adopted to carry out search finding, the desirable a of initial value needed for search finding ₀=5b, f ₀=2b, α ₀=φ;

Function phi (a, f, α) value adopts following formula to solve:

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

Wherein: ${\mathrm{\Φ}}_1=\tan \mathrm{\α}+\frac{\mathrm{\λf}}{a+b}-\frac{a+b}{4f}$

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

Wherein, a is friction pile clear spacing, f is native sagitta, α is stake Vee formation shape soil body densification district and stake back side angle, and b is that stake is wide, and c is the cohesive strength of the soil body, and φ is angle of internal friction, and λ is coefficient of horizontal pressure, and q is Thrust of Landslide load intensity, and K is safety coefficient.

Further, in step 6, according to the independent variable a making function phi (a, f, α) reach minimum value in step 5, f, α determine pile spacing and soil arch equation:

Pile spacing l:l=a+b

Soil arch equation: $\frac{x^2}{{\left(B\sqrt{\mathrm{\λ}}\right)}^2}+\frac{{(y-B)}^2}{B^2}=1$

Wherein: $B=\frac{f}{2}+\frac{a^2}{8\mathrm{\λf}}.$

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 a part for elliptic curve, and B is Y-direction half axial length, and elliptical center point coordinate is (0, B).

Beneficial effect of the present invention is: the friction pile pile spacing based on soil arching effect provided by the invention and stake plate soil pressure defining method, relative to existing method, can improve the rationality of anti-slide pile design, add the utilization of friction pile ability in large-engineering.

Accompanying drawing explanation

In order to make object of the present invention, technical scheme and beneficial effect clearly, the invention provides following accompanying drawing and being described:

Fig. 1 is that friction pile is arranged and dome of natural equilibrium schematic diagram;

Fig. 2 is the stressed sketch of natural equilibrium soil arch;

Fig. 3 is arch springing block plan;

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

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

Fig. 6 is crown section distribution of force figure;

Fig. 7 props up gear sketch for planization silo method calculates 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, and as shown in the figure, this method comprises the following steps: step one: exploration landslide control engineering is on-the-spot, grasps geological mapping data, forms geological mapping report; Step 2: the calculating carrying out Thrust of Landslide according to geology exploration report; Step 3: determine the wide b of stake; Step 4: given accuracy controlled quentity controlled variable eps; Step 5: the minimum value Φ determining function phi _minif, Φ _min≤ eps, then forward step 6 to, otherwise stop calculating, and shows that this landslide engineering adopts anti-slide pile design improper; Step 6: determine pile spacing and soil arch equation; Step 7: calculate stake plate soil pressure.

Be described as follows:

Fig. 2 is that friction pile is arranged and dome of natural equilibrium schematic diagram, wherein, friction pile, stake wide b, stake clear distance a, the pressure arch curve under Thrust of Landslide load intensity q and lateral load intensity λ q effect, for natural equilibrium arch shape, the rise of arch is f, λ is coefficient of horizontal pressure, can calculate by coefficient of static earth pressure ν is Poisson ratio, and the Poisson ratio because of soil is not easy to record, and available λ=1-sin φ carries out approximate treatment.

Fig. 2 is the stressed sketch of natural equilibrium soil arch, due to arch and stressed symmetry, arch is cut open from centre, get OM section from left semiarch to study, at the horizontal thrust T that the effect of O point has right semiarch part to transmit, evenly load q has been acted on after arch, evenly load λ q is had in the effect of arch side, according to the feature of ground compressive property much larger than tensile property, the form of pressure arch can think best natural equilibrium form, there is not shearing and moment of flexure, therefore only there is axle pressure W at M point section, each point stress balance is encircleed by Stabilized Soil, the balance equation of these power to M point power taking square is:

$\frac{{\mathrm{qx}}^2}{2}+\frac{\mathrm{\λ}{\mathrm{qy}}^2}{2}-\mathrm{Ty}=0---\left(1\right)$

Consider whole left semiarch equilibrium equation in X direction:

T＝λqf+R _x(2)

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

R _y＝qa/2 (3)

For left semiarch, distance is got to O point:

$R_{x}f-R_y\frac{a}{2}+\frac{\mathrm{\λ}{\mathrm{qf}}^2}{2}+\frac{{\mathrm{qa}}^2}{8}=0---\left(4\right)$

Formula (3) is substituted into above formula:

$R_x=\frac{{\mathrm{qa}}^2}{8f}-\frac{\mathrm{\λqf}}{2}---\left(5\right)$

R _oxr _oyfor arch springing place counter-force R is at X, the component of Y-direction.

By formula (2), (4), (5) substitute into (1) formula and obtain nature arch equation:

$\frac{x^2}{{\left(B\sqrt{\mathrm{\λ}}\right)}^2}+\frac{(y-B)}{B^2}=1---\left(6\right)$

Wherein $B=\frac{f}{2}+\frac{a^2}{8\mathrm{\λf}}---\left(7\right)$

From formula (6), the shape of dome of natural equilibrium is a part for elliptic curve, and the X of this ellipse is to half axial length y-direction half axial length B, the coordinate of elliptical center point is (0, B), and elliptical center point is in the below of AB line.

Under the condition that fully can form soil arch, arch springing comprises three parts, and one is the pile body as soil arch arch springing supporting member, and two is soil body compressive regions after stake, and three is arch springing and the zone of transition of encircleing body, as shown in Figure 3.

According to Fig. 4 arch springing zone of transition force diagram, X, the Y-direction component in zone of transition and triangular compressive region intersection cross section are respectively:

$R_{\mathrm{ox}}=\frac{q{(a+b)}^2}{8f}-\frac{\mathrm{\λqf}}{2}---\left(8\right)$

$R_{\mathrm{oy}}=\frac{q(a+b)}{2}---\left(9\right)$

T is soil arch thickness, $t=\frac{b}{2\cos \mathrm{\α}}$

For stake Vee formation shape densification district, assuming that zone of transition and triangle pressurized hand over regional boundary place resultant direction and cross section orthogonal, see Fig. 5:

$\tan \mathrm{\α}=\frac{R_{\mathrm{ox}}}{R_{\mathrm{oy}}}---\left(10\right)$

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

$\tan \mathrm{\α}=\frac{a+b}{4f}-\frac{\mathrm{\λf}}{a+b}---\left(11\right)$

Now, the counter-force that stake provides is:

$p_u=\frac{q(a+b)}{b}---\left(12\right)$

$\mathrm{\σ}=\frac{2\sqrt{R_{\mathrm{ox}}^2+R_{\mathrm{oy}}^2}\cos \mathrm{\α}}{b}=\frac{{2R}_{\mathrm{oy}}}{b}=\frac{q(a+b)}{b}---\left(13\right)$

As can be seen from upper two formulas and symmetry, the compressive stress of triangle pressure zone boundary is identical, and in Ye Jici district, each point is all in hydrostatic force state, is stabilizer pole state, it can be said that bright above-mentioned supposition is rational.

According to arch springing failure condition, meet strength of Mohr Coulomb criterion at unfavorable section, consider that safety coefficient K obtains:

KR _y＝R _xtanφ+cb/sin2α (14)

As Fig. 6, when the unfavorable cross section of vault is in state of limit equilibrium, its compressive stress is trapezoidal, wherein

σ _max＝q tan ²(45°+φ/2)+c tan(45°+φ/2)

σ _min＝c tan(45°+φ/2)

Then the limit general pressure of section is:

Consider safety coefficient K, vault destroys bar and is:

KT＝T _max(16)

The determination of pile spacing and soil arch parameter:

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

${\mathrm{\Φ}}_1=\tan \mathrm{\α}+\frac{\mathrm{\λf}}{a+b}-\frac{a+b}{4f}=0---\left(17\right)$

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

${\mathrm{\Φ}}_2=(\frac{{\mathrm{qa}}^2}{4f}-\mathrm{\λqf})\tan \mathrm{\φ}+2\mathrm{cb}/\sin 2\mathrm{\α}-\mathrm{Kqa}=0---\left(18\right)$

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

Thus, friction pile soil arch problem can be summed up as and solves three unknown quantitys a, α and f, meets above three nonlinear equations.This problem is equal to the null value problem asking following formula function phi:

$\mathrm{\Φ}={\mathrm{\Φ}}_1^2+{\mathrm{\Φ}}_2^2+{\mathrm{\Φ}}_3^2=0---\left(20\right)$

The solution of above formula is by the minimal value of solved function Φ and minimal value is 0 to obtain, and when the minimal value of Φ is non-vanishing, and under the wide and Thrust of Landslide effect of the given stake of institute is described, it is inappropriate for adopting friction pile to carry out landslide control.

Matlab can be adopted to provide fminsearch function solve, this function only needs to set up Φ function module and a given initial value can search out the minimal value of function, as long as provide suitable initial value (general desirable a=3b, f=a/3, α=φ), search is more rapidly.

Prop up a gear between step 7 king-pile to put, be arranged on a leading edge and face sky side, consider soil arching effect, prop up gear between stake and can intend turning to a thrust of being born to calculate it by stake, the native sidewall encircleed and prop up the silo that gear forms between stake.Analyze Fig. 6 situation, sidewall horizontal Earth Pressure is:

$q_x=\frac{\mathrm{A\γ}}{P\tan \mathrm{\φ}}(1-e^{-\frac{P}{A}\mathrm{kz}})$

Wherein q _x---inter-pile soil is to the horizontal thrust of baffle plate;

The area of A---ABCED;

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

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

P---the girth of closed section ABCED;

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

γ---gliding mass soil severe;

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

Z---calculation level is to the stake end face degree of depth;

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

δ---Weir Plate Thickness;

k＝tanφtan ²(π/4-φ/2)。

Fig. 7 props up gear sketch for planization silo method calculates 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 gets a cross-sectional length d=3m, width b=2m, cohesive strength c=40kP _ac=40.0kPa, angle of internal friction safety coefficient K=1.2.By result of calculation of the present invention in table 1.

Baffle plate soil pressure distribution result between table 1

Finally brightly be, above preferred embodiment is only in order to illustrate technical scheme of the present invention and unrestricted, although by above preferred embodiment to invention has been detailed description, but those skilled in the art are to be understood that, various change can be made to it in the form and details, and not depart from claims of the present invention limited range.

Claims (8)

1. reach a defining method based on the friction pile pile spacing of soil arching effect and stake plate soil pressure, it is characterized in that: comprise the following steps:

Step one: exploration landslide control engineering is on-the-spot, grasps geological mapping data, forms geological mapping report;

Step 2: the calculating carrying out Thrust of Landslide according to geology exploration report;

Step 3: determine the wide b of stake;

Step 4: given accuracy controlled quentity controlled variable eps;

Step 5: the minimum value Φ determining function phi _minif, Φ _min≤ eps, then forward step 6 to, otherwise stop calculating, and shows that this landslide engineering adopts anti-slide pile design improper;

Step 6: determine pile spacing and soil arch equation;

Step 7: calculate stake plate soil pressure.

2. a kind of friction pile pile spacing based on soil arching effect according to claim 1 and stake plate soil pressure defining method, it is characterized in that: in step one, the report of engineering geological exploration of landslide control engineering Treatment design need be grasped, comprise landslide engineering geological map; Landslide boundary, form and coverage; Landslide engineering log sheet; Sliding bed contour map and bedrock surface contour map; The engineering geology and hydrogeology of slide area; Determine the foundation coefficient of the mechanics index of physics of landslide slip and sliding bed rock (soil), sliding bed rock (soil) horizontal bearing capacity eigenwert and Rock And Soil.

3. the defining method of a kind of friction pile pile spacing based on soil arching effect according to claim 1 and stake plate soil pressure, it is characterized in that: in step 2, be reported as foundation with geological mapping, select least favorable design conditions, adopt coefficient transfer method to carry out the calculating of Thrust of Landslide.

4. the defining method of a kind of friction pile pile spacing based on soil arching effect according to claim 1 and stake plate soil pressure, it is characterized in that: in step 3, the wide b of stake is not less than friction pile arm length 1/6.

5. the defining method of a kind of friction pile pile spacing based on soil arching effect according to claim 1 and stake plate soil pressure, is characterized in that: in step 4, eps be one close to 0 numerical value, desirable 1 × 10 ^-5.

6. the defining method of a kind of friction pile pile spacing based on soil arching effect according to claim 1 and stake plate soil pressure, is characterized in that: in step 5, by nonlinear function optimization method solved function Φ (a, f, α) minimum value Φ _min.

7. the defining method of a kind of friction pile pile spacing based on soil arching effect according to claim 6 and stake plate soil pressure, is characterized in that: the fminsearch in employing matlab software is to carry out search finding, and needed for search finding, a got by initial value ₀=5b, f ₀=2b, α ₀=φ;

Function phi (a, f, α) value adopts following formula to solve:

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

Wherein: ${\mathrm{\Φ}}_1=\tan \mathrm{\α}+\frac{\mathrm{\λf}}{a+b}-\frac{a+b}{4f}$

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

Wherein, a is friction pile clear spacing, f is native sagitta, α is stake Vee formation shape soil body densification district and stake back side angle, and b is that stake is wide, and c is the cohesive strength of the soil body, and φ is angle of internal friction, and λ is coefficient of horizontal pressure, and q is Thrust of Landslide load intensity, and K is safety coefficient.

8. the defining method of a kind of friction pile pile spacing based on soil arching effect according to claim 1 and stake plate soil pressure, it is characterized in that: in step 6, according to making function phi (a in step 5, f, α) reach the independent variable a of minimum value, f, α determine pile spacing and soil arch equation:

Pile spacing l:l=a+b

Soil arch equation: $\frac{x^2}{{\left(B\sqrt{\mathrm{\λ}}\right)}^2}+\frac{{(y-B)}^2}{B^2}=1$

Wherein: $B=\frac{f}{2}+\frac{a^2}{8\mathrm{\λf}},$

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