Field Manual for use of Soiltac in Geotechnical Design PILES

Roberto Tamagnini, Eng. M.Sc.Ph.D.
2020-04-12
Ordine Ingegneri di Roma A23702

STARTUP Earthquake Engineering Field Manual

Application of Nano Technology Soilworks in Geotechnical Design :

Definition of Mohr Coulomb parameters for Chemo Plastic Treatment, Analysis of PILE PROTECTION AGAINST

Liquefaction RISK

Eng. M.Sc. Ph.D. Roberto Tamagnini

Chartership:

Ordine Ingegneri di Roma A23702

INTRODUCTION

The Manual explains how to use the Polymer Soiltac by Soilworks in Geotechnical Design of shallow and deep foundations

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FIRST SAMPLE TESTS – LONG TERM IN SITU

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Figure 1 dry loose sand and cured sample (paper filter membrane without any resistance)

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Figure 2 same sample cured for 4 weeks and immerged in pure water for 1 week

DURABILITY

The stability of the chemical bonds are guaranteed with humidity condition of 100% (full immersion into pure water) applied for 1 week.

The chemical reaction:

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Where:

(A)                        Is the pure water

(B)                        Is the mix vapor+ Hydrogen

(C)                        Is the bonded polymer with H2O

(D)                       Pure Soiltac

A sand has a permeability of 10-6 m/s, means needs 1.000.000 sec to move a particle from point a to b for a distance of 1 meter.

1 Joule = 1 N x 1 m, the Energy needed to move 1 kilo (of inertial mass) of 1 m with an acceleration of 1 m/s2. If the gravitational mass is used the joule should be at rest or divided by 9.8 m/s2

If I apply 1 N (is 100 grams of static water) around the sample the energy needed to cross the sample is 1 N x 1 m x 1.000.000 seconds = 1 MN.

If the sample a surface of 0,0062 m2 (i.e. 10 cm x 2 cm x 2 x 3,14)

1 MN / 62 cm2 = 1 MN/ 10000 x 62 = 6,2 KPa. (The permeability gives a resistance to the flow of 6,2 KPa that is 62 cm under the water level, the sample was immerged under 10 cm of water level for 7 days, means 620% of duration of the worst flooding. (B) is necessarily O and (A) is equal to (C) reduced by (D).

Coincidence of 620% of hydraulic charge and conditions and limit state acceleration of site with an earthquake is not realistic

SAMPLE TREATED IN COLUMNS AND WETTED AFTER 1 WEEK: BRITTLE FAILURE

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Figure 3 Unconfined Compression Test after Wetting

The wetting after curing has produced a shear band.

The critical state has been reached with a discontinuity and the flux of vapor was not due to homogenous filtration from the porous matrix.

Comparison with data of Mokni and Desrue (1998) explains the role of cavitation. 3% of fluid volume has divaricated the sample with a 30-degree inclination of the shear band.

Mokni and Desrue (1998) shows that in biaxial tests crl/cr2 = constant until the initiation of shear band, for each water pressure.

It means that Ko is constant and also the soil bearing capacity in Bi Axial test,

Liquefaction is the condition of biaxial rotation of 3rd invariant.

BI DIRECTIONAL TEST ON SAND – MOKNI AND DESRUE (1998)

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Varying water pressure from 800 KPa to 250 KPa, means 80 meters under the sea level and 25 meters, the rotation of the axis is delayed the cavitation of shear deviation of 0.07, 0.08 and 0.09.

800/250 = 320 %

Sample of laboratory at SOGEA Roma is:

62 cm / 10 cm = 620 %

Tare was consistent but geometrical boundary not, the 3D effects in Undrained Conditions requires FEM but Fluid is disregarded with Viscosity and time. Use of Soiltac allows to treat 3D modelling without FEM and using Wave Speed Monitors. Check against liquefaction is obtained with sealing and coating by the Polymer. Softening is modelled with Wave Trace monitoring and Spectrum Analysis.

IMPROVED STRENGTH AGAINST LIQUEFACTION - DEFINITION OF PARAMETERS

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Figure 4 Sample after wetting : failure

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After Treatment CU (KPa)

Worst Estimate  w it h Flooding CU (KPa)

Estimate with seasonal change and Safety Factor

CU {KPa)

Sand

 

1700

 

80

 

200

 

Pozzolana

 

1700

 

150

 

300

Initial value of CU = 40 KPa

DISCUSSION ON TESTS

Figure 4 Reports the Unconfined Compression Test after Curing (40/50 days at hygroscopic humidity of the atmosphere, figure 5 after full immersion in water for 1 week (after the cured period)

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Figure 5: Columns sample: Unconfined Compressive Strength UCS after curing.

Samples were than wetted to verify chemical stability. Wetting took place for 1 week into pure water at 100% of humidity. This condition for a standard infrastructure designed to be on land is not realistic. It explains the treatment can be used in very humid regions.

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Figure 6: Columns sample: Unconfined Compressive Strength UCS after wetting.

A treatment of soil foundation with Soiltac can prevent liquefaction, a condition in which soil exhibits a behavior like a fluid: mud in case of a threshold of dynamic inertia.

Long term must not be compared with the RETURN PERIOD of 750 years, that is a probability. In case of lsLv of a new bridge the dimensioning is for the event a/g of the site (see INGV), but with the REAL TIME OF OPERATIVTY, generally 100 years with coefficient of utility of an infrastructure. It means, if the treatment is cheaper because it does not change the dimensioned structure, owner can check the performance of the bridge with SEQUOIA piezoelectric accelerometers in the meantime and repeat the treatment.

Masonry building are brittle structures and increase of mass for structural retrofit would not occur. See Marble/ Travertine churches.

SECOND SET OF TEST SHORT TERM - SAMPLE PREPARATIONPicture Placeholder

Figure 2 dry loose sand and cured sample (paper filter membrane without any resistance)

SHORT TERM

The samples are prepared remolding loose sand with a mix of 300 grams of water and different concentrations of polymer SoiltacÒ.

The optimum is computed considering stability of Entropy production, i.e. chemical activity of Soiltac into the pores and stechiomtric balance with environment after 4 days.

LONG TERM for remolded samples

The probability of findings bonds generated by Soiltac molecule is assessed by a single test after 50 days.

SHORT TERM OF SAMPLE WITH DIFFERENT CONCENTRATIONS OF SOILTAC

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Figure 6 Compression after 4 days at 3 different concentrations 300 g of HZ0 + X g of Soiltac (X= 20 ,40 and 60)

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Figure 7 Compression after 4 days at 3 different concentrations 300 g of HZ0 + X g of Soiltac (X=80 ,100 and 120)

STABILITY OF MIX

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Figure 8 Correlation between water/ Soiltac on the gravity direction 1/3 of H20 volume

The points are correlated with logarithmic function in order to visualize the optimum for mix design. Correlation value is low, in order of 83%, but the number of samples is only 6. Equation can be written as

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Maximum value of Resistance to Shear Sliding is for ln(X) = 0, that is X=l. The value of 1, represents the mass stoichiometric equilibrium of the 2 fluids. In this case UCS is 1741,5 KPa.

However, this value is not the value that represents the environmental equilibrium because water content can change due to rainfall or hygroscopic oscillations.

To obtain the hydrothermal equilibrium, the derivative of Entropy must be zero, when X=1:

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For the maximum value of 1741,5 KPa obtainable with X=1 the rate of characteristic is the one of equation (3). This means that an equilibrium with the environment can be reached when the soil has a value of mix design as:

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1541 KPa is the maximum recorded in the test of first peak for 20 g of H2O and 20 g of Soiltac. The hypothesis of 900 KPa is the value that theoretically corresponds to the maximum friction in short term; see Orange Point in figure 2.

SECOND SET OF TESTS - LONG TERM

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Figure 9 Stress Strain behavior after 4 days

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Figure 10 Stress Strain behavior after 4 days and 45 days (creep analysis)

TIME DERIVATIVE - ASSESSMENT OF STIFFENING

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Analysis of data confirm that in the vertical direction the speed of gas molecules is reduced by 10 times thanks to Soiltac

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Figure 11 Stress Strain behavior after 4 days and 50 days (stiffness analysis)

DISCUSSION OF SECOND SET OF TESTS - TIME CONVENIENCE

Soiltac® has been designed for dust control with surface tension. It is very suitable for the control of dynamic load on sands. It prevents cavitation of water. The coalescence of vapor into the porous space allows increasing stiffness and strength.

CERTIFICATION BY SOGEA ROMA (M.I.T. MINISTERO DEI TRASPORTI GEO-LAB)

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RESULTS BY R. TAMAGNINI (2011) THAT DEMONSTRATE THE EFFECTIVENESS OF IDEA

Geotechnical scientific publications rarely report a measure of fluid phase compression, because water liquid is considered uncompressible in fully saturated sands. Numerical and geotechnical analysis of a constant volume test for nuclear waste management is reported in Tamagnini (2011). Paper shows feasibility of the proposed technology. The two clay samples (then with a cohesive matrix) are compressed with the air pressure to verify the confinement for the water flow impermeability. Romero (1999) at UPC Universita Politecnca Catalonia produces data. Changes in thermal value of T, the temperature, is due to the amount of stocked nuclear fuel. The vapor – water phase % changes during air decompression and re compression, the second compression simulates the Entropy cycle. Phase transformation gas-liquid does not allow an increasing in the thermal value of T (constant temperature). Phase changes are convenient for the Retrofit, because old designs are Formula without Temperature (Terzaghi effective stress). Data are obtained during the HADES Project, financed by UE, on the Thermal behavior of the Boom clay; Boom is the region of Mol in Belgium, where the SCKN research center is located. Results are depicted in figure 1.

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Figure 12 Test for constant volume test on Boom clay. Romero (1999) [7]

DISCUSSION OF LABORATORY TEST OF ROMERO (1999)

Pressure wave applied by a seismic event can be assessed by suction cycles 500/0 - 0/500 KPa, the vertical axis of the upper diagram. Suction and capillary stress are represented by the difference in the applied air/gas pressure ua and water pressure uw: (ua – uw). The second parts of the tests: A1-A2 and B1-B2 show irreversibility in the records of the Net mean stress. Entropy is a state variable only and only if irreversibility does not occur. The nonlinear hysteretic data shows that sample has changed position during a phase transition. This is due to the fusion of gas in liquid vapor; the process is not reversible without heating the sample with a source. Confinement is reported by the value of Net stress between 0 and 500 KPa: with an increase of the 20% of density (from 13.7 KN/m3 to 16.7 KN/m3) the sample has shown mechanical stability. Test with “loose” at 13.7 KN/m3 shows that the suction cycle, and then the seismic wave transit, has produced a condition in which shear decreases (Dev. measure) in both cycles compression - decompression, and softening occurred. Confinement is Net mean stress = 0 KPa at the end of the second cycle. The end of the second cycle is the Liquefaction in Earthquake Engineering - FEM modelling.

ENTROPY OF BOLTZMANN:

S = klogW S is the Entropy k is the constant an W the phase space

At the suction values of 1000 KPa and 2 KPa, in the first cycle of decompression,

Confinement:

Net stress = 120 KPa, test loose (13.7 KN/m3) – 1000 KPa of suction

Net stress = 360 KPa, test dense (16.7 KN/m3) – 1000 KPa of suction Maximum is for the double of the phase space W=2W, the

Net stress:

Net stress = 240 KPa test loose (13.7 KN/m3): 120 x 2 KPa

Net stress = 720 KPa test dense (16.7 KN/m3): 360 x 2 KPa

Value of Entropy:

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In the two cases: the uplift of the foundation starts at 1000KPa. In the first (13.7 KN/m3) the double of the phase space W = 120 x 2 = 240, has produced Liquefaction or Friction Sliding, in the second test dense (16.7 KN/m3); g (gravity acceleration) has produced only a radial deformation, and it occurred in the first cycle, corresponding to 180 KPa of deviator stress. Second cycle of recompression does not increase softening for 16.7 KN/m3.

To obtain the same result with a Frictional test the weight of the building should increase of 3 times.

In case of use of Soilworks - Soiltac, increase of strength is obtained with the increase of fluid density, passing from gas to liquid. In case of partially saturated sands, the matrix is compacted removing the capillary forces induced by menisci.  In saturated sands the effects is induced with the viscosity of fluids. Thermal capacity of sand grains is higher than atmosphere, after permeation the fluid mixed with water exchanges heat with solid grains and cooling induces increase  in viscous - plastic response (see test by SOGEA) .

Reducing the Reynolds number of 1000 times:

ln(1000) = 2, 3 × log(1000)

The coefficient 2,3 is the change of base from 2,76 to 10:

 ln(1000) = 2, 3 × 3, 0 = 6, 9

2.3 is the ratio between solid density and water density, 3 are the direction of force control.

EXPLANATION OF PHENOMENA OF HYSTERESIS IN BOOM CLAY WITH TEST OF LABORATORY S3 GRENOBLE. MOKNI AND DESRUE DATA ON BIAXIAL TEST

In order to explain the method developed by Earthquake Engineering the data of are discussed, The photogrammetric display of figure 6 shows with arrows the displacement vectors during shearing,

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The graphic representation of the shear versus axial strains is figure 3 with ratio of the vertical on horizontal effective stress.

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DISCUSSION OF DATA WITH USE OF BOLTZMANN ENTROPY

The spring compression applied by the soil reaction to shearing is:

0 – 9 % before water cavitation

9 -12 % after shear band forming ½ of sample is pushed in the Vertical Gravity direction other half is orienting s1 stress.

 s1/s2 is constant during shear from 0 to 9 %

s1/s2 has a JUMP at 9% (water cavitation)

s1/s2 is lower of 4,5 and reduced of 20% to 3,5 (heat transfer with wave speed)

H height of the sample at s1/s2 with JUMP at 9% -> variable with shear band orientation from 0 to arctan (1 base / 2 base)

Probability of finding the direction of G (9,81 m/s2) at 9 % of shearing is S= log (1 base / 2 base) = -0,69

Probability of finding representation between photogrammetric and graphic data for 1 completed sample is:

S= log (d/H) = 0.09 of S’=log (d’/H) = 0.12

External Entropy after caviation of water: S – S’ = log ( d/d’) = 0.03 or 3% with d/d’

= - 1,0309

If d = ½ mv2 is the integral of the flow and S can be referred to Reynolds. The 3 % of water is adsorbed by environment.

FIRST SET- DATA OF TREATMENT OF SAND ON SAMPLES WITH SOILTAC AND CURING TIME

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Figure reports the effect of time on strength. The dry loose sand is mixed with a fluid mix that interacts with laboratory environment; curves are the stress strain behavior after

1  week

2  week

3  week

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CHEMICAL BONDS AND RESIDUAL EFFECT:

Effect of H20 residual strength after immersion in water for  1 week 3 week

1  week= 3-week curing+ 1 week immerged in water

DISCUSSION OF RESULTS ON VAPOR CONTROL

The water/vapor retention by Soiltac

The chemical reaction:

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Allowed an increase of strength of 20 times from 40 to 940 KPa .

PHYSICAL PRINCIPLE OF THE INTERACTION BETWEEN GAS/WATER/SOLID - SURFACE

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STIFFNESS FROM LABORATORY TESTS IN ROMA ON SAND

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The stiffness of the sample wetted at 2% is 300/0.02 = 15.000 KPa The stiffness of the sample after 45 days is 2800/0.02 = 140.000 KPa

Entrapping the gas phase with Soiltac the axial deformation was for 1 point of the foundation 140.000 KPa. Before the treatment, it is not possible to estimate it with same method. The geophysics suggests that:

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V (shear wave) should be = 48 m/s (27 m/s for remolded) that is too low, because the sand has the consistency of a Rock. This is the result if the sample is considered homogeneous only 1 phase. Empirical correlation Robertson

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The innovation is to correlate Vs with filtration, according the Entropy

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INCREASE OF CLASS FROM S1 - S2 TO A OR B

With Soiltac permeability can be reduced by many orders of magnitude, if the loose sand had 10-4 in dry state and it passed to 10-8 in very compacted (an extreme)

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Suppose it was 100 m/s it should be a response like a 1000 m/s and more after treatment.

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EUROCODE EC8 Soil classification

BROMS THEORY AND HORIZONTAL FORCE – PILE RETROFIT

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The scheme of computation of the Broms theory for horizontal action is Hysteretic, what does it means?

THE HORIZONTAL RESISTANCE IS THE SAME AFTER 3d, 3 times

the Diameter. How is it possible?

Because the pile is cut and a plastic hinge is forming at the depth of 3d

Why is so LONG?

Because in Static Condition the load is VERTICAL

EMPIRISM - ABACO

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The Increase of Cu of 2 times (A to B) reduces the Bending of HALF in SHORT PILE

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For LONG PILES, the quantities on the X and Y-axes have Cu at the denominator.

y  = co

LIQUEFACTION RISK REDUCTION WITH SOILTAC

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Treated SAND - PEAK= 3500 KPa

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Wetted SAND after STRENGTHENING - PEAK= 300 KPa

WETTED SAND - PEAK= 300 KPa

RISK MANAGEMENT

IF:

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A reduction to 8,5% that means 91,5% of ACTION INCREASE ACCORDING THE SAFETY FACTOR, of the Horizontal DESIGN FORCE of the Original Design is SUSTAINABLE DURING THE PEAK ACCELERATION OF THE CATASTROPHIC EVENT.

PILE PROTECTION AGAINST SHOCK WAVE INDUCED BY EARTHQUAKE

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REFERENCES

R. Tamagnini (2004), An extended Cam-clay model for unsaturated soils with hydraulic hysteresis, Geotechnique, 54(3), pp 223-228

J.A. Fernandez Merodo, M.Pastor, P.Mira, L.Tonni, M.I.Herreros, E.Gonzalez and R.Tamagnini (2003) Modelling of diffuse failure mechanisms of catastrophic landslides, Computer Methods in Applied Mechanics and Engineering. Special Publication. Ed. R.J. Borja, vol. 193, 2911-2939

J.A. Fernandez Merodo, R.Tamagnini, M.Pastor and P.Mira (2005) Modelling damage with generalized plasticity, Italian Geotechnical Journal, vol. 4, pp 32-42

R. Tamagnini (2011) On the effective stress principle in unsaturated soils, Italian Geotechnical Journal, vol 3, pp 21-27

E. Soranzo, R. Tamagnini and Wu. W. (2016) Face Stability of shallow tunnels in partially saturated soils, Geotechnicque 65(6) pp. 454-467

Website www.soilworks.com

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