Presentation on theme: "Pressuremeters and other In Situ Testing Equipment"— Presentation transcript:
1 Pressuremeters and other In Situ Testing Equipment Presented by : Louis Marcil, Eng.Roctest Webinar April 2012
2 Presentation Overview INTRODUCTION1. Pressuremeters (PMT) 1.1 Description of the Test1.2 Description of the Equipment (Types of Pressuremeters)1.3 Main Applications1.4 Advantages and Limitations2. Other In Situ Test Equipment2.1 Vane Testers2.1 Cone Penetration Test Equipment (CPT)CONCLUSION
3 Rhomboidal ‘bent’ Pyramid, Egypt INTRODUCTIONIN SITU TESTINGProper characterization of mechanical properties of the ground onto which structures are to be built has a great importance.Pyramid Initial SlopeRhomboidal ‘bent’ Pyramid, Egypt
4 INTRODUCTION IN SITU TESTING Means for characterizing the ground: Laboratory TestingIn Situ Testing- Penetration Resistance Measurement (SPT, CPT)- In Situ Permeability Tests (Packer Test, Rising Head Test...)- Strength and compressibility testing (PMT, Vane Testing, Plate load tests, Flat Dilatometer…)
5 1 PressuremetersPMT = An in situ loading test executed by radial expansion of a cylindrical cavity. The stresses are exerted on the walls of a borehole by mean of a pressurized fluid acting on one inflatable membrane.
7 TYPICAL PRESSUREMETER CURVE 1.1 Test DescriptionTYPICAL PRESSUREMETER CURVEProgressive loading in steps. Waiting period required at every step for stabilization before recording pressure and radial expansionUnload-loading cycleTest duration : 10 minStandards: ASTM NF P , EN_ISO_
8 1.1 Test Description General Testing Procedure Tests executed at various depths in the same boreholeCommon spacings : 1 to 3 m.Borehole cannot be done in one passResults are presented for each elevation giving general profile of the soil.
9 1.1 Test Description Pressuremeter modulus (E) Limit pressure (Pl) Main Parameters:Pressuremeter modulus (E).Limit pressure (Pl)Where:- R : Poisson's ratio of the soil/rock- Vm : the volume of the cavity at mid-point of the testing zone: the variation of volume of the cavity due to the variation of the applied pressure
10 1.1 Test DescriptionThe Making of the Borehole = Critical to make successful tests ! ! !Borehole = Adequate if:1. Undisturbed Soil2. Borehole of Proper Diameter3. Smooth wall borehole
11 1.1 Test DescriptionVarious drilling methods suggested in Standards as per type of soils.Use of rotary drilling with axial injection (towards hole bottom) of mud is applicable in most cases. Slotted casing in large-gravels soils.Ideally: Roller bit for silt, sand, and gravel. 2 7/8 in. to 3 inches. Three-wing bit for clayey soils.Diameter of rods must be one or two sizes smaller than diameter of bit to allow good flow up of cuttingsDo not ram the bit up and down as this will result in an oversized holePopular method : 3-in hollow auger for first portion of the borehole + use of rotary bit in the testing zone onlyGo slowly:Injection pressure: < 500 kPa with borehole full of mudBit rotation: < 60 rpm Flow : < 15 liters per minute Bit pressure: < 200 kPa (100 kg in a 76 mm borehole) Typical advance rate: 15 to 25 cm/minute
12 1.2 The Equipment VARIOUS TYPES OF PRESSUREMETERS: Pre-Boring vs Self-Boring PressuremetersVolume Variations vs Direct Radial Strain MeasurementsMono-cellular vs Tri-cellular ProbesDiameter of the Probe : 33 mm to 95 mmType of Loading: Pneumatic vs HydraulicReading Mode: Manually vs AutomaticallyWorking Capacity: 4,000 kPa to 30,000 kPaVarious Sensitivities
14 1.2 The Equipment Rock Pressuremeters: Model PROBEX Capacity pressure: kPa (3500 psi)Hydraulically loadedFiberglass-reinforced polyurethane membraneCapacity modulus: 0.01 to 30 GPa approx.Testing depth to (date): 300 meters
15 1.2 The Equipment Rock Pressuremeter / Borehole Dilatometer: Model DMP Measures radial deformations by mean of 3 LVDT disposed at 120 °Capacity pressure: kPaFor used in soft to moderately hard rock (Maximum modulus of 50 GPa)
16 1.2 The Equipment Self-Boring Pressuremeters: Interesting tool because minimizes remoldingConfined to soils with few gravelsBOREMAC Pressuremeter(volumetric, hydraulic, mono-cellular probe)
17 1.3 Main Applications Shallow foundations Laterally loaded piles Vertically loaded pilesCompaction controlDesign of pavementOf less use for slope stability problems and embankments
18 1.3 Main ApplicationsSemi-empirical methods vs. methods based on the theory of elasticitySemi-empirical method:1) Bearing Capacity = K x PlThe factor of proportionality K is function to:- Relative depth- Shape of the foundation- Type of ground
19 1.3 Main Applications 2) Settlement : - S is the settlement Ref: Canadian Foundation Engineering Manual- S is the settlement- EM is the pressuremeter modulus.- qa is the allowable bearing capacity- λ2 and λ3 are the coefficients of shape of footing, (L/B)- B is the width of the footing- αp is a coefficient of structure (function to type of soils and E/Pl)
20 1.3 Main Applications3) Lateral Deflection of laterally-loaded structuresP-Y Curve:Various MethodsRobertson et al.Example :VGS Reduction of Rock Pressuremeter TestsDesign P-Y Curves54-inch Diameter Rock Socket(Courtesy: Failmezger, In Situ Soil Testing, VA)
21 1.3 Main Applications Design of High Rise Buildings Petronas Towers (Kuala Lumpur, Malaysia)AT&T Tower(Chicago, USA)
22 1.4 Advantages and Limitations Well-trained operator is required for ensuring:Making a good boreholeTaking care not to burst too many membranesSoils with large gravels are difficult to test. A slotted casing might be required.
23 1.4 Advantages and Limitations Versatile: Can be performed in most types of soils and soft rocksGives an in situ stress strain curveThe loading sequence can be adapted according to the application (long or rapid loading, cyclic loading)Close analogy with laterally-loaded pilesValidity of the test can be controlled from the shape of the curve.
24 2. Other In Situ Testing Equipment Various types of in situ tests can be performed:Penetration Test (SPT, CPT), Vane Test, Plate Loading Test, Flat Dilatometer Test, Packer Test, Compaction Control Test, etc.
25 2.1 Vane Shear Tester For cohesive soils only Test Description Quick and EasyUsed either for designing of shallow or deep foundations
26 Recording sheets from the Model M-1000 Vane Tester 2.1 Vane Shear TesterSu = K (as - af) x CWhere:Su = the undrained shear strength in kg/cm2C = vane form constant in 10-2 x cm-3K = calibration constant for the torque recording head in kg m / cmas = distance in cm between the zero torque reference line to the peak of the curveaf = distance in cm between the zero torque reference line and the circular arc scribed during the first 15 degrees of rotation (corresponds to rod friction)Recording sheets from the Model M-1000 Vane Tester
27 2.2 Cone Penetration Test Dynamic Cone Penetration Test: Procedure: Record number of blow counts required for trusting a conical point into the ground. Size and shape of the point, weight, and the mass falling distance are standardized.Used for soil classification and for compaction control.Model PEM-1 ConeDynamic Penetrometer
28 2.2 Cone Penetration Test 2 1 4 3 Static Cone Penetration Test (CPT) : The most common penetration test.Pushed into the ground.Recording of: tip resistance, friction resistance, pore pressure and others.Models:Handsounding Cone Penetrometer (1)Mechanical Cone (2)Mechanical Friction Cone (3)Electric Cones (4)2143
29 2.2 Cone Penetration Test Static Cone Penetration Test (CPT) : Interpretation and use of results:Soil Classifications using cone and friction resistance.Determination of various parameters from empirical correlations: For instance:- Stiffness and relative density in cohesionless soils Undrained Shear Strength in cohesive soils.
30 CONCLUSION Roctest has specialized in pressuremeters PMT not a routine testing methodRequired well-trained operatorSpecial attention must be given for the making of the boreholePMTproves to be a useful tool for applications :1) Such as for the laterally loaded foundations, and high rise buildings2) Where undisturbed samples cannot be obtained, and where other conventional tests cannot be done (rock & weakly cemented material)3) On large projects where it is justified to put efforts to get better information on the soil/rock