IN-SITU TESTING IN-SITU TESTS. Standart Penetration Test (SPT): In-situ Tests. Assist. Prof. Berrak TEYMUR

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1 IN-SITU TESTING IN-SITU TESTS Ait. Prof. Berrak TEYMUR Provide: alternative deign data in-itu propertie where unditurbed ampling i not poible Large volume of material Method: Standard Penetration Tet (SPT) Cone Penetration Tet (CPT) Preuremeter tet Dilatometer tet Other method (vane hear, permeability etc.) In-itu Tet 1- Standart Penetration Tet (SPT): 63.5kg hammer weight (Donut, afety,automatic trip hammer), 0.76m height, Totaly 45cm penetration through oil. Firt 15cm ignore, Blow # veru lat30cm. Ued primarily in granular oil Tet procedure may be found in ASTM D-1586, BS1377. Standart Penetration Tet (SPT): Advantage Varying diameter, Low cot, Widely ued, Experience. Limitation International tandart of variability of procedure Method of drilling and upporting the hole Hammer mechanim and rod ize ued The plit-poon geometry (minor effect) Method of teting Correction - overburden preure and PWP buildup Correction factor of blow number for fine and, ilty and, ilty oil under GWT ( N 15) N' =

2 SPT Empirical value for Dr and q u of granular and fine oil baed on SPT blow number Beide obtaining oil ample, SPT provide correlation; relative denity and friction angle N Clay Conitency Very oft Soft q u (kpa) < undrained hear trength direct etimate of ettlement Medium Stiff Very tiff >30 Hard >400 Sand & Silt CONE PENETRATION TEST State Very Looe Looe Medium Dene Dene N * (blow/ 300mm) < Friction angle, deg < Relative Denity (%) < The end reitance of the cone at any depth called the cone penetration reitance i (q c ) meaured. q c i the force required to advance the cone divided by the end area. Unlike the SPT, oil ample cannot be recovered during the CPT. Intrumented probe jacked into ground at contant rate of penetration (2cm/ec) Cone reitance (q c ) and leeve friction (q ) meaured cone reitance (q c ) correlate with trength, and friction ratio (q /q c) with material type Should alway be correlated with borehole information Very dene >50 > ASTM D-3441, BS 1377 (Part 9) 2

3 CONE PENETRATION TEST Applicable Soft clay Fine to medium coure and Not Applicable Very tiff clay Hard clay Gravel 60 cone, 10cm 2 bae area, 150cm 2 friction leeve, 10-50mm long ample collection. Advantage CONE PENETRATION TEST Limitation Repeatable and reliable No ample, data, Correlation with CPT are le, Fater and cheaper, Le experience, Continuou data profile. Drainage condition i unknown. CONE PENETRATION TEST Type of cone: Mechanical cone (Dutch cone - reading every 200 mm)- The tip i connected to an inner et of rod and it i firt advanced about 40mm giving the cone reitance. With further thruting, the tip engage the friction leeve. Electrical cone (contant reading)-the tip i attached to a tring of teel rod. It i puhed into the ground at the rate of 20mm/. Wire from the tranducer are threaded through the centre of the rod and continuouly give the cone and ide reitance. Electrical piezocone Seimic cone Friction Ratio : F R < 1% :and, F R > 5% :clay F R = q q c CONE PENETRATION TEST.100 Ued for deign of pile and to etimate the bearing capacity and ettlement of foundation. 3

4 Parameter Determination(Sand) Baed on Meyerhof (1965) Parameter Determination(Clay) q c, MPa < State Very Looe Looe Med dene Dr (%) < Friction angle, deg < Approximate relationhip c u = (q c p)/n k q c = cone reitance p = total over-burden preure Dene N k = for NC clay >20 Very dene = for OC Clay CONE PENETRATION TEST Data collected during electrical CPT q C q S F R u (Mpa) (kpa) (%) (kpa) PC: q C can be correlated to : φ,d r,c U, N 4

5 CPT-Related Webite The Liquefaction Site (and CPT ite): Link page to manufacturer, upplier, and CPT ervice: Liting of available video on CPT and other in-itu tet: The book Cone Penetration Teting in Geotechnical Practice (Lunne, Roberton, & Powell, 1997) THE PRESSUREMETER TEST The Preuremeter tet i an in-itu tet developed by Menard in Applicable for : oft clay, fine to medium and. The preuremeter i a cylindrical device deigned to apply a uniform radial preure to the ide of a borehole in which it i placed. There are two different baic type: The Menard preuremeter which i lowered into a preformed borehole The Self-boring preuremeter which form it own borehole and thu caue much le diturbance to the oil prior to teting THE PRESSUREMETER TEST In both cae, the preuremeter tet involve the application of known tree to the oil and the meaurement of the reulting oil deformation. The ide of the borehole are loaded by preuriing a fluid contained within a flexible rubber membrane. THE PRESSUREMETER TEST (MPT) The device conit of three part (top, cell and bottom) a hown below: The expanion of the cavity i determined either by meauring the volume of fluid needed to preurie the membrane and/or by meauring the movement of the oil at the cavity wall uing lvdt (diplacement tranducer). Generally, preuremeter are deigned for maximum inflation preure in the range MPa in oil and MPa in very tiff oil and weak rock. E and K 0 can be determined. Bowle,

6 Meauring Cell Volume (V) V 0 THE PRESSUREMETER TEST Zone 1 Reloading Zone 2 Peudo Elatic zone Zone 3 V Platic Zone P Zone 1: Soil puhed back to initial tate Zone 2: Peudo elatic, V v P i linear Zone3: Platic Zone THE PRESSUREMETER TEST Alo, the relationhip between E and G i given by E = 2 (1 + µ ). G Vo p G = V P o Meauring Cell Preure (p) For Zone 2 : 2 (1+ µ ) Vo p where E : Young Modulu E = of oil µ : Poion ratio V V o : Volume correponding to beginning of zone 2 at p o p/ V = 1 / (lope of line in zone 2) Preuremeter tet reult can alo be ued to determine the at ret earth preure coefficient ; Ko = P o σ ' Note:In France, hallow and deep foundation deign i all baed on preuremeter tet. FIELD VANE TEST The vane hear tet may be ued during the drilling operation to determine the in-itu undrained hear trength (c u ) of clay oil, particularly oft clay. The vane hear apparatu conit of four blade on the end of a rod. The height, H of the vane i twice the diameter, D. The dimenion of vane are; D=38.1mm, H=76.2mm, 1.6mm thick blade and 12.7mm diameter of rod. Thi tet i performed every 0.75 to 1 m of depth. FIELD VANE TEST The vane of the apparatu are puhed into the oil at the bottom of a borehole without diturbing the oil appreciably. Torque i applied at the top of the rod to rotate the vane at a tandard rate of 0.1º/ec. Thi rotation will induce failure in a oil of cylindrical hape urrounding the vane. The maximum torque, T applied to caue failure i meaured. 6

7 H FIELD VANE TEST where 2 3 D H ad T = cuπ H = 2 D 2/3 : uniform end hear a = 3/5 : parabolic end hear 1/2 : triangular end hear FIELD VANE TEST When ; H/D= 2 & a=2/3 T c u = D ( c ) = λ ( c ) 1,2 u deign u field T : Nm f(c u,h,d) D are rapid, economical and extenively ued give good reult in oft and medium-tiff clay error can occur due to poor calibration of torque meaurement and damaged vane correlation with preconolidation preure and OCR exit λ 1,0 0,8 0,6 0,4 0 PI % 120 FIELD TESTS-Plate Loading Tet I carried out to etimate the bearing capacity and ettlement beneath the ingle footing. A loading plate i circular or quare in hape and i manufactured from machined teel plate with a min. thickne of 25mm. The diamater of circular plate range from mm. The load i either of gravity type applied through a platform or reaction type applied by a hydraulic jack. The plate loading tet procedure may be found in ASTM D-1194, ASTM D-1195 and ASTM D

8 PLATE LOAD TEST Mot reliable way to obtain the ultimate bearing capacity at a ite i to perform a load tet. PLATE LOAD TEST Procedure 1) Pile hould be driven firt, to avoid exce vibration & looening of oil in excavation area. 2) Excavate a hole a certain depth that the tet i to be performed. Tet hole depth > 4B 3) A load i placed on the plate (uually teel) and ettlement are recorded from a gauge. Load increment 1/5 bearing capacity of oil or 1/10 etimated failure load. Time of loading 1 hr & hould be ame duration for all increment. Bowle, ) Tet hould continue until ettlement = 25 mm or, until capacity of teting apparatu i reached. PLATE LOAD TEST PLATE LOAD TEST Settlement (cm) If H = 2.5cm failure 50 q ult = 50 t/m 2 Load (t/m 2 ) δ lim Settlement Load Hard/dene oil Looe/oft oil δ lim 1/2 load correponding to 10 mm ettlement Note: Plate load tet reult do not include effect of CONSOLIDATION Load q Coefficient of Subgrade Reaction, k : (ue ecant) : k = q / [unit: kg/cm 3,kN/m 3 ] Settlement Ued to obtain E: when modelling oil a elatic pring (Winkler) 4 d y EI 4 dx = kby 8

9 Coring of Rock When a rock layer i encountered during a drilling operation, rock coring may be neceary. For coring of rock, a core barrel i attached to a drilling rod. A coring bit i attached to the bottom of the core barrel. The coring i advanced by rotary drilling. Water i circulated through the drilling rod during coring and the cutting i wahed out. To evaluate the rock quality encountered, Rock Quality Deignation (RQD) i ued. RQD= ΣLength of recovered piece equal to or larger tha n 101.6mm Theoretica l length of rock cored very poor and i excellent rock quality. Geophyical Teting Advantage relatively cheap compared to borehole and in-itu teting option non-detructive (no hole/excavation are required) Diadvantage reult are often inconcluive or unreliable not yet fully accepted by the indutry. GEOPHYSICAL METHODS Ueful in ground invetigation in reconnaiance tage Supplementary method (not uitable for all oil) Capable of etimating depth to bedrock etimating depth to water table filling in detail between borehole GEOPHYSICAL METHODS 1) Seimic Refraction Method: Seimic wave have different velocitie in different type of oil. Two type of tre wave: P Wave : plane wave 200 m/ in and to 2500 m/ in clay S Wave : hear wave Le cot than other in-itu tet Definitive interpretation of the reult i difficult, o hould be ued for preliminary work 9

10 GEOPHYSICAL METHODS Seimic refraction urvey are ueful in obtaining preliminary information about the thickne of the layering of variou oil and the depth to rock or hard oil at a ite. They are conducted by impacting the urface at a point and oberving the firt arrival of the diturbance (tre wave) at other point. The impact can be created by a hammer blow or by a mall exploive charge. The firt arrival of diturbance wave at variou point can be recorded by geophone. V V rock L T GEOPHYSICAL METHODS P-S wave velocitie: o oil = E ( 1 µ ) o υp = υ = = ( L3 L1 ) ( T T ) 3 G γ g 1 γ g ( 1 2µ )( 1+ µ ) Firt arrival time to detector are determined : υ p 2 2µ = υ 1 2µ For a typical Poion ratio 0.3, the ratio; υ υ p = 1.87 GEOPHYSICAL METHODS GEOPHYSICAL METHODS 2) Electrical Reitivity Method: Difference in electrical reitance of different oil type. Method * Place 4 electrode with equal pacing A. * Apply a direct current to outer electrode I. * Meaure potential drop in inner electrode. The reitivity of oil i determined by: V:Voltage drop Craig, 1992 ρ = 2πLV I The reitivity urvey i particularly ueful in locating gravel depoit within a finegrained oil. 10

11 GEOPHYSICAL METHODS 3) Cro Hole Seimic Survey: Two hole are drilled a ditance, L, apart. A vertical impule i created at the bottom of one of the borehole by an impule. The hear wave generated are recorded by a tranducer at the other borehole. Method Shear wave velocity: Shear modulu : V = L t G = V 2 γ g SOIL EXPLORATION REPORT Scope Decription of tructure Decription of location of ite Geological etting Detailed field exploration Subgrade condition Water table condition Foundation recommendation Concluion and limitation Summary Goal: etimate geometry of oil trata and ground water and etimate pertinent engineering propertie Field Invetigation identify material and layering, retrieve ample and engineering propertie through in-itu teting Laboratory Teting determine engineering propertie from ample 11