JGJ T 93-95桩基低应变动力检测规程.doc

Trade Standard of the Peoples Republic of ChinaSpecification for Low Strain Dynamic Testing of PilesJGJ / T 93 95Beijing 1991Specification for Low Strain Dynamic Testing of PilesJGJ / T 93 - 95Contents1. General42. Terms, Symbols and Codes42.1 Terms42.2 Symbols and Codes53. General Stipulations73.1 Test Method73.2 Quantity of Test73.3 Instrument Apparatus83.4 Preparations before Test83.5 Test Procedures83.6 Test Report84. Reflected Wave Method94.1 Scope94.2 Instrument Apparatus94.3 Field Test94.4 Processing and Judging of Test Data105. Mechanical Impedance Method115.1 Scope115.2 Instrument Apparatus115.3 Field Test145.4 Processing and Judging of Test Data146. Dynamic Parameter Method186.1 Scope186.2 Instrument Apparatus186.3 Field Test196.4 Processing and Judging of Test Data206.5 Frequency Method217. Sound Transmission Method227.1 Scope227.2 Instrument Apparatus227.3 Field Test227.4 Processing and Judging of Test Data24Appendix A Preparations before Mechanical Impedance Method Test27Appendix B Format of Test Report28Appendix C Explanation for Wording in the Specification29Additional Description29Description of Stipulations缺原文1 General1.0.1 To carry out the principle of “Planning for one hundred years, Putting quality first” for construction projects and to secure the quality of low strain dynamic testing of foundation piles, this specification is formulated.1.0.2 This specification applies to the low strain dynamic test of concrete filling piles and pre-cast piles.1.0.3 To calculate the vertical load of single pile by using the mechanical impedance method and the dynamic parameter method in the specification, the reliable comparison data of dynamic and static vertical bearing loads of single pile in the area shall be available.1.0.4 The results of the test made in accordance with this specification shall be put forward by qualified test personnel from the organization of approved qualification.1.0.5 For low strain dynamic testing of foundation piles, apart from this specification, it shall also be in conformity with the stipulations of relevant existing State standards.2. Terms, Symbols and Codes2.1 Terms2.1.1 Mechanical ImpedanceThe mechanical impedance of a system is the ratio of the force to this system and the response of the system.2.1.2 Mechanic AdmittanceIt is the reciprocal of the mechanical impedance.2.1.3 Trace FilterIt is the band-through filter of which the center frequency changes with a variable frequency. In the test of mechanical impedance method, it is used to filter out the vibration interference other than the frequency of activation.2.1.4 Wave Speed (up )It is the transmission speed of elastic wave in the concrete of pile body.2.1.5 Measurement Pile Length (L0)The pile length calculated according to the average wave speed (upm,) of piles in the working section.In which, D is the frequency distance between two adjacent main peaks of the mechanical admittance curve.2.1.6 Theory Value of the Mechanical Admittance (N)The average value of the mechanical admittance calculated with wave speed, density of concrete (r) and pile section (A).2.1.7 Geometry Average Value of the Mechanical Admittance (Nom)The geometry average value calculated with the mechanical admittance curve of actual measurement. In which, P is average peak value and Q average valley value.2.1.8 Maximum Peak Value of Mechanical Admittance (Np)The geometry average value calculated with maximum peak value and its adjacent valley values in the mechanical admittance curve of actual measurement.2.1.9 Fix Coefficient (l)The parameter indicates the fix condition of pile bottom.In which, 0 is the resonance frequency of univalence.2.2 Symbols and Codes2.2.1 axIt is maximum transversal acceleration value in x direction;2.2.2 ayIt is maximum transversal acceleration value in the direction perpendicular to a x ;2.2.3 azIt is maximum vertical acceleration value;2.2.4 AVibration amplitude of sound wave; section area of pile;2.2.5 AdMaximum peak to peak value of first vibration shock wave of “frequency-initialspeed” method;2.2.6 AjIThe value of sound wave vibration amplitude spot testing in j time at i test point;2.2.7 dDiameter of pile; inside diameter of sound wave test tube;2.2.8 d Outside diameter of pillar shape sound wave energy exchanger;2.2.9 DOutside diameter of sound wave test tube;2.2.10 0The natural frequency of pile-earth system in dynamic parameter method;2.2.11 1The resonance frequency of univalence in the mechanical impedance method;2.2.12 DThe difference of frequencies of adjacent resonance peaks in the mechanical admittance curve of good piles2.2.13 Gp The converted weight of pile in vibration;2.2.14 Ge The Converted weight of earth in vibration;2.2.15 h The rebound height of the monkey;2.2.16 HThe falling distance of the monkey;2.2.17 KdMeasurement dynamic rigidity of pile;2.2.18 Kd Anticipated dynamic rigidity of pile;2.2.19 Kd m Actual site measured average dynamic rigidity of pile;2.2.20 Kt z Inclination slope of adjacent test points in sound time-deepness curve;2.2.21 I The distance between outside walls of two test tubes;2.2.22 L Overall pile length;2.2.23 L The deepness of the defect of the pile;2.2.24 Lo The measurement length of the pile;2.2.25 Le The length in the earth of the pile part;2.2.26 m The converted mass of pile and earth in vibration;2.2.27 N The theory value of the mechanical admittance;2.2.28 No The actual measurement value of the mechanical admittance;2.2.29 No m The actual measurement geometric average value of the mechanical admittance;2.2.30 Np The value of maximum peak amplitude of the mechanical admittance;2.2.31 q The attenuation quantity of sound wave amplitude;2.2.32 mq The average attenuation quantity of sound wave amplitude;2.2.33 qD The critical value of attenuation quantity judged with sound wave amplitude;2.2.34 re Radium of diffusion of the earth in vibration;2.2.35 R Calculated value of vertical load of single pile;2.2.36 SAllowable settlement value of the pile;2.2.37 Sa The sensibility of acceleration sensor;2.2.38 Sn The sensibility of speed sensor;2.2.39 t The interval of time between the first impact and the second impact after rebound in dynamic parameter method; the original value of sound time in the testing of sound transmission method;2.2.40 t Modifying value of sound time;2.2.41 Dt The difference of sound time between adjacent test points in sound time-deepness curve;2.2.42 t0 The delay time of sound wave testing instrument from emitting to receiving system;2.2.43 tc The transmission time of sound wave in concrete;2.2.44 mt The average value of sound time;2.2.45 tj i The sound time value spot testing in j time at i testing point;2.2.46 tr The arrival time of the reflected wave from pile bottom;2.2.47 tr The arrival time of reflected wave from the defect part of the pile;2.2.48 u0 The initial speed of pile head vibration;2.2.49 up The speed of longitudinal wave in pile concrete;2.2.50 upm The average value of speed of longitudinal wave in pile concrete in the working section;2.2.51 ut The sound speed in the thickness direction of testing tube wall;2.2.52 uw The sound speed in water;2.2.53 W0 Mass of the monkey;2.2.54 aThe coefficient of sensibility of speed sensor in the testing system corresponding to 0;2.2.55 bf The adjusting coefficient used in “frequency method”;2.2.56 bn The adjusting coefficient used in “frequency-initial speed method”;2.2.57 gp The weightiness of the pile;2.2.58 ge The weightiness of the lower part of the pile Le/3 and the earth within the range;2.2.59 eThe coefficient of bumping;2.2.60 zThe coefficient of transversal vibration of activator;2.2.61 hThe comparison coefficient for testing dynamic and static rigidity of pile bearing load;2.2.62 K Safety coefficient;2.2.63 lFix coefficient;2.2.64 st The standard difference of sound time;2.2.65 sItThe relative standard difference of sound time;2.2.66 sIA The relative standard difference of wave amplitude;2.2.67 jThe inner friction angle of lower part of the pile Le/3 and the earth within the range.3. General Stipulations3.1 Test Method3.1.1 The test methods specified in this specification are reflected wave method, mechanical impedance method, dynamic parameter method and sound transmission method.3.1.2 Applicable scope and technical requirements are set for each of above said methods and they shall be selected to use according to different testing objects and specific testing requirements. One or more methods can be selected to test and check. For multi-section connected long pre-cast piles, more than one method should be used so as to make a comprehensive analysis and judgement.3.2 Quantity of Test3.2.1 For constructions and structures of one-column-one-pile, test shall be made to all foundation piles.3.2.2 For those of non one-column-one-pile, spot test shall be made as per construction shift. The quantity of spot test shall be determined by the relevant departments in the light of the importance of the project, the class of anti-seism, geographic conditions, the process of pile making and the purpose of the test. When testing the integrity of concrete filling piles, the number of spot test shall not be less than 20% of the total number of that batch of piles and also not less than 10 pieces. When testing the bearing load of concrete filling piles, the number of spot test shall not be less than 10% of the total number of that batch of piles and also not less than 5 pieces. For concrete pre-cast piles, the number of spot test shall not be less than 10% of the total number of that batch of piles, and not less than 5 pieces.In case the number of unqualified piles is over 30% of the quantity spot tested, spot retest shall be made by double the quantity. After retest, if unqualified ones still exceed 30% of spot tested ones, test shall be made to all piles. For sound transmission method, the double the quantity retest can be made by using other testing methods.3.3 Instrument Apparatus3.3.1 The performance of the instruments and equipment shall meet the requirements of specific testing method.3.3.2 The test instrument shall be dust and moisture proof and can be normally operated at ambient temperature of 10 50 . When computer is used on site, measures shall be taken to maintain or lower the temperature.3.3.3 Tough measures shall be taken to protect sensors from water or moisture. When handling, anti-shock protection shall be provided3.3.4 When the instrument is not in using for a long time, they shall be energized periodically as per the instructions. For long distance transportation, they shall be packed in anti-shock boxes.3.3.5 Overall check and test shall be made to instruments and equipment once a year and their technical criteria shall meet quality standards of the instruments.3.4 Preparations before Test3.4.1 Before testing, following documents shall be available: engineering geological data, foundation design drawings, original construction records (records of piling, hole-drilling and concrete filling, etc.) and layout of piles.3.4.2 Before testing, following preparations shall be made: site investigation, pre-test treatment of single pile to be tested, checking of performance of test instrument and equipment, determination of contents and requirements of the test in the light of the features of the construction project, the type of foundation piles and the geological environment located. Through site testing, test method and technical parameters of the instrument shall be finalized.3.4.3 For concrete filling piles to be tested, the test shall not be made until the specified curing age is reached. For driven piles, the test shall not be made until the stop period specified by the specification for foundation soil is reached.3.5 Test Procedures3.5.1 The test procedures shall be done according to the specification of definite method.3.6 Test Report3.6.1 The test report shall be simple, clear and practical. It shall contain foreword, engineering geology, pile design and summary of construction, brief introduction to the principles and test methods, the instruments and equipment employed in the test and test analysis results (including layout of piles to be tested, schedule of analysis of results and original records of test), conclusion and suggestions.3.6.2 The cover and the inside cover of the test report shall be printed as the format specified in Appendix B of this specification.4. Reflected Wave Method4.1 Scope4.1.1 This method applies to test the integrity of the pile body, to judge the type of defects and their locations in the pile body. This method is also used to check pile length and to evaluate the class of strength of pile concrete.4.2 Instrument Apparatus4.2.1 The instruments should consist of sensors, amplifying, filtration, recording, processing and monitoring systems, and the activation equipment and special attachments.4.2.2 Sensors shall be wide band speed type or acceleration type. For speed type sensors, the sensibility shall be greater than 300 mV/cm/s while for acceleration type, greater than 100 mV/g.4.2.3 The gain of amplifying system shall be greater than 60 dB and the long-term variation shall be less than 1%. The converted noise level at input side shall be less than 3V. The width of band shall not be narrower than 10 1000 Hz. The wave filtration frequency shall be adjustable.4.2.4 The number of simulation / digital converter shall not be less than 8 bits. The sampling time should be 50 100 s and adjustable at several stages. The capacity of the cache for data sampling of each channel shall not be less than 1kB.Note: Bit is the number of calculating digital in binary system.4.2.5 Multi-channel sampling system shall have consistency and its deviation of vibration amplitude shall be less than 3% and phase deviation, less than 0.1ms.4.2.6 The different purposes of tests shall be met in accordance with activation conditions, test requirements and by changing activation frequency and energy. The activation equipment of suitable material and weight shall be selected.4.3 Field Test4.3.1 For piles to be tested, surface skim shall be removed, pile head shall be flat and main steel reinforcement extruded out from the pile head shall be cut.4.3.2 Before testing, instruments and equipment shall be checked and they must not be used unless their performances are normal.4.3.3 Trial test shall be made on each working section to select activation type and receiving conditions so as to optimize them.4.3.4 The activation point should be selected at the center of the pile head and the sensor shall be firmly fixed to the pile head. For piles of diameter over 350mm, two or more sensors shall be installed.4.3.5 In case there is much interference at random, signal shall be reinforced and repeated activation and receiving shall be made.4.3.6 To increase the resolution of the test, small energy activation shall be used. And sensors and amplifiers of high interception frequency shall be used.4.3.7 For determining shadow defect of the pile, transversal activation and horizontal speed type sensor receiving shall be used simultaneously to assist your judgement.4.3.8 Two or more re-tests shall be made to each single pile tested. In case abnormal wave curve appears, investigations shall be made timely on site. After diminishing factors affecting the test, retest shall be made. The wave curve of the retest shall be similar with the original one.4.4 Processing and Judging of Test Data4.4.1 The integrity of the pile shall be determined according to the wave shape, phase, amplitude, frequency and the arrival time of the on-coming waves and reflected waves in wave diagrams.4.4.2 The wave speed up in concrete pile body and the deepness of defect in pile body L shall be calculated respectively according to following formula: In which, L overall pile length; tr The arrival time of the reflected wave from pile bottom; tr The arrival time of the reflected wave from the defect part of the pile; upm The average value of the speed of longitudinal wave in several test qualified pile bodies in one working section.4.4.3 When the shape of the reflected wave is regular and its display is clear, the reflected wave from pile bottom is obvious and easy to read its arrival time and the average wave speed in pile concrete is high, the integrity of the single pile is good.4.4.4 When the arriva