Static force touching equipment, commonly known as static force touching instrument, generally consists of three parts, namely: ① static force touching probe: ground resistance sensor; ② measurement and recording instrument: measurement and recording of all kinds of resistance to the probe; ③ penetration system: including touching the main body and the counterforce device, *** with the responsible for the probe pressed into the soil. Touching the host with the help of the probe rod will be mounted on the bottom end of the probe into the soil; counterforce device is to provide the host in the process of penetrating the probe of the required counterforce. At present, the widely used static touching car set the above three parts as a whole. Static force touching car with penetration depth (penetration force is generally greater than 10t), high efficiency and low labor intensity advantages. But it is only suitable for convenient transportation, flat terrain and can drive into the car survey site use. Penetration force equal to 5t or less than 5t, generally light static force touch instrument. When using, generally will be the above three parts of the separate shipment to the survey site, the test and then the three parts of the organic connection. In inconvenient transportation, survey depth is not big or soft soil layer area, light static force touching is widely used. It has the advantages of easy transportation, low test cost and flexibility. The penetration force of the static force touching instrument is generally 2t-20t, the maximum penetration force is 20t, because the limit of the force of the slender probe rod can not be too large, too large easy to bend or break. Penetration force of 2t-3t, generally for the hand-cranked chain type electric cross plate - touch probe dual-purpose instrument. Penetration force greater than 5t, generally hydraulic host. Now introduces several major and commonly used touch probe instrument.
(A) commonly used static touch instrument
1.CLD-type static touch - cross plate shear dual-use instrument
Built by the Sichuan Provincial Institute of Building Research and the East China Electric Power Design Institute, currently developed by the Shanghai Xinwei Machine Factory, Zhejiang Nangang Geological Instrument Factory and Jiangsu Rugao Engineering Surveying Machinery Factory and other production (see Chapter 6) Figure 6-3).
CLD-1 type, the maximum penetration force of 2t, total weight (including tools) 0.2t, with the probe area of 10cm2, with the cross plate size of 50mm × 100mm × 2mm, the host weighs 50kg, the maximum external dimensions of 100cm × 30cm × 145cm. this machine is lightweight, multi-purpose machine, especially suitable for soft soil areas.
CLD-3 type, the maximum penetration force is 3t, the host weighs 65kg, can be hand-cranked on both sides, the host frame is stronger than CLD-1 type, other specifications with CLD-1 type. The penetration force of this machine is larger and lighter than that of CLD-1 type, and the penetration depth is also increased accordingly.
2.bracketed static probe
Designed by the third design institute of the scientific research institute of the ministry of railways, produced by zhejiang ningbo survey machinery factory (now zhenhai telecommunication factory survey machinery sub-factory), the model for the DY-5 type. The machine has a small and lightweight, compact structure and other characteristics, is a lightweight static probe. Its main technical parameters are as follows: rated penetration force of 5t, rated pull-up force of 7.6t, penetration rate of 0.5-1.6m/min, pull-up rate of 3m/min, the cylinder stroke of 0.5m.
Research and development by the China State Shipbuilding Industry Corporation Survey Research Institute, produced by Hangzhou Fuyang Scientific Instrumentation Factory, the MJ-2 trailer-mounted static touchdown machine, with a lightweight and compact structure. Static force touching machine, has the advantages of lightweight and flexible, small area, stable performance, etc., is a medium penetration capacity of the equipment. Its main performance and technical specifications are as follows: total penetration force of 10t, penetration speed of 1m/min, pulling speed of 2m/min, the maximum stroke of 1.2m, the machine weighs 430kg, dimensions of 385cm × 135cm × 230cm, power 3.5/4.5kW, power supply voltage of 380V, with ground anchors 4-8. .
3. Static touchdown car
Currently, China's production of static touchdown car manufacturers, mainly Ningbo, Zhejiang Province, Ningbo Surveying Machinery Factory, Jiangsu Province, Rugao Surveying Machinery Factory, Dalian Tensile Machinery Factory, Shenyang Prospecting Machinery Factory and Shanghai Geological Instrumentation Factory, etc.. The touchdown car produced by the factory penetration capacity has reached 20t, are closed car box, can not be affected by climatic conditions in the field operation.
The product specifications of Zhejiang Ningbo Survey Machinery Factory are listed in Table 2-2.
(B) probe
1. probe types and specifications
Probe is the key component of the static touch probe. It includes friction cylinder and cone head two parts, there are strict specifications and quality requirements. At present, the probe used at home and abroad can be divided into three types (see Figure 2-22).
(1) single-use (bridge) probe: a probe type unique to China. It is the cone head and outer sleeve connected together, and thus can only measure a parameter. This deep head structure is simple, low cost, durable, is the most used in our country a probe. It has played a positive role in promoting the development and application of static touch testing technology in China, and has accumulated considerable experience since its application began in the early 1960s, and has established numerous empirical relational formulas regarding the relationship between test results and engineering properties of the soil. Due to the low cost of testing, it has been widely adopted by survey units. However, it should be noted that this probe has fewer functions and its specifications are not harmonized with international standards, which does not facilitate international exchanges and limits its application.
(2) dual-use (bridge) probe: it is a cone head and friction cylinder separately, can be measured at the same time cone head resistance and sidewall friction two parameters of the probe. It is commonly used at home and abroad and has a wide range of uses.
Table 2-2 Ningbo Survey Machinery Factory touch probe
(3) multi-purpose (pore pressure) probe: it is generally in the dual-purpose probe on the basis of installing a probe can be measured when touching the super pore water pressure device produced by the probe. the late 70's, foreign countries began to apply. Domestic has introduced a variety of, such as China University of Geosciences introduced Fugro pore pressure static probe. Domestic has been successfully developed, such as Shanghai Tongji University developed pore pressure probe, has been produced by Zhejiang Wenling Nanguang Geological Instrument Factory. There is also a hole pressure probe developed by the Academy of Scientific Research of the Ministry of Railway. Pore pressure probe can measure at least three parameters, namely, cone tip resistance, sidewall friction and pore water pressure, multi-functional, wide range of uses, in foreign countries has been widely used. In our country, it will also get more and more applications.
In addition, there are multi-functional probes that can measure wave velocity, pore slope, temperature and density, etc., and will not be introduced one by one. Commonly used probe specifications are shown in Table 2-3.
The more functions of the probe, the more test results, the wider the use; but the corresponding cost of testing and maintenance costs are also higher. Therefore, according to the purpose of the test and conditions, the selection of the appropriate probe. The different bottom areas of the probes listed in Table 2-3 are mainly to adapt to different soil strengths. The larger the bottom area of the probe, the higher the compressive strength it can withstand; another reason is that there can be more space to install additional sensors. However, in the general soil layer, the probe with international standards should be preferred, that is, the probe top angle of 60 °, the bottom area of 10 cm2, the side wall friction cylinder surface area of 150 cm2, in order to carry out technical exchanges, easy to apply and brainstorming.
Figure 2-22 Types of static touch probes
a. Single-use probe; b. Dual-use probe; c. Multiple-use probe
1-Cone head; 2-Top column; 3-Resistance strain gauge; 4 -sensor; 5-outer sleeve; 6-probe tube for single-use probe or sidewall sensor for dual-use probe; 7-probe rod joint for single-use probe or friction tube for dual-use probe; 8-probe rod joint; L -Single probe effective side wall length; D - cone head diameter; a - cone angle
Table 2-3 common probe specifications
2. Problems related to the probe design
The problem can be briefly explained in a few points: ① probe hollow column and its top column should be in good contact. Probe hollow column and its top column should have good contact, using the top ball contact is best, so that the sensor force is uniform, but also easy to process. ② processing hollow column (elastic element) of steel should have high strength, good elasticity, stable performance, small coefficient of thermal expansion and corrosion resistance and other characteristics. Domestic general selection of 60Si2Mn (spring steel) and 40CrMn steel hollow column. Other parts can be used 40Cr or 45 steel, need to make good heat treatment. (3) by the formula (2-41) can be seen, the size of the hollow column strain and formation resistance and hollow column ring cross-sectional area. In the case of the same ground resistance, the greater the strain (that is, the more sensitive), it can withstand the maximum load will be the smaller. To take both into account, as mentioned earlier, a good choice of steel can be made. But this is not enough, in order to adapt to different areas, different soft and hard soil penetration needs, manufacturers are generally producing several different rated load (when the hollow column material must be, it is equivalent to different cross-sectional area) of the probe selection. Generally in the soft soil area can choose the rated load of some smaller sensitive probe; on the contrary, the choice of the rated load of some of the larger probe. The Ministry of Railway "static force touching technical rules (TBJ37-93)" stipulates that: probe specifications, processing tolerances and update standards should be in line with Table 2-4, Table 2-5 and Figure 2-23, Figure 2-24 requirements. The insulation performance of the probe shall be in accordance with the following provisions: the insulation resistance of the probe shall be more than 500MΩ when it is shipped from the factory, and the insulation resistance shall not be less than 500MΩ after 2h of constant pressure under 500kPa of water pressure, and the insulation resistance of the probe used for on-site testing shall not be less than 20MΩ. 6) For all kinds of probes, the length of any part of the probe that is not connected with the probe shall be less than 1,000mm within a length of 1,000mm, counting from the bottom of the cone. 1000mm length range from the bottom of the cone, the diameter of any rod connected to it shall not be greater than the diameter of the probe; in order to reduce the frictional resistance of the probe rod and soil friction resistance needs to be added to reduce the friction resistor, can only be set up in the position above the specified range. (7) probe storage should be equipped with moisture-proof, shockproof special probe box (box), and stored in dry, cool premises.
Table 2-4 single-bridge probe specifications
Table 2-5 double-bridge probe and hole pressure probe specifications
Continued
Note: ① a = FA / A, FA = 1/4 πd2, a value of the hole pressure probe is not restricted.
②e1, e2 for the spacing in the working state.
Figure 2-23 single-bridge probe shape
Figure 2-24 double-bridge probe (top) and hole pressure probe (bottom) shape
(C) measurement and recording instrumentation
China's static touch probes are almost all used in the electrical resistance strain sensor. Therefore, with its supporting recording instruments are mainly the following four types: ① resistance strain gauge; ② automatic recording plotter; ③ digital force gauge; ④ data acquisition instrument (microcomputer).
1. Resistance Strain Gauge
From the 60's until the mid-70's, resistance strain gauges have been used. Resistance strain gauge has the advantages of high sensitivity, large measuring range, high precision and good stability. However, its operation is by manually adjusting the balance, tracking readings, easy to cause errors; and can not be read continuously, can only be carried out at intervals (generally 5-10s, i.e., 10-20cm per penetration), and can not get a continuous change of the touch probe curve. After improvement, the emergence of a digital force gauge, such as Shanghai Xinwei machine factory production of digital force gauge and the new up to the telecommunication factory production of JC-X2 static touch probe measuring instrument. Digital force measuring instrument and the past use of strain gauge comparison, its advantages are: small size, light weight, without manual tracking, with digital display is not easy to see the wrong, but also can rate coefficients entered into the instrument directly read resistance value. Designed by the Wuhan Municipal Survey Institute, Wuhan radio factory production of digital force gauge that has the above features. The main disadvantage of the above two instruments is the need for manual recording.
2. Automatic recorder
In order to realize the automatic recording, so there is an automatic recorder. China's current production of static touch automatic recorder are modified with electronic potential difference meter. These electronic potential difference meter are only one range range. In order to be able to measure the rated resistance value of the probe in the resistance layer, but also in order to ensure the accuracy of the measurement in the soft layer, generally use the method of changing the supply bridge voltage to realize. Early instruments for optional fixed bridge voltage method, generally divided into 4-5 gears, the bridge voltage were 2, 4, 6, 8, 10V, can be selected according to the degree of softness and hardness of the stratum. The advantage of this method is that the voltage is stable and reliable; however, the workload of data organization is large. Now there are automatic recorders that can make the bridge voltage continuously adjustable. Figure 2-25 is ZSJ-2 type double pen automatic recorder working principle diagram.
(1) automatic recorder working principle: shown in Figure 2-25, the measured DC signal sent by the sensor, the measurement circuit and the instrumentation within the compensation voltage is compared to produce an unbalanced voltage, amplified by the amplifier 105-6 times to obtain a sufficiently large power to drive the reversible motor rotation. Reversible motor through a set of mechanical transmission device, one side of the measurement circuit to drive the rolling contacts of the sliding wire resistance, so that the compensation voltage and the measured signal balance; one side of the pointer and the recording pen along the graduated scale left and right to move. At this time there is no signal input and output in the amplifier, the motor stops rotating, and the indicated value of the pointer on the index scale is the voltage value of the measured signal. If the measured signal changes, the newly generated potential difference value signal is sent to the amplifier again, so that the rolling contacts of the slide wire resistor and move to a new balance point, the measured signal and the compensation voltage and reach a new balance, the pointer moves to a new position .......
At the same time, the self-leveling machine through a set of transmission mechanism, at a certain speed to roll the recording paper. In this way, as the pointer moves and the recording paper is rolled, the recording pen will continuously record the size of the measured signal at each depth on the recording paper - the static touchdown curve.
(2) the main components of the instrument: in addition to the paper-walking mechanism, the dual-pen recorder parts are composed of two sets.
Figure 2-25 ZSJ-2 type double pen automatic recorder working principle diagram
①measurement circuit: and strain gauge, also uses a double bridge circuit, the difference is that the automatic recorder is used in the DC internal bridge, transmitting DC signals. In order to provide a stable DC voltage to the external bridge, the automatic recorder is specially equipped with a bridge voltage regulator. The stabilized voltage range is generally 0-20V, continuously adjustable to adapt to the calibration probe and penetration into different soft and hard ground layers.
②Transistor amplifier: in the recorder, the amplifier's role is to measure the circuit to send the DC signal △ U amplified into a sufficient to drive the reversible motor rotation of the AC signal, and when the DC signal △ U change in polarity, the phase of the output AC signal also changed, so that can drive the reversible motor positive and negative rotation, so that the measurement system to achieve automatic balance.
3 reversible motor: its role has been described above.
④ Instrumentation of the paper mechanism: static touch automatic recorder in addition to the measured signal display, but also must be the signal with the depth of the change in the situation recorded on the paper tape, in order to accurately and timely record the resistance value of each position of the stratum. For this reason, the recorder replaces the synchronous motor in the original potentiometer paper walking system with a pair of self-aligning angle machines. The sending angle machine and the friction wheel are connected together through a gear set and mounted on the chassis of the touch probe host, so that the friction wheel is close to the touch probe rod. When the touch probe rod is pressed down, the friction wheel rotates with it, driving the rotor of the transmitter to rotate. The receiver is fixed in the instrument, and the paper walking mechanism of the gear set connected, when the transmitter rotates it also follow the rotation, driving the recording paper according to the 1:100 (or other) ratio of movement, so that the depth of the touchdown recorded.
(3) Advantages and disadvantages: automatic recorder compared with the strain gauge, the sensitivity is not as good as the strain gauge, its range is small. However, the automatic recorder has a depth control device, which can continuously and automatically record the penetration resistance curve of the soil layer, improving the efficiency and quality of field work, and thus it is most widely used at present.
3. Digital force gauge
Digital force gauge is a kind of precision test instrument. This instrument can display a number of digits, with a small size, light weight, high precision, stable and reliable, easy to use, can be read directly into the total resistance and the calculation of penetration index is simple, etc., is a lightweight chain cross plate - static touching of the dual-use machine supporting the measurement of the instrument, the domestic has been a number of production. The disadvantage of this instrument is interval reading, manual record.
4. Microcomputer applications in the static probe
The above introduction of the measurement and recording instrumentation are not perfect, some can only be manually spaced readings, can not draw; some can only draw, can not display print data. These instruments can still meet the needs of general production, but the information is organized in a large workload, low efficiency. Microcomputer acquisition and processing of data has been widely used in static touch testing. Such as Shanghai Geological Instrument Factory and Changchun Institute of Geology *** with the successful development of the GCJW-1-type static touch probing microcomputer real-time processing system, all the operations using Chinese characters man-machine dialogue, easy for the general staff to grasp and operate. When touching, it can draw the relationship curves between cone tip resistance and depth, sidewall resistance and depth; when finalizing the hole, it can automatically draw the relationship curves between the resistance ratio and depth. Through man-machine dialogue, it can carry out layering, and automatically draw the layered histogram, print out the layer number, layer elevation, layer thickness, elevation and the value of touching parameters. The system in the work of parameter selection, parameter processing, formula selection and Chinese characters to draw the table header, charts and other aspects are more flexible and innovative, can be used with a variety of static touchdown machine supporting. Another example is the pore pressure touchdown instrument introduced from the Netherlands by China University of Geosciences, which can measure four parameters at the same time, i.e., cone tip resistance, sidewall friction, pore water pressure and pore inclination, and it can draw various curves at the same time, and carry out digital display, magnetic tape recording and printing. Its data acquisition and processing are completely completed by the microcomputer (see Figure 2-26).
(D) penetration system
Static force touching penetration system consists of touching the main body (penetration device) and counterforce device two major components. The role of the touching host is to the bottom of the probe equipped with a probe one by one into the soil. Touching the host according to its penetration mode, can be divided into intermittent penetration type and continuous penetration type; according to its transmission mode, can be divided into mechanical and hydraulic type (see Figure 2-27); according to its assembly mode can be divided into vehicle-mounted type, drag bucket type and floor-standing type and so on.
The function of the counterforce device is to balance the counteraction of penetration resistance to the penetration device. From the equipment point of view, the size of the static contact penetration depth depends mainly on three factors: ① the size of the penetration equipment capacity; ② the size of the contact probe cross-section and its cooperation with the probe rod; ③ the size of the reaction force. Counterforce is not enough, the ability of the whole penetration equipment will not give full play to, visible counterforce device is very important. Counterforce acquisition, generally under the ground anchor and the use of the car's own weight two kinds. Nowadays, the touchdown car are comprehensive utilization of these two methods, the effect is good. Screw anchor machine has hydraulic, electric, hand-cranked three types.
Anchor anchor blade, now more tend to single-winged piece type, so that the ground anchor on the soil is less disturbed, under the anchor is also easier. Blade diameter φ200, φ250, φ300 and φ400mm and so on several kinds, should be based on the size of the required reaction force and the soil layer soft and hard to choose a different diameter of the anchor. The depth of anchor is about 1.0-1.5m. In the general stratum each anchor can provide 10-20kN of reaction force. Generally 2-4 anchors, more 6-8 anchors.
When the estimated ground anchor reaction force can not meet the requirements of the depth of touching, and the use of increasing the number of ground anchors or change to other reaction force program and have difficulties, can consider adding a friction reducer on the probe. Friction reducer outer diameter to be larger than the probe rod, added to the probe friction cylinder from the top of the 1m leaning out. It can weaken the soil on the friction resistance of the probe rod, to achieve the same equipment conditions under the effect of increasing the depth of touch probing.
(E) probe rod
It also has certain specifications and requirements, the probe rod should be sufficient strength, should be used in high-strength seamless tubing, and its yield strength should not be less than 600MPa. probe rod and connector connection should have good interchangeability. Probe with conical threaded connection, connection shall not have shaking phenomenon; with cylindrical threaded connection of the probe, between the buckle, the shoulder should be able to screw tightly affixed. Probe rods should be straight, no cracks and damage. The length of each rod is generally 1m, its diameter should be the same as the diameter of the probe; but single probe rod diameter should be smaller than the diameter of the probe.
(F) cable
The role of the cable is to connect the probe and measurement recording instrument. As the probe function is different, the corresponding cable number of stamens is also different, the least with a single bridge probe four-pistil cable, more than dozens of stamens, the stamens should be shielded from each other, in the output signal can not interfere with each other. The cable should be good waterproof and insulation, joints should be sealed. Its diameter should be smaller than the inner diameter of the probe rod, so that it can be smoothly through the probe rod, connecting the probe and the instrument.
Figure 2-26 Borehole Pressure Touchdown Data Acquisition System
Figure 2-27 Common Touchdown Mainframe Types
1-Cylinder; 2-Piston Rod; 3-Bracket; 4 -probe rod; 5-base; 6-high pressure oil pipe; 7-padding; 8-dust cover; 9-probe; 10-screw; 11 -nut; 12 - gearbox; 13 -guide; 14 -motor; 15 -cable wire; 16 -crank; 17 -sprocket; 18 -gear pulley; 19-pressurized chain; 20-long shaft pin; 21-mountain platen; 22-padded pressure block