| With increasing development and investment in infrastructure, many buildings, roads, water conservancy, hydropower engineering and other public foundation were developed rapidly. The complex geological environment and more unpredictable factors easily cause accidents and bring huge economic losses and casualties. To making the engineering construction to achieve more economic, more reasonable, and more stable, people have to made a lot of research on geotechnical properties. With all kind of the research, new methods of in-situ test, new experiences and new theories appear constantly make in-situ test theory constantly improve and develop.The soil mechanics experiment is applied various experimental device to detect all kinds of pressure stress and strain, shear stress and strain of the soil features technology. At present, the most of the soil mechanics test soil in the laboratory. This requires that the soil samples must be "fresh". That means try to our best to protect the soil samples at the scene of the state of physical and chemistry. Laboratory soil tests characteristic has the advantage of easy operation, reliable data; Its disadvantage is obvious, that is have to keep the soil sample fresh and a longer experimental period. In addition, after the soil samples extracted from the exploration has large changes in its original state. So, in-situ test is very necessary.Deep hole geological exploration are generally adopted the soil samples and take them back to indoor geotechnical mechanics in accordance with the relevant national standards for the experimental testing and analysis. In addition, collecting the sample needs to keep samples’ mechanical properties not change. The traditional test method has greatly increased the related geological exploration work, it doesn’t go with the current social reality of the development. Geological experts main need is technical data of soil, if the tests can get the technical data in-situ, it is the best way to get the soil properties. Geotechnical exploration and expect to have reliable, lightweight soil with deep hole appeared in situ detection apparatus.This paper presents the necessity of in-situ geotechnical exploration, through tests detailed, in-situ test instructions on safety, stability of foundation engineering construction and securty of social development. First of all, the paper introduced current shear strength test and shear strength instrument, such as direct shear test, single shear experiment, ring shear test and triaxial compression of soil sampling method. At the same time, it talk about the status and development of shear strength test instrument and points out the shortage of indoor shear test. Later, in-situ testing methods and shear strength of in-situ test method are introduced. Vane shear test can basically test at natural torsional shear stress condition of diiferent layer, the measured intensity can better reflect the natural soil strength. But the vane shear test only for soft soil and silt, for relatively hard plastic clay and mixed with gravel soil don’t work. The comprehensive comparison between indoor and outdoor shear strength test method and test instruments, puts forward a new kind of deep hole in-situ direct shear testing method and developed a deep hole in-situ direct shear test instrument.In the second chapter, shear strength theory were studied. The paper expounds the coulomb’s law: when the stress range is not big, relationship between the shear strength and the normal stress approximate to a straight line. According to the coulomb formula, the soil shear strength indexes are cohesion and friction Angle. Then the paper introduces the Mohr-coulomb failure criterion and soil balance condition. After that it analyze the shear strength test method, the direct shear test include three different test with different drainage conditions: slow shear test, fast shear and consolidated quick shear test. Finally, using the finite difference method to build modeling, and using FLAC 3D software to simulate direct shear test. Focusing on analysis of soil test under vertical stress and shear stress and strain distribution. Calculation results show that distribution of shear stress and shear strain is not the uniform in direct shear test. At begining, stress and strain around the shear test sample cup’s side is big. In the whole process, o shear stress and shear strain expand from the soil samples edge to the central area. After soil samples failure, shear stress and shear strain become uniform on the shear plane.The third chapter expounds structure design of deep hole in-situ direct shear test apparatus. It introduced the aspects such as structure, working mechanism, choice of sampling. It analyses holder system, vertical load and horizontal load system. Deep hole in-situ direct shear testing concept is put forward, and the soil sample testing process are introduced in details. First, drill a depth of about 5 to 50 m hole, then put direct shear test instrument into the bottom of the deep hole, and test soil for compressive strain and shear strain test. After shear test, take back the device, and perpare for the next test.The fourth chapter introduces the deep hole in-situ direct shear apparatus parameter design. Power system, sampling system, backup system parameters is studied, using finite element analysis software to analysis stress and strain. Then it introduces the power system and power load matching. Using finite element simulation method to determine the load size. First determine the action about the force. By comparing the advantages and disadvantages of motor and airbag, finally selectd motor as power system, and calculate the load size. Analyzed stress and strain of test sample cup in the sampling process. For sampling the soil in the process of cutting were studied.Using finite element analysis software to analysis stress and strain of the vertical pressure’s piston and horizontal loading important power transmission components.The fifth chapter analysies pressure sensor and displacement sensor of the deep hole in-situ direct shear test apparatus. Select suitable pressure sensor, and introduces its basic structure and working principle. Through the finite element calculation, simulate different modulus, thickness to diameter ratio of matching error of pressure sensor. Due to the deep hole in-situ direct shear test apparauts internal institutions is small, displacement sensor cannot install in the apparaut. So it need design and product new displacement sensor for the deep hole in-situ direct shear test apparauts. By finite element method, displacement sensor elastic beams are analyzed. The displacement sensor maximum range is 9 mm and accuracy is 0.1 mm. At last, it is introduced saw ring and saw ring drive circuit. Due to some of the cohesive soil as hardness as the rock, so saw ring can reduce the difficulty of sampling process. Saw ring is based on the working principle of ultrasonic moto. The paper estimated the load of sawing and control ring spinning.The stepper motor control system and data acquisition system were studied at sixth chapter. The system control scheme is closed loop control system. The stepper motor control model was studied, the stepping motor speed control algorithm was estimated. Finally, it built stepper motor control system. This paper realize data acquisition system of deep hole in-situ direct shear test instrument. It includes AD converter, signal amplifying circuit, data processing circuit and display circuit.The seventh chapter expounds the deep hole in-situ direct shear testing apparatus prototype, and test each unit and system behavior. Test prototype can achieve design goal. Set up a deep hole in-situ direct shear testing platform in the laboratory. Test results were obtained, draw the stress-strain diagram, and get the shear strength indexes of soil, c=10kpa, φ=42.1。. The results proved that the deep hole in-situ direct shear test instrument working very well.The eighth chapter is introduced design optimization in the process of research and development, includes vertical, horizontal loading system and backup system. After the original structural design and optimization of structure design are analyzed and compared. Mechanical structural design optimization and comparison is important part of the mechanical innovation design process, based on the component optimization design, reduce the friction from the mechanism motion, the energy loss and improve the testing accuracy. In fact, the mechanical structure of the whole equipment can make apparatus stable work.The innovations of this paper are following five points:(1) According to the basic theory of soil mechanics shear strength and Mohr-coulomb failure criteria, the soil mechanics shear strength test method is studied. By using soil mechanics software, deep hole in-situ direct shear testing model is established, and puts forward the concept of deep hole in-situ direct shear testing.(2) Deep hole in-situ direct shear test apparatus prototype was developed. Deep hole in-situ direct shear test instrument is based on mechanical and electrical integration, design and manufacture the sensor and actuator integrate together. Keeping the strength and service life and reducing space, lightweight, make the equipment reliability and improve test efficiency.(3) Realize the deep hole in-situ direct shear test. Building a deep hole in situ testing platform to test soil samples in different shear strength under positive pressure, and obtain a series of relevant test data.(4) Put forward deep hole in-situ direct shear test instrument information integration method. Holder system has pressure sensor which can determined appropriate support pressure; Mechanical stress is measure by the piston’s pressure sensor and the compressive stress by recording the corresponding strain displacement of the screw; Apparatus can finish automatic test action. All the data information through the electrical steel cable back to the ground control system. |
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