Composite Pipe Pile Planting Technology And Test Research Based On Special Stratum In Guangxi

The two kinds of special strata,argillaceous rock and limestone,are widely distributed in Guangxi area.The lithology of argillaceous rocks varies greatly,and the water is easy to soften and disintegrate.Limestone is easy to dissolve and produce geological problems such as dissolution ditch,dissolving trough,karst cave and fissure.Because of the particularity of the two kinds of formation,at this stage there are extensive use of static pressure pipe pile and bored pile applied in Guangxi mudstone and limestone areas of varying degrees of problems,seriously affect the safety of the project,causing great waste of resources.In order to solve the present stage of pile foundation in Guangxi mudstone and limestone formation problems in use,the stress mechanism and construction technology through studying the characteristics,different types of pile foundation pile,summarizes the engineering properties of Guangxi District summary of mudstone and limestone,respectively put forward rotary drilling pile method and high pressure DTH hammer jet grouting pile method of mudstone and limestone strata,and explore through the field test of two planting pile construction by composite pile and rotary drilling DTH jet composite pile.The main work and research results are as follows:1?The stress mechanism of pile foundation is analyzed,and the ultimate bearing capacity of two kinds of composite pipe piles is calculated by using the standard empirical formula.The theoretical calculation results show that the soil around the pile to soil or gravel based,pile-mortar contact surface of ultimate lateral resistance is higher than that of mortar-limit soil pile side resistance,the pile and the pile of mortar as a whole,side friction interface failure occurred in the mortar pile soil interface.When the rotary drilling pile soil composite pipe with hard rock,the mortar pile soil contact surface is larger,the composite pile diameter reaches a certain value,the resistance will be higher than the theoretical limit on the side of pile-mortar contact surface of ultimate bearing capacity,the lateral resistance of interfacial.damage may occur in the pile-mortar interface.2?The two methods of rotary digging pile method and DTH hammer high pressure jet grouting pile method are explored,and the site construction process is designed.The design of rotary digging composite pipe pile is carried out in a project in Nanning,and the design of DTH high pressure jet grouting composite pipe pile is selected for a regular project.In the interim,the selection of pipe pile,the calculation of pipe end pressure and the determination of construction parameters are analyzed in detail,and field tests are carried out according to the design and construction process.The results of construction pile show that the two pile method has the advantages of high pile forming speed,good pile forming effect and stable pile quality.3?The static load tests of two kinds of composite pipe piles are carried out.The test results show that the bearing capacity of composite pipe pile meets the design requirements and the rebound rate of pile body is higher under the test stratum condition.The theory and the static load test results were compared and analyzed,the static load test of maximum load value is far less than the theoretical value of ultimate bearing capacity,shows two kinds of composite pile in static load test conditions,there is still a large amount of surplus capacity4?The static pressure pile,rotary digging pile and rotary drilling pile composite were compared,the static load test results show that under the same load,the diameter of 500mm static pile settlement is the largest,800mm rotary drilling pile of rotary drilling pile composite minimum.According to the analysis of the maximum load,the pile can bear the load value about 1.75 times of the static pressure pipe pile and 1.80 times of the bored pile when the settlement is 1 millimeters per square meter.5?On the static,rotary drilling pile,composite pile and rotary drilling DTH high-pressure jet pile composite technology and economy.The results show that the static single pile while the lowest cost,but the Guangxi mudstone and limestone area of pile end to rock,limited applicability.The rotary excavation composite pipe pile is superior to rotary digging pile in terms of cost,construction period and pile quality.The DTH high pressure jet grouting composite pile has the advantages of fast construction speed,stable quality of pile forming,and can adapt to all kinds of strata,but the cost is relatively high compared with other pile type.