Research On Settlement Control Of Beam Making Yard Of High Fill Subgrade In Rainy Mountain Area

At present,the construction of highways in our country is developing vigorously,and the center of construction has shifted from east to west,and from plains to mountainous areas.In the development process,the subgrade forms such as high fill and deep excavation,half fill and half excavation are extremely common,so the design forms of high embankment and viaduct have appeared.When prefabricating beams in mountainous areas,beam-making yards are often built on high-filled subgrades due to site limitations.Although this mode can reduce land acquisition and save construction costs,it is due to the large height of subgrade filling and uneven filling thickness.,There may be problems such as uneven settlement.In order to ensure the production quality and production efficiency of T beams during the use of the beam-making yard on the high embankment,it is necessary to study and control the uneven settlement of the beam-making yard.Aiming at the uneven settlement of the prefabricated beam field on the high-fill subgrade in the rainy mountainous area,this paper carried out the dynamic compaction test of the subgrade,the indoor test of the gravel soil filler,and the finite element analysis of the force and deformation of the beam pedestal under various working conditions.As well as the monitoring of the force and deformation of the beam field pedestal,the specific research contents include:First,three types of dynamic compaction tests were carried out on the field.The test results showed that with the increase of compaction energy,the cumulative compaction volume also gradually increased,and the optimal number of compactions could be 8 times.The compaction degree and foundation bearing capacity of each site after dynamic compaction were tested,and the results showed that the compactness of each sampling point after dynamic compaction was greater than 93%,which met the requirements of construction acceptance,and the foundation bearing capacity was increased respectively than before dynamic compaction.22.8%,71.4%,114.3%.The calculation of the foundation bearing capacity shows that the field area should be subjected to a 2000 kN·m dynamic compaction treatment to meet the requirements of the foundation bearing capacity required for beam making.Secondly,particle analysis test,natural moisture content test,fine-grained soil limit moisture content test,heavy compaction test,triaxial test and compression creep test were carried out on the site argillaceous sandstone gravel soil.The test results showed that: The soil-rock ratio of the rock-soil filler is about 1:3,and the gradation is good;the triaxial test results under the conditions of natural moisture content and optimal moisture content show that the cohesive force and internal friction angle of the gravel soil filler are 45 kPa,32°,39.41 kPa,25.06°.The test results provide a reference basis for finite element analysis.Thirdly,the settlement values of the beam-making stage,the tensioning stage and the unloading stage at the end seat were separately fitted under the action of multiple cyclic loads.The fitting results show that with the continuous cycle of the beam-making cycle,the vertical of each stage is Deformation gradually stabilizes.The results of finite element analysis and on-site monitoring show that under the action of multi-cycle loads,the base reaction force changes periodically with time,and the two ends of the pedestal increase significantly in the tension stage,reaching 231 kPa,and the end base reaction force in the lateral direction is:Outside points>inside points;the normal stress of the pedestal also changes periodically with the beam load.In the tension stage,the compressive stress at the longitudinal 1/4L and 3/4L of the pedestal increases significantly to 272 kPa,while the pressure at 1/2L Tensile stress of about 59 kPa;the distribution of subgrade settlement along the longitudinal direction of the subgrade(the direction of the pedestal)shows a trend of "large at both ends and small in the middle",and the increase in settlement tends to be slow with the increase of time.Along the direction of the cross section of the subgrade,as the height of the fill increases,the settlement of the top surface of the subgrade gradually increases.The finite element simulation value of roadbed settlement is basically the same as the on-site monitoring value over time,but the simulation value is about 12-25% smaller.Finite element simulation under heavy rain conditions,the beams were fabricated after the rainfall lasted for 12h,24h,and 36h.The results showed that as the rainfall duration gradually increased from 12h to 36h,the matrix suction of the slope soil continued to decrease,and the rainfall infiltration depth With the continuous increase,the distribution range of the seepage rate gradually expands,the maximum uneven settlement of the roadbed has increased by 56% compared with the absence of rainfall,while the plastic zone of the slope gradually expands upwards,and the safety factor gradually decreases from 1.346 when there is no rainfall to 1.217.The slope stability is gradually decreasing,and there is a danger of local damage.Finally,in view of the uneven settlement of the pedestal,the allowable differential settlement control index is proposed,and 1mm/m is taken as the limit to control the uneven settlement.When the uneven settlement of the pedestal exceeds the limit,methods such as additional support height adjustment devices and pressure grouting are proposed to reduce the uneven settlement of the pedestal.