碳中和、碳达峰中秸秆降解排水技术的应用与刚柔复合厚壳层地基的关系

Relationship between the application of straw degradation drainage technology in carbon neutrality and emission peak and rigid flexible thick shell foundation

在深厚软基及吹填造地上采用环保型秸秆可降解排水板替代塑料排水板进行真空预压施工时,每年可节约生产塑料排水板原材料聚乙烯(PE)和聚丙烯(PP)混合原材料1.4~1.5亿吨,每年可避免向大气排放约6800亿立方的CO气体。环保型秸秆降解排水板主要原材料为农田里废弃的秸秆原料,通过晾晒、烘干、粉碎切割、产生小于1 cm长的秸秆纤维绒与固体热融胶、少量锯木纤维、少量椰壳纤维等混合料,再投放到螺旋热融挤压设备中搅拌软化后挤出秸秆排水板板芯成品,后续再热融黏合上双面防淤堵滤膜层,最终形成工程上能用的整体式秸秆降解排水板。采用秸秆降解排水板处理后的深厚软基,可彻底解决塑料排水板处理软地基后继续排水的困局,在真空预压施工验收完1年后其板芯纤维分子结构链逐渐被生物菌分解断链使排水通道失去排水功能,同时还避免了水泥搅拌桩施工时易缠桩及植入预制管桩时易被拉扯桩而影响整体成桩质量的问题。当深厚软基地基承载力特征值处理后达到≥70 kPa以上、工后沉降值≤15 cm时,深厚软基厚壳层再按《复合地基技术规范》的要求,设计出植入大直径≥Φ1000 mm的水泥土或薄壁刚性复合疏桩的长度、间距,桩土协同后形成以刚性体为主、柔性体为辅的刚柔复合厚壳层复合地基,其具有整体承载力高、沉降小(可控)、差异沉降小(可控)、整体稳定、整体抗水平推力大、造价低、工期短等优点,不仅能提供地基承载力极限值为500~1000 kPa,还能为投资方节约综合成本20%以上。

When using environmental friendly straw degradable drainage board instead of plastic drainage board for vacuum preloading construction on deep soft foundation and hydraulic reclamation land,140-150 million tons of mixed raw materials of polyethylene(PE)and polypropylene(PP)can be saved every year,and about 680 billion cubic meters of COgas can be avoided from being discharged into the atmosphere every year.The main raw material of environment-friendly straw degradation drainage board is"straw raw material discarded in farmland".Through sun-cure,crushing and cutting,the mixture of straw fiber velvet less than 1cm long and solid hot-melt glue,a small amount of sawn fiber and a small amount of coconut shell fiber is produced.Then put into the spiral hot-melt extrusion equipment to stir and soften and extrude the finished product of straw drainage board core.After reheating and thawing,the double-sided anti silting filter membrane layer is bonded to form an integral straw degradation drainage board that can be used in engineering.The deep soft foundation treated with straw degradation drainage board can completely solve the dilemma of continuous drainage after the plastic drainage board is used to treat the soft foundation.One year after the acceptance of vacuum preloading construction,the molecular structure chain of the core fiber is gradually broken down by biological bacteria,resulting in the loss of drainage function of the drainage channel.In addition,it also avoids the problems that the cement mixing pile is easy to wrap the pile during construction and the pile is easy to be pulled when the precast pipe pile is implanted,which will affect the overall pile quality.When the characteristic value of bearing capacity of deep soft foundation is greater than or equal to 70 k Pa after treatment and the post construction settlement value is less than or equal to 15 cm,the length and spacing of cement soil or thin-wall rigid composite sparse pile with large diameter of≥Φ1000 mm are designed for the thick shell of deep soft foundation according to the requirements of technical code for composite foundation[1].After pile-soil cooperation,rigid body is formed.The rigid flexible composite thick shell composite foundation supplemented by flexible body has the advantages of high overall bearing capacity,small settlement(controllable),small differential settlement(controllable),overall stability,large overall horizontal thrust resistance,low cost and short construction period.It can not only provide the limit value of foundation bearing capacity of 500-1000 k Pa,but also save more than 20%of the comprehensive cost for the investor.