滨海区软弱地基工程特性及水泥搅拌桩加固效果

Engineering Characteristics of Weak Subsoil in Coastal Area and Reforcement Effectiveness Using Cement⁃mixed Pile

东南滨海区深厚复杂软弱地基具有地下水位高、淤泥质软土厚度大、地基强度低等特点,地基沉降变形难以控制。依托汕头至汕尾高速铁路地基加固工程,通过现场原位试验及室内试验分析滨海地区软土工程特性,提出采用水泥搅拌桩法进行地基加固,并对搅拌桩配合比及施工方案进行优化设计。地基加固后通过成桩质量检测对加固效果进行分析。结果表明:工点软土地基土体抗剪强度为28.7 kPa,地下水位埋深1.2~2.0 m,淤泥质软土层对水泥土成桩效果有较大影响;基于软土地基工程特性,施工采用“四搅四喷”成桩工艺,搅拌桩水灰比0.55、灰砂比0.40、水泥掺量为20%;经现场取芯测试和复合地基荷载试验可知,水泥土强度在0.520~2.953 MPa;地基沉降随荷载增加逐渐减缓,水泥搅拌桩复合地基最大沉降量为7.48 mm,地基承载力为180 kPa;桩体强度和地基承载力均满足规范要求。

The southeastern coastal region of China presents deep and complex soft foundations characterized by high groundwater levels,considerable thickness of muddy soft soils,and low foundation strength,posing challenges in foundation treatment and control of settlement deformations.Leveraging the foundation reinforcement project of the Shanshan high speed railway,this study carried field test and laboratory tests to analyze the engineering characteristics of soft soils in coastal area.A method involving cement mixing piles for foundation treatment was proposed,alongside optimization of mix ratios and construction schemes.Following treatment,the efficacy of reinforcement was assessed through quality inspections of the piles.The Results reveal a shear strength of 28.7 kPa for the soft soil foundation in coastal area,with groundwater levels buried at depths ranging from 1.2~2.0 m.The presence of muddy soft soil layers significantly impacts the formation of cement soil piles.Based on the engineering properties of soft soil foundations,construction adopts the“four-stirring and four-spraying”pile forming process,with a water-cement ratio of 0.55,a cement-sand ratio of 0.40,and a cement content of 20%.Through field coring tests and composite foundation load tests,the strength of cement soil ranges from 0.520~2.953 MPa.Furthermore,the increase in foundation settlement gradually diminishes with growing loads.The maximum settlement value of the cement mixing pile composite foundation is 7.48 mm,with a foundation bearing capacity of 180 kPa.Both the pile strength and foundation bearing capacity adhere to specification requirements.