摘要
主要介绍了依据现场原位压板载荷试验而建立的一套地基设计的新理论。地基设计中地基沉降计算与地基承载力合理确定的问题是土力学中的经典问题。现代土力学理论虽然发展了土的本构模型和现代数值计算方法,解决了非线性等复杂的计算难题,但实际工程设计中,目前采用的仍是传统的半理论半经验的方法,这是土力学理论创立近百年以来都没很好解决的一个问题。问题的根本原因是什么?应如何破解?本文认为对于结构性的硬土地基,传统理论依据室内土样试验求参数,由于取样扰动等的影响,这样得到的参数不能反映原位土的特性,从而使依据这些参数计算的结果与实际结果差异大。为解决这个难题,依据现场原位压板载荷试验曲线建立了切线模量法的计算模型并反算出模型的3个土体参数:初始切线模量E_(t0),黏聚力c和内摩擦角φ。该法所需参数少,物理意义明确,参数来源于现场原位试验,避免了取样扰动影响,精度可靠,可以计算基础沉降的非线性直到破坏的全过程。对于地基承载力,提出了用切线模量法计算实际基础的荷载沉降的p–s曲线,根据p–s曲线依据强度和变形双控的原则确定最合适的地基承载力的方法,实现变形控制设计,解决了以往直接由压板载荷试验曲线确定承载力存在的尺寸效应问题。对软土地基的沉降计算,在Duncan-Chang模型基础上,用压缩试验的e–p曲线构建了非线性沉降的实用计算方法,并建立了用压缩模量E_(s1-2)求e–p曲线的方法,这样只用压缩模量E_(s1-2)即可进行非线性沉降计算。由于一般饱和软土的E_(s1-2)为2~4 MPa,变化范围小,参数简单而较为可靠,从而使方法易于应用。该项研究为破解土力学的百年难题提供了新的思路,值得进一步发展完善,为现代地基设计提供更科学的新方法。
A set of new theory of foundation design is introduced based on in-situ plate loading tests.The calculation of foundation settlement and the reasonable determination of bearing capacity in foundation design are the classic problems in soil mechanics.Although the modern soil mechanics theories have developed soil constitutive models and numerical methods to solve complex problems such as nonlinearities,the actual engineering design around the world is still using the traditional semi-theoretical and semi-empirical method.It is a problem that has not been solved well since the foundation of soil mechanics theory for nearly a hundred years.What is the root cause of the problem?How to solve it?It is believed that for the structured hard soils,the traditional theories are based on the indoor soil sample tests to obtain parameters.Due to the influences of sampling disturbances,the parameters obtained in this way cannot reflect the characteristics of the in-situ soils,so that the calculated results based on such parameters are not consistent with actual conditions and the results vary greatly.In order to solve this problem,the model for calculating the tangent modulus method is established based on the in-situ plate loading test curve,and the three soil parameters of the model are inversely calculated:initial tangent modulus E_(t0),cohesion c and internal friction anglej.The proposed method requires few parameters and has clear physical meaning.The parameters are derived from the in-situ tests,avoiding the influences of sampling disturbance,and the accuracy is reliable.It can be used to calculate the whole process from the nonlinearity of foundation settlement to failure.For the bearing capacity of foundation,the relation curve of the pressure and settlement(p-s curve)of the actual foundation is calculated by the tangent modulus method.According to the p-s curve,a method to determine the most suitable bearing capacity of foundation based on the principles of dual-control of strength and deformation realizes the deformation control design.At the same time,this method can solve the problem of the size effect of the bearing capacity directly determined by the plate loading test curve in the past.For the settlement calculation of soft soil foundation,on the basis of the Duncan-Chang model,a practical method for calculating the nonlinear settlement is established using the e-p curve of the compression tests.And a method for calculating e-p curve with compressive modulus E_(s1-2)is established,so that only the compressive modulus E_(s1-2)can be used to calculate the nonlinear settlement.Since the compressive modulus E_(s1-2)of general saturated soft soils is about 2~4 MPa,the range of change is small,the parameters are simple and reliable,and the proposed method is easy to apply.This research provides a new idea for solving the century-old problems of soil mechanics and a more scientific new method for modern foundation design,which is worthy of further development and improvement.
作者
杨光华
YANG Guang-hua(Guangdong Research Institute of Water Resources and Hydropower,Guangzhou 510635,China;The Geotechnical Engineering Technology Center of Guangdong Province,Guangzhou 510635,China)
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2021年第1期1-18,共18页
Chinese Journal of Geotechnical Engineering
基金
国家自然科学基金项目(52078143)。
关键词
地基沉降
承载力
切线模量法
压板载荷试验
foundation settlement
bearing capacity
tangent modulus method
plate loading test
