煤夹层地质条件下单桩承载特性分析

Analysis of Single Pile Load-Bearing Characteristics in Geological Condition of Laminated Coal

以南宁市地质条件下某桩基工程为例,采用有限元法对持力层存在煤夹层条件下桩基础的变形、应力进行计算,分析了煤夹层应力分布特征及其承载力的验算问题。研究表明:(1)当煤层厚度相同时,埋深越大,沉降越小;当煤层埋深相同时,煤层越厚,沉降也越大。(2)当埋深在1d～3d(d为桩径)时,煤层对持力层应力分布所起的"扩散传递"作用十分突出,超过3d时则影响很小;煤夹层越厚,扩散效果越明显,但当其厚度达到1.0 m时,煤夹层对持力层应力的扩散作用明显减弱。(3)煤层埋深越小,其最大主应力越大。桩端以下应力扩散的主要影响范围在3d以内,煤层越薄,其内部应力越大,煤层厚度增大也会导致沉降增大。模拟值与实测值吻合较好。

As an example of a pile foundation engineering in Nanning,the finite element method is used to calculate the deformation and stress of single pile under geological conditions of laminated coal.The stress distribution characteristics and the bearing capacity problem are analyzed.Studies show that：（1）When the coal seam thickness is the same,the greater the depth,the smaller the settlement.When the coal seam buried depth is the same,the thicker coal seam,the greater the settlement.（2）When the buried depth in the range of 1d and 3d（d is pile diameter）,the coal seam on the stress distribution in the bearing stratum plays an important role in＂diffusion transfer＂,but effect little when more than 3d.The thicker laminated coal,the more obvious diffusion effect.However,when the thickness reaches 1.0 m,the diffusion effects decrease significantly.（3） The smaller coal seam buried,the greater the maximum principal stresses.The main sphere of influence for stress diffusion under pile tip is 3d,the thinner coal seam,the greater the internal stress.The increase of coal seam thickness can lead to increased subsidence.Simulation results are in good agreement with the measured values.