The complex propagation behaviours of hydraulic fracture (HF) at bedding planes (BPs) and the produced complicated fracture geometry are essential to enhance the production of shale gas reservoirs. To better understand the complex propagation behaviour of HF at BPs with different bond strengths, the propagation behaviour, including arrest, crossing, and deviation, was identified first from post-fracturing shale specimens. The discontinuous stress and displacement fields on both sides of a BP ahead of an HF were then determined using the numerical simulation method. Finally, three mechanisms—principal stress jump, Cook–Gordon debonding or Poisson effect, and elastic dissimilarity—were explored in detail to interpret the complex propagation behaviour. The results revealed that HF is arrested/deviated only at extremely weakly cemented or fully opened BPs, whereas HF crosses strongly cemented BPs. The high heterogeneity of the BPs in cementing strength is responsible for the complex propagation behaviour of HF. The principal stress jump at a BP is caused by the difference in stiffness between the BP and the rock matrix. The maximum tensile principal stress ahead of the HF cannot be transmitted across the weakly cemented or fully opened BPs, suggesting that the HF cannot cross BPs. The principal stresses may rotate at a weakly cemented BP, and the rotated principal stresses tend to terminate or deviate an HF. Because of Cook–Gordon debonding and the Poisson effect, if a weakly cemented BP is present and is roughly normal to an advancing HF, the BP may break at some distance ahead of the fracture tip and induce a secondary fracture along the BP. The HF then reaches the opened BP and deviates towards the BP. The propagation process of L- or T-shaped fractures can be interpreted both by the Cook–Gordon debonding and Poisson effect from the viewpoints of stress and displacement. The three mechanisms often operate together when an HF deviates towards a weak BP; while for a special case, there may be only one dominant mechanism.

水力压裂（HF）在层理面（BPs）上的复杂传播行为以及所产生的复杂的裂缝几何形状对于提高页岩气储层的产量至关重要。为了更好地了解HF在具有不同粘结强度的BP处的复杂传播行为，首先从压裂后的页岩样品中确定了传播行为，包括阻滞，穿越和偏移。然后使用数值模拟方法确定HF之前BP两侧的不连续应力场和位移场。最后，详细研究了三种机理-主应力跳跃，库克-戈登脱粘或泊松效应以及弹性不相似性-来解释复杂的传播行为。结果表明，HF仅在极弱胶结或完全打开的BP处被阻止/偏移，而HF穿过强胶结的BP。胶结强度中BP的高度异质性是HF复杂传播行为的原因。BP处的主应力跳跃是由BP与岩石基体之间的刚度差异引起的。HF之前的最大拉伸主应力无法通过弱胶结或完全打开的BP传递，这表明HF无法穿越BP。主应力可能在弱粘结的BP处旋转，并且旋转的主应力趋于终止或偏离HF。由于Cook-Gordon脱粘和泊松效应，如果存在弱胶结的BP，并且与前进的HF大致垂直，BP可能会在骨折尖端之前的某个距离处破裂，并沿BP引发继发性骨折。HF然后到达打开的BP并向BP偏移。从应力和位移的角度，Look或T形裂缝的传播过程可以通过Cook-Gordon脱胶和泊松效应来解释。当HF偏向弱BP时，这三种机制通常一起起作用。而在特殊情况下，可能只有一个主导机制。