Bioinspired composites, capable of tailoring mechanical properties by the strategy of making full use of their advantages and bypassing their drawbacks, are vital for numerous engineering applications such as lightweight ultrahigh-strength, enhanced toughness, improved low-/high- velocity impact resistance, wave filtering, and energy harvesting. Helicoidal composites are examples of them. However, how to optimize the geometric structure to maximize the low-velocity impact resistance of helicoidal composites has been ignored, which is vital to the lightweight and high strength for aerospace, defense, ship, bridge, dam, vessel, and textile industries. Here, we combined experiments and numerical simulations to report the dynamic response of helicoidal composites subjected under low-velocity impact (0–10 m/s). Our helicoidal structures, inspired by the Stomatopod Dactyl club, are fabricated using polylactic acid (PLA) by FFF in a single-phase way. The helicoidal strategy aims to exploit, to a maximum extent, the axial tensile strength of filaments and simultaneously make up the shortage of inter-filament contact strength. We demonstrate experimentally that the low-velocity impact resistance has been enhanced efficiently as the helicoidal angle varies, and that the 15° helicoidal plate is better than others, which has also been confirmed by the numerical simulations. The findings reported here provide a new routine to design composites systems with enhanced impact resistance, offering a method to improve impact performance and expand the application of 3D printing.

Combined with the pressure sensitive characteristics of corrugated diaphragm and the strain sensing characteristics of fiber Bragg grating (FBG), a kind of FBG sensor is developed to measure the seepage pressure change of soil in a small range. By carrying out the soil seepage flow monitoring test and the laboratory slope model test, and comparing the theoretical and measured values of these tests, it can be found that: it is feasible to apply FBG seepage pressure sensor to the seepage pressure monitoring of soil mass. The sensor can guarantee the validity and reliability of data in the medium-term or long-term monitoring process, and shows superior performance compared with conventional seepage pressure sensor. The FBG seepage pressure sensor has the characteristics of high sensitivity, stable long-term performance, high precision and strong real-time performance. It provides a new measurement method for the seepage pressure monitoring of soil mass within the range of 0 to 100 kPa.

The shear strength reduction method provides an effective tool of numerical analysis for landslides reliability analysis. However, it ignores the failure probability of the secondary failure surfaces and requires huge computational cost. To avoid these common criticisms, an intelligent multiple response surfaces method for system reliability using multiple response-surface method (MRSM) and least-squares support vector machine (LSSVM) is presented to evaluate the stability of complex multistage historic landslides with multiple sliding surfaces. Deterministic analysis of each sliding surface is first performed using the finite element method of sliding surface stress analysis, which is applied to obtain the safety factors of different sliding surfaces from the stress fields generated by finite element simulations. The LSSVM model with excellent nonlinear fitting ability is then employed to construct the multiple response-surface method (MRSM) of the sliding surfaces and a genetic algorithm (GA) is adopted to optimize the LSSVM. This proposed methodology is finally applied to investigate the probability of system failure of the Zhenggang landslide in southwestern China. The results indicate that the proposed approach can reduce the computational cost of finite element analysis in direct Monte Carlo simulation (MCS) by proper training using a limited of samples, and the calculation accuracy meets the engineering requirements of complex multistage historic landslides.

Energy pile foundation has dual functions of bearing capacity and the utilization of shallow geothermal energy， the depth of foundation and operation modes have a certain impact on the heat transfer performance of the energy pile. Relying on the energy pile foundation with cap under the condition of 3.0 m buried depth， which belongs to the Hydraulic and Engineering Building of China Three Gorges University （Yichang city， Hubei province）， two series of field thermal response tests are conducted with 16-day test duration， the operation modes are 16 h heating-8 h self-cooling intermittent heating process （IH-16） and continuous 24 h heating process （CH-24）， respectively. The temperature， thermal induced strain of energy piles and cap are measured. The heat transfer efficiency values in the stable heating stage under CH-24 and IH-16 heating modes are about 5.32 kW and 5.38 kW， respectively. The neutral points of both CH-24 and IH-16 test conditions are appeared at 0.78 times the length of the pile from pile top， resulting in pile top displacements of 0.38 mm and 0.19 mm， the average temperature rise of the pile body is 8.9 ℃ and 4.7 ℃， respectively； and the thermal disturbance range is about 1.7 m. The maximum constraint stress of pile body under CH-24 test condition is -3.01 MPa， which is 79% higher than that under IH-16 mode of -1.68 MPa. The IH-16 test produced an additional tensile stress of about 1.75 MPa at the position of the cap corresponding to the non-operating diagonal pile， which was about 73.2% of the C40 concrete tensile strength value. There were slight deformation differences in the cap under both two operating modes， which should be considered during design and operation.