## 1 Introduction
Given the same tubular pile, the bearing capacity of open-ended tubular piles was 0.2-0.3 times lower than that of closed-ended ones [12]. Through multiple tests, [PERSON] et al. found that, given the same foundation, the soil plug height in piles was positively related to the inner diameter and radius-thickness ratio of open-ended tubular piles [13]. [PERSON] et al. carried out numerical simulation analyses on the penetration process of tubular piles under the influences of different factors. They concluded that the plugging effect is positively related to the pile-soil friction coefficient. However, it is negatively related to the pile diameter (at the same wall thickness). Overall, the radius-thickness ratio of piles is a decisive factor influencing the soil plug height [14]. Concerning the bearing capacity of pile foundations, [PERSON] et al. conducted a pile pressing test into soft clay to investigate the influences of end conditions on the bearing capacity of tubular piles. They found that the total radial stress during the construction of tubular piles was directly related to excess pore water pressure and the soil plug degree, presenting a linear increase with reductions in the IFR. Fingings revealed that the end resistance on the annual section was independent of the IFR [15]. [PERSON] et al. investigated the influences of pile end conditions and the closing degree of soil plugs on the resistance development of pile bodies, proposing an estimation formula for the vertical bearing capacity of open-ended tubular piles, which could estimate the vertical bearing capacity of tubular piles well [16]. [PERSON] et al. discussed the bearing mechanism of dry sand soil plugs through a tubular pile model loading test and characterised the plugging effect using the DEM model. The results showed that, with increases in the relative soil plug density, the pressing strength on the pile increased. The DEM simulation results agreed well with test results when the pressing strength on the pile was relatively small [17]. [PERSON] et al. studied the influences of soil plugs on the bearing capacity and carried out tests on 60 model piles. Results revealed that tubular piles reached the complete soil plug state in loose and medium-density sandy soils during static pressure piling but were in a partial soil plug state in compact sandy soils. The bearing capacity of tubular piles was related to the PLR, and its increase rate in compact sandy soils was higher than that in loose and medium-density sandy soils [18]. [PERSON] et al. compared the influences of the soil plug degree on the bearing capacities of single open-ended and closed-ended steel tubular piles, revising 24 open-ended steel tubular pile models. They believed that the ultimate soil plug height was closely related to the piling mode and compactness of strata [19]. In general, common penetration monitoring methods have certain disadvantages, such as being time-consuming, labour-intensive, and difficult to operate. Further, they often have a low measurement accuracy and cannot adequately conduct standard dynamic monitoring of penetration. Moreover, studies on the construction effect of large-diameter tubular piles face issues regarding insufficient field displacement measurement data and visual monitoring data from indoor tests. Therefore, they cannot reflect the entire production process and sphere of influence of the construction effect. Digital photography is used for technological support in this study, given its low cost, high measurement accuracy, and simple operation [20; 21]. Therefore, this paper intends to use digital photography technology to monitor the dynamic penetration value and squeezing effect of large-diameter pipe piles on the spot. According to the monitoring results, the relationship between the dynamic penetration value of large-diameter pipe piles, the impact frequency and strata structure is analysed, the evolution law and influence range of squeezing effect is analysed, and laboratory tests are carried out to provide additional explanations.