Evaluation of a new nomogram for Ferrara ring segment implantation in keratoconus

AIM:To evaluate the short-term clinical outcomes of Ferrara rings in keratoconus using an optimized nomogram developed after several years of research and retrospective analysis of clinical data.METHODS:This prospective longitudinal non-comparative clinical trial evaluated 88 eyes of 88 patients(age 18-62 y)with keratoconus diagnosis from two Spanish centers.Ferrara ring segment(AJL Ophthalmic)implantation was performed in all cases,using the mechanical procedure in 25 eyes(28.4%)and a femtosecond laser-assisted procedure in 63 eyes(71.6%).The ring segments implanted in each case were selected using a new optimized nomogram that considered variables such as anterior corneal asphericity and astigmatism or the discrepancy among astigmatism and coma orientations.Visual,refractive,corneal topographic,aberrometric,and pachymetric changes after surgery were evaluated during a 3-month follow-up.RESULTS:The implants induced a significant refractive change as well as an improvement in uncorrected(UDVA)and corrected distance visual acuity(CDVA;P<0.001).Postoperative CDVA of 0.10 log MAR or better was achieved in 28.4%and 46.5%of eyes,respectively.Two eyes(2.3%)lost two or more lines of CDVA whereas a total of 53.5%of eyes gained lines of CDVA.A significant central anterior and posterior corneal flattening was induced(P≤0.003),with a significant reduction of anterior(P<0.001)and posterior corneal astigmatisms(P=0.048),and a change in anterior asphericity(P<0.001).Total primary coma(6 mm pupil)change was also statistically significant(preoperative 3.66±3.04μm vs postoperative 2.33±2.26μm,P<0.001).No significant differences were found in the effect of ring segments between cases implanted using the mechanical and femtosecond techniques(P≥0.101).CONCLUSION:The implantation of Ferrara rings based on the nomogram evaluated is safe and effective for promoting a visual rehabilitation in keratoconus,with a relevant control of primary coma aberration.

Preliminary results of a new intrastromal corneal ring segment as a tissue saving procedure in photorefractive keratectomy to correct moderate to high myopia

AIM:To evaluate the clinical results after implantation of a new intrastromal corneal ring segment(ICRS)associated with photorefractive keratectomy(PRK)to correct high myopia(HM)patients with thin corneas.METHODS:We evaluated 42 eyes of 23 HM patients that had ICRS implantation followed by PRK.The mean age of patients was 29.1±7.12 y(range 18 to 40 years old).Uncorrected visual acuity(UCVA),best corrected visual acuity(BCVA),keratometry,spherical equivalent,pachymetry,and aberrometry were compared using ANOVA with repeated measurements evaluated preoperatively and at last follow-up visit after the procedures.The refractive predictability and simulated/real corneal ablation were also assessed.RESULTS:The mean follow-up time after PRK was 6.8±1.6 mo.The mean preoperative UCVA improved from 20/800 preoperative to 20/100 after ICRS and 20/35 after PRK.The mean preoperative BCVA was 20/25(range from 20/30 to 20/20)and remained unchanged after ICRS implantation.Following the PRK the mean BCVA was 20/25(range from 20/30 to 20/20).The mean spherical equivalent decreased from-7.25±1.12(range-5.00 to-9.00)preoperatively to-3.32±1.0(range-2.00 to-5.00)postoperatively(P<0.001)after ICRS implantation and decreased from-2.44±1.51 preoperatively to 0.32±0.45(range-0.625 to 0.875)postoperatively(P<0.001)after PRK.The change in BCVA and topographic astigmatism was statistically significant(P<0.0001).CONCLUSION:ICRS in HM associated with PRK can be a tissue saving procedure and an alternative surgical option for correction of moderate to high myopia.

Ferrara ring segments implantation for treating keratoconus

AIM: To investigate the efficacy of Ferrara rings (FR) implantation in the treatment of keratoconus.METHODS: It was a retrospective case series descriptive study. The sample was comprised of 50 patients 79 eyes diagnosed with progressive keratoconus. This included 24 (48%) males and 26 (52%) females between the age of 13 and 44 years. All participants underwent surgical implantation of FR in the period between January 2009 and September 2010 at Jordan University Hospital. Thorough ophthalmologic examinations were applied to measure vital variables for each pathological condition before and after surgery. RESULTS: Findings indicated an overall significant postoperative improvement in both uncorrected visual acuity (UCVA) and best spectacle corrected visual acuity (BSCVA) throughout follow up visits. Moreover, results illustrated a significant decrease in spherical equivalent (SE) and keratometric readings (lower, higher and the average). CONCLUSION: Surgical intervention strategies are being frequently developed to meet the needs of patients with keratoconus. The implantation of Ferrara rings has proven to be a safe and feasible alternative procedure for the treatment of mild-moderate keratoconus especially for patients with contact lenses intolerance. We have found that this procedure has improved visual outcomes in all eyes studied. Nevertheless, further research is needed to investigate long term outcomes.

Clinical outcomes after intrastromal corneal ring segments reoperation in keratoconus patients

AIM:To evaluate the clinical outcomes after Ferrara intrastromal corneal ring segments(ICRS)reoperation in patients with keratoconus.METHODS:A total of 37 keratoconus eyes implanted with intrastromal corneal ring segments,which had an ICRS exchange,addition,reposition or removal were evaluated.Uncorrected visual acuity(UCVA),best corrected visual acuity(BCVA),keratometry(K),asphericity(Q)and pachymetry at the thinnest point(PTP)of the cornea were evaluated using a corneal tomography(Oculus Pentacam,USA)RESULTS:The mean follow-up time after the reoperation was 30.5±9.7 months.The mean UCVA improved from 20/300 to 20/80(P=0.005);the mean BCVA improved from 20/160 to 20/50(P=0.0002),the mean keratometry reduced from 49.33±4.19D to 46.16±3.90D(P=0.0001),the mean pachymetry at the thinnest point increased from 450±42.9μm to 469±40.8μm(P=0.0001).The asphericity increased from-0.84±0.74 to-0.35±0.81(P=0.15)and the spherical equivalent reduced from-4.64±4.87D to-3.04±3.45D(P=0.137).The changes in the asphericity and spherical equivalent were not statistically significant.CONCLUSION:Ferrara ICRS implantation showed to be a reversible and readjustable surgical procedure for keratoconus treatment.Good outcomes can be obtained even after removal,addition,reposition or exchange of ICRS.

Investigation of the efficiency of intrastromal ring segments with cross-linking using different sequence and timing for keratoconus

· AIM: To evaluate and compare the efficacy and stability of intrastromal corneal ring segment(ICRs)implantation with cross-linking(CXL) using different sequence and timing.· METHODS: In this single retrospective study, 86 keratoconic eyes subjected the ICRs implantation. We analyzed only 41 eyes that had complete follow-ups.They were divided into three groups: ICRs implantation was applied only(group normal), ICRs first followed by CXL immediately(group CXL-S), CXL first followed by ICRs long after(group CXL-B). The visual acuity,refractive results, keratometry were compared preoperatively and 1y postoperatively. Their differences among the three groups were also analyzed.·RESULTS: Group normal comprised 25 eyes, group CXL-S 8 eyes, and group CXL-B 8 eyes. There were improvements in the mean uncorrected distance visual acuity(UDVA) and the mean corrected distance visual acuity(CDVA) compared preoperatively and 1y postoperatively [UDVA: 0.31(P =0.030) logarithmic minimum angle of resolution(log MAR) group normal, 0.4(P =0.020) group CXL-S, 0.45(P =0.001) group CXL-B;CDVA : 0. 21 log MAR( P = 0. 013) group normal, 0. 30(P =0.036) group CXL-S; 0.26(P =0.000) group CXL-B].The refractive and topographic outcomes also showed improvements. In terms of comparisons among the three groups, all the P values were above 0.05, showing no significant difference. But only group CXL-B had improvement in UDVA and CDVA for all the patients.·CONCLUSION: With safety and good visual outcomes,ICRs implantation is a viable alternative for keratoconus.No significant difference was found among these three groups.

Double intrastromal corneal ring segment implantation: a new approach for improved clinical outcomes in keratoconus patients

AIM:To evaluate the clinical outcomes after subsequent implantation of a new intrastromal corneal ring segment(ICRS)model followed by an additional short-arc ICRS implant in keratoconus patients.METHODS:This retrospective single-arm cohort study evaluated 25 eyes of 21 keratoconus patients implanted with the new ICRS followed by 140-arch length ICRS(140-ICRS)implantation.Uncorrected distance visual acuity(UDVA,logMAR),corrected distance visual acuity(CDVA,logMAR),sphere,astigmatism,keratometry,spherical equivalent(SE),and asphericity were compared preoperatively and postoperatively after both ICRS implantation.RESULTS:The average follow-up time after 140-ICRS implantation was 6.40±2.20mo.The mean preoperative UDVA improved from 1.27±0.14 preoperative to 0.52±0.26 after both ICRS implantation(P=0.03).The mean sphere value reduced from-5.34±2.74 preoperatively to-2.06±1.84 postoperatively(P<0.001)after the first ICRS implantation and decreased to-0.59±1.54 postoperatively(P<0.001)after 140-ICRS implantation.The mean preoperative astigmatism was-3.72±1.56 and improved to-2.82±1.08 after the first ICRS implantation,and following the 140-ICRS implantation,the mean astigmatism was-1.37±0.67(P=0.001).The SE and asphericity changes were statistically significant(P<0.001).The researchers did not find intraoperative or postoperative complications for both procedures.CONCLUSION:The combination of 2 different ICRSs can efficiently regularize the cornea,reduce the SE,and improve visual acuity in selected keratoconus patients.

Artificial neural network to guide intracorneal ring segments implantation for keratoconus treatment:a pilot study

Background:To analyze the clinical results of an artificial neural network(ANN)that has been processed in order to improve the predictability of intracorneal ring segments(ICRS)implantation in keratoconus.Methods:This retrospective,comparative,nonrandomized,pilot,clinical study included a cohort of 20 keratoconic eyes implanted with intracorneal ring segments KeraRing(Mediphacos,Belo Horizonte,Brazil)using the ANN(ANN group)and 20 keratoconic eyes implanted with KeraRing using the manufacturer’s nomograms(nomogram group).Uncorrected distance visual acuity(UDVA),corrected distance visual acuity(CDVA)(visual acuity is expressed in decimal value and in LogMAR value in brackets),manifest refraction,corneal topography,tomography,aberrometry,pachymetry and volume analysis(Sirius System.CSO,Firenze,Italy)were performed during the preoperative visit;and the two groups,ANN group and nomogram group,did not differ significantly preoperatively in all of the parameters evaluated.These preoperative values were compared with the results obtained at the third-month visit.Mann-Whitney test and Wilcoxon test were used for the statistical analyses.Results:The spherical equivalent and the keratometric values decreased significantly in both groups.The CDVA improved from 0.60±0.23(0.22 LogMAR)pre-operatively to 0.73±0.21(0.14 LogMAR)post-operatively in the ANN group(p<0.005),and from 0.54±0.19(0.27 LogMAR)pre-operatively to 0.62±0.19(0.21 LogMAR)post-operatively in the nomogram group(p<0.01),with statistically significant difference between the two groups(p<0.05),being better in the ANN group.Coma-like aberrations decreased significantly in the ANN group,while in the nomogram group they did not change significantly,but no statistically significant difference was found between the two groups.Conclusions:ANN to guide ICRS provides an increase in the visual acuity,reduction in the spherical equivalent and improvement in the optical quality of keratoconus patients.ANN gives better results when compared with the manufacturer’s nomograms in terms of better corrected vision and reduction of the coma-like aberrations.The constant inclusion of new cases will make the predictability of ANN increasingly better as the software finetunes its learning.

Artificial neural network to guide intracorneal ring segments implantation for keratoconus treatment:a pilot study

Background:To analyze the clinical results of an artificial neural network(ANN)that has been processed in order to improve the predictability of intracorneal ring segments(ICRS)implantation in keratoconus.Methods:This retrospective,comparative,nonrandomized,pilot,clinical study included a cohort of 20 keratoconic eyes implanted with intracorneal ring segments KeraRing(Mediphacos,Belo Horizonte,Brazil)using the ANN(ANN group)and 20 keratoconic eyes implanted with KeraRing using the manufacturer's nomograms(nomogram group).Uncorrected distance visual acuity(UDVA),corrected distance visual acuity(CDVA)(visual acuity is expressed in decimal value and in logMAR value in brackets),manifest refraction,corneal topography,tomography,aberrometry,pachymetry and volume analysis(Sirius System,CSO,Firenze,Italy)were performed during the preoperative visit;and the two groups,ANN group and nomogram group,did not differ significantly preoperatively in all of the parameters evaluated.These preoperative values were compared with the results obtained at the third-month visit.Mann-Whitney test and Wilcox on test were used for the statistical analyses.Results:The spherical equivalent and the keratometric values decreased significantly in both groups.The CDVA improved from 0.60±0.23(0.22 logMAR)preoperatively to 0.73±0.21(0.14 logMAR)postoperatively in the ANN group(P<0.005),and from 0.54±0.19(0.27 logMAR)preoperatively to 0.62±0.19(0.21 logMAR)postoperatively in the nomogram group(P<0.01),with statistically significant difference between the two groups(P<0.05),being better in the ANN group.Coma-like aberrations decreased significantly in the ANN group,while in the nomogram group they did not change significantly,but no statistically significant difference was found between the two groups.Con elusions:ANN to guide ICRS provides an increase in the visual acuity,reduction in the spherical equivalent and improvement in the optical quality of keratoconus patients.ANN gives better results when compared with the manu facturer's no mograms in terms of better corrected vision and reduction of the coma-like aberrations.The constant inclusion of new cases will make the predictability of ANN increasingly better as the software finetunes its learning.

The number of intracorneal ring segments in asymmetric and central cones

Background:To compare the results of single versus double intracorneal ring segment(ICRS)(KeraRing)implantation in keratoconus with respect to different cone locations.Methods:Twenty-two eyes of 18 patients with totally asymmetric cones(20-80%or 0-100%distribution along steep axis)were implanted with single ICRS(Group 1),38 eyes of 32 patients with central or partially asymmetric cones(50-50%or 40-60%distribution along steep axis)were implanted with double ICRS(Group 2),at a depth of 80%of the site of implantation,in channels created with femtosecond laser device.All patients had uncorrected and corrected distance visual acuities(UDVA and CDVA,respectively)of≤0.3 Snellen lines.Results:In both groups,patients had median UDVA and CDVA gain of 3 Snellen lines(P>0.05).Postoperative improvement in indices of vertical asymmetry and height decentration in Group 1;simulated keratometry,corneal astigmatism and anterior corneal asphericity values in Group 2 were greater(P<0.05).A total of 10 eyes(45.5%)in Group 1 were recommended double ring implantation by the manufacturer’s nomogram,but underwent single ICRS implantation and achieved visual,refractive,tomographic outcomes comparable to that in Group 2,although corneal cylindrical correction was less and final topographic astigmatism was greater.Conclusion:Double ICRS implantation seems to be superior in terms of keratometry,corneal astigmatism and anterior corneal asphericity improvement.Single ICRS implantation in totally asymmetric cones seems to provide satisfactory visual,refractive and tomographic results,similar to double ICRS implantation in central and partially asymmetric cones,by inducing central shift of the cone.

大直径盾构隧道纵向刚度增强措施研究

为研究不同环缝接头结构对盾构隧道纵向刚度的增强效果,采用等效连续化模型计算得到断面直径对隧道纵向拉压、纵向抗剪和纵向抗弯刚度的影响规律,将隧道纵向刚度增强措施与管片环缝接头结构相联系,采用数值模拟深入探究了9种环缝接头结构的力学性能,对比得到增强隧道纵向刚度效果最优的环缝接头结构。结果表明:直径对纵向拉压和纵向抗弯刚度影响较小,对纵向抗剪刚度影响较大;环缝接头刚度增强措施能够显著减小管片位移,提高隧道纵向刚度,提升效果为:斜螺栓>弯螺栓,定位榫>剪力销>凹凸榫;螺栓型式和纵向刚度增强措施均对螺栓最大剪切应力有较大影响,竖向荷载下受螺栓型式影响较大,水平向荷载下受管片环缝接头刚度增强措施影响较大;结合经济性和有效性,当接头螺栓为弯螺栓时,设置定位榫是一种相对较优的选择。

盾尾密封失效诱发砂土地基盾构管片环失稳坍塌研究

盾构管片环失稳坍塌案例时有发生,探究其失稳坍塌发生条件对于预防重大安全事故发生具有重要意义。基于Midas GTS建立30环考虑环缝螺栓作用的荷载−结构计算模型,从盾尾管片环地基掏空和盾尾姿态突变2个方面探讨盾构管片环结构失稳破坏过程及失稳坍塌的发生条件。结果表明:盾尾渗漏使盾尾壳体失去了周围地基的有效约束作用,盾尾发生前仰后俯的姿态变化,隧道结构发生横向“横鸭蛋”和纵向挠曲变形,最终导致部分管片环坍塌。盾尾下沉位移是诱发管片环失稳坍塌的主要因素,盾尾下沉导致隧道纵向变形快速发展,快于盾尾渗漏引起管片环周围地基掏空所导致的隧道纵向变形。当盾尾下沉位移大于0.50 m且掏空范围大于5环、盾尾下沉位移大于0.45 m且掏空范围大于10环、盾尾下沉位移大于0.40 m且掏空范围大于11环时,环缝最大张开量超过单根螺栓极限应力时的环缝张开量47.43 mm,部分纵向螺栓被拉断,管片外水土发生喷射,加快管片环外砂土快速流失。当盾尾下沉位移大于0.5 m且掏空范围大于9环时,环缝最大张开量超过65.2 mm,管片环椭圆率超过46.1‰,最终诱发多环管片环失稳坍塌。研究结果可为盾尾渗漏诱发的重大安全风险评判提供参考。

盾构隧道通用环管片拟合排版技术

为实现通用环排版计算步骤和结果与管片实际偏差计算在隧道坐标下的统一,以准确、高效开展基于隧道轴线的管片轴线拟合,进而优化盾构通用环管片排版技术,首先明确了隧道三维坐标系的选取方法及盾构管片空间姿态的表示方法,提出了盾构通用环管片排版端面中心三维坐标的计算方法及起始环的定位方法。根据某盾构隧道工程实例,利用研发软件进行排版拟合,结果表明:该方法得到的排版结果与隧道设计轴线的拟合效果良好;将拟合得到的管片排版端面中心坐标与实际测量结果进行对比,能够得到施工偏差方向及具体数值,可为后续排版和纠偏提供定量控制指导,该研究成果还可实现管片楔形量的试算,从而优化管片设计参数,为盾构隧道的设计及建设提供技术支持。

环端面不平整条件下衬砌管片抗剪承载特性研究

在衬砌管片拼装过程中难免出现环端面不平整(或环缝间垫片局部脱空)的情形,进而在顶推力作用下管片容易产生局部开裂破损,严重时甚至危及衬砌结构安全。鉴于此,以衬砌管片抗剪原型试验为基础,在ABAQUS数值分析平台上建立P2型标准块管片的精细化模型,管片上部设置千斤顶靴板,底部设置垫片并使右侧垫片脱空。在靴板上逐级施加均布荷载,以分析局部脱空情况下衬砌管片在逐级顶推力作用下的力学响应,探讨环端面不平整条件下衬砌管片的裂缝发展过程及抗剪承载特性。数值模拟结果表明:顶推力加载至850 kN,管片脱空端竖向位移达到2 mm,管片内弧面上部出现第1道裂缝,内置钢筋仍处于弹性阶段;加载至1120 kN,脱空端竖向位移达到6 mm,内弧面上出现2道新裂缝,同时第1道裂缝进一步扩展形成内外贯穿性裂缝,即管片裂缝发展过程大致为内弧面→上环端面→外弧面,且裂缝附近上层纵向钢筋达到屈服强度;考虑到内外贯穿裂缝给衬砌管片带来较大渗漏水隐患,认为P2型标准块管片的抗剪承载力(即屈服荷载)约为1120 kN。将数值模拟结果与原型试验结果进行对比,二者所得管片裂缝分布与扩展规律大致一致,抗剪承载力基本相符,验证了数值模拟结果的可靠性。研究成果可为盾构隧道的衬砌设计与掘进施工提供参考依据。

改进UNet++的杉木CT图像年轮分割

为解决裂纹、虫孔和节子等缺陷影响下的年轮准确分割问题。以医疗CT为实验设备,重构125张杉木横切面CT图像为研究对象,经裁切、旋转、翻转等预处理实现数据扩充,提出改进UNet++模型用于年轮分割。改进UNet++模型采用增加卷积块、下采样层、跳跃连接和上采样层的方式,将学习深度增加至6层,以BCEWithLogitsLoss和ReLU分别作为损失函数和激活函数,RMSProp作为优化函数,对杉木横切面CT图像进行年轮分割,并对年轮分割性能进行评价。结果显示:改进UNet++模型对于杉木横切面CT图像的年轮分割的像素准确率为97.81%,骰子系数为98.89%,交并比为95.29%,平均交并比为84.75%,充分提取杉木年轮特征,分割效果最好。与U-Net模型和UNet++模型相比,改进UNet++模型在多数年轮被裂纹和虫孔切割,无法形成完整圆形闭合曲线的条件下,使分割的年轮具有很好的完整性和连续性,消除分割过程中的断裂和噪声现象;年轮分割结果不受裂纹、节子、虫孔等缺陷影响,结构非常清晰,有效解决多种缺陷干扰下的虫孔误分割和密集年轮欠分割等问题。

电力隧道渗漏水成因分析及治理措施研究

电力隧道内电缆数量较多,电缆及其他电力设施对水非常敏感,如果积水淹没电缆(尤其是电缆接头部位),可能会造成事故和损失。文章详细分析了暗挖、盾构等结构形式隧道的渗漏水成因,对管片、环梁、沉降缝、墙体及管孔等部位渗漏水治理措施进行研究,提出了针对性的治理建议并进行了试点应用,为电力隧道渗漏水治理工作提供参考。

标准环加转弯环盾构管片排版及拼装选型算法研究

[目的]为解决人工进行标准环+转弯环(双面楔形)盾构管片排版和选点中存在的主观性强、计算繁琐、重复工作量大等问题,特对其进行算法研究,以解决实际工程问题。[方法]开发了标准环+转弯环管片自动排版、拼装选型及预测算法软件。基于成熟施工经验,依据隧道线形和管片转角计算管片排版计划,实现了管片排版的自动化计算。提出了综合考虑隧道线形、盾尾间隙、推进油缸行程和盾构机趋势的标准环+转弯环管片选型计算方法和决策算法,实现了管片自动拼装选点。在此基础上,通过建立盾构姿态变化与盾尾间隙和油缸行程变化量的关系式,实现了未来2环标准环+转弯环管片拼装点位和管片型号的预测。[结果及结论]研究成果在广州地铁12号线成功应用,显著提升了现场标准环+转弯环管片排版、选型的工作效率,降低了人力成本,并优化了盾构隧道施工工序。

Clinical outcomes after implantation of a new intrastromal corneal ring with 140-degree of arc in patients with corneal ectasia

AIM：To evaluate the clinical and tomographic outcomes after implantation of a new intrastromal corneal ring segment（ICRS） with 140-degrees of arc in eyes with corneal ectasia.METHODS：We evaluated patients with corneal ectasia implanted with Ferrara 140° ICRS from April 2010 to February 2015.Outcome measures included preoperative and postoperative corrected distance visual acuity（CDVA）,keratometry simulated（K） reading,tomographic astigmatism and asphericity.All patients were evaluated using the Pentacam Scheimpflug system.RESULTS：The study evaluated 58 eyes.The mean followup was 16.81±10.8 mo.The CDVA（logM AR） improved from 0.5±0.20（20/60） to 0.3±0.21（20/40）（P〈0.01）.The average K reduced from 49.87±7.01 to 47.34±4.90 D（P〈0.01）.The asphericity changed from-0.60±0.86 to-0.23±0.67 D（P〈0.01）.The mean preoperative tomographic astigmatism decreased from-8.0±3.45 to-4.53±2.52 D（P〈0.01）.CONCLUSION：The new ICRS model with 140-degrees of arc effectively improve the visual acuity and reduce the high astigmatism usually found in patients with corneal ectasia.

环段吊装方案对风电混塔管片变形的影响分析

混凝土塔架采用预制管片通过水平和竖向节点组合而成,其组装需要现场进行吊装,吊装质量直接影响整塔的服役性能。在吊装方案中,吊钩吊点布置会导致管片受力存在差异。当环氧树脂结构胶尚未达到设计强度时,环段的整体性也未达到预期设计性态,管片起吊时由于重力影响而产生较大变形,严重时可能会导致管片的错台、崩边等工程质量问题。为了探究典型吊装工况对混塔吊装环段性态的影响,基于非线性有限元软件,以实际工程为背景,设计了3种不同的吊装工况(理想、工程、设计),研究了不同工况下混塔环段变形随吊装方式的影响。结果表明:通过调节各个吊带长度,将吊点处吊带沿多个方向布置,可使吊带内力均匀分布,从而减小管片的变形。

盾构隧道超近间距下穿运营盾构隧道管片环变形规律研究

为研究盾构下穿既有盾构隧道施工过程中既有隧道管片环分块变形规律,依托北京地铁19号线盾构近距离下穿7号线既有盾构隧道的工程实例,采用FLAC3D软件建立考虑管片分块拼装的三维计算模型,并结合实时监测技术对盾构穿越过程中既有隧道管片环分块变形进行监测。研究结果表明:在盾构近距离下穿既有线施工过程中,既有线管片沉降呈现“双峰式”,且新建隧道先行盾构上方既有隧道管片沉降更大;既有线管片整体向新建隧道掘进方向偏移,管片环分块水平位移程度在不同点位表现出差异化,其中各环两侧管片的水平位移最为明显且互相对称,拱顶和拱底仅发生整体偏移;既有隧道受后行盾构掘进影响时间较先行盾构更长,引起既有线管片向开挖方向偏移量更大,引发的管片水平位移也更加显著。既有线在发生整体偏移的同时,管片向两侧发生水平位移,最终管片水平位移表现取决于管片整体朝下穿隧道掘进方向的偏移量与管片环自身形变的叠加作用。

护盾式TBM隧道管片壁后豆砾石分布规律

作为管片与围岩间的连接层,TBM隧道中的豆砾石对管片受力具有重要意义。受施工技术、地质条件等影响,豆砾石填充不密实、分布不均匀的现象时常发生,导致管片出现错台、开裂、渗漏水等灾害,故探明豆砾石分布特征是分析管片受力的基础。对此,依托青岛地铁TBM隧道项目,采用地质雷达对管片壁后豆砾石分布特征进行现场测试,并进行单环管片豆砾石吹填数值模拟,分析了隧道直行段、转弯段豆砾石在管片壁后的迁移过程,讨论了地质条件、吹填压力、塌方等因素对吹填质量的影响规律。结果表明:在TBM隧道施工中,拱顶、隧底及转弯段外侧下部为豆砾石空洞多发部位,拱顶与隧底空洞长度大于1m,主要表现为层间脱空,转弯段外侧下部豆砾石空洞规模较小且不密实;地质条件越差,豆砾石出现空洞的概率及规模越大,强风化地层表现最为明显;塌方通过阻碍豆砾石迁移路径、增加碰撞耗能影响豆砾石吹填质量,但影响范围仅在塌方处;提升豆砾石吹填压力可以改善拱顶和隧底豆砾石填充状态,地质条件越好,改善程度越明显,强风化地层豆砾石吹填质量改善不明显;管片壁后豆砾石空洞按照形成原因分为3类:碰撞耗能、塌方掉块和转弯段间隙变小,并给出了3类空洞的多发部位、特征及施工控制建议。